JP6385298B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system including a terminal and a base station.

  2. Description of the Related Art Conventionally, a system that can confirm the safety of a person when a disaster occurs is known. For example, Patent Document 1 discloses a safety confirmation system in which a safety confirmation server and a plurality of terminals are connected as such a system. Specifically, each of the plurality of terminals exchanges terminal information by short-range communication with other terminals. The safety confirmation server transmits an inquiry signal to another terminal for a terminal that has not received a response signal among terminals that have transmitted the confirmation signal. Further, the terminal having the terminal information included in the inquiry signal transmits the terminal information to the safety confirmation server.

  Further, conventionally, terminal-to-terminal (D2D: device to device) communication in which terminals (terminals: User Equipment) communicate with each other without using a base station (eNB: evolved NodeB) is known. D2D communication is also referred to as D2D Proximity Services (ProSe). Proximity Services is standardized in Release 12 of 3GPP (3rd Generation Partnership Project) as shown in Patent Documents 1 to 3. In particular, Patent Document 2 discloses “Proximity discovery” (hereinafter referred to as “D2D discovery service”), which is a proximity detection service in D2D Proximity Services.

  The D2D discovery service can be executed by an LTE (Long Term Evolution) terminal having a D2D discovery function and an application program using D2D Proximity Services. In addition, a service that enables proximity detection between terminals located in a range where the eNB supports D2D discovery is being studied.

  In the D2D discovery service, by executing an application program that uses D2D Proximity Services, a terminal can be arbitrarily selected from a radio resource pool dedicated for discovery assigned by an eNB or a radio resource pool set in advance by a SIM (Subscriber Identity Module) or the like. One or more resources (blocks) are selected and a discovery signal is transmitted. As a result, the terminal notifies its own existence to other terminals. Also, the terminal receives all or part of the radio resources for discovery in order to discover the presence of other terminals.

  The discovery signal includes a ProSe (Proximity Service) UE ID and a ProSe Application ID. The ProSe Application ID is a dedicated ID assigned for each application program. Therefore, each of the plurality of application programs using D2D makes a transmission request for a discovery signal including ProSe Application ID to the control unit of the own terminal. Each application program can identify the presence of another terminal that is executing the same application program based on the discovery signal of the other terminal received at the terminal. At that time, the terminal notifies the user of the terminal by displaying the identification result on the display.

JP 2013-149058 A

3GPP TR 36.843 V12.0.1 (2014-03): 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Study on LTE Device to Device Proximity Services; Radio Aspects (Release 12) 3GPP TR 23.703 V12.0.0 (2014-02): 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on architecture enhancements to support Proximity-based Services (ProSe) (Release 12) 3GPP TS 23.303 V12.1.0 (2014-06): 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Proximity-based services (ProSe); Stage 2 (Release 12)

  In the technique of Patent Document 1, in response to an inquiry from a safety confirmation server at the time of a disaster, each of a plurality of terminals transmits safety information of its own terminal and other terminals that have exchanged information by short-range communication at each timing. . Therefore, the communication traffic in the safety confirmation system increases due to the short-distance communication traffic between the terminals and the communication traffic between the terminals and the safety confirmation server.

  The present invention has been made in view of the above problems, and an object thereof is to provide a communication system capable of reducing communication traffic at the time of a disaster.

  According to an aspect of the present invention, a communication system includes a base station, and a first terminal and a second terminal capable of inter-device communication. Each of the first terminal and the second terminal can transmit a discovery signal used to notify the partner terminal of at least the presence of the terminal without going through the base station. The first terminal transmits the discovery information including the first information for confirming the safety of the person. When the second terminal receives the discovery signal including the first information from the first terminal, the second terminal includes the second information for notifying the safety of the first terminal and transmits the discovery information. . The first terminal receives a discovery signal including the second information from the second terminal.

  According to the present invention, it is possible to reduce communication traffic during a disaster.

1 is a diagram for explaining a schematic configuration of a communication system 1. FIG. It is a figure for demonstrating the example of transmission / reception of the discovery signal in the radio | wireless resource pool of the subframe for discovery. It is a functional block diagram for demonstrating the functional structure of UE11. It is a figure for demonstrating the functional structure of eNB21. 3 is a sequence chart for explaining the flow of processing performed in the communication system 1; 4 is a flowchart for explaining a flow of processing performed in an eNB 21. It is a flowchart for demonstrating the flow of the process performed in UE11. It is a flowchart for demonstrating the flow of the process performed in UE12. It is a figure for demonstrating schematic structure of the communication system 1A which is a modification of the communication system. It is a sequence chart for demonstrating the flow of the process performed in the communication system 1A. It is a flowchart for demonstrating the flow of the process performed in UE11 of the communication system 1A. It is a functional block diagram for demonstrating the structure of the discovery signal transmission part 1561 (refer FIG. 3). It is a figure for demonstrating the hardware constitutions of UE11.

