JP2017200223A - User terminal, mobile communication system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a user terminal which can suppress the duplication of a radio resource, when the user terminal performing D2D communication allocates the radio resource.SOLUTION: The user terminal includes a control unit which controls to search for another user terminal which has a specific function including reporting a radio resource to be used for the D2D communication. The control unit, after receiving from a first user terminal a first message which includes identification information indicating that the specific function is valid, performs processing to transmit to the first user terminal a second message to establish a connection with the first user terminal. After establishing the connection with the first user terminal in response to the reception of a third message in response to the second message from the first user terminal, the control unit halts to search for another user terminal which has the specific function. On detecting the deterioration of a reception state from the first user terminal, the control unit resumes the search for another user terminal which has the specific function.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a mobile communication system and a user terminal that support D2D communication.

  In 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, introduction of inter-terminal (Device to Device: D2D) communication is being studied as a new function after Release 12 (see Non-Patent Document 1).

  In D2D communication, a plurality of adjacent user terminals perform direct inter-terminal communication without going through a network. On the other hand, in cellular communication, which is normal communication of a mobile communication system, a user terminal performs communication via a network.

  Note that not only a case where a network device such as a base station performs the assignment of radio resources used for D2D communication, but also a case where a user terminal that performs D2D communication performs the assignment. When the user terminal that performs D2D communication assigns radio resources, the D2D communication can be performed even when the network situation is unstable due to, for example, the occurrence of a disaster such as an earthquake.

3GPP Technical Report “TR 22.803 V12.1.0” March 2013

  When a network situation is unstable due to the occurrence of a disaster, it is assumed that a network is constructed by a plurality of user terminals that perform D2D communication. In this case, when each user terminal assigns radio resources, there is a possibility that interference occurs due to duplication of radio resources.

  Therefore, an object of the present invention is to provide a mobile communication system and a user terminal that can suppress duplication of radio resources when a user terminal that performs D2D communication assigns radio resources.

  The user terminal which concerns on one Embodiment is a user terminal in the mobile communication system which supports D2D communication which is direct inter-terminal communication. The said user terminal is provided with the control part which performs control which searches for the other user terminal which has a specific function including notifying the radio | wireless resource used for the said D2D communication. The control unit receives a first message including identification information indicating that the specific function is valid from the first user terminal, and then establishes a connection with the first user terminal. The second message is transmitted to the first user terminal. The control unit establishes a connection with the first user terminal in response to receiving a third message corresponding to the second message from the first user terminal, and then performs the specific function. Stop searching for other user terminals. When the control unit detects a deterioration in the reception state from the first user terminal, the control unit resumes searching for another user terminal having the specific function.

  According to the mobile communication system and the user terminal according to the present invention, it is possible to suppress duplication of radio resources when a user terminal that performs D2D communication assigns radio resources.

FIG. 1 is a configuration diagram of an LTE system. FIG. 2 is a block diagram of the UE. FIG. 3 is a protocol stack diagram of a radio interface in the LTE system. FIG. 4 is a configuration diagram of a radio frame used in the LTE system. FIG. 5 is a diagram illustrating a data path in cellular communication. FIG. 6 is a diagram illustrating a data path in D2D communication. FIG. 7 is an explanatory diagram for explaining a situation where the scheduling UE 100 according to the present embodiment is broadcasting a message including identification information. FIG. 8 is an explanatory diagram for explaining a situation in which the scheduling UE 100 according to the present embodiment performs scheduling. FIG. 9 is an explanatory diagram for explaining a buffer status report according to the present embodiment. FIG. 10 is a flowchart for explaining the operation of the UE 100 according to the present embodiment. FIG. 11 is a sequence diagram illustrating an operation example in which the UE 100 according to the present embodiment connects to the scheduling UE 100. FIG. 12 is an explanatory diagram for describing an operating environment of case 1A in receiving a signal from another UE 100. FIG. 13 is a sequence diagram for explaining the operation of case 1A in receiving a signal from another UE 100. FIG. 14 is a sequence diagram for explaining an operation in case 1A in receiving a signal from another UE 100. FIG. 15 is an explanatory diagram for explaining the synchronization correction operation according to the embodiment. FIG. 16 is an explanatory diagram for describing an operating environment of case 2A in receiving a signal from another UE 100. FIG. 17 is an explanatory diagram for describing radio resources used when transmitting specific information in case 2A in receiving a signal from another UE 100. FIG. 18 is an explanatory diagram for explaining the operating environment of case 1B in the activation of the scheduling function. FIG. 19 is a sequence diagram for explaining the operation of case 1B in the activation of the scheduling function. FIG. 20 is a flowchart for explaining the operation of case 1B in the activation of the scheduling function. FIG. 21 is a sequence diagram for explaining the operation of case 2B in the activation of the scheduling function. FIG. 22 is a flowchart for explaining the operation of case 2B in the activation of the scheduling function.

