KR20140090103A - Method for discovery of communication between devices and apparatus therefor - Google Patents

Abstract

Disclosed are a discovery method and apparatus for device-to-device (D2D) communications between terminals. A D2D discovery method comprises the steps of: receiving, from a discoverable terminal, a D2D discovery participation message; requesting a gateway connected to a D2D server to measure proximity between a discovery terminal and the discoverable terminal; receiving a proximity measurement result from the gateway; and requesting the discovery terminal and discoverable terminal to start a D2D discovery procedure when the proximity measurement result satisfies a preset criterion, thereby effectively performing a discovery procedure.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for direct communication between terminals,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a direct communication technology, and more particularly, to a method and an apparatus for effectively disassembling a terminal performing direct communication between terminals.

In a cellular communication environment, a general method by which terminals transmit and receive data is through a base station. That is, when there is data to be transmitted to the second terminal, the first terminal transmits the data to the first base station to which the first terminal belongs. The first base station transmits the data received from the first terminal to the second base station to which the second terminal belongs through the core network. Finally, the second base station transmits the data received from the first base station to the second terminal. Here, the first base station and the second base station may be the same base station or different base stations.

Meanwhile, device-to-device (D2D) communication means that terminals communicate directly without going through a base station. That is, the first terminal can directly communicate with the second terminal without going through the base station to transmit / receive data.

In order to perform D2D communication, a discovery terminal must first discover a nearby discoverable terminal through a discovery procedure. The search terminal can quickly find the search terminal when the search terminal exists in a nearby location, but it has to perform the discovery procedure for a long time when the search terminal is located far away. Therefore, there is a problem that the power consumption of the search terminal increases in this case.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for performing a discovery procedure based on proximity between terminals.

Another object of the present invention is to provide an apparatus for performing a discovery procedure based on proximity between terminals.

According to an aspect of the present invention, there is provided a D2D discovery method comprising: receiving a D2D discovery participation message from a paired search terminal; requesting a gateway connected to a D2D server to measure proximity between the search terminal and the paired search terminal Receiving a proximity measurement result from the gateway and requesting the search terminal and the sought terminal to initiate a D2D discovery procedure when the proximity measurement result meets a predetermined criterion.

Here, the discovery method may further include allocating a physical channel for D2D discovery to the search terminal and the sought-search terminal after requesting the start of the D2D discovery procedure.

Here, the D2D discovery participation message may indicate that the piconeting terminal participates in the D2D discovery procedure requested by the search terminal.

Here, the gateway may be a packet data network gateway.

Here, the proximity may be measured based on the strength of a reference signal transmitted / received between the search terminal and the searched terminal.

Here, the proximity may be measured based on the location information of the search terminal and the location information of the search terminal.

Here, the preset reference may be a minimum distance that allows D2D communication between the search terminal and the search terminal.

According to another aspect of the present invention, there is provided a D2D discovery method comprising: receiving a D2D communication start request message from a search terminal and a sought-search terminal; receiving a D2D communication setup request message To the gateway connected to the D2D server, and when the proximity between the search terminal and the sought-search terminal satisfies a predetermined criterion, indicating that the D2D communication setup between the search terminal and the slave terminal is completed And receiving a D2D communication setup response message.

Here, the D2D communication start request message may be received from the search terminal that recognized the existence of the sought-after terminal and the sought terminal that recognized the existence of the search terminal.

Here, the gateway may be a packet data network gateway.

Here, the D2D communication setup request message may include a network identifier of the search terminal and a network identifier of the search terminal.

Here, the proximity may be measured based on the strength of a reference signal transmitted / received between the search terminal and the searched terminal.

Here, the proximity may be measured based on the location information of the search terminal and the location information of the search terminal.

Here, the preset reference may be a minimum distance that allows D2D communication between the search terminal and the search terminal.

According to another aspect of the present invention, there is provided a proximity measuring method comprising: allocating a radio resource for transmitting a proximity measurement reference signal to a first terminal; The method comprising the steps of: allocating a radio resource for reception of the proximity measurement reference signal; acquiring reception result information on the proximity measurement reference signal from the second terminal; And determining whether to start the direct communication between the terminals.

Here, the BS may allocate radio resources for proximity measurement to the first MS and the second MS based on a request from the D2D server.

Here, the reception result information may be a reception intensity of the proximity measurement reference signal.

Here, if the reception strength is equal to or greater than a preset reference value, it can be determined to start D2D communication between the first terminal and the second terminal.

Here, if the reception strength is less than a preset reference value, it can be determined to cancel D2D communication between the first terminal and the second terminal.

Here, the predetermined criterion may be a minimum reception strength at which D2D communication is possible between the first terminal and the second terminal.

According to the present invention, since the discovery procedure is performed when the search terminal and the sought-search terminal exist at a position where D2D communication is possible, the discovery procedure can be effectively performed.

1 is a conceptual diagram illustrating a network structure for D2D communication.
2 is a conceptual diagram illustrating a terminal structure for D2D communication.
3 is a flowchart illustrating a first procedure of a limited discovery procedure according to an embodiment of the present invention.
4 is a flowchart illustrating a second procedure of the limited discovery procedure according to an embodiment of the present invention.
5 is a flowchart illustrating a third procedure of the limited discovery procedure according to an embodiment of the present invention.
FIG. 6 is a flowchart illustrating a fourth procedure of the limited discovery procedure according to an embodiment of the present invention.
7 is a flowchart illustrating a resource release procedure in limited discovery in accordance with an embodiment of the present invention.
FIG. 8 is a flowchart illustrating a D2D connection establishment procedure in limited discovery according to an embodiment of the present invention.
9 is a flowchart illustrating a proximity measurement and reporting procedure according to an embodiment of the present invention.
10 is a flowchart illustrating a first process of a D2D communication setup procedure according to an embodiment of the present invention.
11 is a flowchart illustrating a second process of the D2D communication setting procedure according to an embodiment of the present invention.
12 is a flowchart illustrating a D2D communication release procedure by a user according to an embodiment of the present invention.
13 is a flowchart illustrating a D2D communication release procedure by a base station according to an embodiment of the present invention.
14 is a flowchart illustrating a D2D bearer release procedure according to an embodiment of the present invention.
15 is a flowchart illustrating a first procedure of an open discovery procedure according to an embodiment of the present invention.
FIG. 16 is a flowchart showing a second procedure of the open discovery procedure according to an embodiment of the present invention.
17 is a flowchart showing a third process of the open discovery procedure according to an embodiment of the present invention.
18 is a flowchart illustrating a D2D connection establishment procedure in an open discovery according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

BACKGROUND ART [0002] As communication devices supporting various new services such as a smart phone, a tablet PC and the like are rapidly spreading, traffic in a communication network is rapidly increasing. In addition, if the Internet of things (IoT), which uses objects such as communication between people and objects, and communication between objects and objects, is activated, the traffic transmitted to the base station will increase to such an extent that it can not be handled by the current base station It is expected.