  The communication system according to each embodiment of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals are assigned to the same members. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Hereinafter, the application program is referred to as “application” for short.

<A. System configuration>
FIG. 1 is a diagram for explaining a schematic configuration of the communication system 1. Specifically, FIG. 1 is a diagram showing a communication state in a certain situation. Specifically, FIG. 1 is a diagram illustrating a state in which the operation of one eNB (specifically, an eNB 22 described later) is stopped due to a disaster.

  Referring to FIG. 1, the communication system 1 includes a plurality of UEs (User Equipment) 11 to 14, a plurality of eNBs (evolved NodeBs) 21 and 22, and an MME (Mobility Management Entity) 30. The eNBs 21 and 22 and the MME 30 are connected via a wired communication. The MME 30 is connected to the external network NW.

  The MME 30 is a node that performs mobility management such as location registration of mobile stations, calling, and handover between base stations. The MME 30 communicates with the eNBs 21 and 22 via a gateway (not shown).

  The eNB 21 and the eNB 22 are adjacent to each other. The eNB 21 configures the cell 291. The eNB 22 configures the cell 292. The UE 11 is located in the cell 291 and communicates with the eNB 21. Although UE12-14 is located in the cell 292, since eNB22 has stopped, it cannot communicate with eNB22.

  Each of the plurality of UEs 11 to 14 can perform D2D communication (communication between devices that performs direct communication) with other UEs that exist nearby without going through the eNB. Specifically, each of the UEs 11 to 14 is an LTE terminal (a portable terminal conforming to the LTE standard) having a D2D discovery function. Typically, UEs 11-14 are smartphones.

  A plurality of applications that use the D2D discovery service (hereinafter also referred to as “D2D-compatible applications”) are installed in advance in the UEs 11 to 14. The D2D-compatible application is an application that can use the D2D Proximity Service as described above. Examples of D2D-compatible applications include various applications such as SNS, games, advertisements, and communication applications in addition to disaster information application # 1 described later.

  The UEs 11 to 14 are assigned “ProSe UE ID” as an identifier of a terminal capable of executing D2D Proximity Services. In the communication system 1, the eNBs 21 and 22 control D2D communication authentication, radio resource pool allocation, generation of timing reference signals, and the like on the condition that the operation is not stopped. It is also possible to cause the UE to perform the above control instead of the eNB.

  The UE 11 arbitrarily selects a radio resource for transmitting a D2D discovery signal based on the radio resource pool information from the eNB 21. Moreover, UE11 and UE12-14 perform transmission / reception of a discovery signal mutually, without going through eNB21 and 22 (that is, without receiving allocation of a radio | wireless resource by eNB). Note that when the eNB 22 is not stopped, the UEs 12 to 14 arbitrarily select a radio resource for transmitting a D2D discovery signal based on the radio resource pool information from the eNB 22.

  Each of the UEs 11 to 14 transmits a discovery signal for notifying the surrounding UEs of the existence of the UE itself using a radio resource for arbitrarily transmitting a discovery signal. Although details will be described later, the discovery signal includes at least a ProSe Application ID for identifying an application and a ProSe UE ID for identifying a UE.

  The explanation is supplemented as follows. In D2D communication, studies are currently being conducted on the assumption that communication and UE are discovered on an application basis. Specifically, an ID is assigned to each application, and the UE sends a discovery signal including the ID to be detected by the partner UE.

  Hereinafter, when the eNBs 21 and 22 are not distinguished from each other, they are simply described as “eNB 20”. Further, when the UEs 11 to 14 are not distinguished, they are simply referred to as “UE10”.

<B. Outline of processing>
Hereinafter, an outline of processing in the communication system 1 will be described.

  The UE 11 transmits information for confirming the safety of the person included in the discovery signal. When each of the UEs 12 to 14 receives a discovery signal including information for confirming the safety of a person from the UE 11, the UE 12 to 14 includes the information for notifying the safety of the UE 11 and transmits the discovery signal. UE11 receives the discovery signal containing the information (henceforth "safety information") for notifying safety from each of UE12-14.

