KR20150050340A - Method and apparatus for device to device communication and method and apparatus for controlling device to device communication - Google Patents

Abstract

A first terminal in a first cell of the first base station receives a synchronization signal and a synchronization channel broadcasted on the downlink by the first base station. The first terminal acquires synchronization for D2D communication using the synchronization signal and the synchronization channel. The first terminal may transmit first information for D2D communication to a first data channel for cellular communication in order to request allocation of a first resource for D2D communication when the first terminal is connected to the first base station, To the first base station. The first terminal receives, from the first base station, D2D control information including information on the first resource allocated to the first terminal. The first terminal broadcasts a second data channel for D2D communication using the D2D control information.

Description

TECHNICAL FIELD [0001] The present invention relates to a D2D (Device to Device) communication method and a D2D communication control method,

The present invention relates to D2D communication in which a terminal directly communicates with a counterpart terminal.

In a communication environment in which a mobile communication network is established based on a base station, studies are underway to establish a radio path for direct communication between terminals that are geographically close to each other and use the radio path for communication.

Direct communication between terminals, that is, D2D communication, means communication between terminals without relaying the base station by transmitting data wirelessly and other terminals receiving data directly. D2D communication is performed using radio resources, and the frequency of a licensed band may be used.

On the other hand, mobile communication operates on a base station basis. A terminal located in an in-coverage area of a cell constructed as a base station can perform D2D communication under the control of a base station.

Also, since D2D communication can be directly performed between terminals, a terminal located out-of-coverage can perform D2D communication without being under the control of a base station.

In addition, since terminals located at a cell boundary may communicate with each other through D2D, terminals within the cell range and terminals outside the cell range must be able to communicate with each other.

Meanwhile, the terminals participating in the D2D communication must maintain the time and frequency synchronization, and a synchronization procedure for the time and frequency synchronization is required.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a control method for performing D2D communication in a cell range of a base station.

It is another object of the present invention to provide a method and a control method for performing D2D communication by a terminal outside the cell boundary or cell range of a base station.

According to an embodiment of the present invention, a D2D (Device to Device) communication method is provided in which a first terminal in a first cell of the first base station communicates directly with a second terminal without relaying a first base station. The D2D communication method includes: receiving a synchronization signal and a synchronization channel broadcasted on a downlink by the first base station; Acquiring synchronization for D2D communication using the synchronization signal and the synchronization channel; To request allocation of a first resource for D2D communication when the first terminal is connected to the first base station, transmitting first information for D2D communication to the first base station via a first data channel for cellular communication, ; Receiving, from the first base station, D2D control information including information on the first resource allocated to the first terminal; And broadcasting the second data channel for D2D communication using the D2D control information.

Wherein the first information is at least one of a first identifier of the first terminal and a second identifier of a first group to which the first terminal belongs; Information about the first resource that the first terminal desires to use; And information about a size of data to be transmitted by the first terminal.

The transmitting of the first information may include transmitting a BSR (Buffer Status Report) message including the first information to the first base station.

Wherein the D2D control information includes at least one of the first identifier and the second identifier; At least one of a position of the first resource, a size of the first resource, and a number of the first resources; And a repetition period of the first resource and a repetition number of the first resource.

The step of receiving the D2D control information may include receiving the D2D control information from the first base station via at least one of a first control channel and a first response channel for the downlink.

The D2D communication method may further comprise: after the first access point is randomly connected to the first base station via a random access channel when the first terminal is in an idle state, To the first base station via a data channel.

Wherein the step of receiving the D2D control information comprises the steps of: when the first terminal is connected to the first base station, using the first identifier included in the D2D control information, the D2D control information is information for the first terminal ; And determining whether the D2D control information is information for the first terminal using the second identifier included in the D2D control information when the state of the first terminal is in an idle state .

Broadcasting the second data channel includes broadcasting a first identification channel including information on whether the first terminal transmits the first data using the second data channel; Broadcasting a second control channel for demodulating the first data; And broadcasting the second data channel to broadcast the first data.

The step of receiving the D2D control information may further include the step of, when the second terminal is located in the second cell of the second base station, comparing the difference between the synchronization time used by the first base station and the synchronization time used by the second base station Receiving from the first base station the D2D control information further comprising second information for the first base station; And changing the synchronization time using the second information.

According to another embodiment of the present invention, there is provided a method for a first terminal to control D2D (Device to Device) communication between terminals. Broadcasting the first synchronization signal and the first synchronization channel on the uplink when the first terminal operates as a central control device for managing synchronization and resources for D2D communication; Receiving a first message from a second terminal requesting allocation of a first resource for D2D communication; And allocating the first resource to the second terminal.

The first synchronization channel may include information on a first identifier of the first terminal and a type of the first synchronization signal.

Wherein the first synchronization channel includes information indicating that the first synchronization channel is a channel for synchronization of D2D communication, information indicating the first synchronization signal, information on the accuracy of the first synchronization signal, The synchronization information for the first synchronization signal, the position information of the first terminal, the strength of the first synchronization signal, and the first synchronization signal, And may further include at least one of the number of used terminals.

Wherein the step of broadcasting the first synchronization signal and the first synchronization channel comprises the steps of: when the second terminal fails to receive the second synchronization signal broadcasted on the downlink by the base station, Receiving a broadcast instruction; And operating as the central control unit in response to the broadcast instruction.

Wherein the broadcasting of the first synchronization signal and the first synchronization channel comprises broadcasting the first synchronization signal on the basis of the second synchronization signal when receiving a second synchronization signal broadcasted on the downlink by the base station, ; Broadcasting the first synchronization signal based on the GPS signal when receiving a Global Positioning System (GPS) signal without receiving the second synchronization signal; Broadcasting the first synchronous signal based on the third synchronous signal when receiving a third synchronous signal which is not received by the second synchronous signal and the GPS signal but is broadcast by another central control apparatus; And broadcasting the first synchronization signal based on a predetermined time when the second synchronization signal, the GPS signal, and the third synchronization signal are not received.

The D2D communication control method comprising the steps of: transmitting information on the second synchronous signal and the second synchronous channel to a base station when receiving a second synchronous signal and a second synchronous channel broadcasted by another central control apparatus; And stopping broadcasting the first synchronization signal when receiving a broadcast stop instruction from the base station.

Wherein the broadcasting of the first synchronization signal and the first synchronization channel comprises transmitting a second message indicating that the second terminal having received the first synchronization signal and the first synchronization channel has connected to the first terminal, Receiving from a second terminal; And counting the number of terminals using the first synchronization signal based on the second message.

The D2D communication control method comprising the steps of: changing a synchronization time for the first synchronization signal based on the second synchronization signal when receiving a second synchronization signal broadcasted on a downlink by a base station; And reporting information on the first terminal operating as the central control device to the base station so that the base station can determine whether the first terminal continues to operate as the central control device.

According to another embodiment of the present invention, there is provided a D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without relaying a first base station. The D2D communication method may further include receiving a first synchronization signal and a second synchronization signal from a third terminal operating as a central control device for managing synchronization and resources for D2D communication when the first terminal is located outside a first cell of the first base station, Receiving a first synchronization channel; Transmitting a BSR message to the third terminal through a request channel for requesting resource allocation when the first synchronization signal and the first synchronization channel are received; Receiving information on a first resource allocated to the first terminal from the third terminal through a response channel; And broadcasting a first identification channel including information on whether the first terminal transmits the first data using the first resource.

