USER EQUIPMENT AND COMMUNICATION METHOD OF USER EQUIPMENT

Disclosed is a user equipment that supports device-to-device communication. A user equipment according to an embodiment of the present invention comprises: a communication unit for broadcasting a discovery message for informing another user equipment of the user equipment itself, and receiving a discovery message broadcasted from another user equipment; and a control unit for, when at least one discovery message is received, extracting an ID of at least one other user equipment from the at least one received discovery message, selecting at least one ID out of the extracted ID on the basis of status information indicating an importance of the at least one other user equipment, and broadcasting a discovery message including the selected ID.

FIELD OF THE INVENTION

Devices and methods consistent with what is disclosed herein relate to a user equipment and a communication method of a user equipment, and more particular, to a user equipment that relays a discovery message of a user equipment that supports direct communication between equipments and a communication method of a user equipment for relay.

Recently, many ongoing efforts have been made to Proximity-based Service (ProSe) technology to facilitate direct communication between user equipments by using a conventional communication method of a mobile system without allowing a user equipment (UE) to access a network via higher-level entities than a base station.

Despite many possibilities to utilize the ProSe technology, the Device-to-Device communication between user equipments is difficult to ensure mobility of a user equipment unless a network on an upper node is not provided, so that there is limit on the possible range of communication.

DESCRIPTION OF THE RELATED ART

One technical task of the present disclosure is to provide a user equipment for relaying a discovery message of a user equipment that supports direct communication between equipments and a communication method of a user equipment for relay.

SUMMARY

According to an exemplary embodiment, there is provided a user equipment that supports direct communication between equipments including a communicator configured to broadcast a discovery message for informing another user equipment of the user equipment itself and receive a discovery message broadcasted from another user equipment, and a controller configured to, in response to at least one discovery message being received, extract at least one identification (ID) of another user equipment from the at least one received discovery message, select at least one ID from the at least one extracted ID based on status information indicating importance of the another user equipment, and broadcast a discovery message including the at least one selected ID.

The user equipment may further include a storage configured to store IDs of a plurality of user equipments constituting a group which is provided with service for the direct communication between equipments and status information respectively given to the IDs, wherein the controller is further configured to retrieve status information given to the at least one extracted ID in the storage and select at least one ID from the at least one extracted ID based on the retrieved status information.

The another user equipment may be given status information corresponding to one of a plurality of roles constituting a pre-arranged command system, and wherein the controller is further configured to select at least one ID from the at least one extracted ID based on whether the status information given to the another user equipment is status information corresponding to a role to be reported and ordered according to the command system.

The storage may be further configured to store ratings that indicate priorities of the status information given to the IDs, and wherein the controller is further configured to, in response to receiving a plurality of discovery messages, determine ratings of respective IDs extracted from the plurality of received discovery messages, and select at least one ID from the extracted IDs according to priorities of the determined ratings.

The controller may be further configured to modify the ratings stored in the storage based on at least one of status information of the another user equipment included in the received discovery message and status information of the user equipment itself.

The controller may be further configured to modify the ratings stored in the storage based on a state which enables communication via a network, a present time, integration with another group which is provided with the service for direct communication between equipments, and group division of the user equipments.

The controller may be further configured to broadcast a discovery message including another ID which is not broadcasted among the plurality of IDs at different periods according to the determined ratings.

The controller may be further configured to select IDs equal to or less than a predetermined number according to a size of a packet that is transmittable through the discovery message among the plurality of IDs based on the determined ratings, and in response to all of a plurality of IDs on a same rating not being transmitted through the discovery message, select a number of IDs which are transmittable through the discovery message based on a number of times each of the plurality of IDs on the same rating is relayed.

The controller may be further configured to extract at least one ID of another user equipment and relay information indicating a number of times the at least one ID is relayed from the received discovery message, broadcast a discovery message including at least one ID selected from the at least one extracted ID based on the status information and relay information obtained by adding a number of times the at least one selected ID is relayed once, and in response to a plurality of discovery messages including the same ID being received, broadcast a discovery message including the same ID based on a discovery message including relay information that indicates a fewest number of times of relays among the plurality of received discovery messages.

The user equipment may further include a display configured to display a screen, and an input unit configured to receive a user input, wherein the controller is further configured to display nodes indicating one or a plurality of user equipments which relay the at least one extracted ID and bridges indicating paths where the at least one extracted ID is relayed visually on the display, and in response to a user input selecting one or a plurality of nodes displayed on the display being received, create a channel for communication with another user equipment corresponding to the selected node.

According to an exemplary embodiment, there is provided a communication method of a user equipment that supports direct communication between equipments, the method may include receiving at least one discovery message broadcasted from another user equipment, extracting at least one ID of another user equipment from the at least one received discovery message, selecting at least one ID from the at least one extracted ID based on status information indicating importance of the another user equipment, and broadcasting a discovery message including the at least one selected ID.

The method may further include storing IDs of a plurality of user equipments constituting a group which is provided with service for direct communication between equipments and status information respectively given to the IDs, wherein the selecting comprises retrieving status information given to the at least one extracted ID, and selecting at least one ID from the at least one extracted ID based on the retrieved status information.