  Through the above processing, the UE 11 can obtain safety information from each of the UEs 12 to 14. The discovery signal is multicast. Each of the UEs 11 to 14 receives the discovery signal. Therefore, an increase in communication traffic can be suppressed as compared with the conventional configuration in which terminals communicate individually when a disaster occurs. Furthermore, since an increase in communication traffic is suppressed, the occurrence of congestion can be suppressed.

  In addition, since the discovery signal has a small amount of data, the data processing load of the UE on the reception side of the discovery signal is small. Therefore, the power consumption of the UE on the receiving side can be reduced.

<C. Terminology>
Hereinafter, terms used in the present embodiment will be described.

  (1) “Disaster information app” typically means (i) transmitting the safety information of the user of the UE equipped with the disaster information app, (ii) collecting the status of surrounding users in a list It is an application that has functions such as displaying the safety status and (iii) collecting information collected on the bulletin board server. The disaster information application is, for example, a setting button for setting (for example, selecting or describing) its own safety information (safe, rescue required, etc.), a transmission button for transmitting safety information, a screen for displaying surrounding safety information, etc. It has.

  (2) A discovery signal including information for confirming the safety of a person is also referred to as “disaster information expression”. “Expression” means a code transmitted on the discovery signal.

  Specifically, the “information for confirming the safety of a person” is information for the user himself / herself who uses the disaster information application to confirm the safety of the user of the surrounding disaster information application. The information may include information such as a person's name for specifically identifying the surrounding people.

  Disaster information expressions are typically useful in the surrounding areas, such as “Prose UE ID”, “Prose Application ID”, information for confirming the safety of people around you, and information that represents a safe place. Information.

  (3) A discovery signal including information for notifying safety is referred to as “safety information expression”. More specifically, the “information for notifying safety” is information representing the user's own situation (for example, safe, injured, need help, etc.) of the disaster information application. The safety information expression typically includes “Prose UE ID”, “Prose Application ID”, and information for notifying safety.

<D. Discovery signal transmission / reception example>
FIG. 2 is a diagram for explaining an example of discovery signal transmission / reception in a radio resource pool of a subframe for discovery. Referring to FIG. 2, radio resource pools P1, P2, P3,... Are assigned as subframes for discovery by eNB 21 and eNB 22 in a predetermined frequency band.

  Further, the discovery subframe is allocated from the eNB as a radio resource pool that is a set of a plurality of radio resources divided by time and frequency. Each UE arbitrarily selects one or a plurality of radio resources from the radio resource pool, and transmits a discovery signal using the radio resources. Hereinafter, LTE subframes assigned for transmission / reception of discovery signals such as the radio resource pools P1, P2, and P3 are referred to as “discovery subframes”.

  In particular, FIG. 2 illustrates a format in which one application discovery signal is transmitted using one radio resource. In one discovery subframe, a plurality of users transmit discovery signals for a plurality of applications. For example, in FIG. 2, in the radio resource pool P1, the user of the UE 11 is transmitting a discovery signal (in this case, disaster information expression) of the disaster information application # 1. Further, in the radio resource pool P2, each user of the UEs 12 to 14 transmits a discovery signal (in this case, safety information expression) of the disaster information application # 1.

  In addition, discovery signals of three types of apps # 1, # 2, and # 3 are transmitted in the wireless resource pools P1 and P2. Depending on the standard, discovery signals of a plurality of applications may be transmitted using one radio resource. Alternatively, a discovery signal for one application may be transmitted using a plurality of radio resources.

  A detailed description of the discovery subframe is as follows. The D2D communication can be applied to LTE using a TDD (Time Division Duplex) method and LTE using an FDD (Frequency Division Duplex) method.

  In the case of FDD LTE, a part of the uplink subframes of the uplink channel is allocated for discovery. The UE 10 transmits and receives a discovery signal using an LTE subframe (that is, a discovery subframe) assigned for the discovery. The period of the discovery subframe can be set to 10 to 20 seconds, for example.

  In the case of TDD LTE, an uplink subframe, a downlink subframe, and a D2D subframe are switched in a time frame at the same frequency. For example, the usage of the subframe is switched in the order of the uplink subframe, the downlink subframe, the discovery subframe, the uplink subframe, and so on.