The D2D communication method may further comprise: determining whether a reception strength of a second synchronization signal broadcasted on the downlink by the first base station is equal to or less than a first threshold value, or if a radio link failure (RLF: Radio Link failure occurs, it may be determined that the first terminal is located outside the first cell.

The step of receiving the first synchronizing signal and the first synchronizing channel may include calculating a difference between a synchronizing time for the first synchronizing signal and a synchronizing time for the second synchronizing signal.

The step of transmitting the BSR message to the third terminal may include transmitting the request channel including information on the synchronization time difference to the third terminal.

Determining that the first terminal is located in the first cell when the reception intensity of the second synchronization signal is greater than the first threshold; Calculating a difference between a synchronization time for the first synchronization signal and a synchronization time for the second synchronization signal when the first terminal is located in the first cell and transmitting the difference to the third terminal; And changing the synchronization time using the second synchronization signal.

According to an embodiment of the present invention, a terminal can perform D2D communication in a structure under the control of a mobile communication base station.

Also, according to the embodiment of the present invention, D2D communication can be performed even when the terminal is located at a cell boundary or outside a cell boundary.

According to the embodiment of the present invention, in the D2D communication of the central control type, the base station or the central control device performs the synchronization management and the D2D communication management function of the terminal, so that stable transmission performance can be provided and consistent D2D communication management And the power consumption of the terminal can be efficiently reduced.

1 is a diagram showing a communication environment of D2D communication.
2 is a diagram illustrating a concept of an uplink channel used in D2D communication.
3 is a flowchart showing a process of transmitting data by a terminal located in a cell.
4 is a diagram showing the types of channels used for D2D communication.
5 is a flowchart showing a process of transmitting data by a UE located outside a cell.
6 is a flowchart illustrating a process of transmitting / receiving data when a terminal that has performed D2D communication in a cell moves out of a cell.
7 is a flowchart illustrating a process of transmitting / receiving data when a UE that has performed D2D communication outside the cell moves into a cell.
8 is a diagram showing a configuration of a terminal.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, a terminal is referred to as a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS), a high reliability mobile station ), A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) MS, AMS, HR-MS, SS, PSS, AT, UE, and the like.

In addition, the base station (BS) includes an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B an eNodeB, an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) BS, ABS, HR-BS, Node B, eNodeB, AP, RAS (Personal Area Network), and so on), a high reliability relay station , BTS, MMR-BS, RS, HR-RS, small base station, and the like.

One. D2D  Resources and motivation for communication

1-1. Wireless resource structure

In direct communication between terminals, that is, D2D communication, in order to reduce the complexity of the terminal, the frequency of the uplink band is used among frequency bands used in mobile communication. Specifically, the terminal transmits a signal for D2D communication on the uplink and receives the signal transmitted by the other terminal. The resources of the uplink band can be divided into resources for cellular communication (for example, communication between a base station and a terminal) and resources for D2D communication (direct communication between terminals). Specifically, the resources for D2D communication can be further divided into base station control resources and non-control resources. A base station control resource is a resource allocated to a terminal located in a cell by a base station. The base station can broadcast the location information and the range information of the base station control resource with a predetermined value through the cell control channel. Alternatively, the terminal may receive the location and range information of the base station control resource from the D2D communication server. On the other hand, the uncontrolled resource means a resource used by a terminal that is not connected to the base station, and the central control device can allocate the uncontrolled resource to the terminal. The central control device may be a terminal, or a device that is not a terminal.

Meanwhile, the base station can allocate a synchronization signal transmission area required for synchronization of the terminals. The base station may use some resources of the uplink band for the synchronization signal, and the synchronization signal resource may be a non-control resource.

Meanwhile, the base station can manage and transmit / receive base station control resources. The base station can also manage and transmit / receive non-control resources.

Hereinafter, for convenience of explanation, a case where a channel used for D2D communication is divided into frequency units and time units (e.g., subframes) will be described as an example.

1 is a diagram showing a communication environment of D2D communication.

The terminals UE1 to UE3 located in the cell 10 of the base station BS1 can perform the mobile communication or the cellular communication CM2 through the relay of the base station BS1. In addition, the terminals UE1 to UE3 located in the cell 10 of the base station BS1 can perform the D2D communication CM1 under the control of the base station BS1.

The terminal UE3 placed in the cell 10 can perform the D2D communication CM1 even when the time offset is managed with the terminal UE4 located in the cell 20 of the neighboring base station BS2. Specifically, the terminal UE3 can perform the D2D communication CM1 with the terminals UE1, UE2, and UE4 located in the D2D communication range 30 of the terminal UE3.

The terminals UE6 to UE9 located outside the cells 10 and 20 of the base stations BS1 and BS2 can perform the D2D communication CM1 under the control of the centralized control device UE9. Specifically, the terminal UE9 can perform the D2D communication CM1 with the terminals UE6 to UE8 located in the D2D communication range 40 of the terminal UE9. When the terminal UE9 has the function of the central control device, it can operate as the central control device. The functions of the central control unit include a function of managing and allocating radio resources required for D2D communication and a function of managing synchronization for D2D communication.

1-2. Time synchronization at cell boundaries

In order for a terminal to participate in D2D communication, a certain level of time synchronization must be maintained. For example, the UE (e.g., UE1) located in the cell 10 can use the synchronization signal broadcasted on the downlink by the base station BS1, or use the control signal transmitted together with the data channel, Lt; / RTI >

For D2D communication, a time synchronization procedure using a synchronization signal transmitted through an uplink is required. For example, a terminal (e.g. UE3) located at the cell 10 boundary or a terminal located outside the cells 10, 20 (e.g. UE6) requires additional synchronization procedures. The signal for uplink time synchronization can be broadcast by a general terminal or a central control device for managing the synchronization of the D2D communication.

The base station BS1 can receive a synchronization signal broadcast by the terminal or the central control unit using resources of the uplink band, and can change the broadcast reference value of the received synchronization signal. Further, the base station BS1 can instruct the central control device to transmit the synchronization signal or to stop the transmission of the synchronization signal. The terminal equipped with the function of controlling the D2D communication can perform the function of the central control device. A terminal operating as a central control device may be located within the cells 10, 20, at the boundary of the cells 10, 20, or outside the cells 10, 20.

A process of keeping time synchronization between a UE (e.g., UE3) located at the boundary of cells 10 and 20 is as follows. The terminal UE3 periodically receives a downlink synchronization signal broadcasted by the base station BS1. When the terminal UE3 fails to acquire the synchronization signal, it searches the uplink physical channel broadcasted by the central control unit. The central control device searches for a synchronization signal broadcasted by another central control device, and directly broadcasts an uplink synchronization signal when it fails to receive an uplink synchronization signal. In transmitting the synchronization signal, the central control unit may report the information of its own and the synchronization signal to the base station (e.g., BS1) or may request permission to transmit the synchronization signal.

On the other hand, a physical channel used for synchronization of a terminal can be divided into a synchronization signal and a synchronization channel. Specifically, synchronization signals (e.g., Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS)) physically include information for synchronization acquisition of the terminals. The central control device broadcasts a synchronization signal and a synchronization channel using frequency division multiplexing (FDM) or code division multiplexing (CDM) to distinguish the synchronization signals transmitted from the other central control devices . The time position of the synchronization signal can be fixed and can be allocated in a constant period in the uplink band. Since the synchronization signal only includes information for the terminal to acquire synchronization, additional information can be broadcast through the synchronization channel. Concretely, the synchronization channel includes synchronization channel display information, time information, synchronization signal information, standalone information, relay information, accuracy, physical cell ID, central control device ID, mobility information, time Change information, location information, signal strength information, and terminal connection information. On the other hand, some of the information in Table 1 may be included in a synchronization signal other than a synchronization channel in order to enable quick acquisition by the terminal.