The another user equipment may be given status information corresponding to one of a plurality of roles constituting a pre-arranged command system, wherein the selecting comprises selecting at least one ID from the at least one extracted ID according to whether the status information given to the another user equipment is status information corresponding to a role to be reported and ordered according to the command system.

The storing may include storing ratings that indicate priorities of the status information given to the IDs, wherein the selecting comprises, in response to a plurality of discovery messages being received, determining ratings of respective IDs extracted from the plurality of received discovery messages, and selecting at least one ID from the extracted IDs according to priorities of the determined ratings.

The method may further include modifying the stored ratings based on status information of the another user equipment included in the received discovery message and status information of the user equipment itself.

The modifying may include modifying the stored ratings based on a state which enables communication via a network, a present time, integration with another group which is provided with the server for direct communication between equipments, and group division of the user equipments.

The broadcasting may include broadcasting a discovery message including another ID which is not broadcasted among the plurality of IDs at different periods according to the determined ratings.

The selecting may include selecting IDs equal to or less than a predetermined number according to a size of a packet that is transmittable through the discovery message among the plurality of IDs based on the determined ratings, and in response to all of a plurality of IDs on a same rating not being transmitted through the discovery message, selecting a number of IDs which are transmittable through the discovery message based on a number of times each of the plurality of IDs on the same rating is relayed.

The extracting may include extracting at least one ID of another user equipment and relay information indicating a number of times the at least one extracted ID is relayed from the received discovery message, wherein the broadcasting comprises broadcasting a discovery message including at least one ID selected from the at least one extracted ID based on the status information and relay information obtained by adding a number of times the at least one selected ID is relayed once, and in response to a plurality of discovery messages including the same ID being received, broadcasting a discovery message including the same ID based on a discovery message including relay information that indicates a fewest number of times of relays among the plurality of received discovery messages.

The communication method may further include displaying nodes indicating one or a plurality of user equipments which relay the at least one extracted ID and bridges indicating paths where the at least one extracted ID is relayed visually on the display, and in response to a user input selecting one or a plurality of nodes displayed on the display being received, creating a channel for communication with another user equipment corresponding to the selected node.

According to various embodiments, a user equipment and a communication method of the present disclosure provide direct communication between a user equipment and an important user equipment or a target user equipment over a wider range.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description of the present disclosure, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIGS. 1A, 1B, and 1Care views illustrating the number of cases of a mobile communication system according to an embodiment of the present disclosure.

FIG. 1Ais a view illustrating a mobile communication system in its normal operation. Referring toFIG. 1A, a mobile communication system may include user equipments100-1,100-2,100-3,100-4and100-5and base stations200-1,200-2and200-3.

The base stations200-1,200-2and200-3may communication with the user equipments100-1,100-2,100-3,100-4and100-5within respective cells50-1,50-2and50-3where communication is available. Specifically, the base station200-1may communicate with the user equipments100-1and100-2in the cell50-1. The base station200-2may communicate with the user equipments100-3and100-4in the cell50-2. The base station200-3may communicate with the user equipment100-5in the cell50-3. The user equipments100-1,100-2,100-3,100-4and100-5may communicate with one another through the base stations200-1,200-2and200-3connected to a network although the user equipments100-1,100-2,100-3,100-4and100-5are dispersedly located across the huge area.

FIG. 1Bis a view illustrating that some of the base stations stop their operations in the mobile communication system ofFIG. 1A. Referring toFIG. 1B, the base stations200-2and200-3may stop operating. Accordingly, the cells50-2and50-3where the base stations200-2and200-3that stop operating are located may change to non-communicable areas, i.e. shaded areas.

The user equipment100-3located in the non-communicable area may directly communicate with the user equipment100-2located in the area50-1, which is a communicable area. The user equipment100-3may communicate with the user equipment100-2via D2D communication, access the base station200-1through the user equipment100-2connected to the base station and perform network communication.

FIG. 1Cis a view illustrating that all the base stations stop operating in the mobile communication system ofFIG. 1A. Referring toFIG. 1C, all the base stations200-1,200-2and200-3may stop operating. That is, network communication is not available in all areas. The user equipments100-1and1002next to each other may perform communication only via direct communication between equipments.

The present disclosure suggests a method for setting direct communication between user equipments across the huge area when network communication is not established via a base station as shown inFIGS. 1B and 1C.

FIG. 2is a block diagram provided to explain the configuration of a user equipment according to an embodiment of the present disclosure.

Referring toFIG. 2, a user equipment100may include a communicator110, a storage120, a display130, an input unit140and a controller150.

The communicator110may perform communication with an external apparatus. To be specific, the communicator110may perform wireless communication with another user equipment. The communicator110may comply with a communication method such as GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN, normally referred to as 3G), Evolved-UTRAN (E-UTRAN, referred to as LTE), etc. according to mobile communication system standards.

The communicator110may broadcast a discovery message for informing another user equipment of the user equipment itself. To be specific, the communicator110may broadcast a discovery message for informing another user equipment nearby of the presence of the user equipment100or identifying another user equipment nearby. For reference, a discovery method may have two types in terms of relation between a user equipment itself and the other use equipment. A first model may be “I am here” method on the purpose of advertising a user equipment itself, and a second model may be “who is there” method for solicitation to another user equipment neighboring the user equipment and receiving a response accordingly. According to the first mode, the user equipment advertising itself may be referred to as an announcer, and the other user equipment that receives that advertisement may be referred to as a monitor. According to the second model, the user equipment that gives solicitation may be referred to as a discoverer, and the other user equipment that responds to the solicitation may be referred to as a discoveree.