[Outline of Embodiment]
The mobile communication system which concerns on embodiment is a mobile communication system which supports D2D communication which is direct communication between terminals. The mobile communication system includes a first user terminal having a scheduling function for allocating radio resources used for the D2D communication. When the scheduling function is valid, the first user terminal sends a message including identification information indicating that the first user terminal is a scheduling terminal that allocates the radio resource, periodically or aperiodically. Broadcast to.

  The mobile communication system according to the embodiment further includes a second user terminal that searches for the scheduling terminal. When the second user terminal detects a signal including the message by searching for the scheduling terminal, the second user terminal establishes at least synchronization with the first user terminal that broadcasts the message.

  In the mobile communication system according to the embodiment, the second user terminal is synchronized with the first user terminal using a signal including the message or a synchronization signal transmitted from the first user terminal. Establish.

  In the mobile communication system according to the embodiment, the second user terminal establishes a connection with the first user terminal in addition to the establishment of the synchronization.

  In the mobile communication system according to the embodiment, when the second user terminal detects a signal including the message, the second user terminal starts a random access procedure for establishing a connection with the first user terminal, One user terminal transmits a temporary identifier used for transmitting the radio resource allocated to the second user terminal to the second user terminal based on the random access procedure.

  In the mobile communication system according to the embodiment, the second user terminal omits transmission of information for connection in an RRC layer in the random access procedure, and the second user terminal is for the D2D communication. The connection in the RRC layer is performed using the setting value defined in advance.

  In the mobile communication system according to the embodiment, the first user terminal omits transmission of a contention resolution message used for determining success or failure of the random access procedure in the random access procedure.

  In the mobile communication system according to the embodiment, the second user terminal establishes only connection in the PHY layer with the first user terminal, and the second user terminal establishes connection in the PHY layer. After the establishment, it waits for a message in the PHY layer from the first user terminal.

  In the mobile communication system according to the embodiment, the second user terminal includes a receiving unit that receives data from the first user terminal, and the second user terminal is connected to the first user terminal. If there is no data to be transmitted / received after the establishment, the intermittent reception for intermittently starting the reception unit is performed.

  In the mobile communication system according to the embodiment, the second user terminal has the scheduling function, and when the second user terminal does not detect a signal including the message, the scheduling function is enabled. To do.

  In the mobile communication system according to the embodiment, the second user terminal activates the scheduling function when the signal including the message is not detected and the remaining battery capacity exceeds a threshold value.

  In the mobile communication system according to the embodiment, the first user terminal receives a buffer status report indicating an amount of untransmitted data from the second user terminal after establishing a connection with the second user terminal. Then, the first user terminal allocates the radio resource to the second user terminal according to the buffer status report.

  In the mobile communication system according to the embodiment, the untransmitted data is classified into a plurality of logical channel groups having different priorities, and the second user terminal transmits the untransmitted data of each of the plurality of logical channel groups. The first user terminal allocates the radio resource to the second user terminal according to the priority based on the buffer status report.