Accordingly, device-to-device (D2D) communication is considered as a way to improve the performance of the existing mobile communication network at a low cost. In the case of D2D communication technology using a cellular communication scheme, a mobile station can directly transmit and receive data with neighboring mobile stations without relaying the base station. In this case, since it uses the existing cellular communication method, it can support higher security, wide coverage, and fast data transfer rate than the communication methods such as WiFi direct, zigbee, and bluetooth .

In order to efficiently utilize such D2D communication, it is necessary to find a friend terminal in the vicinity, a terminal for transmitting an advertisement to an unspecified number of terminals, and the like. In addition, it is necessary to find a peripheral terminal using the minimum power, and the change of the existing cellular communication network or the terminal should be minimized in order to add a function of detecting the peripheral terminal.

Throughout the specification, the network can be, for example, a wireless Internet such as WiFi (Wireless Fidelity), a WiBro (Wireless Broadband Internet) or a WiMax (World Interoperability for Microwave Access) A 3G mobile communication network such as a Wideband Code Division Multiple Access (WCDMA) or CDMA2000, a High Speed Downlink Packet Access (HSDPA) or a High Speed Uplink Packet Access (HSUPA) A 3.5G mobile communication network, a 4G mobile communication network such as an LTE (Long Term Evolution) network or an LTE-Advanced network, and a 5G mobile communication network.

Throughout the specification, a terminal may be referred to as a mobile station, a mobile terminal, a subscriber station, a portable subscriber station, a user equipment, an access terminal, And may include all or some of the functions of a terminal, a mobile station, a mobile terminal, a subscriber station, a mobile subscriber station, a user equipment, an access terminal, and the like.

Here, a desktop computer, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone, an e- a book reader, a portable multimedia player (PMP), a portable game machine, a navigation device, a digital camera, a digital multimedia broadcasting (DMB) player, a digital audio recorder, A digital picture recorder, a digital picture player, a digital video recorder, a digital video player, or the like can be used.

In the entire specification, a base station includes an access point, a radio access station, a node B, an evolved Node B, a base transceiver station, an MMR Mobile Multihop Relay) -BS, and may include all or some of the functions of a base station, an access point, a radio access station, a Node B, an eNodeB, a base transceiver station, and an MMR-BS.

In the D2D communication, the terminal must transmit discovery information to neighboring terminals in order to inform its existence. Also, the terminal can receive the discovery information and confirm the existence of the peripheral terminal. Thus, an entity for allocating and managing discovery information for discovery of a terminal is needed.

1 is a conceptual diagram illustrating a network structure for D2D communication.

Referring to FIG. 1, the D2D server is connected to a packet data network-gateway (P-GW) through a D2Dxc and a D2Dxu interface. D2Dxc is an interface for control, it can perform functions such as terminal authentication, measurement / assignment / release of physical channel for discovery of terminal, operation / release of procedure for D2D communication according to user's request through P-GW have. D2Dxu is an interface for data transmission. It performs functions such as establishing relation among terminals, allocating / managing discovery information, managing according to user connection / release request by using P-GW, S5, S1-U and LTE-Uu interfaces. can do.

2 is a conceptual diagram illustrating a terminal structure for D2D communication.

Referring to FIG. 2, a terminal structure for D2D communication includes at least one D2D application (D2D App # 01, ..., D2D App #n) and a protocol structure of a terminal for existing cellular communication through an IP layer Follow. On the other hand, in the D2D communication, establishment / release of relation between terminals for discovery, allocation / release of discovery information, and delivery of user input are performed through D2D App middleware (i.e., D2D application → D2D App middleware → D2D Server). In addition, the D2D App middleware can perform transmission / reception and filtering of the discovery information.

In the D2D communication, the terminal's discovery procedure can be classified into open discovery and restricted discovery. Open discovery is a procedure for performing discovery with an unspecified user, and limited discovery is a procedure for performing discovery with a specific user. Here, a specific user means a user (for example, a friend) who has agreed to perform the discovery procedure in advance. Discovery using a social networking application (SNA) is an example of limited discovery.

FIG. 3 is a flowchart illustrating a first procedure of a limited discovery procedure according to an embodiment of the present invention, FIG. 4 is a flowchart illustrating a second procedure of a limited discovery procedure according to an embodiment of the present invention, FIG. 5 is a flowchart illustrating a third procedure of the limited discovery procedure according to an embodiment of the present invention, and FIG. 6 is a flowchart illustrating a fourth procedure of the limited discovery procedure according to an embodiment of the present invention.

3 to 6, the first terminal is connected to the MME (mobility management entity) 1 and the second terminal is connected to the MME 2. Also, the first terminal and the second terminal may be connected to the same MME. The first terminal and the second terminal may be connected to the same base station (eNB) or may be connected to different base stations (eNB).

The first terminal may send a D2D discovery request message to the D2D server for discovery of the second terminal (SlOO). The D2D discovery request message includes an indentifier of the first terminal, an ID of the second terminal, an application ID (e.g., a telephone number of the first terminal, a telephone number of the second terminal, social network service (SNS) information, And the like.

Upon receiving the D2D discovery request message, the D2D server can perform authentication of the application based on the application ID included in the D2D discovery request message (S101).

The D2D server can obtain the network ID (NUE_ID 1) of the first terminal and the network ID (NUE_ID 2) of the second terminal from the PGW (PDN gateway). That is, the D2D server can transmit an ID query message to the PGW (S102). The ID query message may include an ID of a first terminal, an ID of a second terminal, and the like. The PGW can perform a policy control and charging (PCC) check on the first and second terminals according to the ID query of the D2D server (S103, S104). Thereafter, the PGW may transmit the network ID of the first terminal and the network ID of the second terminal to the D2D server (S105). Here, the network ID may mean international mobile subscriber identity (IMSI), IP address information, and the like.