Information Remarks About synchronous channel display - information indicating (indicating) the sync channel
- A synchronization channel including synchronization channel indication information can be broadcast so that other terminals can distinguish Time information Time information such as SFN (System Frame Number) information Sync signal information Information about the synchronization signal mapped to the synchronization channel Standalone Information Information (e.g., synchronization acquisition using GPS or the like) indicating that the synchronization channel is broadcast without synchronization of the base station, Relay information - information indicating that it is a synchronous channel broadcast based on the synchronization of the base station
- In the case of a synchronous channel broadcast based on the synchronization of the base station, type information indicating uplink synchronization or downlink synchronization
- In the case of a device that broadcasts the synchronization of the peripheral central control device by relaying, accuracy The accuracy of the synchronization signal (eg, error range, or hop count if base station synchronization is relayed) Physical cell ID The cell identifier of the base station used as the reference value Central Control Unit ID Identifier of the device broadcasting the synchronization signal Mobility information Information indicating that the central control device is a moving device, or information indicating the moving speed of the central control device (e.g., high speed, low speed, fixed) Time change information (For example, an offset between the synchronous time and the synchronous synchronizing time, a time at which the time change is to be applied (the time at which the time change is to be executed)) of the synchronization synchronizing time of the synchronizing signal transmitted from the apparatus, Location information Location information of the central control unit Signal strength information Signal strength of the central control unit Terminal connection information (For example, the number of terminals using the synchronization signal of the central control device) indicating that there is a terminal using a synchronization signal of the central control device or another central control device, Type of Synchronization Source - Indicate the characteristics of the device (eg eNodeB, UE, broadcasting UE, CH, etc)

On the other hand, the central control device can broadcast the communication parameters necessary for D2D communication by broadcasting the cell system information broadcast by an LTE (Long Term Evolution) base station (e.g., BS1) in the synchronization channel in addition to the information in Table 1 . Here, the communication parameters required for D2D communication may include channel information (e.g., time / frequency information, size, period, transmission power, etc.) used for D2D communication, and availability information of the D2D communication channel.

On the other hand, the central control device periodically transmits the synchronization channel and can transmit the synchronization channel by periodically changing the position of the synchronization channel in order to avoid collision with another channel. Specifically, the central control apparatus changes the transmission position of the synchronization channel by using a time division multiplexing (TDM) method to transmit the synchronization channel, so that another central control apparatus that transmits the synchronization channel at the same position avoids collision . In transmitting the synchronization channel, the central control device receives the synchronization channel broadcast area that it does not transmit at a certain period, and confirms whether another central control device transmits the synchronization channel. The central control device can stop the transmission of the synchronization signal or the synchronization channel or request the interruption of the transmission of the other central control device in order to avoid the collision of the synchronization signal when the other central control device confirms to transmit the synchronization channel .

Meanwhile, the central control unit can broadcast control information similar to the system information broadcasted by the base station (e.g., BS1) through the synchronization channel. Specifically, the central control device can transmit the information of the synchronization channel using the same procedure and channel structure as the data channel.

2 is a diagram illustrating a concept of an uplink channel used in D2D communication.

In FIG. 2, a synchronization signal SYNC_SIG, a synchronization channel SYNC_CH, a control channel CTR_CH, and a data channel DATA_CH transmitted through an uplink are illustrated for convenience of explanation.

On the other hand, when the central control apparatus broadcasts the synchronization signal in the uplink, the synchronization signal can be transmitted under the following conditions. Specifically, when the central control unit acquires the synchronization signal of the base station (e.g., BS1), it refers to the synchronization signal obtained and broadcasts the synchronization signal. When the central control unit fails to acquire the synchronization signal of the base station (e.g., BS1), it acquires the synchronization reference value (e.g., GPS signal) and broadcasts the synchronization signal. For example, the central control device may acquire a signal such as a Global Positioning System (GPS) signal, acquire synchronization information from a wired network, and broadcast the synchronization signal with reference to the obtained signal or information. When the central control device acquires the synchronization signal transmitted from another central control device, the synchronization signal can be transmitted with reference to the acquired synchronization signal. When the central control device can not acquire the synchronization reference (e.g., the synchronization signal of the base station, the GPS signal, or the synchronization signal of the other central control device), the synchronization signal can be transmitted by designating the synchronization reference (time) arbitrarily.

On the other hand, the base station (e.g., BS1) may determine the necessity of the central control device and instruct the peripheral terminal to broadcast the synchronization signal with the central control device. Specifically, the base station BS1 can instruct the peripheral terminal to operate as a central control device when the terminal is located at the cell boundary or out of the cell range. For example, when the base station BS1 recognizes that the signal of the terminal UE3 moving at the boundary of the cell 10 is deteriorated, it can instruct the peripheral terminal to broadcast the synchronization signal at the central control device have. Further, the base station BS1 can instruct the peripheral terminal to operate as a central control device when neighboring cells are not built around. For example, when the terminal UE3 is located in an area where no cell is arranged according to the base station construction structure, the base station BS1 can instruct the peripheral terminal to broadcast the synchronization signal as a central control device. In addition, when the terminal requests the base station to the central control apparatus, the base station BS1 can instruct the peripheral terminal to operate as a central control apparatus. For example, when the terminal UE3 requests the base station BS1 that a synchronization signal is required, the base station BS1 may instruct the peripheral terminal to broadcast the synchronization signal as a central control device

Meanwhile, it is necessary to send and receive messages for distributed synchronization. The procedure is as follows. Specifically, the base station (e.g., BS1) requests confirmation of whether the peripheral terminal can operate as a central control device. For example, the base station BS1 may transmit a request message over a paging channel, a broadcast channel, or a data channel. The terminal receiving the request message replies whether it can operate as a central control device. For example, the terminal can include (indicate) its mobility, signal strength, power state, and location information in a response message. A terminal that does not satisfy the condition does not respond. The base station BS1 receiving the response message instructs the terminal that has transmitted the response message that the base station BS1 operates as a central control device. For example, the base station BS1 can check at least one condition and transmit at least one of the terminals that have transmitted the response message by using the indication message. The terminal receiving the instruction message performs the function of the central control unit. The terminal can transmit a response message to the instruction message.

On the other hand, when many terminals (central control apparatuses) transmit a synchronization signal, a collision may occur, and therefore, a procedure is required for some terminals to stop the transmission of the synchronization signal. However, a problem may arise if the transmission of the synchronization signal used by the other terminal is interrupted, and a procedure for avoiding this is needed. Specifically, in the case where the terminal operates as a central control apparatus, a procedure for releasing a broadcast of a redundant synchronization signal is as follows. When the central control apparatus starts the synchronous signal broadcasting, it receives the synchronous signal broadcasted by the peripheral central control apparatus. When the central control device detects the synchronization signal of the other central control device, it receives the synchronization channel of the other central control device. The central control device reports the reception information (synchronization signal, synchronization channel) to the base station (e.g., BS1). The base station BS1 uses the reported information to detect whether a redundant synchronization signal is being broadcast. When a redundant synchronization signal broadcast is detected, the base station BS1 instructs at least one of the central control devices that broadcast the redundant synchronization signal to stop the broadcast of the synchronization signal. Upon receiving the synchronization signal broadcast stop instruction, the terminal stops the synchronization signal broadcast and can respond to the interruption completion. On the other hand, the terminal operating as the central control device can directly stop the operation of the central control device without the control of the base station (e.g. BS1).