  In the mobile communication system according to the embodiment, after the first user terminal establishes a connection with the second user terminal, the first user terminal allocates the radio resource to the second user terminal, and the first user terminal Instead of performing a retransmission process for retransmitting the radio resource allocation information based on a retransmission request from the second user terminal, the user terminal may receive a request from the second user terminal or the second user terminal The radio resource allocation information is repeatedly transmitted according to the type of communication method between the two.

  The mobile communication system according to the embodiment further includes a third user terminal in which the first user terminal does not manage the allocation of the radio resource, and the first user terminal is connected to the third user terminal. When the signal including the message is detected and the synchronization timing between the third user terminal and the D2D communication is deviated, correction for matching the synchronization timing is performed.

  In the mobile communication system according to the embodiment, the first user terminal does not set the predetermined subframe of the first user terminal in order to match the synchronization timing, and the first user terminal The head of the next subframe after the predetermined subframe is made to coincide with the head of the subframe of the third user terminal.

  The mobile communication system according to the embodiment further includes a fourth user terminal that is different from the first user terminal and the second user terminal, and the second user terminal is connected to the first user terminal. The second user terminal includes the message from the fourth user terminal when the second user terminal detects a signal including the message from the fourth user terminal. Scheduling terminal information indicating that a signal has been detected is transmitted to the first user terminal.

  In the mobile communication system according to the embodiment, the second user terminal stops searching for the scheduling terminal after establishing a connection with the first user terminal, and the second user terminal If detected, the search for the scheduling terminal is resumed.

  The mobile communication system according to the embodiment further includes a fifth user terminal that broadcasts specific information directed to a specific user terminal, and the first user terminal receives the specific information from the fifth user terminal. When the specific user terminal is not the first user terminal, the specific information is broadcast to transfer the specific information.

  In the mobile communication system according to the embodiment, the second user terminal detects a signal including the message from the first user terminal again after establishing a connection with the first user terminal, and The second user terminal enables the scheduling function of the second user terminal when the signal strength of the signal including the message detected again is equal to or less than a threshold value.

  In the mobile communication system according to the embodiment, the first user terminal receives battery information indicating a battery state from the second user terminal after establishing a connection with the second user terminal, and The first user terminal requests the second user terminal to become the scheduling terminal instead of the first user terminal based on the battery information and the remaining battery level of the first user terminal. .

  In the mobile communication system according to the embodiment, when the second user terminal becomes the scheduling terminal, the first user terminal is synchronized with a timing at which the second user terminal starts broadcasting the message, Stop broadcasting the message.

  The user terminal which concerns on embodiment is a user terminal in the mobile communication system which supports D2D communication which is direct communication between terminals. The user terminal includes a control unit that controls a scheduling function for assigning radio resources used for the D2D communication. The control unit performs control to periodically or aperiodically broadcast a message including identification information indicating that the user terminal is a scheduling terminal that allocates the radio resource when the scheduling function is valid. .

  The user terminal which concerns on embodiment is a user terminal in the mobile communication system which supports D2D communication which is direct communication between terminals. The said user terminal is provided with the control part which performs control which searches the scheduling terminal which allocates the radio | wireless resource used for the said D2D communication. When the control unit detects a signal including a message including identification information indicating that another user terminal is the scheduling terminal, the control unit performs control to establish a connection with the other user terminal that broadcasts the message. .

[Embodiment]
(LTE system)
FIG. 1 is a configuration diagram of an LTE system according to the present embodiment.

  1, the LTE system includes a plurality of UEs (User Equipment) 100, an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core) 20. The E-UTRAN 10 and the EPC 20 constitute a network.

  The UE 100 is a mobile radio communication device, and performs radio communication with a cell (serving cell) that has established a connection. UE100 is corresponded to a user terminal.

  The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Node-B). The eNB 200 corresponds to a base station. The eNB 200 manages a cell and performs radio communication with the UE 100 that has established a connection with the cell.