  Note that there is no distinction between transmission and reception in discovery subframes. Discovery signals are transmitted and received in one discovery subframe.

<E. Functional configuration>
(E1.UE)
FIG. 3 is a functional block diagram for explaining the functional configuration of the UE 11. Referring to FIG. 3, UE 11 includes an application execution unit 151, a D2D management unit 152, a GUI (Graphical User Interface) unit 153, a storage unit 154, a reception unit 155, and a transmission unit 156. . The GUI unit 153 includes a display unit 1531 and an input unit 1532. The receiving unit 155 includes a D2D discovery signal receiving unit 1551. The transmission unit 156 includes a discovery signal transmission unit 1561.

  The application execution unit 151 reads out D2D-compatible disaster information application # 1, application # 2, application # 3,... Stored in advance in the storage unit 154 from the storage unit 154, and executes each application. Hereinafter, a configuration in which settings for performing D2D communication (settings such as a user ID and a ProSe Application ID) are performed will be described as an example. Each application # 1, # 2, # 3,... That is executing sends a discovery signal transmission / reception request to the D2D management unit 152 when transmission / reception of the discovery signal becomes necessary.

  The D2D management unit 152 manages various processes related to D2D communication. Specifically, when receiving a discovery signal transmission / reception request transmitted from each application # 1, # 2, # 3,..., The D2D management unit 152 manages (controls) discovery signal transmission / reception.

  The display unit 1531 of the GUI unit 153 displays various types of information. The input unit 1532 receives various inputs from the user.

  The receiving unit 155 receives data transmitted from the eNB (eNB 21 in the case of FIG. 1) and various data (user data and the like) transmitted from other UEs (UEs 12 to 14 in the case of FIG. 1). Receive. In particular, the discovery signal receiving unit 1551 of the receiving unit 155 receives a discovery signal (for example, safety information expression) transmitted from another UE.

  The transmission unit 156 transmits data (such as user data) to the eNB (eNB 21 in the case of FIG. 1) or to other UEs in the case of D2D communication. In particular, the discovery signal transmission unit 1561 transmits a discovery signal (for example, disaster information expression). Specifically, a discovery signal corresponding to each application is multicast transmitted on condition that each application is activated and executed.

  In addition, since UE12-14 has the same functional structure as UE11, the functional structure of UE12-14 is not demonstrated repeatedly.

(E2. ENB)
FIG. 4 is a diagram for explaining a functional configuration of the eNB 21. With reference to FIG. 4, the eNB 21 includes a main control unit 251, a storage unit 252, a communication control unit 253, a wireless communication unit 254, and an antenna 255.

  The main control unit 251 controls the overall operation of the eNB 21. The main control unit 251 corresponds to the CPU. More specifically, the main control unit 251 is realized by the CPU executing an OS (Operating System) and various programs.

  The storage unit 252 stores the OS, various programs, and various data received (acquired) from the eNB 20. The storage unit 252 includes a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), and the like.

  The communication control unit 253 controls communication with the UE located in the cell 291 configured by the eNB 21 and communication with the MME 30. The wireless communication unit 254 performs various processes for transmitting data from the antenna 255 and various processes for receiving a signal received by the antenna 255. The wireless communication unit 254 typically performs baseband conversion and the like.

  In addition, since eNB22 also has the functional structure similar to eNB21, the functional structure of eNB22 is not demonstrated repeatedly.

<F. Control structure>
(F1. Communication system 1)
FIG. 5 is a sequence chart for explaining the flow of processing performed in the communication system 1. Referring to FIG. 5, in sequence SQ2, UE 11 transmits position information indicating the current location of UE 11 to eNB 21 configuring cell 291 that is located. In sequence SQ <b> 4, UEs 12 to 14 transmit location information representing their current locations to eNB 22 configuring cell 292.

  In sequence SQ6, the eNB 21 performs radio resource control for each of normal communication via the eNB 21 and D2D communication not via the eNB 21 with respect to the UE 11. Radio resource control includes authentication, resource pool allocation, synchronization processing, and the like. In sequence SQ8, the eNB 22 performs radio resource control for each of the normal communication via the eNB 22 and the D2D communication not via the eNB 22 for each of the UEs 12 to 14.

  It is assumed that a disaster occurs after these processes, and the eNB 22 stops operating (stops function) in sequence SQ10.