The communicator110may receive a discovery message broadcast from another user equipment. Specifically, the communicator110may receive a message from another user equipment for notifying the another user equipment itself or a message for giving the solicitation for a response from the user equipment100neighboring the another user equipment.

The communicator110may include a transmitting/receiving antenna for transmitting and receiving one or a plurality of wireless signals, an amplifier for amplifying an electric signal, a module for channel decoding/encoding, modulation/demodulation and Fourier conversion/inversion, etc.

The communicator110may communicate with a base station device. The communicator110may obtain information necessary for filtering a discovery message through signaling with the base station device. The filtering may refer to extracting only the part of information needed from a plurality of received discovery messages, and the base station device may refer to information serving as a reference required for filtering.

The storage120may store programs and data for driving and operating the user equipment100. The storage120may store the information obtained from the base station device through the communicator110. Specifically, the storage120may store IDs of a plurality of user equipments constituting a group that receives service for direct communication between equipments. The ID may refer to identification information for distinctly identifying each user equipment in the group. The storage120may store status information given to respective stored IDs of a plurality of user equipments. The status information may indicate how important a user equipment is. The importance of a user equipment may be determined by a user of a user equipment when the user signed up for direct communication service between equipments. When one of members of a group signed up for direct communication service between equipments, the importance of the user equipment of the member may be determined by hierarchy between the members. In a general sense, a user equipment may be given status information corresponding to any one of a plurality of roles constituting the pre-arranged command system.

According to an embodiment, a ProSe application server (AS) managing direct communication between equipments may store status information corresponding to the position input as user information when a user equipment joins a group. The ProSe AS may distribute the ID and status information stored therein to user equipments in the group. The user equipment may store IDs and status information received from an upper node.

The storage120may store the segmented ratings of status information. Specifically, the storage120may store the ratings that indicates priorities of the status information. The priorities of the ratings may be used as criteria for selecting an ID to be relayed.

The storage120may be implemented with various non-temporary storage media. For example, the storage120may be a magnetic recording type HDD, a flip flop recording type SDD, a flash memory, an optical recording medium, or the like. The storage120may be embedded in a user equipment or connected via an interface.

The display130may display a screen. Specifically, the display130may provide a user with information and display a screen providing an interface for receiving a user input.

The display130may display change of the IDs and/or the status information stored in the storage120. Specifically, the display130may display a screen to inform a user of IDs and/or status information renewed or added based on the information included in a discovery message or the information received from a base station.

The display130may visually display a screen indicating a connection relation between the user equipment and another communicable user equipment. The display130may visually display a screen indicating the number of times of relays and paths through the connection to another user equipment based on the received discovery message. The display130may display a screen receiving a user input for communication connection to another user equipment. An example of an interface screen will described in detail with reference toFIG. 20.

The display130may be embodied with various display units such as liquid crystal display (LCD), organic light-emitting diode (OLED), plasma display (PD), vacuum fluorescent display (VFD), field emission display (FED), electro luminescence display (ELD), etc.

The input unit140may receive a user input. Specifically, the input unit140may be embodied with one or more of devices where various functions supported by the user equipment100is set or selected by a user. The input unit140may be embodied with a physical button member provided on the user equipment100or a touch panel detecting a touch. The touch panel may be embodied with a touch screen capable of inputting and outputting simultaneously with the display130.

The controller150may control each element of the user equipment100. The controller150may control each element of the user equipment100for mobile communication and D2D communication of the user equipment100.

In response to at least one discovery message being received, the controller150may extract at least one ID of another user equipment from the received discovery message. The controller150may, if the communicator110receives a discovery message, extract one or a plurality of IDs included in a discovery message from another user equipment. The controller150may extract at least two IDs. One of the IDs may be the ID of another user equipment which broadcasts the received discovery message, and the other ID may be the ID of yet another user equipment relayed by the another user equipment.

The controller150may select at least one of the IDs extracted based on the status information. The controller150may select at least one of the IDs extracted based on the status information indicating the importance of another user equipment.

The controller150may retrieve status information corresponding to the extracted ID with reference to the IDs and the status information stored in the storage120and select an ID based on the retrieved status information. The controller150may determine whether the ID extracted based on the retrieved status information is an ID to be relayed to yet another user equipment.

The controller150may select at least one ID from the IDs extracted based on whether the status information given to another user equipment is status information corresponding to a role to be reported and ordered according to a command system. In the above example, each of user equipments of the members of a group may be given the corresponding status information. Based on the report from subordinate to superior and the order from the superior to the subordinate according to the hierarchy of the group, the user equipments may identify the user equipment of a member who is always needs to be communicated, i.e. a superior, based on the ID and the status information.

In response to a plurality of discovery messages being received, the controller150may determine the rating of each of the plurality of IDs extracted from the received plurality of discovery messages. The rating may be determined by the result retrieved from the storage120that stores the ID and rating of the user equipment of the group. The controller150may select an ID having a higher priority of the ratings among the plurality of extracted IDs as an ID for the relay.