  Note that “cell” is used as a term indicating a minimum unit of a radio communication area, and is also used as a term indicating a function of performing radio communication with the UE 100.

  The eNB 200 has, for example, a radio resource management (RRM) function, a user data routing function, and a measurement control function for mobility control and scheduling.

  The EPC 20 includes MME (Mobility Management Entity) / S-GW (Serving-Gateway) 300 and OAM 400 (Operation and Maintenance). The EPC 20 corresponds to a core network.

  The MME is a network node that performs various types of mobility control for the UE 100, and corresponds to a control station. The S-GW is a network node that performs transfer control of user data, and corresponds to an exchange.

  The eNB 200 is connected to each other via the X2 interface. Moreover, eNB200 is connected with MME / S-GW300 via S1 interface.

  The OAM 400 is a server device managed by an operator, and performs maintenance and monitoring of the E-UTRAN 10.

  Next, the configuration of the UE 100 will be described.

  FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100 includes an antenna 101, a radio transceiver 110, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, a memory 150, and a processor 160. Have. The memory 150 and the processor 160 constitute a control unit.

  In this embodiment, a control part performs control which allocates the radio | wireless resource used for D2D communication on behalf of several UE100. Details will be described later.

  The UE 100 may not have the GNSS receiver 130. Further, the memory 150 may be integrated with the processor 160, and this set (that is, a chip set) may be used as the processor 160 '.

  The antenna 101 and the wireless transceiver 110 are used for transmitting and receiving wireless signals. The antenna 101 includes a plurality of antenna elements. The radio transceiver 110 converts the baseband signal output from the processor 160 into a radio signal and transmits it from the antenna 101. Further, the radio transceiver 110 converts a radio signal received by the antenna 101 into a baseband signal and outputs the baseband signal to the processor 160.

  The user interface 120 is an interface with a user who owns the UE 100, and includes, for example, a display, a microphone, a speaker, and various buttons. The user interface 120 receives an operation from the user and outputs a signal indicating the content of the operation to the processor 160.

  The GNSS receiver 130 receives a GNSS signal and outputs the received signal to the processor 160 in order to obtain location information indicating the geographical location of the UE 100.

  The battery 140 stores power to be supplied to each block of the UE 100.

  The memory 150 stores a program executed by the processor 160 and information used for processing by the processor 160.

  The processor 160 includes a baseband processor that modulates / demodulates and encodes / decodes a baseband signal, and a CPU (Central Processing Unit) that executes programs stored in the memory 150 and performs various processes. . The processor 160 may further include a codec that performs encoding / decoding of an audio / video signal. The processor 160 executes various processes and various communication protocols described later.

  FIG. 3 is a protocol stack diagram of a radio interface in the LTE system.

  As shown in FIG. 3, the radio interface protocol is divided into layers 1 to 3 of the OSI reference model, and layer 1 is a physical (PHY) layer. Layer 2 includes a MAC (Media Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer. Layer 3 includes an RRC (Radio Resource Control) layer.

  The physical layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. The physical layer provides a transmission service to an upper layer using a physical channel. Data is transmitted between the physical layer of the UE 100 and the physical layer of the eNB 200 via a physical channel.

  The MAC layer performs data priority control, retransmission processing by hybrid ARQ (HARQ), and the like. Data is transmitted via the transport channel between the MAC layer of the UE 100 and the MAC layer of the eNB 200. The MAC layer of the eNB 200 includes a MAC scheduler that determines an uplink / downlink transport format (transport block size, modulation / coding scheme, and the like) and an allocated resource block.

  The RLC layer transmits data to the RLC layer on the receiving side using functions of the MAC layer and the physical layer. Data is transmitted between the RLC layer of the UE 100 and the RLC layer of the eNB 200 via a logical channel.

  The PDCP layer performs header compression / decompression and encryption / decryption.

  The RRC layer is defined only in the control plane. Control signals (RRC messages) for various settings are transmitted between the RRC layer of the UE 100 and the RRC layer of the eNB 200. The RRC layer controls the logical channel, the transport channel, and the physical channel according to establishment, re-establishment, and release of the radio bearer. If there is an RRC connection between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 is in a connected state, otherwise, the UE 100 is in an idle state.