The D2D server may transmit a D2D invite request message to the second terminal for user confirmation of the second terminal (S106). The D2D invitation request message may include an ID of the first terminal, an application ID, and the like. The second terminal receiving the D2D invite request message may send a D2D invite response (result) message to the D2D server in response to the D2D invite request message if it wishes to participate in the limited discovery ( S107). When the D2D server receives the D2D invite response (result) message, it may send a D2D discovery response message to the first terminal in response to the D2D discovery request message (S108). That is, the D2D discovery response message may indicate that the second terminal participates in limited discovery.

After confirming that the first terminal and the second terminal participate in limited discovery, the D2D server may transmit a D2D location monitor request message to the PGW for the first proximity confirmation (S109). The D2D location monitoring request message may include a network ID of the first terminal, a network ID of the second terminal, and the like.

The PGW can monitor the location of the first terminal and the second terminal based on the request of the D2D server (S110), and confirm the proximity between the first terminal and the second terminal based on the monitoring result (S111 ). Here, concrete monitoring methods and proximity confirmation methods will be described later. The PGW may transmit a D2D location monitor response message including proximity confirmation information between the first terminal and the second terminal to the D2D server (S112). The D2D location monitor response message may include a network ID of the first terminal, a network ID of the second terminal, and the like.

The D2D server can determine whether the first terminal and the second terminal are located at a position where they can communicate with each other based on proximity confirmation information. If the first terminal and the second terminal exist in a location where D2D communication is possible, the D2D server may transmit a D2D discovery information allocation message to each terminal (S113, S114). The D2D discovery information assignment message may include discovery information of the first terminal, discovery information of the second terminal, and the like. That is, the D2D server can assign a D2D discovery ID to each terminal by transmitting a D2D discovery information allocation message.

On the other hand, if the first terminal and the second terminal are located in a position where D2D communication is impossible with each other, the D2D server may not proceed the D2D discovery procedure any further. That is, in this case, the D2D server does not transmit the D2D discovery information allocation message to each terminal.

Here, the step S113 is performed before the step S114, but the order of execution is not limited thereto. That is, S114 may be performed before S113, or S114 may be performed simultaneously with S113.

The first terminal and the second terminal recognize that D2D discovery can be performed when receiving the D2D discovery information allocation message from the D2D server.

The resource allocation for D2D discovery is then started. The D2D server transmits a discovery configuration request message including the network ID of the first terminal and the network ID of the second terminal to the PGW, and the PGW receives the discovery configuration request message and the discovery configuration request message including the network ID of the first terminal Request message to the SGW (serving gateway). That is, the discovery setup request message including the network ID of the first UE may be sequentially transmitted to the eNB through the SGW and the MME 1 (S115).

When the eNB receives the discovery setup request message including the network ID of the first MS, the eNB may transmit a radio resource control (RRC) connection reconfiguration message to the first MS in step S116. That is, the base station eNB may request the first UE to measure the PDCH state of the current cell for securing the physical discovery channel (PDCH) resource by transmitting an RRC connection re-establishment message. Here, the PDCH can be used for the discovery procedure of the D2D communication.

The first MS can transmit an RRC connection reconfiguration complete message to the eNB in step S117 and measure the PDCH state of the current cell in step S118 in response to the RRC connection reestablishment message. The first UE may transmit a measurement report message including the measured PDCH status information to the eNB (S119). The base station eNB may select a PDCH for the first UE based on the PDCH status information and may transmit an RRC connection reassignment message including the selected PDCH information to the first UE in step S120.

The first MS may transmit an RRC connection re-assignment complete message to the eNB in response to the RRC RR Assignment message (S121). Upon receiving the RRC Connection Reset Assignment Complete message, the base station eNB may send a discovery configuration response message including the network ID of the first UE to the MME 1. That is, the discovery setup response message may be sequentially transmitted to the PGW via the MME 1 and the SGW (S 122). In addition, when the RRC connection reallocation completion message is transmitted, the first UE can broadcast a message including the discovery information on the PDCH allocated to the first UE, and transmits the discovery information transmitted from the other UE to the UE through the PDCH (S123).

Meanwhile, the D2D discovery resource allocation procedure for the first terminal and the D2D discovery resource allocation procedure for the second terminal can be performed simultaneously. That is, when the D2D setup request message is received from the D2D server, the PGW may transmit a discovery setup request message including the network ID of the second terminal to the SGW. That is, the discovery setup request message including the network ID of the second terminal may be sequentially transmitted to the base station eNB through the SGW and MME2 (S124).

When the eNB receives the discovery setup request message including the network ID of the second terminal, the eNB may transmit an RRC connection re-establishment message to the second terminal (S125). That is, the base station eNB may request the second terminal to measure the PDCH state of the current cell for securing the PDCH resource by transmitting an RRC connection re-establishment message. Here, the PDCH can be used for the discovery procedure of the D2D communication.

In step S126, the second UE can transmit an RRC connection re-establishment completion message to the eNB in response to the RRC connection re-establishment message (step S126), and measure the PDCH state of the current cell (step S127). The second UE may transmit a measurement report message including the measured PDCH status information to the eNB (S128). The eNB may select a PDCH for the second UE based on the PDCH status information and may transmit an RRC connection reassignment message including the selected PDCH information to the second UE in step S129.

The second MS may transmit an RRC connection reset allocation complete message to the eNB in response to the RRC RR Assignment message (S130). Upon receiving the RRC Connection Reset Assignment Complete message, the base station eNB may send a Discovery Setup Response message including the network ID of the second terminal to the MME 2. That is, the discovery setup response message can be sequentially transmitted to the PGW through the MME 2 and the SGW. When receiving the network ID of the first terminal and the network ID of the second terminal through the discovery setup response message, the PGW transmits a discovery setup response message including the network ID of the first terminal and the network ID of the second terminal to the D2D server (S131).

In addition, when the RRC connection reallocation completion message is transmitted, the second UE can broadcast a message including the discovery information through the PDCH allocated to the second UE, and can receive the discovery information transmitted by the other UE through the PDCH (S132).