The controller150may modify the rating stored in the storage120based on at least one of status information of another user equipment included in the received discovery message and status information of the user equipment itself. The controller150may modify the stored ratings based on the status information included in or detected by the discovery message informed of the change of the ratings. Modification of the ratings may be made when the group is reorganized, the senior is replaced, and the command is temporarily granted. The status information indicating such situation may be contained in a discovery message broadcasted from another user equipment.

The controller150may modify the ratings based on a state that enables communication via a network, a current time, integration with another group that is provided with service for direct communication between equipments, segmentation of groups of user equipments. For example, the controller150may give a higher ranting to an ID of a user equipment capable of network communication and indicate the user equipment as an important user equipment capable of UE-to-Network relay. If the identified present time passes to the night time or the identified present time is a distribution time, the controller150may give a higher ranting to a user equipment of a user given a particular task at that time. If the group to which the user belongs is a police agency and the police agency is integrated with the fire agency, the controller150may modify the ratings according to the hierarchy where status is added and changed in the integrated group.

The broadcast discovery message may be created in a packet of a limited size. The user equipment may not relay all the extracted IDs if the extracted plurality of IDs exceed a predetermined number.

In this aspect, the controller150may select IDs equal to or less than a predetermined number based on the determined ratings according to a size of a packet transmitted via a discovery message among the plurality of IDs. The controller150may create a discovery message by selecting IDs from the highest priority to the lowest priority.

When the part of a plurality of IDs on the same rating is selected, that is, when it is not possible to transmit all of the plurality of IDs on the same rating via a discovery message, the part of IDs that is to be contained in the packet of the size set based on the number of times each of the plurality of IDs is relayed. Specifically, the controller150may select IDs on the same rating from the smallest number of times of relays to the greatest number of times of relays. This is because the smaller number of times of relays of the IDs may ensure high quality communication until communication between equipments is established.

The controller150may broadcast a discovery message at a different period according to the ID rating. The controller150may not relay the same ID based on the status information, but broadcast a discovery message including an ID having a lower priority, which is not broadcasted, at a longer period. The detailed description thereof will be described below with reference toFIG. 13.

The received discovery message may include at least one ID of another user equipment and relay information indicating the number of times the ID is relayed. The controller150may include relay information indicating the number of times the ID of another user equipment is relayed in a discovery message including the ID of another user equipment, not the ID of the user equipment100itself.

The controller150may extract at least one ID of another user equipment and relay information indicating the number of times the ID is relayed from the received discovery message. The controller150may broadcast a discovery message including at least one ID selected from the extracted IDs based on the status information and relay information obtained by adding the number of times the selected ID is relayed once. That is, the controller150may add the number of times the user equipment100itself is relayed, once to the relay information.

In response to a plurality of discovery messages including the same ID being received, the controller150may broadcast a discovery message including the same ID based on a discovery message including relay information indicating the fewest number of times of relays among the plurality of received discovery messages. Other user equipments near the user equipment100may store the same status information. The user equipment100may likely receive discovery messages including the same ID having a higher priority from other user equipments nearby. Therefore, the user equipment100may create a discovery message based on the number of times of relays and the smaller number of relay information. The controller150may correspond the received same ID to the ID of another user equipment relayed by the smaller number of times, and abandon the remaining IDs. The detailed description will be made below with reference toFIG. 14.

The controller150may create a D2D communication channel for direction communication between equipments. The controller150may create a one-to-one communication channel between a user equipment and another user equipment based on the ID of another user equipment discovered by the received discovery message. The controller150may transmit a signal for requesting connection to the user equipment of the selected ID for D2D communication to a user equipment which broadcasts the received discovery message. Another user equipment that receives a request signal may relay a signal that requests connection to another user equipment that broadcasts the selected ID for D2D communication based on the received discovery message.

The controller150may, in response to a user input selecting a node for indicating another user equipment displayed on the display130being received through the input unit140, create a channel for communication with another user equipment corresponding to the selected node.

The controller150may include a Read-Only Memory (ROM) that stores a control program for controlling the CPU and the user equipment100and a Random Access Memory (RAM) that stores signals or data input from outside the user equipment100or is used as a storage area for a task performed by the user equipment100. The CPU may include at least one of a single-core processor, a dual-core processor, a triple-core processor, and a quad-core processor. The CPU may be a mobile processor specialized for a handheld device. The processor, ROM and RAM may be interconnected via an internal bus.

The user equipment100may relay information that identifies a user equipment of an important user to another user equipment by using a discovery message of a limited size.

FIG. 3is a block diagram illustrating a network hierarchy for direct communication between equipments according to an embodiment of the present disclosure.

Referring toFIG. 3, a user equipment UE A300and a user equipment UE B300′ may support direct communication between equipments. The user equipment UE A300and the user equipment UE B300′ both support the communication scheme of the E-UTRAN. A side link between the UEs may be generated via the PC5 interface by distinguishing the uplink and downlink between the eNB and the UE, both of which are upper nodes.

The AS may consist of MAC layers320and320′ and PHY layers310and310′. The MAC layers320and320′ may receive a discovery message from the ProSe Protocol layers330and330′ and determine a radio resource for broadcasting the received discovery message. The MAC layers320and320′ may build a Protocol Data Unit (PDU) created from a discovery message to be in a predetermined format, and transmit the MAC PDU to the PHY layer in order to transmit the PDU to the determined radio resource.