Meanwhile, a method of acquiring a synchronization of a general terminal that does not operate as a central control device is as follows. Specifically, the general terminal can receive the uplink synchronization signal when the peripheral central control device broadcasts the synchronization signal in the uplink. The general terminal receiving the uplink synchronization signal can transmit a connection confirmation message to the central control unit. For example, the general terminal can transmit a connection confirmation message to the central control device after completing the synchronization channel reception. When the central control device does not receive the connection confirmation message, the central control device can arbitrarily stop the synchronization signal broadcasting. The central control device can suspend the interruption of the synchronous signal broadcast when the connection acknowledgment message is received. The central control unit may use a counting procedure or channel to manage the number of terminals connected to it. For example, when the general terminal transmits the connection confirmation message to the central control apparatus using the uplink channel, the central control apparatus counts the connection confirmation message and confirms whether the terminal is connected or the number of the access terminals . The central control unit confirms that the connection confirmation message is received, and can respond to the terminal that has transmitted the connection confirmation message. For example, the central control device can broadcast the connection information included in the synchronization channel. On the other hand, when the general terminal releases the connection, the general terminal can report the release to the central control device. For example, the general terminal can include (indicate) the connection release request in the connection confirmation message. Upon receipt of the release request, the central control device instructs the terminal requesting the release of the connection to release the connection. For example, the central control device can broadcast (display) the interruption of the synchronous signal broadcasting in the synchronous channel. The terminal which has been instructed to release the connection can respond to the central control apparatus after confirming the connection cancellation.

1-3. Time synchronization outside the cell

Synchronization procedures of the terminals UE6 to UE9 which are not located in the cells 10 and 20 of the base stations BS1 and BS2 will be described.

The general terminals UE6 to UE8 that do not have the function of the central control unit can transmit the uplink synchronization signal (the synchronization signal broadcasted by the central control unit UE9 via the uplink) or the downlink synchronization signal (the base stations BS1 and BS2) And a synchronization signal for broadcasting through the downlink). The general terminals UE6 to UE8 do not broadcast the signal until synchronization is obtained. If the general terminals UE6 to UE8 transmit signals in the asynchronous state, it is difficult to acquire synchronization and may interfere with other communications.

On the other hand, the procedure for acquiring the synchronization when the UEs 9 having the function of the central control unit have no synchronization is as follows. Specifically, the terminal UE9 receives synchronization information (e.g., GPS signal) that can be referred to in addition to the synchronization signals of the base stations BS1 and BS2. When the UE 9 receives reference synchronization information, it broadcasts a synchronization signal and a synchronization channel after a predetermined time elapses. For example, the UE 9 can use a timer, and the timer value (period) can be specified differently according to the capability of the UE 9. That is, when the terminal UE9 has a high priority, the synchronization signal and the synchronization channel can be transmitted quickly. The terminal UE9 that transmits the synchronization channel receives the synchronization signal and the synchronization signal of the other terminal (central control apparatus). For example, since the terminal UE9 does not receive a signal when it transmits a synchronous signal and a synchronous channel, the terminal UE9 does not receive the signal of the other synchronous signal Signal and a synchronization channel. The UE 9 receives the synchronization channel of the other central control device and confirms the information. The terminal UE9 can suspend the transmission of its own synchronization signal when it is confirmed that another central control apparatus transmits the synchronization signal and the synchronization channel. For example, when the priority of the UE 9 is lower than the priority of the other central control devices, the synchronization signal broadcasting can be stopped. When the terminal UE 9 stops transmitting the synchronization signal, the synchronization signal and the interruption information of the synchronization channel transmission can be displayed (included) on the synchronization channel.

On the other hand, a description will be given of a case where the central control device UE9, which broadcasts a synchronization signal and a synchronization channel outside the cells 10 and 20, moves into the cell 20. FIG.

The terminal UE9 operating as the central control device searches for the downlink synchronization signal even outside the cells 10 and 20. When the UE 9 acquires the downlink synchronization signal of the base station BS2, it determines that the UE 9 is located in the cell 20, and based on the synchronization time of the received downlink synchronization signal, Can be changed. The terminal UE9 can display (include) synchronous time changing information in its own synchronizing signal and synchronizing channel. The terminal UE9, which has acquired the downlink synchronization signal of the base station BS2, can report its own information, which is connected to the base station BS2 and operates as a central control device. The base station BS2 can stop the operation of the terminal UE9 as a central control device by referring to the information reported by the terminal UE9.

1-4. Time synchronization between cells

When the cells 10 and 20 constructed by the base stations BS1 and BS2 use different time synchronization, D2D communication can be complicated. Therefore, the network performs a procedure for maintaining synchronization between the cells 10, 20 so that time synchronization between the cells 10, 20 can be maintained.

The base station BS1 or BS2 or the UEs UE3 and UE4 can measure or calculate the synchronous time difference of the inter-cell 10 and 20 when the time synchronization between the cells 10 and 20 is not maintained. The UEs UE3 and UE4 can perform D2D communication using the calculated synchronization time difference information.

Specifically, the terminal UE3 located in the cell 10 of the base station BS1 and receiving the downlink synchronization signal broadcast by the base station BS1 performs D2D communication according to the central control of the base station BS1.

When the terminal group information set in the terminal UE3 is not included in the control information of the base station BS1 (e.g., system information or control information instructed by the base station BS1) The terminal UE 3 may transmit the terminal group information stored in the terminal UE3 to request the D2D communication.

The base station BS1 requests another upper node using a network procedure to collect terminal group information and time synchronization information managed by the neighboring cell 20. [ Based on the collected information, the base station BS1 determines whether or not the terminal UE3 supports D2D communication, and can transmit the determined D2D control information to the terminal through a broadcast channel or a data channel. The D2D control information may include an offset between the time synchronization information of the neighboring cell 20 and the time synchronization information currently used in the cell 10. [ The D2D control information may further include D2D control information of the neighboring cell 20. [

The terminal UE3 receives the uplink channel based on the D2D control information received from the base station BS1, and performs D2D communication. Specifically, the terminal UE3 changes its synchronization time according to a synchronization time difference value (offset) between the cells 10 and 20, receives an indicator channel, a control channel, and a data channel, 20 can communicate with the terminal UE4 in the D2D.

2. In the cell D2D  Communication

In the D2D communication, a broadcast or multicast type physical layer structure is used in which the transmitting terminal transmits data and all the surrounding terminals directly receive data. In such a physical layer structure, in order to support a function that only some terminals participate in D2D communication, a method of dividing terminals into groups and performing D2D communication between terminals included in the corresponding group is suitable. For this purpose, the uplink band is divided into group resources (e.g., the uplink band is divided into frequency axes and a certain bandwidth is allocated to the terminal group), and group resources are used for D2D communication.

In the cells 10 and 20, the group resources are allocated to the UEs at the time of creation of the UE group, and the BSs BS1 and BS2 can transmit the group resources to the UEs using an RRC (Radio Resource Control) message. A terminal belonging to a group receives a group resource, and a terminal belonging to a plurality of groups can receive a plurality of group resources.