If the first terminal receives the discovery information from the second terminal through the PDCH allocated to the first terminal, the first terminal can recognize the second terminal (S133). Similarly, if the second terminal receives the discovery information from the first terminal through the PDCH allocated to the second terminal, the second terminal can recognize the first terminal (S134).

Here, by performing the first proximity check procedure, the first terminal does not transmit or receive the message including the discovery information until the second terminal enters the D2D communication range. Thus, the first terminal can reduce power consumed in performing D2D communication. In order to confirm the proximity of the first terminal and the second terminal, the PGW may include cell ID, tracking area information, routing area information, discovery area information that can be defined for discovery, etc. And interworking with a location server may be considered.

7 is a flowchart illustrating a resource release procedure in limited discovery in accordance with an embodiment of the present invention.

Referring to FIG. 7, the D2D server may release the discovery procedure (i.e., disassociate resource allocation for discovery) when there is a request from the terminal. The discovery procedure can be canceled only by the request of one terminal.

The first terminal and the second terminal may request disassembly of the discovery procedure after recognizing existence of each other (i.e., recognizing the discovery information). At this time, the discovery procedure can be canceled at the request of the first terminal, and the discovery procedure can be canceled at the request of the second terminal. That is, the first terminal may request the discovery procedure to be released by transmitting a discovery notification message to the D2D server (S141). Similarly, the second terminal may request release of the discovery procedure by sending a D2D discovery notification message to the D2D server (S142).

When the D2D server receives the D2D discovery notification message from at least one of the first terminal and the second terminal, the D2D server may transmit a discovery release request message to the PGW. The discovery release request message can be sequentially transmitted to the base station eNB via the PGW, SGW, and MME (S143). That is, the D2D server may request the base station eNB to release the discovery of the first and second terminals (i.e., release the resources allocated for the discovery) by transmitting a discovery release request message. Here, the discovery release request message may include the network ID of the first terminal, the network ID of the second terminal, and the like.

Upon receiving the discovery release request message, the base station eNB may transmit an RRC connection re-establishment message to the first terminal (S144). That is, the base station eNB requests the first terminal to release the discovery procedure by transmitting an RRC connection re-establishment message.

The first MS may transmit an RRC connection reset completion message to the eNB in response to the RRC connection re-establishment message (S145). After that, the first UE stops transmitting the message including the discovery information on the PDCH, and stops receiving the discovery information transmitted by the other UE through the PDCH. Also, a release cause suitable for the application of the first terminal can be delivered.

In addition, if the discovery release request message is received, the eNB may transmit an RRC connection re-establishment message to the second terminal (S146). That is, the base station eNB requests the second terminal to release the discovery procedure by transmitting an RRC connection re-establishment message.

The second terminal may transmit an RRC connection reset completion message to the eNB in response to the RRC connection re-establishment message (S147). Thereafter, the second terminal stops transmitting the message including the discovery information on the PDCH, and stops receiving the discovery information transmitted by the other terminal through the PDCH. In addition, a cause of the cancellation appropriate to the application of the second terminal can be delivered.

Upon receiving the RRC connection re-establishment complete message, the base station (eNB) may retrieve the PDCH allocated to each terminal and send a discovery release response message to the MME in response to the discovery release request message have. The discovery release response message may be sequentially transmitted to the D2D server via the MME, the SGW, and the PGW (S148). The discovery release response message may include the network ID of the first terminal, the network ID of the second terminal, and the like. When the D2D server receives the discovery release response message, the D2D server can retrieve the discovery information allocated to each terminal.

FIG. 8 is a flowchart illustrating a D2D connection establishment procedure in limited discovery according to an embodiment of the present invention.

Referring to FIG. 8, the D2D server can establish D2D communication when there is a request from the terminal. The setting procedure of the D2D communication can be performed by the request of the two terminals to perform the D2D communication.

The first terminal and the second terminal can request the D2D communication setting after recognizing the existence of each other (i.e., recognizing the discovery information). That is, the first terminal can request the D2D communication setup with the second terminal by transmitting the D2D discovery notification message to the D2D server (S151). In addition, the second terminal may request the D2D communication setup with the first terminal by transmitting a D2D discovery notification message to the D2D server (S152).

Upon receiving the D2D discovery notification message from the first terminal and the second terminal, the D2D server instructs the PGW to establish a D2D communication between the first terminal and the second terminal by transmitting a communication start request message to the PGW (S153). The D2D communication start request message may include a network ID of the first terminal, a network ID of the second terminal, and the like.

The PGW may measure the proximity between the first terminal and the second terminal when receiving the D2D communication start request message (S154). Specific methods for measuring the proximity will be described later.

If the proximity satisfies a preset criterion (i.e., the first terminal and the second terminal are in a position where D2D communication is possible), the PGW can establish D2D communication between the first terminal and the second terminal (S155 ). A specific method of setting the D2D communication will be described later. On the other hand, if the proximity does not satisfy the preset criteria (i.e., the first terminal and the second terminal are located in a position where D2D communication is impossible), the PGW establishes D2D communication between the first terminal and the second terminal Do not.

After completing the D2D communication setup between the first terminal and the second terminal, the PGW may transmit a D2D communication start response message in response to the D2D communication start request message (S156). That is, the PGW can inform the D2D server that the D2D communication setup response between the first terminal and the second terminal is completed by transmitting the D2D communication start response message. The D2D communication start response message may include a network ID of the first terminal, a network ID of the second terminal, and the like.

9 is a flowchart illustrating a proximity measurement and reporting procedure according to an embodiment of the present invention.

Referring to FIG. 9, the PGW may perform a second-order proximity measurement between the first terminal and the second terminal. The first proximity measurement is performed through S110 and S111 shown in FIG. 4, and the second proximity measurement means S154 shown in FIG.

The PGW can measure the secondary proximity based on the results of the first proximity measurement, the network load, and the traffic volume. First, the PGW can inform the SGW of the start of the proximity measurement procedure by sending a D2D measurement configuration request message to the SGW. The D2D measurement setup request message can be sequentially transmitted to the base station (eNB) via the SGW and the MME (S201). The D2D measurement setup request message may include a network ID of a first terminal, a network ID of a second terminal, a pair ID, and the like. If the pair ID is not assigned to the first terminal and the second terminal, the PGW may perform the second proximity measurement procedure after first setting the pair ID.