FIG. 4is a view provided to explain initial discovery of a user equipment according to an embodiment of the present disclosure.

Referring toFIG. 4, a user equipment410and other user equipments420-1,420-2,420-3,430-1,430-2, and430-3may be dispersedly located at different positions.

The user equipment410may broadcast a discovery message with a preset intensity of a signal. A range440to which a broadcast signal reaches from the user equipment100may be determined based on the intensity of a signal. The user equipment410may broadcast a discovery signal of stronger intensity than the intensity of a signal in communication with the base station.

The user equipments420-1,420-2and420-3near the user equipment410may be located within a reachable range of a broadcasting signal. The user equipments420-1,420-2and420-3may identify the presence of the user equipment410. However, the user equipments430-1,430-2and430-3out of the range440may not recognize the user equipment410.

FIG. 5is a view provided to explain an example embodiment of relay of a discovery message.

Referring toFIG. 5, a user equipment510of A may broadcast a discovery message “who is there?” of the second model. A user equipment520-1of B and a user equipment520-2of Z in the range540where a broadcast signal arrives may recognize the user equipment510of A, and broadcast a discovery message for informing a user equipment itself, which is including the IDs of the user equipments520-1and520-2. A user equipment530of C may be within a range550where a broadcast signal of the user equipment520-1of B reaches. The user equipment530of C may identify that from the response signal broadcasted by the user equipment520-1of B that the user equipment520-1of B may communicate with the user equipment510of A. However, the user equipment530of C may not identify the presence of the user equipment520-2of Z.

FIG. 6is a view provided to explain another example embodiment of relay of a discovery message.

Referring toFIG. 6, a group network610of one to N may be formed. Specifically, a user equipment A620, a user equipment B630, and a user equipment C640, which are next to one another, may form a 1:2 D2D network. The user equipment A620, the user equipment B630, and the user equipment C640each may store identification information of other user equipments to communicate with one another. That is, the user equipment A620may store IDs of the user equipment B630and the user equipment C640, the user equipment B630may store IDs of the user equipment A620and the user equipment C640, and the user equipment C640may store IDs of the user equipment A620and the user equipment B630. The user equipment C640and a user equipment D650may recognize each other through a discovery procedure. The user equipment D650may directly communicate only with the user equipment C640.

The user equipment C640may transmit identification information A and B of the user equipment A620and the user equipment B630, which is communicated when the user equipment C640is relayed to the user equipment D650. In the same manner, the user equipment C640may transmit identification information D of a new user equipment650that is communicated when the user equipment C640is relayed to the user equipment A620and the user equipment B630in the group. Consequently, a 1:3 group network610′ may be newly formed.

As described above, transmitting identification information of all members in a group to a new network subscriber may be limited due to the size of a transmission message. Also, as the number of members in the group increases, the traffic for forming a network will increase in arithmetic progression.

FIG. 7is a view provided to explain broadcasting of a discovery message according to an embodiment of the present disclosure.

Referring toFIG. 7, a user equipment710of A may broadcast a discovery message “I am A” according to the first model. A user equipment720of B within a range715to which a broadcasting signal of the user equipment710of A reaches may receive a plurality of discovery messages721from another user equipment nearby.

The user equipment720of B may select an ID for relay from among IDs included in the received plurality of discovery messages721based on the status information. The ID for relay may be selected by a filter module722. The filter module722may select A having a high priority as the ID for relay based on the stored status information or ratings.

The use equipment720of B may broadcast a discovery message including ‘A&’ that indicates the important member A is relayed for the first time. A user equipment730of C within the reach of the broadcasting signal of the user equipment720of B may receive a plurality of discovery messages731from other user equipments.

The user equipment730of C that receives a discovery message723of the user equipment720of B may recognize communication with the user equipment710of A through the user equipment720of B.

A filter module732of the user equipment730of C may select an ID for relay from among the plurality of extracted IDs. The user equipment730of C may broadcast a discovery message including ‘A&&’ indicative of relaying the important member A for the second time. A user equipment740of D within a range735to which a broadcast signal of the user equipment730of C reaches may receive a plurality of discovery messages from other user equipments.

The user equipment740of D that receives a discovery message733of the user equipment730of C may recognize communication with the user equipment710of A through the user equipment730of C.

A filter module742of the user equipment740of D may select an ID for relay from among the plurality of extracted IDs. The user equipment730of D may broadcast a discovery message including ‘A&&&’ indicative of relying the important member A for the third time.

The D may make a phone call to the user equipment710of A that is recognized through the discovery message relayed by using the user equipment740. The user equipment740of D may transmit a signal to the user equipment710of A through the relay of the user equipment730of C and the user equipment720of B.

Referring toFIG. 8, a user equipment1840may be connected to EPS830for providing MCPTT service through RAN interface (Uu or Um) in an on state where a network of an upper node operates normally. The MCPTT may stand for Mission Critical Push-to-Talk and refer to service that provides direct call between UEs using the LTE method for disaster safety communication. The Evolved Packet System (EPS)830may include a Home Subscriber Server (HSS), a Mobile-services Switching Center (MSC), a Mobility Management Entity (MME), and Gateways (GW).