  The user of UE11 starts disaster information application # 1. The user of the UE 11 creates information for confirming the safety of the person using the UI of the disaster information application # 1 (fills in, selects, etc.). In the sequence SQ12, the UE 11 typically transmits the disaster information expression by multicast based on the transmission instruction by the user based on the completion of the creation of the information for confirming the safety of the person.

  Each of the UEs 12 to 14 receives a disaster information expression. Each of the UEs 12 to 14 displays the content of “information for confirming the safety of a person” included in the disaster information expression on the condition that the disaster information application # 1 is activated. Each user of UE12-14 creates using information for notifying safety using disaster information application # 1 (it fills in, selects, etc.). In sequence SQ14, each of the UEs 12 to 14 typically transmits a safety information expression by multicast based on a transmission instruction from the user based on the completion of creation of information for confirming the safety of a person.

(F2. ENB 21, 22)
FIG. 6 is a flowchart for explaining the flow of processing performed in the eNB 21. FIG. 6 is also a flowchart for explaining the flow of processing performed in the eNB 22 before the operation stops.

  With reference to FIG. 6, in step S2, eNB21 acquires the positional information on UE (specifically UE11) located in the cell 291 which eNB21 comprises. In step S4, the eNB 21 performs radio resource control so that the UE located in the cell 291 can perform D2D communication. In addition, as above-mentioned, eNB21 also performs the radio | wireless resource control regarding normal communication via eNB21.

(F3.UE11)
FIG. 7 is a flowchart for explaining the flow of processing performed in the UE 11. Referring to FIG. 7, in step S12, UE 11 starts communication with eNB 21 in the normal communication mode, for example, when entering cell 291 or when the power is turned on. In step S14, the UE 11 receives a control signal for D2D communication (specifically, a signal for radio resource control) from the eNB 21. After this, it is assumed that a disaster has occurred.

  In step S16, the UE 11 determines whether or not the disaster information application # 1 is activated. As described above, the disaster information application # 1 is activated by a user operation. When it is determined that it is activated (YES in step S16), in step S18, the UE 11 determines whether communication with the eNB 21 is possible. When it is determined that it has not been activated (NO in step S16), UE 11 advances the process to step S16.

  When it is determined that communication is possible (YES in step S18), in step S20, the UE 11 receives input of information for confirming the safety of the person. When the operation of eNB 21 is also stopped and it is determined that communication is not possible (NO in step S18), UE 11 advances the process to step S16.

  In step S22, UE11 transmits the disaster information expression containing the information for the safety confirmation input. In step S24, UE11 receives the safety information expression which each of UE12-14 transmitted.

(F4. UE12-14)
FIG. 8 is a flowchart for explaining the flow of processing performed in the UE 12. FIG. 8 is also a flowchart for explaining the flow of processing performed in the UEs 13 and 14.

  Referring to FIG. 8, in step S102, UE 12 starts communication with eNB 22 in the normal communication mode, for example, when entering cell 292 or when power is turned on. In step S <b> 104, the UE 12 receives a control signal for D2D communication (specifically, a signal for radio resource control) from the eNB 22. After this, it is assumed that a disaster has occurred.

  In step S106, the UE 12 determines whether or not the disaster information application # 1 is activated. When it is determined that it is activated (YES in step S106), in step S108, the UE 12 determines whether communication with the eNB 22 is possible. If it is determined that it has not been activated (NO in step S106), UE 12 causes the process to proceed to step S106.

  If it is determined that the operation of the eNB 22 is stopped and communication is impossible (NO in step S108), in step S110, the UE 12 receives the disaster information expression multicasted by the UE 11. In step S112, the UE 12 decodes the received disaster information expression.

  In step S114, the UE 12 accepts input of information for confirming the safety of the person. In step S116, the UE 12 transmits a safety information expression including the input safety information.

  When the operation of the eNB 22 is not stopped and it is determined that communication is possible (YES in step S108), in step S118, the UE 12 receives the disaster information expression multicasted by the UE 11. In this case, the UE 12 ends the series of processes without decoding the received disaster information expression.

  As described above, the UE 12 transmits a safety information expression (a discovery signal including safety information) to the UE 11 on condition that communication with the eNB 22 is not possible.

<G. Modification>
Next, a modified example of the communication system 1 will be described.

(First modification)
FIG. 9 is a diagram for explaining a schematic configuration of a communication system 1A that is a modification of the communication system 1. Specifically, FIG. 9 is a diagram illustrating a state in which the operation of the eNB 22 is stopped due to a disaster.