When receiving the D2D measurement setup request message, the base station eNB may determine a terminal to transmit a measurement signal (e.g., PM-SRS) and a terminal to receive (S202). That is, the base station eNB may determine the first terminal to be the transmitting terminal, determine the second terminal to be the receiving terminal, conversely determine the first terminal to be the receiving terminal and the second terminal to be the transmitting terminal. Hereinafter, a case where the first terminal is the transmitting terminal and the second terminal is the receiving terminal will be described.

The base station eNB may transmit an RRC connection re-establishment message to the first terminal to transmit the measurement signal (S203). The RRC connection reset message may include configuration information necessary to transmit a measurement signal. For example, the RRC connection reset message may include information for transmission of the PM-SRS. The first MS may transmit an RRC connection re-establishment completion message to the eNB in response to the RRC connection re-establishment message (S204).

Meanwhile, the base station eNB may transmit an RRC connection re-establishment message to the second terminal to receive the measurement signal (S205). The RRC connection reset message may include configuration information necessary to receive the measurement signal. The second terminal may transmit an RRC connection reset completion message to the eNB in response to the RRC connection re-establishment message (S206).

The base station eNB may recognize that the measurement is performed between the first terminal and the second terminal when the RRC connection reestablishment completion message is received from both the first terminal and the second terminal. Accordingly, the base station eNB may transmit a D2D measurement configuration response message to the MME in response to the D2D measurement setup request message. The D2D measurement setting response message can be sequentially transmitted to the PGW via the MME and the SGW (S207). The D2D measurement setup response message may include a pair ID.

The first terminal may transmit a measurement signal (e.g., PM-SRS) to the second terminal after transmitting the RRC connection reset completion message (S208, S210). The second terminal may receive the measurement signal transmitted from the first terminal and transmit a measurement report message including the result of receiving the measurement signal (for example, intensity of the measurement signal, SNR, SINR, etc.) eNB) (S209, S211). The base station eNB may determine to start / cancel the D2D communication based on the result information included in the measurement report message (S212). For example, when the result information included in the base station (eNB) measurement report message is equal to or greater than a preset reference, it is possible to determine the start of D2D communication. On the other hand, if the result information included in the measurement report message is less than a preset reference, It is possible to decide to release the communication. Here, the preset reference may mean a minimum signal strength or a minimum distance at which D2D communication is possible between the first terminal and the second terminal.

After determining to start / cancel the D2D communication, the base station eNB may send the D2D measurement report message including the information on the D2D communication start / cancellation decision, the pair ID, etc. to the MME. The D2D measurement report message may be sequentially transmitted to the PGW via the MME and the SGW (S213).

FIG. 10 is a flowchart illustrating a first procedure of a D2D communication setup procedure according to an embodiment of the present invention, and FIG. 11 is a flowchart illustrating a second procedure of a D2D communication setup procedure according to an embodiment of the present invention.

Referring to FIGS. 10 and 11, the D2D communication setup procedure may refer to S155 shown in FIG. When receiving the D2D communication start request message from the D2D server, the PGW may perform the PCC check of the first terminal and the second terminal to perform D2D communication through communication with the PCRF (S250). After completing the PCC check, the PGW may initiate the D2D bearer setup procedure for D2D communication by sending a D2D Bearer Request message to the SGW. The SGW may send a D2D Bearer Request message to the MME (S251). The D2D bearer request message may include a pair ID and the like.

Upon receiving the D2D Bearer Request message, the MME can select the D2D bearer ID. Here, the D2D bearer ID may mean information that is localized in the UE. In addition, the MME can configure ProSe management (PSM) information of a non-access stratum (NAS) level for the first terminal. Here, the profile management information may include a pair ID, a D2D bearer ID, a D2D bearer QoS, a D2D bearer TFT (traffic flow template), and the like. The MME may transmit a D2D bearer setup request message including the proxy management information to the eNB (S252).

Upon receiving the D2D bearer setup request message for the first UE, the eNB may map the D2D bearer QoS included in the D2D bearer setup request message to the D2D radio bearer QoS. Thereafter, the base station eNB may transmit an RRC connection re-establishment message to the first terminal (S253). Here, the RRC connection re-establishment message may include a D2D resource block ID, a D2D radio bearer QoS, project management information, and the like.

When the first terminal receives the RRC connection re-establishment message, it can store the D2D resource block ID, the D2D bearer TFT, and the like in accordance with the proposal management request. Thereafter, the first MS transmits an RRC connection re-establishment completion message to the eNB to inform that the D2D radio bearer has been created (S254).

Upon receiving the RRC connection re-establishment completion message, the base station eNB may inform the MME that a D2D radio bearer has been created by sending a D2D bearer setup response message (S255). Here, the D2D bearer setup response message may include a pair ID, a D2D bearer ID, and the like.

On the other hand, the NAS of the first terminal can configure the management management response information including the pair ID and the D2D bearer ID, and can transmit a direct transfer message including the management management response information to the base station eNB (S256). The base station eNB may construct an uplink NAS transport message based on the management response response information included in the direct transmission message and may transmit the uplink NAS transport message To the MME (S257).

In addition, when receiving the D2D bearer request message, the MME can configure the NAS management information for the second terminal. Here, the profile management information may include a pair ID, a D2D bearer ID, a D2D bearer QoS, a D2D bearer TFT, and the like. The MME may transmit the D2D bearer setup request message including the proposal management information to the eNB (S258).

Upon receiving the D2D bearer setup request message for the second terminal, the base station eNB may map the D2D bearer QoS included in the D2D bearer setup request message to the D2D radio bearer QoS. Thereafter, the base station eNB may transmit an RRC connection re-establishment message to the second terminal (S259). Here, the RRC connection re-establishment message may include a D2D resource block ID, a D2D radio bearer QoS, pro management information, and the like.

Upon receiving the RRC connection re-establishment message, the second terminal may store the D2D resource block ID, the D2D bearer TFT, and the like in accordance with the profile management request. Thereafter, the second UE transmits an RRC connection re-establishment completion message to the base station eNB to inform that the D2D radio bearer has been created (S260).