An MCPTT application service810may include an MCPTT server consisting of a configuration management server, a group management server, an identity management server, a floor control server, etc. The configuration management server may configure data of an MCPTT client device. This configuration management server may manage MCPTT service configuration supported by an MCPTT service provider. A group management server may manage the groups supported by the MCPTT service provider.

Client devices included a single group may use the same group management server for the group. An identification management server may authenticate an MCPTT user. That is, the identification management server may include authentication means for confirming credentials of a user. A floor control server may control access for the use and sharing of resources of a plurality of users. The MCPTT server may track the MCPTT UE, allocate resources, control transmission of the uplink and the downlink of the media, and the like.

An SIP core820may provide rendezvous (combination of contact addresses and URI determination) and service control (application service selection) functions.

The user equipment UE1840may support bearer services and applications associated with MCPTT. The user equipment UE1840may also function as a relay node of the UE-to-Network relay. The user equipment UE1840may be directly connected to a user equipment UE2850to relay network communication of the user equipment UE2850.

Referring toFIG. 9, a user equipment3910may be connected to a user equipment4920in a state where a network on an upper node is off. The user equipment3910and the user equipment4920may use ProSe technology and support an application regarding the off-network MCPTT service.

FIG. 10is a flowchart provided to explain a relay method according to a first embodiment of the present disclosure.

Referring toFIG. 10, a user equipment UE-11001may perform group member discovery at step S1010. The user equipment UE-11001may broadcast a discovery message in a first mode or a second mode. The discovery message may not be for a specific UE but may be a message for searching for all the neighboring members in the group to which the user equipment UE-11001belongs. The user equipment UE-11001may discover a user equipment UE-R1002which is one of group members. The user equipment UE-R1002that receives a discovery message of the user equipment UE-11001may recognize the presence of the user equipment UE-11001nearby. For convenience of explanation, it is assumed that the user equipment UE-11001is given important status information.

The user equipment UE-R1002may perform group member discovery at step S1020. The user equipment UE-R1002may broadcast its own discovery message. The user equipment UE-R1002that performs discovery may discover user equipments nearby such as the user equipment UE-11001and the user equipment UE-21003.

The user equipment UE-R1002may broadcast a message including a remote user list where an ID of a user equipment to which important status information is given is sorted out among the discovered user equipments at step S1030. The user equipment UE-R1002may transmit a message including the ID of the user equipment UE-11001and the ID of the user equipment UE-R1002itself to the user equipment UE-21003. The user equipment UE-21003may recognize the presence of the user equipment UE-11001which is communicable through the user equipment UE-R1002.

The user equipment UE-11001and the user equipment UE-21003may perform communication through the relay of the user equipment UE-R1002at step S1040.

FIG. 11is a flowchart provided to explain a relay method according to a second embodiment of the present disclosure.

Referring toFIG. 11, a user equipment UE-11101may perform group member discovery at step S110. A user equipment UE-R1102may perform group member discovery at step S1120. Steps S1110and S1120may correspond to steps S1010and S1020ofFIG. 10. Therefore, the detailed description will be omitted.

The user equipment UE-11101discovered by the discovery of the user equipment UE-R1102may broadcast a message including a remote user list where the ID of the user equipment UE-11101and the IDs of user equipments UEs of interest at step S1130. A broadcasting signal of the user equipment UE-11101may not reach the user equipment UE-21103.

In response to a message of the user equipment UE-11101received at step S1130, the user equipment UE-R1102may transmit the ID of interest of the user equipment UE-11101in the remote user list to the user equipment UE-11101at step S1140.

The user equipment UE-11101that recognizes the presence of the user equipment UE-21103of its interest may perform communication with the user equipment UE-21103through the user equipment UE-R1102at step S1150.

FIG. 12is a flowchart provided to explain a relay method according to a third embodiment of the present disclosure.

Referring toFIG. 12, the user equipment UE-11201may broadcast a discovery message at step S1210. The user equipment UE-21202that receives a discovery message may determine whether the received packed needs to be relayed at step S1220. The UE-21201may select an ID that needs to be relayed from the IDs included in a discovery message packet of the user equipment UE-11201based on the status information.

The user equipment UE-21201may broadcast a discovery message including the ID of the user equipment UE-11201to which important status information is given at step S1230. The user equipment UE-31203that receives a broadcasting signal of the user equipment UE-21201may recognize the presence of the user equipment UE-11201through the user equipment UE-21202.

FIG. 13is a view provided to explain broadcasting of a discovery message according to another embodiment of the present disclosure.

Referring toFIGS. 13 and 7,FIG. 13may include the user equipments710,720,730and740ofFIG. 7. A user equipment750of H within the range715where the broadcasting signal of the user equipment710of A reaches and a user equipment760of E within the range735where the broadcasting signal of the user equipment730of C reaches may be further added.

According to a relay method ofFIG. 7, the user equipment720of B may relay only the ID ‘A’ to which important status is given according to the status information. The user equipment750of H may broadcast a discovery message including “I am H”, but the user equipments730,740and760of C, D and E out of the range of reach may not recognize the user equipment750of H.