  With reference to FIG. 9, the communication system 1 </ b> A includes a plurality of UEs 11 to 14, a plurality of eNBs 21 and 22, an MME 30, and a server 40. The communication system 1A is different from the communication system 1 in that the server 40 is provided.

  The server 40 is connected to the MME 30 via an external network NW by wire. The server 40 functions as a bulletin board server that posts safety information.

  Although details will be described later, in the communication system 1, the safety information included in the safety information expression received by the UE (UE11 in the case of FIG. 9) is transmitted via the operating eNB (in the case of FIG. 9, the eNB 21). , Transmitted to the server 40. UE11 transmits each safety information received from each UE12-14 as user data with respect to eNB21.

  FIG. 10 is a sequence chart for explaining the flow of processing performed in the communication system 1A. Referring to FIG. 10, sequences SQ2 to SQ14 are the same as those in FIG. For this reason, the description of the processes from sequences SQ2 to SQ14 will not be repeated.

  In sequence SQ16 after sequence SQ14, UE11 transmits the safety information received from each UE12-14 to eNB21. In sequences SQ18 and SQ20, the eNB 21 transmits the received safety information to the server 40 via the MME 30.

  Therefore, the server 40 stores a plurality of safety information. Therefore, a user such as a UE that can access the server 40 can check the safety of others based on the stored safety information.

  FIG. 11 is a flowchart for explaining a flow of processing performed in the UE 11 of the communication system 1A. Referring to FIG. 11, steps S12 to S24 are the same as those in FIG. For this reason, description about the process from step S12 to S24 is not repeated.

  In step S26 after step S24, the UE 11 extracts safety information from the safety information expressions sent from the UEs 12 to 14, and transmits the extracted safety information to the eNB 21. At this time, if the safety information itself does not include information for identifying an individual, the UE 11 transmits the safety information to the eNB 21 in a state where the ProSe UE ID included in the safety information expression is associated with the safety information.

  As described above, the UE 11 notifies the server 40 of the safety information via the eNB 21 based on the reception of the safety information expression (discovery signal including the safety information) from the UE 12.

(Second modification)
Next, the structure which reduces the collision between the signals (refer FIG. 2) of each application # 1, # 2, # 3 is demonstrated. FIG. 12 is a functional block diagram for explaining the configuration of the discovery signal transmission unit 1561 (see FIG. 3).

  Referring to FIG. 12, discovery signal transmission section 1561 includes a radio resource allocation section 1591 and a data generation section 1592. The data generation unit 1592 generates data to be transmitted by D2D communication in addition to the discovery signal based on the application data.

  By the way, according to the 3GPP specifications, the arrangement of discovery signals (including disaster information expressions and safety information expressions) on the radio resource pool is random, and collision may occur. Accordingly, the radio resource allocating unit 1591 uses a hash function as an example to detect a discovery signal on the radio resource pool from ID information such as IMEI (International Mobile Equipment Identifier), IMSI (International Mobile Subscriber Identity), and ProSe UE ID. Determine the placement.

  Specifically, the radio resource allocation unit 1591 of the UE 11 selects one or a plurality of radio resources in the radio resource pool allocated by the eNB 21. Further, the discovery signal transmission unit 1561 transmits a discovery signal such as a disaster information expression and a safety confirmation expression using the selected radio resource. The radio resource allocation unit 1591 determines the arrangement of discovery signals so that discovery signals are not allocated to the same radio resource in the radio resource pool using a predetermined function such as a hash function.

  According to said structure, the collision of a discovery signal can be reduced. Therefore, the UE 11 can collect the safety information of each of the UEs 12 to 13 with the smallest possible number of receptions. It also leads to a reduction in retransmission, resulting in a reduction in congestion. Furthermore, since processing is reduced, power consumption can be suppressed.

(Third Modification)
In the above, for example, as illustrated in FIG. 1, the case where the UE 12 to 14 cannot communicate with the eNB 21 due to the operation of the eNB 22 where the UEs 12 to 14 are located being stopped due to a disaster is given as an example. However, the present invention is not limited to this.