Upon receiving the RRC connection re-establishment completion message, the base station eNB may inform the MME that a D2D radio bearer has been created by sending a D2D bearer setup response message (S261). Here, the D2D bearer setup response message may include a pair ID, a D2D bearer ID, and the like.

On the other hand, the NAS of the second terminal can construct pro management response information including the pair ID and the D2D bearer ID, and can transmit a direct transfer message including the pro management response information to the base station eNB (S262). Upon receiving the direct transfer message, the base station eNB may configure the uplink NAS transport message based on the proxy management response information included in the direct transfer message, and may transmit the uplink NAS transport message to the MME (S263).

Upon receiving the D2D bearer setup response message and the uplink NAS transport message (i.e., projec- tion management response information) for the first terminal and the second terminal, the MME can confirm that the preparation of D2D communication for all terminals is completed have. The MME may then send a D2D bearer response message to the SGW in response to the D2D Bearer Request message (i.e., S251), and the SGW may send the received D2D Bearer Response message to the PGW (S264) . The D2D bearer response message may include a pair ID, a D2D bearer ID, and the like.

Although it has been described that the procedure for setting the D2D bearer for the first terminal (S252 to S257) is performed earlier than the procedure for setting the D2D bearer for the second terminal (S258 to S261), the order of performing the D2D bearer is not limited thereto . That is, the D2D bearer setup procedure for the first terminal may be performed concurrently with the D2D bearer setup procedure for the second terminal, or the D2D bearer setup procedure for the first terminal may be performed later than the D2D bearer setup procedure for the second terminal .

Upon receiving the D2D Bearer Response message, the PGW determines that the pair can perform D2D scheduling, and can transmit a D2D command message to the SGW accordingly. The SGW may transmit the received D2D command message to the MME (S265). The D2D command message may include a pair ID and the like.

If the MME receives the D2D command message, the MME may transmit a PSM D2D command message for the first terminal and the second terminal to the eNB (S266, S268). The base station (eNB) can start L2 scheduling when it receives the PSM D2D command message. That is, the base station eNB can set a traffic flow of the application as a D2D radio bearer using the D2D packet filter of the D2D bearer TFT included in the management information received through S252 and S258. The base station eNB may transmit an RRC status message including the set D2D radio bearer information to each mobile station (S267, S269). That is, the base station eNB can instruct each terminal to start the D2D communication by transmitting an RRC status message.

When the UE receives the RRC status message, the UE can perform the D2D communication using the radio bearer indicated by the RRC status message (S270).

FIG. 12 is a flowchart illustrating a D2D communication release procedure by a user according to an embodiment of the present invention, FIG. 13 is a flowchart illustrating a D2D communication release procedure by a base station according to an embodiment of the present invention, Is a flowchart illustrating a D2D bearer release procedure according to an embodiment of the present invention.

12 to 14, the D2D communication release procedure can be divided into a D2D communication release by the user and a D2D communication release by the base station.

First, if the user of the first terminal desires to cancel the D2D communication, the user can transmit a D2D service end message to the D2D server through the first terminal (S310) . The D2D server receiving the D2D service termination message can notify the termination of the D2D service by transmitting a D2D service termination message to the second terminal performing D2D communication with the first terminal (S311).

Thereafter, the D2D server may request the connection between the first terminal and the second terminal by transmitting a D2D communication stop request message to the PGW (S312). The PGW may send a D2D communication stop response message to the D2D server in response to the D2D communication stop request message (S313). The D2D communication stop request message may include the network ID of the first terminal, the network ID of the second terminal, and the like, and the D2D communication stop response message may include the network ID of the first terminal, the network ID of the second terminal, have.

In step S320, the eNB determines whether D2D communication between the first terminal and the second terminal is possible based on the proximity measurement result. Here, the proximity measurement between the first terminal and the second terminal can be performed through the procedure shown in FIG.

If the D2D communication between the first terminal and the second terminal is impossible (i.e., the first terminal and the second terminal are far away) as a result of proximity measurement, the base station eNB transmits a D2D measurement report message to the MME, The start of the release can be notified. The D2D measurement report message can be sequentially transmitted to the PGW via the MME and the SGW (S321). The D2D measurement report message may include proximity measurement results, a pair ID, and the like.

When the D2D measurement report message is received, the PGW may notify the start of D2D communication release by transmitting a communication stop indication message to the D2D server (S322). The D2D communication stop indication message may include a network ID of the first terminal, a network ID of the second terminal, and the like. The D2D server may transmit a D2D communication stop confirmation message to the PGW in response to the D2D communication stop instruction message (S323). Thereafter, the D2D server can notify the end of the D2D service by transmitting a D2D service termination message to the first terminal and the second terminal (S324, S325).

In the D2D communication release procedure, the following D2D bearer release procedure may be performed after S332 of the D2D communication release procedure by the terminal and S332 after the D2D communication release procedure by the base station (eNB).

When the D2D communication stop request message is received (S312) or the D2D communication stop confirmation message is received (S323), the PGW may transmit a D2D bearer deletion request message to the SGW. The SGW may send a D2D Bearer Deletion Request message to the MME (S330). The D2D bearer deletion request message may include a pair ID, a D2D bearer ID, and the like.

Upon receiving the D2D Bearer Deletion Request message, the MME may configure the NAS management information for the first terminal. The profile management information may include a pair ID, a D2D bearer ID, and the like. The MME may transmit a D2D bearer deactivation request message including proce- dure management information to the eNB (S331).

When the eNB receives the D2D bearer deactivation request message, the eNB may transmit an RRC connection re-establishment message to the first terminal (S332). That is, the base station eNB may request the release of the D2D bearer by transmitting an RRC connection re-establishment message to the first terminal. The RRC connection reset message may include a D2D resource block ID, profile management information, and the like.

Upon receiving the RRC connection re-establishment message, the first UE can release the D2D bearer and the D2D radio bearer, and may transmit an RRC connection re-establishment completion message to the eNB (S333). In step S334, the eNB may send a D2D bearer deactivation response message to the MME in response to the D2D bearer inactivation request message, indicating that the D2D radio bearer has been released. The D2D bearer deactivation response message may include a pair ID, a D2D bearer ID, and the like.