The user equipment720of B may relay a discovery message723′ including ‘H’ at predetermine periods although the rating of status information given to ‘H’ is lower than that of ‘A’. The user equipment720of B may temporarily raise the rating of ‘H’ or give a temporary status. The user equipment720of B may then broadcast the discovery message723′ that includes relay information ‘H&’ and status information on the rating of ‘B’ temporarily raised or temporary status.

The user equipment730of C that receives the discovery message723′ may broadcast a discovery message733′ including ‘H&&’ according to the rating raised by the status information or the temporary status.

The user equipment740of D that receives the discovery message733′ and the user equipment760of E may obtain information for accessing the user equipment750of H through the user equipment730of C.

FIG. 14is a view provided to explain conditions for filtering a receiving of a discovery message according to an embodiment of the present disclosure.

Referring toFIG. 14, a user equipment1410of D may receive a plurality of discovery messages1421,1431and1441from a plurality of other user equipments1420,1430and1440. Referring to the received plurality of discovery messages1421,1431and1441, the IDs of the user equipments as broadcasting sources may be different from one another by ‘A’, ‘B’ and ‘C’, but the ID to be relayed may be the same as ‘A’ to which status information of importance is given.

The user equipment1410of D may create a discovery message1411based on a discovery message including relay information indicating the fewest number of times of relays from among a plurality of discovery messages including the same ID ‘A’. The user equipment1410of D may extract the relay information from the plurality of discovery messages and identify what the discovery message having the smallest number of times of relays of ‘A’ is. InFIG. 14, a discovery message1421for informing a user equipment1420itself may have the smallest number of times of relays. The user equipment1410of D may broadcast a discovery message1411that includes “I am D” for informing the user equipment1410itself and the ‘A&’ indicating that the ID is relayed once based on the discovery message1421.

In the same manner, a user equipment1450of E may receive a plurality of discovery messages1411and1461including ‘A’. The user equipment1450of E may reject the discovery message1461and broadcast a discovery message1451including ‘D’ as a broadcasting source and ‘A&&’ indicating that the ID is relayed twice based on the discovery message1411having the fewest number of times of relays.

The relay method of a discovery message allows a user equipment that receives a message to recognize the shortest path.

FIG. 15is a view provide to explain the number of cases of a direct communication system between equipments according to an embodiment of the present disclosure.

FIG. (A) shows user equipments1510and1511that support direct communication between equipments may directly broadcast and receive a discovery message. As shown inFIGS. 15(B) and 15(C), the transmission and relay of a discovery message may be through upper nodes1520,1521and1530.FIG. 15(B)shows that a discovery message may be transmitted and received by the base station1520that is disconnected to a network but performs a relay function.FIG. 15Cshows that a discovery message may be transmitted and received by a gateway1530that is disconnected to a network but performs a relay function between the base stations1520and1521.

Such the relay of an upper node may expand the range of broadcasting a discovery message of a user equipment beyond a macro cell range.

FIG. 16is a view provided to explain a first communication scenario to which mobile communication between equipments is applied according to an embodiment of the present disclosure.

The staffs of the fire agency and the staffs of the police agency involved in a disaster site may include a fire chief and a police chief to manage the disaster. The ID of a user equipment1610of the fire chief may be given status information corresponding to the role of the fire chief in accordance with the organization structure of a command system to manage the disaster site. The ID of a user equipment1620of the police chief may be given status information corresponding to the role of the police chief.

The user equipment1610of the fire chief and the user equipment1620of the police chief may broadcast a discovery message including its respective ID. However, the user equipments1610and1620may be at a distance where a broadcasting signal is not directly detected.

User equipments1630and1640each may relay a discovery message at a distance close to the user equipment1610of the fire chief and the user equipment1620of the police chief.

Since the relay helps recognize the presence of the user equipments and the communicable paths, the police chief may make a phone call for requesting a helicopter to the fire chief by using the user equipment1620.

FIG. 17is a view provided to explain a second communication scenario to which mobile communication between equipments is applied according to an embodiment of the present disclosure.

Referring toFIG. 17, members of the fire department team A may be dispersedly located across the huge disaster area. A leader1710of the fire department team A in charge of the operations may not be available. As a result, a member1720having a higher rank may be determined as a temporary leader of the fire department team A.

Such situation may lead to modification of the ratings given to the IDs. Specifically, the user equipment of the temporary leader1720of the fire department team A may broadcast a discovery message including an ID, a state where a temporary leader is assigned, and status information corresponding to a leader. The broadcasted discovery message may also be transmitted to a user equipment in a range where the signal broadcasted from the user equipment of the temporary leader1720does not reach by the relays of user equipments of the other members1730and1740.

The user equipment which receives a discovery message may modify the rating corresponding to the ID of the user equipment of the temporary leader1720to the rating corresponding to a user equipment of a leader.

FIG. 18is a view provided to explain a third communication scenario to which mobile communication between equipments is applied according to an embodiment of the present disclosure.

Referring toFIG. 18, a user1810may call a taxi without accessing a network. The user equipment of the user1810may gradually increase the intensity of a broadcasting signal1811and broadcast a message for searching for a taxi nearby.

User equipments1820and1830that receive broadcasting signals of the user equipment of the user1810may relay discovery messages through respective broadcasting signals1821and1831.