  In the various processes described above, for example, the UEs 12 to U14 are located in the cell 291 configured by the eNB 21 at the time of disaster occurrence or immediately before, and cannot communicate with any base station in the communication system 1 after the disaster occurrence. It can also be applied to cases where

<H. Hardware configuration>
FIG. 13 is a diagram for explaining the hardware configuration of the UE 11. Referring to FIG. 13, UE 11 has a CPU 101 that executes various programs including applications # 1, # 2, # 3..., ROM (Read Only Memory) 102, RAM (Random Access Memory) 103, flash It includes at least a memory 104, operation keys 105, a speaker 106, a camera 107, a touch screen 108, a wireless communication IF (Interface) 109, an antenna 110, and a reader / writer 111. The touch screen 108 includes a display 1081 and a touch panel 1082. The components 101 to 109 and 111 are connected to each other by a data bus.

  The reader / writer 111 can be loaded with a memory card 900 and records information on the memory card 900 or reads information from the memory card 900.

  The antenna 110 is connected to the wireless communication IF 109. The antenna 110 and the radio communication IF 109 are used for radio communication with another UE, a fixed telephone, and a PC (Personal Computer) via eNB, for example.

  The ROM 102 is a nonvolatile semiconductor memory. The ROM 102 stores a boot program for the UE 11 in advance. The flash memory 104 is a nonvolatile semiconductor memory. The flash memory 104 may be configured as a NAND type as an example. The flash memory 104 stores various data such as an operating system of the UE 11, various programs for controlling the UE 11, data generated by the UE 11, and data acquired from an external device of the UE 11 in a volatile manner.

  The processing in the UE 11 is realized by software executed by each hardware and the CPU 101. Such software may be stored in the flash memory 104 in advance. The software may be stored in a memory card 900 or other storage medium and distributed as a program product. Alternatively, the software may be provided as a program product that can be downloaded by an information provider connected to the so-called Internet. Such software is downloaded via the antenna 110 and the wireless communication IF 109 and then temporarily stored in the flash memory 104. The software is read from the flash memory 104 by the CPU 101 and further stored in the flash memory 104 in the form of an executable program. The CPU 101 executes the program.

  An essential part of the present invention can be said to be software stored in the flash memory 104 or other storage medium, or software that can be downloaded via a network. The recording medium is not limited to DVD-ROM, CD-ROM, FD, and hard disk, but is fixed such as semiconductor memory such as magnetic tape, cassette tape, optical disk, optical card, mask ROM, EPROM, EEPROM, and flash ROM. A medium carrying a program may be used. The recording medium is a non-temporary medium that can be read by the computer. The program here includes not only a program directly executable by the CPU but also a program in a source program format, a compressed program, an encrypted program, and the like.

  Note that the hardware configurations of the UEs 12, 13, and 14 are the same as those of the UE 11, and thus will not be described repeatedly here.

  The embodiment disclosed this time is an exemplification, and the present invention is not limited to the above contents. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 1A communication system, 40 servers, 151 application execution unit, 152 D2D management unit, 154, 252 storage unit, 155 reception unit, 156 transmission unit, 251 main control unit, 253 communication control unit, 254 wireless communication unit, 291 292 cell, 1551 discovery signal reception unit, 1561 discovery signal transmission unit, 1591 radio resource allocation unit, 1592 data generation unit, 109 radio communication IF, NW external network, P1, P2, P3 radio resource pool.

Claims (5)

A communication system comprising a base station and a first terminal and a second terminal capable of inter-device communication,
Each of the first terminal and the second terminal can transmit a discovery signal used to notify the partner terminal of at least the presence of the terminal without going through the base station,
The first terminal transmits first information for confirming the safety of a person included in the discovery signal,
When the second terminal receives a discovery signal including the first information from the first terminal, the second terminal sends second information for notifying the safety to the first terminal. Send it in the signal,
The communication system, wherein the first terminal receives a discovery signal including the second information from the second terminal.   The communication system according to claim 1, wherein the second terminal transmits a discovery signal including the second information to the first terminal on condition that communication with the base station is not possible.   The communication system according to claim 1 or 2, wherein the discovery signal is transmitted by a predetermined application corresponding to the inter-device communication.   The first terminal receives the second information from the second terminal to a predetermined server device via the base station based on the reception of the discovery signal including the second information. The communication system according to any one of claims 1 to 3, wherein: Each of the first terminal and the second terminal is
In the radio resource pool allocated by the base station, select one or more radio resources, and transmit the discovery signal using the selected radio resources,
The arrangement | positioning of the said discovery signal is determined so that the said discovery signals may not allocate to the same radio | wireless resource in the said radio | wireless resource pool using a predetermined function. Communications system.