In addition, the first terminal may configure the proxy management response information including the pair ID, the D2D bearer ID, and the like, and may transmit a direct transfer message including the proxy management response information to the base station eNB (S335). When receiving the direct transmission message, the base station eNB may transmit the uplink NAS transport message including the management management response information to the MME (S336).

On the other hand, if the D2D bearer deletion request message is received, the MME can configure the NAS management information for the second terminal. The profile management information may include a pair ID, a D2D bearer ID, and the like. The MME may transmit the D2D bearer deactivation request message including the proce- dure management information to the base station eNB (S337).

When the eNB receives the D2D bearer deactivation request message, the eNB may transmit an RRC connection re-establishment message to the second terminal (S338). That is, the base station eNB may request the release of the D2D bearer by transmitting an RRC connection re-establishment message to the second terminal. The RRC connection reset message may include a D2D resource block ID, profile management information, and the like.

Upon receiving the RRC connection re-establishment message, the second UE can release the D2D bearer and the D2D radio bearer, and may transmit an RRC connection re-establishment completion message to the base station eNB indicating that the D2D radio bearer is released (S339). The base station eNB may send a D2D bearer deactivation response message to the MME indicating that the D2D radio bearer is released in response to the D2D bearer inactivation request message (S340). The D2D bearer deactivation response message may include a pair ID, a D2D bearer ID, and the like.

In addition, the second terminal can configure the proxy management response information including the pair ID, the D2D bearer ID, and the like, and can transmit the direct transfer message including the proxy management response information to the base station eNB (S341). When receiving the direct transmission message, the base station eNB may transmit the uplink NAS transport message including the management management response information to the MME (S342).

When the D2D bearer deactivation response message and the proxy management response information are received for all terminals, this means that the D2D communication between the first terminal and the second terminal is canceled. Therefore, in this case, the MME may send a D2D bearer deletion response message to the SGW in response to the D2D bearer delete request message. The SGW may send a D2D Bearer Deletion Response message to the PGW (S343). The D2D bearer deletion request message may include a pair ID, a D2D bearer ID, and the like.

Here, it is described that the bearer reset procedure (S331 to S336) for the first UE is performed before the bearer reset procedure (S337 to S342) for the second UE, but the order of performing the bearer is not limited thereto. That is, the bearer re-establishment procedure for the first terminal can be performed simultaneously with the bearer re-establishment procedure for the second terminal, or the bearer re-establishment procedure for the first terminal can be performed later than the bearer re-establishment procedure for the second terminal .

An open discovery-based service is a service based on the assumption that a mobile station discovers a discoverable mobile station without mutual agreement between the mobile stations. The search terminal performs registration for open discovery and performs transmission of the discovery information. The search terminal receives the discovery information transmitted by the search terminal and acquires the service information desired by the user. After the discovery of the terminal, the service using the D2D communication depends on the user's selection. An example of a typical open discovery is commercial advertising services.

FIG. 15 is a flowchart showing a first procedure of an open discovery procedure according to an embodiment of the present invention, FIG. 16 is a flowchart showing a second procedure of an open discovery procedure according to an embodiment of the present invention, Is a flowchart illustrating a third procedure of the open discovery procedure according to an embodiment of the present invention.

15 to 17, the first terminal (i.e., the search terminal) that has executed the D2D service by the user transmits the discovery information registration request message to the D2D server to thereby obtain the information of the second terminal (S401). The discovery information registration request message may include a service category of a first terminal, a telephone number, an application ID, and other information (e.g., a URL, a basic menu, and the like).

When receiving the discovery information registration request message, the D2D server can perform application authentication (S402), and then send an ID query message (UE ID query message) to the PGW (S403). That is, the step of transmitting the ID query message may be performed to obtain a unique ID (i.e., a network ID) capable of identifying a user in the 3GPP network based on the telephone number of the first terminal.

If the PGW receives the ID query message, it can perform PCRF and PCC check procedures (S404 and S405). After performing the PCC check process, the PGW may transmit an ID query response message including the network ID (e.g., IMSI, IP address, etc.) of the first terminal to the D2D server in response to the ID query message (S406) .

The D2D server may allocate the discovery information of the first terminal to be transmitted through the discovery physical channel, and may transmit the D2D discovery information allocation message including the allocated discovery information to the first terminal (S407). The discovery information may include an ID of the first terminal (e.g., A100), a service category (e.g., D3F2), and the like.

The D2D server may start a procedure for transmitting the discovery information of the first terminal through the discovery physical channel by transmitting a discovery setup request message including the network ID of the first terminal to the PGW. The discovery setup request message may be sequentially transmitted to the base station eNB via the PGW, the SGW, and the MME (S408).

When receiving the discovery setup request message, the eNB may transmit an RRC connection reset message to the first terminal for measuring the status of the discovery physical channel (S409). The first MS may transmit an RRC connection reset completion message to the eNB in response to the received RRC connection re-establishment message (S410). Thereafter, the first UE may perform a measurement operation of the Discovery physical channel (i.e., PDCH) based on the configuration information included in the RRC connection re-establishment message (S411).

The first terminal may transmit a measurement report message including a measurement result of the discovery physical channel to the eNB (S412). The base station eNB may determine a radio resource to be used for transmission of the discovery information based on the measurement result of the discovery physical channel, and may transmit an RRC connection re-establishment message including information of the determined radio resource to the first terminal at step S413. The first MS may transmit an RRC connection reset completion message to the eNB in response to the received RRC connection re-establishment message (S414).

Then, the base station eNB may transmit a discovery setup response message to the MME in response to the discovery setup request message to inform that the setup for transmitting the discovery information of the second terminal is completed. The discovery setup response message may be sequentially transmitted to the D2D server via the MME, the SGW, and the PGW (S415). The discovery setup response message may include the network ID of the first terminal. After transmitting the RRC connection reset completion message, the first UE may transmit the discovery information through the PDCH (S416, S420).

Meanwhile, the second terminal can execute the D2D service (S417) and set the service category (for example, D3F2) to be detected (S418). After that, the second terminal can receive the discovery information transmitted through the PDCH (S419), and obtain the ID of the terminal that transmitted the discovery information corresponding to the service category to be discovered through category filtering (S421, S422). If the ID of the terminal that transmitted the discovery information corresponding to the service category is acquired, the second terminal may transmit the discovery information inquiry message to the D2D server to acquire detailed information on the discovery information (S423). The discovery information inquiry message may include the ID of the terminal that transmitted the discovery information and the like.