On the other hand, the terminal transmission resource is a resource allocated by the base stations BS1 and BS2 when the terminal requests transmission. The base stations BS1 and BS2 may allocate some of the group resources as terminal transmission resources. The BSs BS1 and BS2 may allocate resources to the MS by transmitting a control message through a downlink channel, periodically allocate resources, or continuously allocate a plurality of subframes. On the other hand, when there is no problem in the power consumption of the terminal, the terminal can always receive all the control channels and data channels of the band. A group identifier for identifying a terminal group may be allocated by the base stations BS1 and BS2 to transmit and receive messages, and the terminal may use a group identifier for data / demodulation of a data channel or a control channel. The base station may have the function of a central control unit. In this case, the control signal and the control channel can be transmitted / received using the uplink bandwidth.

FIG. 3 is a flowchart showing a process of transmitting data by a terminal UE1 located in the cell 10. FIG.

The terminal UE1 receives the synchronization channel and the system information channel transmitted by the base station BS1 (S110). Specifically, the terminal UE1 receives the D2D communication information through the synchronization channel and the system information channel. For example, the terminal UE1 may receive location information of a resource for D2D communication, resource information related to a terminal group, and the like.

The terminal UE1 requests the base station BS1 for D2D communication (S120). Specifically, when the state of the terminal UE1 is in a connected state in which the terminal UE1 is connected to the base station BS1, the method used in the cellular communication can be extended. For example, the UE1 may transmit a message requesting resource allocation for D2D communication (e.g., a Scheduling Request message or a BSR (Buffer Status Report) message) to the BS1 . The UE1 can use the SR (Scheduling Request) message used in the cellular communication as it is and transmit the D2D communication related information to the BS1 via the data channel. The terminal UE1 can transmit D2D communication related information to the base station BS1 using a data channel used in cellular communication. That is, the terminal UE1 may display the D2D communication related information on a data channel (for example, a Physical Uplink Shared Channel (PUSCH)) used for cellular communication with the base station BS1 and transmit the information to the base station BS1.

When the UE1 is in an idle state in which the UE1 is not connected to the BS1, the UE1 transmits the D2D communication to the BS1 (S120). Specifically, the terminal UE1 randomly connects to the base station BS1 via a random access channel (RACH) using a random access procedure used in cellular communication, requests D2D communication to the base station BS1, And transmits the information to the base station BS1. On the other hand, the random access procedure can be used even when the state of the terminal UE1 is the connected state. Of the radio resources used as the RACH, a certain resource can be used separately for the random access procedure for the D2D communication request. That is, the base station BS1 may allocate radio resources of a predetermined size for the D2D communication request, or may designate some of the random access codes for the D2D communication request. The base station BS1 can recognize that the information received through the resource designated for the D2D communication request is information for D2D communication. On the other hand, the terminal UE1 can transmit additional D2D communication related information to the base station BS1 after the random access procedure. For example, the terminal UE1 can transmit D2D communication related information to the base station BS1 using the uplink data channel. Here, the D2D communication related information may include at least one of the information in Table 2 below.

Information Remarks Terminal group information - D2D communication group identifier to be used by the sending terminal
- Resource information to be used by the sending terminal
- Authorization information of the transmitting terminal (information indicating whether the transmitting terminal is authorized to use D2D communication) Terminal information - the identifier of the sending terminal
- location information of the sending terminal
- transmission power information of the transmitting terminal
- mobility information of the sending terminal
- Power state of sending terminal Service characteristics - Priority
- Data rate
- Service type etc. Cycle - One-time transmission or periodic transmission Buffer information - Size of data to send

The base station BS1 receiving the D2D communication request transmits the D2D control information to the UE1 and the UE1 receives the D2D control information in step S130. Specifically, the base station BS1 may transmit the D2D control information using the downlink control channel or the response channel according to the type of the received D2D communication request. For example, the base station BS1 can display simple D2D control information on a downlink control channel (e.g., Physical Downlink Control Channel (PDCCH)) and transmit it. Alternatively, the base station BS1 may transmit D2D control information using a response channel (e.g., RAR (Random Access Response) or PDSCH (Physical Downlink Shared Channel)). The base station BS1 provides an identification method so that the terminal UE1 can receive a message including the D2D control information. For example, when the state of the terminal UE1 is in a connected state, the base station BS1 displays an identifier (e.g., C-RNTI (Cell-Radio Network Temporary Identifier) can do. When the terminal UE1 is in the idle state, the base station BS1 may transmit and display a plurality of D2D control information and a group identifier on one data channel (e.g., PDSCH). Here, the D2D control information includes at least one of terminal group identification information, terminal identification information, location information of a resource, size information of a resource, number information of a resource, transmission power information of a resource, a repetition period of allocated resources, And may include at least one.

The terminal UE1 receives the D2D control information transmitted by the base station BS1 and broadcasts an identification channel, a control channel, and a data channel for D2D communication using the allocated information (S140). Specifically, the terminal UE1 uses the terminal group identification information or the terminal identification information included in the D2D control information to determine whether the D2D control information is information for the terminal UE1. The UE1 can generate a control channel and a data channel and broadcast the allocated resources. The terminal UE1 can display brief information necessary for the receiving terminal to demodulate the data channel in the identification channel. If the receiving terminal can demodulate the signal only by the information included in the identification channel, the terminal UE1 can omit the broadcasting of the control channel. Specifically, the identification channel may include position information of a control channel or a data channel, and the receiving terminal may know the position of a control channel or a data channel through position information included in the identification channel after receiving the identification channel.

On the other hand, the terminal UE1 broadcasts the presence or absence of data transmission on the identification channel, and the receiving terminal UE2 and the base station BS1 receive the identification channel broadcast by the terminal UE1, can do. The base station BS1 may determine a resource for which transmission is not indicated through the received identification channel, determine a resource for which transmission is not indicated as an unused resource, and assign a resource determined as an unused resource to another terminal.

On the other hand, a procedure of receiving data by the terminal UE2 located in the cell 10 is as follows. Specifically, the terminal UE2 acquires the synchronization signal of the base station BS1 and receives the D2D control information through the system information of the base station BS1. The terminal UE2 receiving the D2D control information receives the identification channel transmitted by the terminal UE1. The terminal UE2 receives and demodulates the control channel and the data channel of the indicated resource when it is indicated that the D2D communication data is being broadcast to the received identification channel. The terminal UE2 omits the demodulation operation for the control channel and the data channel corresponding to the position information included in the identification channel when none of the broadcast D2D communication data is displayed on the received identification channel.

On the other hand, when a brief collision management procedure for D2D communication is used, data resources may be redundantly allocated to a plurality of terminals. Procedures for supplementing this are described.

The transmitting terminal UE1 requests the base station BS1 to transmit the D2D communication data using the random access channel (RACH). A collision may occur when a plurality of terminals UE1 and UE3 request data transmission at the same time or using the same identifier or the like.

The base station BS1 replies using the response channel that it has received the data transmission request. For example, when a small amount of data transmission is requested, the base station BS1 indicates and delivers the D2D communication resources allocated to the response channel, and the plurality of terminals UE1 and UE3 use D2D And performs communication. In this case, a collision may occur between the terminals UE1 and UE3, but a conflict resolution procedure is not used to reduce the complexity.