An equipment device of a taxi1840may receive the relayed discovery message of a user1811. The equipment device of the taxi1840may transmit a response message including the position of the taxi1840to the user equipment1830for the user1810. The response message of the equipment device of the taxi1840may be transmitted to the user equipment of the user1810through the relays of the user equipments1820and1830. By repeating the above procedure, the user1810may recognize the taxi1840at the shortest distance from the user180and at which exact position the taxi1840is located. The user1810may make a phone call to a taxi driver and inform the taxi driver of the place and time to take a taxi.

FIG. 19is a view provided to explain a fourth communication scenario to which mobile communication between equipments is applied according to an embodiment of the present disclosure.

Referring toFIG. 19, a large-scale mountain bike crew may move toward the shaded mountain. There is a leader1910in crew. Some part of the crew members1940may still be a cell phone coverage1951.

The ID of a user equipment of the leader1910ahead of all members may be distributed to user equipments of crew members by the broadcasting of the discovery message and the relay of the discovery message by other user equipments1920and1930located in the middle. The ID of a user equipment that is connectable to a base station1950and located at the back may also be distributed to the user equipments of the crew members by the broadcasting of the discovery message and the relay of the discovery message by the user equipments1920and1930.

FIG. 20is a view provided to explain a user interface screen according to an embodiment of the present disclosure.

Referring toFIG. 20, a user equipment2010may display a user interface screen2020. The user interface screen2020may include graphic objects indicating the user equipment2010and other user equipments. The user interface screen2020may include a plurality of concentric circles based on a route2030indicating the user equipment2010. The user interface screen2020may include nodes2040indicating other user equipments along the circumferences of the plurality of concentric circles. Nodes corresponding to other user equipments capable of communication without relay may be arranged on the circumference closest to the route2030. On the next circumference, nodes corresponding to other user equipments capable of communication after one relay may be arranged. On the following circumference, nodes corresponding to other user equipments capable of communication after two relays may be arranged.

Nodes located on three circumferences may be connected through bridges indicating communicable relations. The bridge may show a path all the way through to a node for communication.

A user may select a node2050displayed on the interface screen2020by touching. The user equipment2010may transmit a request message for communication connection to the neighboring user equipment which is relayed to another user equipment corresponding to the node2050selected by the user.

FIG. 21is a flowchart provided to explain a communication method of a user equipment according to an embodiment of the present disclosure.

Referring toFIG. 21, a user equipment may receive at least one discovery message from another user equipment at step S2110. A user equipment may receive broadcasting of a discovery message created for informing another user equipment itself and relaying discovery messages of other neighboring user equipments from another user equipment.

At least one ID may be extracted from the received discovery message at step S2120. The user equipment may extract at least one ID, for example, the ID of another user equipment or the relayed ID from one or a plurality of discovery messages broadcasted from another user equipment.

At least one ID may be selected from the IDs extracted based on the status information at step S2130. The user equipment may select at least one ID from the IDs extracted based on the status information indicating importance of another user equipment.

The discovery message including the selected ID may be broadcasted at step S2140. The user equipment may broadcast a discovery message for relaying the ID of the important user equipment selected based on the status information.

The above communication method may further include storing IDs of user equipments constituting a group which is provided with service for direct communication between equipments and status information given to the IDs, and selecting at least one ID from the IDs extracted by retrieving the stored status information.

The status information may be represented by ratings indicating priorities, and the ID having a highest priority may be selected from among the plurality of IDs extracted based on the ratings.

The broadcasted discovery message may further include relay information indicating the number of times the ID is relayed. The communication method may further include extracting relay information, adding the number of times of relays as once, and relaying a discovery message including the ID.

The communication method may further include visually displaying nodes representing one or a plurality of user equipments that relay the extracted ID and bridges representing paths the extracted ID is relayed, and in response to a user input selecting one or a plurality of nodes displayed on the display being received, creating a channel for communication with another user equipment.

The communication method according to an embodiment of the present disclosure may relay information for identifying a user equipment of an important user to another user equipment by using a discovery message of a limited size. The communication method may be implemented on a user equipment having the configuration ofFIG. 2, or on other communicable devices.

While the present disclosure has been described that all elements of an embodiment are coupled to one another or operate in combination, it is to be understood that the present disclosure is not limited to the disclosed embodiments. That is, within the scope of the present disclosure, all of the elements may be selectively coupled to one another in one or more of combinations. In addition, although all of the elements may be implemented as one independent hardware, some or all of the elements may be selectively combined to embody as a computer program including a program module performing a part or all of the functions in one or a plurality of hardware. The codes and code segments that constitute a computer program may be easily deduced by those skilled in the art. Such a computer program may be stored in a non-transitory computer readable medium readable by a computer, readable and executed by a computer, thereby realizing an embodiment of the present disclosure.

The non-transitory readable recording medium may not be a medium for storing data for a short time such as a register, a cache, a memory, etc., but mean a medium that semi-permanently stores data and is readable by a device. Specifically, the above-described programs may be stored in non-volatile readable recording media such as CD, DVD, hard disk, Blu-ray disk, USB, memory card, ROM, etc.

Although exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles and spirit of the present disclosure. Accordingly, the scope of the present disclosure is not construed as being limited to the described exemplary embodiments, but is defined by the appended claims as well as equivalents thereto.