The D2D server may transmit the discovery information inquiry result message to the second terminal in response to the discovery information inquiry message (S424). The discovery information query result message may include detailed information about the discovery information (e.g., a URL, a basic menu, and the like). The second terminal can display the received discovery information inquiry result message (S425).

In open discovery, the user of the terminal can select the discovery ID to transmit. In this case, the discovery ID selected by the user can be transmitted to the D2D server, and the D2D server can confirm whether the D2D service is accepted after checking whether the discovery ID is duplicated or not.

18 is a flowchart illustrating a D2D connection establishment procedure in an open discovery according to an embodiment of the present invention.

Referring to FIG. 18, the second terminal (i.e., the search terminal) may transmit a D2D connection request message to the D2D server based on the discovery information acquired through the open discovery procedure (S451). The D2D connection request message may include discovery information (e.g., A100) of the first terminal (i.e., the paired terminal), an ID (e.g., telephone number) of the second terminal,

When receiving the D2D connection request message, the D2D server can request the ID of the second terminal by transmitting an ID query message to the PGW (S452). The transmission step of the ID query message is a procedure for acquiring a unique ID (e.g., a network ID) capable of identifying a user in the 3GPP network based on the telephone number of the second terminal.

The PGW can perform the PCRF and PCC check when receiving the ID query message (S453, S454). The PGW may then send an ID query response message including the network ID (e.g., IMSI, ID address, etc.) of the second terminal to the D2D server (S455).

When receiving the ID query response message, the D2D server may initiate a connection establishment procedure for D2D communication between the first terminal and the second terminal by transmitting a D2D communication start request message to the PGW (S456). The D2D communication start request message may include a network ID of the first terminal, a network ID of the second terminal, and the like.

If the D2D communication start request message is received, the PGW may perform a proximity measurement procedure to determine whether D2D communication is possible between the first terminal and the second terminal (S457). Here, the proximity measurement procedure may be the same as the procedure described with reference to FIG.

If it is determined that the D2D communication between the first terminal and the second terminal is possible through the proximity measurement procedure, the D2D communication establishment procedure between the first terminal and the second terminal may be performed (S458). Here, the D2D communication setting procedure may be the same as the procedure described with reference to FIG. 10 and FIG.

When the D2D communication setup between the first terminal and the second terminal is completed, the PGW may transmit a D2D communication start response message to the D2D server in response to the D2D communication start request message (S459). The D2D communication start response message may include a network ID of the first terminal, a network ID of the second terminal, and the like.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

Claims (20)

A D2D discovery method performed in a D2D server supporting device-to-device (D2D) communication between a discovery terminal and a discoverable terminal,
Receiving a D2D discovery participation message from the sought-after terminal;
Requesting a gateway connected to the D2D server to measure proximity between the search terminal and the slave terminal;
Receiving a proximity measurement result from the gateway; And
And requesting the search terminal and the sought terminal to initiate a D2D discovery procedure if the proximity measurement result meets a predetermined criterion. The method according to claim 1,
The discovery method includes:
Further comprising allocating a physical channel for D2D discovery to the search terminal and the sought terminal after requesting initiation of the D2D discovery procedure. The method according to claim 1,
Wherein the D2D discovery participation message indicates that the called terminal participates in the D2D discovery procedure requested by the search terminal. The method according to claim 1,
Wherein the gateway is a packet data network (PDN) gateway. The method according to claim 1,
Wherein the proximity is measured based on an intensity of a reference signal transmitted and received between the search terminal and the sought terminal. The method according to claim 1,
Wherein the proximity is measured based on location information of the search terminal and location information of the search terminal. The method according to claim 1,
Wherein the predetermined criterion is a minimum distance at which the D2D communication is possible between the search terminal and the sought-search terminal. A D2D discovery method performed in a D2D server supporting device-to-device (D2D) communication between a discovery terminal and a discoverable terminal,
Receiving a D2D communication start request message from the search terminal and the sought-search terminal;
Transmitting a D2D communication setup request message between the search terminal and the slave terminal to a gateway connected to the D2D server; And
And receiving a D2D communication setup response message from the gateway indicating that the D2D communication setup between the search terminal and the sought-search terminal has been completed, if the proximity between the search terminal and the sought-search terminal satisfies a predetermined criterion D2D discovery method. The method of claim 8,
Wherein the D2D communication initiation request message is received from the search terminal that recognized the existence of the sought-after terminal and the sought terminal that recognized the existence of the search terminal. The method of claim 8,
Wherein the gateway is a packet data network (PDN) gateway. The method of claim 8,
Wherein the D2D communication setup request message includes a network identifier of the search terminal and a network identifier of the search terminal. The method of claim 8,
Wherein the proximity is measured based on an intensity of a reference signal transmitted and received between the search terminal and the sought terminal. The method of claim 8,
Wherein the proximity is measured based on location information of the search terminal and location information of the search terminal. The method of claim 8,
Wherein the predetermined criterion is a minimum distance at which the D2D communication is possible between the search terminal and the sought-search terminal. A method for measuring proximity between terminals performed in a base station,
Allocating a radio resource for transmission of a reference signal for proximity measurement to a first terminal;
Allocating a radio resource for reception of the proximity measurement reference signal to a second terminal;
Obtaining reception result information on the reference signal for proximity measurement from the second terminal; And
And determining whether to initiate a direct device to device (D2D) communication between the first terminal and the second terminal based on the reception result information. 16. The method of claim 15,
The base station comprises:
And a radio resource for proximity measurement is allocated to the first terminal and the second terminal based on the request of the D2D server. 16. The method of claim 15,
Wherein the reception result information is a reception intensity of the proximity measurement reference signal. 18. The method of claim 17,
And determine to start D2D communication between the first terminal and the second terminal when the reception strength is equal to or greater than a preset reference. 18. The method of claim 17,
And determining to cancel the D2D communication between the first terminal and the second terminal when the reception intensity is less than a preset reference. 19. The method of claim 18,
Wherein the predetermined criterion is a minimum reception strength that enables D2D communication between the first terminal and the second terminal.

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