The transmitting terminal UE1 transmits specific information for the D2D communication request to the base station BS1. When a plurality of terminals UE1 and UE3 successfully receive the response channel transmitted by the base station BS1, a plurality of terminals UE1 and UE3 transmit a message including specific information for a D2D communication request to the base station BS1 ), A collision may occur. The base station BS1 can release resources allocated to the UEs UE1 and UE3 when a plurality of messages collide and demodulation is impossible. When only the message of the terminal UE1 is received and the base station BS1 can demodulate the message, the response message is transmitted to the terminal UE1.

The base station BS1 allocates a D2D communication resource and transmits it to the UE1. Specifically, the base station BS1 can transmit the D2D communication resource information by including it in the D2D control information.

When the terminal identification information (terminal identification information included in the received D2D control information) indicated in the resource indicates the terminal UE1, the terminal UE1 performs D2D communication using the received D2D communication resource. When the UE identification information included in the received D2D control information does not indicate the UE3, the UE3 determines that resource allocation has failed. The UE (UE3) that has failed in resource allocation resumes the resource allocation procedure.

Meanwhile, the terminal UE1 may perform D2D communication through the D2D communication procedure outside the cell, which will be described later, in the cell 10. In this case, the base station BS1 can perform the function of the central control device.

3. Outside the cell D2D  Communication

The D2D communication at the out of coverage of the cells 10 and 20 which can not be controlled by the base stations BS1 and BS2 is controlled by the central control unit.

Required functions for D2D communication can be performed only when time synchronization is maintained between terminals, and the central control device provides a synchronization signal for D2D communication. Also, the central control device broadcasts the synchronization signal and the synchronization channel, and the peripheral terminal that receives the broadcast signals uses time synchronization. The central control unit performs radio resource management and allocation functions necessary for D2D communication, and peripheral terminals transmit / receive data under the control of the central control unit.

4 is a diagram showing the types of channels used for D2D communication.

As shown in FIG. 4A, the synchronization signal / channel SYNC_SIG / CH, the request channel REQ_CH, the response channel RSP_CH, the identification channel IND_CH, the control channel CTR_CH, Used for D2D communication. 4B, there is a synchronization time SYNC_TIME between the synchronization signal / channel SYNC_SIG / CH and the request channel REQ_CH, a 3 ms time between the request channel REQ_CH and the response channel RSP_CH There is a 3 ms time interval between the response channel RSP_CH and the identification channel IND_CH and there is a time interval between the identification channel IND_CH and the control channel CTR_CH. FIG. 4C shows an identification channel IND_CH. Each of the signals and the channels (SYNC_SIG, REQ_CH, RSP_CH, IND_CH, CTR_CH, and DATA_CH) may be mapped to different forms from those of FIGS. 4A, 4B, and 4C when mapped to physical resources, The time interval between the channels may also be variable.

The frame structure used in the central control scheme is shown in Table 3 below.

Signal or channel Remarks Sync signal / channel (SYNC_SIG / CH)
1) Synchronization signal transmitted in the uplink band
2) Sync signal: Only signals such as PSS / SSS broadcast, cell identifier etc.
3) Synchronization channel: Specific environmental information related to D2D communication
3-1) Fixed position: Similar to SIB (System Information Block) 1 of cellular communication system
3-2) broadcast # 0 Broadcast specific control information by data channel
3-3) A method for distinguishing characteristics of a synchronous channel, a method for distinguishing among plural synchronous channels The data channel (DATA_CH) 1) channel for broadcasting data
2) Using CRC (Cyclical Redundancy Check)
3) Transmitting using terminal identifier or group identifier The control channel (CTR_CH) 1) channel for broadcasting data modulation / demodulation information
2)
3) Use PDCCH format (many can be omitted) The identification channel (IND_CH) 1) Indication of data channel (DATA_CH) usage information
1-1) Includes information indicating whether the transmitting terminal transmits data using the allocated data channel or resource
1-2) Includes resource location information of control channel or data channel
2) Used by the receiving terminal to monitor and demodulate
3) Display only brief demodulation information or mid-term demodulation information
4) Purpose to reduce power consumption of receiving terminal
5)
6) In the case of stopping the transmission of the data channel, the transmitting terminal releases the transmission of the identification channel corresponding to the data channel to be interrupted
7) The central control unit continues to receive the identification channel and identify the released channel The request channel (REQ_CH) 1) a channel for requesting resource allocation by the transmitting terminal
2) For 1: 1 communication: Transmitting terminal transmits to central control device
3) Conflict based
4) Distinction by multiple TDMs
5) Additional information needed: BSR, type information (eg, one shot, periodic, QoS (Quality of Service), etc.) The response channel (RSP_CH) 1) The central control unit displays the modulation / demodulation information
2) For 1: 1 communication: When the central control unit responds to the sending terminal
3) The central control unit maps 1: 1 with the transmission: request channel (REQ_CH), or in the PDCCH format
4) Response channel (RSP_CH) of the request channel (REQ_CH): Positioned at a position separated from the request channel (REQ_CH) by a predetermined time (for example, 4 ms)
5) Display of resource information of data channel (DATA_CH)
5-1) Location, length and cycle of resources

FIG. 5 is a flowchart showing a process of transmitting data by a UE 6 located outside the cells 10 and 20. FIG.

The terminal UE6 acquires a synchronization signal (S200). Specifically, the terminal UE6 can receive the synchronization signal broadcasted on the uplink by the terminal UE9 operating as the central control device. Alternatively, the terminal UE6 can receive a synchronization signal broadcasted by a simple synchronization device.

The terminal UE6 receives the synchronization information and the terminal coverage communication information and sets a communication environment (S201). Specifically, the terminal UE6 can receive information similar to the SIB of the base stations BS1 and BS2. The terminal UE6 can receive the location, period, and fixed value information of the D2D communication resources. The terminal UE6 can receive information on the frame format.

The terminal UE6 determines whether or not the D2D communication is performed (S210). Specifically, when data is input to the D2D transmission buffer, the terminal UE6 can determine the start of D2D communication using the amount of data and the type of data (QoS). For example, when data is input to the vacant D2D transmission buffer, the terminal UE6 can immediately start the D2D communication. In another example, when additional data is input to the D2D transmission buffer in which the data existed, the UE 6 can restart the D2D communication if the additional data is high QoS information.

In order to request the D2D communication, the terminal UE6 transmits a request channel (RSQ_CH) to the UE (9) serving as a central control device (S220). Specifically, the UE 6 can request resources for D2D communication from the UE 9 using a 1: 1 communication scheme (e.g., Physical Uplink Control Channel (PUCCH)). The UE 6 can transmit a BSR message to the UE 9 via a request channel (RSQ_CH) in order to request resource allocation.

If the resource requested by the terminal UE6 conflicts with the resources requested by the other terminals UE7 and UE8 in operation S230, the terminal UE9 determines that it is not possible to allocate resources requested by the terminal UE6 S241). In the case where the request resource conflicts, the UE 9 can not interpret the resource request, and thus does not allocate the D2D communication resource to the UE6. That is, if the requested resource conflicts (S230), the UE 6 is not allocated the requested resource.

If the request resource conflicts (S230), the UE6 reselects the requested resource and transmits a request channel (RSQ_CH) again to the UE (UE9) to request D2D communication (S242, S243). Specifically, the UE 6 can distribute resources using a hashing method in order to avoid collision. For example, the UE 6 can arbitrarily select at least one of N (N is a natural number) resources for D2D communication and request the UE 9 to allocate the selected resource. On the other hand, if a resource collision occurs more than a predetermined number of times, the UE 6 receives the communication information again and then transmits a request channel (RSQ_CH). Specifically, the UE 9 expands the requested channel resource amount (e.g., N + 10) when the resource utilization rate increases by a certain rate or more. The UE 6 can arbitrarily select at least one of N + 10 resources and request the UE 9 to allocate the selected resource.

If the requested resources do not collide with each other (S230), the UE 9 allocates the D2D communication resource to the UE 6 through the response channel RSP_CH (S250). More specifically, the UE 9 can allocate periodic resources to the UE 6 when periodic allocation is required. The UE 9 can transmit a response channel (RSP_CH) in the PDCCH format. The location of the acknowledgment channel RSP_CH may be 1: 1 mapped to the location of the request channel RSQ_CH. On the other hand, when the same resources are allocated as duplicates, the error continues. To avoid this, the terminal UE9 needs a function of managing resource allocation redundancy, and can listen to signals of other terminals during a talk-spurt time of a voice.

In order to support the receiving terminal, the terminal UE6 displays allocation information on the identification channel IND_CH (S260). Specifically, the terminal UE6 broadcasts an identification channel (IND_CH) including information on the presence / absence of data transmission. Not only the terminal UE6 but also other transmitting terminals transmit an IND_CH to notify its own data transmission. A terminal (UE9) operating as a receiving terminal and a central control device can receive an identification channel (IND_CH) and confirm the currently used data resource.

The terminal UE6 periodically uses the allocated resources to transmit data (S270, S280). Specifically, the UE 6 broadcasts the demodulated / demodulated information on the control channel CTR_CH and broadcasts the data on the data channel DATA_CH.

Meanwhile, a process of receiving data by the UE 7 located outside the cells 10 and 20 is as follows. Specifically, the terminal UE7 acquires a synchronization signal broadcasted on the uplink by the terminal UE9 operating as a central control device. The terminal UE7 receives the identification channel (IND_CH) broadcasted by the transmitting terminal UE6 and confirms the area transmitted by the transmitting terminal UE6. The terminal UE7 receives the control channel (CTR_CH) broadcasted by the transmitting terminal UE6 and recognizes the demodulation information. The terminal UE7 receives a data channel (DATA_CH) broadcast by the transmitting terminal UE6.

The procedure for releasing the D2D communication is as follows. Specifically, the terminal UE9 operating as the central control device continuously monitors the identification channel IND_CH to grasp the state of the currently used channel. The terminal UE9 determines a channel whose usage has been canceled for a predetermined time or longer through an identification channel IND_CH and allocates the channel whose use is canceled for a predetermined time or longer to another terminal. For example, when the terminal UE9 determines that the terminal UE6 does not use the allocated data channel (DATA_CH) for a certain period of time, it assigns the data channel (DATA_CH) allocated to the terminal UE6 to another terminal .

4. At the cell boundary D2D  Communication

The D2D communication mode at the boundary between the cells 10 and 20 will be described in detail.

The D2D communication should be maintained when the terminal UE3 performing the D2D communication in the cell 10 moves out of the cell 10. [ To this end, when the terminal UE3 is out of the cell 10, it must be able to receive data using only previously acquired information. On the other hand, when the terminal UE3 performing D2D communication outside the cell 10 moves into the cell 10, the D2D communication should be maintained and should be maintained without collision with the D2D communication controlled by the base station BS1 .

The procedure for determining whether the UE 3 has moved out of the cell 10 in the cell 10 is as follows.

Specifically, when the terminal UE3 is idle, the base station BS1 periodically transmits a synchronization signal (e.g., PSS / SSS, a CRS (Cell Specific Reference Signal), and a PBCH (Physical Broadcast Channel) . When the strength of the base station synchronization signal received by the terminal UE3 is lower than a predetermined reference value, the terminal UE3 determines that the terminal UE3 is out of the cell 10 range. The UE UE 3 which has determined that the UE 3 is out of the cell 10 can perform the cell selection / reselection procedure according to the LTE procedure and if the cell selection / The final decision is made by out-of-coverage.

When a state of the terminal UE3 is in a connected state, the terminal UE3 transmits a radio link failure (RLF: Radio Link Failure) between the terminal UE3 and the base station BS1, ) Of the above-mentioned range. Specifically, if the RLF occurs during data transmission / reception or the strength of the received signal is lower than the reference range, the UE 3 performs the RLF recovery procedure according to the LTE procedure. If the RLF recovery procedure fails, the UE UE 3 makes a final decision with out-of-coverage.

6 is a flowchart illustrating a process of transmitting / receiving data when the UE 3 performing D2D communication in the cell 10 moves out of the cell 10. FIG. In FIG. 6, for convenience of explanation, a case where the terminal UE3 recognizes that it is located outside the cell 10 will be described as an example.

The terminal UE3 searches for an uplink synchronization signal (S310). The uplink synchronization signal can be broadcast by the central control unit. The central control device may be a terminal.

The terminal UE3 calculates a time difference between the time of the downlink synchronization signal (the synchronization signal broadcast by the base station BS1) and the uplink synchronization signal obtained in the step S310 (S320). When the UE 3 acquires the uplink synchronization signal, the terminal UE3 receives the uplink synchronization channel. The uplink synchronization channel may be broadcast by the central control unit.

The terminal UE3 displays the time difference calculated in step S320 on the request channel (RSQ_CH) and transmits it to the central control apparatus (S330). Having received the request channel (RSQ_CH), the central control unit determines whether to change its synchronization time and responds to the terminal UE3.

When the terminal UE3 desires to receive data, it receives the identification channel IND_CH broadcast by the transmitting terminal using the uplink synchronization signal, and transmits the control channel CTR_CH corresponding to the information contained in the identification channel IND_CH ) And a data channel (DATA_CH) (S340).

On the other hand, when the terminal UE3 desires to transmit data, Data is transmitted using the above-described procedure in the D2D communication outside the cell (S340).

7 is a flowchart illustrating a process of transmitting / receiving data when a terminal UE3 that has performed D2D communication outside the cell 10 moves into the cell 10. FIG. In FIG. 7, for convenience of explanation, a case where the terminal UE3 recognizes that it is located in the cell 10 will be described as an example.

The terminal UE3 searches for a downlink synchronization signal broadcasted by the base station BS1 (S410).

The terminal UE3 calculates the time difference between the time of the uplink synchronization signal (synchronization signal broadcast by the central control apparatus) and the downlink synchronization signal obtained in the step S410 (S420).

The terminal UE3 displays the time difference calculated in step S420 on the request channel (REQ_CH) and transmits it to the central controller (S430). The central control device may be a terminal. Upon receiving the request channel (REQ_CH), the central control unit determines whether to change its synchronization time and responds to the terminal UE3.

When the terminal UE3 desires to receive data, it receives the identification channel IND_CH broadcast by the transmitting terminal using the downlink synchronization signal, and transmits the control channel CTR_CH corresponding to the information contained in the identification channel IND_CH ) And a data channel (DATA_CH) (S440).

On the other hand, when the terminal UE3 desires to transmit data, Data is transmitted using the above-described procedure in the D2D communication in the cell (S440).

8 is a diagram showing a configuration of the terminal 100. As shown in Fig. The terminals UE1 to UE9 may be configured similar to the terminal 100 of FIG.

The terminal 100 includes a processor 110, a memory 120, and a radio frequency (RF) converter 130.

The processor 110 may be configured to implement the procedures, functions and methods associated with the terminals UEl through UE9 described above. In addition, the processor 110 may be configured to implement the procedures, functions, and methods associated with the terminal UE9 operating as the central control device described above.

The memory 120 is coupled to the processor 110 and stores various information related to the operation of the processor 110. [

The RF converter 130 is connected to the processor 110 and transmits / receives a radio signal. The terminal 100 may have a single antenna or multiple antennas.

Meanwhile, although the case where the central control device is mainly a terminal has been described by way of example, this is merely an example. The central control device may be a device or a base station rather than a terminal.

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, It belongs to the scope of right.

Claims (20)

A D2D (Device to Device) communication method in which a first terminal in a first cell of the first base station communicates directly with a second terminal without relaying a first base station,
Receiving a synchronization signal and a synchronization channel broadcasted on the downlink by the first base station;
Acquiring synchronization for D2D communication using the synchronization signal and the synchronization channel;
To request allocation of a first resource for D2D communication when the first terminal is connected to the first base station, transmitting first information for D2D communication to the first base station via a first data channel for cellular communication, ;
Receiving, from the first base station, D2D control information including information on the first resource allocated to the first terminal; And
Broadcasting the second data channel for D2D communication using the D2D control information
≪ / RTI > The method according to claim 1,
Wherein the first information comprises:
At least one of a first identifier of the first terminal and a second identifier of a first group to which the first terminal belongs;
Information about the first resource that the first terminal desires to use; And
Wherein the first terminal includes information on a size of data to be transmitted
D2D communication method. 3. The method of claim 2,
Wherein the transmitting the first information comprises:
And transmitting a BSR (Buffer Status Report) message including the first information to the first base station
D2D communication method. The method of claim 3,
The D2D control information includes:
At least one of the first identifier and the second identifier;
At least one of a position of the first resource, a size of the first resource, and a number of the first resources; And
A repetition period of the first resource and a repetition number of the first resource
D2D communication method. 5. The method of claim 4,
Wherein the step of receiving the D2D control information comprises:
And receiving the D2D control information from the first base station via at least one of a first control channel and a first response channel for the downlink
D2D communication method. 6. The method of claim 5,
After the first terminal is randomly connected to the first base station via a random access channel in a state where the first terminal is in an idle state, Lt; RTI ID = 0.0 > 1 < / RTI >
D2D communication method. The method according to claim 6,
Wherein the step of receiving the D2D control information comprises:
Determining whether the D2D control information is information for the first terminal using the first identifier included in the D2D control information when the first terminal is connected to the first base station; And
Further comprising determining whether the D2D control information is information for the first terminal using the second identifier included in the D2D control information when the first terminal is in an idle state
D2D communication method. 6. The method of claim 5,
Broadcasting the second data channel comprises:
Broadcasting a first identification channel including information on whether the first terminal transmits the first data using the second data channel;
Broadcasting a second control channel for demodulating the first data; And
And broadcasting the second data channel to broadcast the first data.
D2D communication method. The method according to claim 1,
Wherein the step of receiving the D2D control information comprises:
Further comprising second information on a difference between a synchronization time used by the first base station and a synchronization time used by the second base station when the second terminal is located in a second cell of the second base station, Receiving control information from the first base station; And
And changing the synchronization time using the second information
D2D communication method. As a method for a first terminal to control D2D (Device to Device) communication between terminals,
Broadcasting the first synchronization signal and the first synchronization channel on the uplink when the first terminal operates as a central control device for managing synchronization and resources for D2D communication;
Receiving a first message from a second terminal requesting allocation of a first resource for D2D communication; And
And allocating the first resource to the second terminal,
Wherein the first synchronization channel includes information on a first identifier of the first terminal and a type of the first synchronization signal
D2D communication control method. 11. The method of claim 10,
Wherein the first synchronization channel comprises:
Information indicating that the first synchronization channel is a channel for synchronization of D2D communication, information indicating the first synchronization signal, information on accuracy of the first synchronization signal, information indicating that the first terminal is a moving device, And the number of terminals using the first synchronous signal, at least one of the moving speed of the first terminal, the changing information of the synchronous time for the first synchronous signal, the position information of the first terminal, One more
D2D communication control method. 12. The method of claim 11,
Wherein the broadcasting of the first synchronization signal and the first synchronization channel comprises:
Receiving a broadcast instruction for the first sync signal from the base station if the second terminal fails to receive a second sync signal broadcasted on the downlink by the base station; And
And operating as the central control unit in response to the broadcast instruction
D2D communication control method. 12. The method of claim 11,
Wherein the broadcasting of the first synchronization signal and the first synchronization channel comprises:
Broadcasting the first synchronous signal based on the second synchronous signal when receiving a second synchronous signal broadcasted on the downlink by the base station;
Broadcasting the first synchronization signal based on the GPS signal when receiving a Global Positioning System (GPS) signal without receiving the second synchronization signal;
Broadcasting the first synchronous signal based on the third synchronous signal when receiving a third synchronous signal which is not received by the second synchronous signal and the GPS signal but is broadcast by another central control apparatus; And
Broadcasting the first synchronizing signal based on an arbitrarily determined time when the second synchronizing signal, the GPS signal, and the third synchronizing signal are not received
D2D communication control method. 12. The method of claim 11,
Transmitting information on the second sync signal and the second sync channel to a base station when receiving a second sync signal and a second sync channel broadcasted by another central control unit; And
Stopping broadcasting of the first synchronization signal when receiving a broadcast stop instruction from the base station
The D2D communication control method further comprising: 12. The method of claim 11,
Wherein the step of broadcasting the first synchronization signal and the first synchronization channel comprises:
Receiving from the second terminal a second message indicating that the second terminal having received the first synchronization signal and the first synchronization channel has connected to the first terminal; And
And counting the number of terminals using the first synchronization signal based on the second message
D2D communication control method. 12. The method of claim 11,
Changing a synchronization time for the first synchronization signal based on the second synchronization signal when receiving a second synchronization signal broadcasted on a downlink by a base station; And
Reporting to the base station information about the first terminal operating as the central control device so that the base station can determine whether the first terminal continues to operate as the central control device
The D2D communication control method further comprising: A D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without relaying a first base station,
Receiving a first synchronization signal and a first synchronization channel from a third terminal operating as a central control device for managing synchronization and resources for D2D communication when the first terminal is located outside a first cell of the first base station ;
Transmitting a BSR message to the third terminal through a request channel for requesting resource allocation when the first synchronization signal and the first synchronization channel are received;
Receiving information on a first resource allocated to the first terminal from the third terminal through a response channel; And
And broadcasting a first identification channel including information on whether the first terminal transmits the first data using the first resource
D2D communication method. 18. The method of claim 17,
The first base station may receive a second synchronization signal broadcast on the downlink at a first threshold value or a first base station and a first base station, , Determining that the first terminal is located outside the first cell
Further comprising: 19. The method of claim 18,
Wherein the receiving the first synchronization signal and the first synchronization channel comprises:
And calculating a difference between a synchronization time for the first synchronization signal and a synchronization time for the second synchronization signal,
Wherein the transmitting the BSR message to the third terminal comprises:
And transmitting the request channel including information on the synchronization time difference to the third terminal
D2D communication method. 19. The method of claim 18,
Determining that the first terminal is located in the first cell when the reception strength of the second synchronization signal is greater than the first threshold;
Calculating a difference between a synchronization time for the first synchronization signal and a synchronization time for the second synchronization signal when the first terminal is located in the first cell and transmitting the difference to the third terminal; And
Changing synchronization time using the second synchronization signal
Further comprising:

Images