  A NAS (Non-Access Stratum) layer located above the RRC layer performs session management, mobility management, and the like.

  FIG. 4 is a configuration diagram of a radio frame used in the LTE system. In the LTE system, OFDMA (Orthogonal Frequency Division Multiplexing Access) is used for the downlink, and SC-FDMA (Single Carrier Frequency Multiple Access) is used for the uplink.

  As shown in FIG. 4, the radio frame is composed of 10 subframes arranged in the time direction, and each subframe is composed of two slots arranged in the time direction. The length of each subframe is 1 ms, and the length of each slot is 0.5 ms. Each subframe includes a plurality of resource blocks (RB) in the frequency direction and includes a plurality of symbols in the time direction. A guard interval called a cyclic prefix (CP) is provided at the head of each symbol. The resource block includes a plurality of subcarriers in the frequency direction. A radio resource unit composed of one subcarrier and one symbol is called a resource element (RE).

  Among radio resources allocated to the UE 100, a frequency resource can be specified by a resource block, and a time resource can be specified by a subframe (or slot).

  In the downlink, the section of the first few symbols of each subframe is a control region mainly used as a physical downlink control channel (PDCCH). The remaining section of each subframe is an area that can be used mainly as a physical downlink shared channel (PDSCH). Further, cell-specific reference signals (CRS) are distributed and arranged in each subframe.

  In the uplink, both ends in the frequency direction in each subframe are control regions mainly used as a physical uplink control channel (PUCCH). Further, the central portion in the frequency direction in each subframe is an area that can be used mainly as a physical uplink shared channel (PUSCH). Further, a demodulation reference signal (DMRS) and a sounding reference signal (SRS) are arranged in each subframe.

(D2D communication)
Next, normal communication (cellular communication) of the LTE system and D2D communication will be compared and described.

  FIG. 5 is a diagram illustrating a data path in cellular communication. Here, the case where cellular communication is performed between UE100-1 which established the connection with eNB200-1 and UE100-2 which established the connection with eNB200-2 is illustrated. A data path means a transfer path of user data (user plane).

  As shown in FIG. 5, the data path of the cellular communication goes through the network. Specifically, a data path that passes through the eNB 200-1, the S-GW 300, and the eNB 200-2 is set.

  FIG. 6 is a diagram illustrating a data path in D2D communication. Here, the case where D2D communication is performed between UE100-1 which established the connection with eNB200-1 and UE100-2 which established the connection with eNB200-2 is illustrated.

  For example, D2D communication is started when one UE 100 of UE 100-1 and UE 100-2 discovers the other UE 100 existing in the vicinity. In order to start D2D communication, the UE 100 has a function of discovering another UE 100 existing in the vicinity of the UE 100 (Discover). Further, the UE 100 has a (Discoverable) function that is discovered from other UEs 100.

  As shown in FIG. 6, the data path of D2D communication does not go through the network. That is, direct radio communication is performed between UEs. In this way, if the UE 100-2 exists in the vicinity of the UE 100-1, the network traffic load and the battery consumption of the UE 100 are reduced by performing D2D communication between the UE 100-1 and the UE 100-2. The effect of doing etc. is acquired.

(Scheduling UE)
Next, the scheduling UE 100 according to the present embodiment will be described with reference to FIGS. FIG. 7 is an explanatory diagram for explaining a situation where the scheduling UE 100 according to the present embodiment is broadcasting a message including identification information. FIG. 8 is an explanatory diagram for explaining a situation in which the scheduling UE 100 according to the present embodiment performs scheduling. FIG. 9 is an explanatory diagram for explaining a buffer status report according to the present embodiment.

  The scheduling UE 100 has a scheduling function for allocating radio resources used for D2D communication.

  As shown in FIG. 7, the scheduling UE 100 broadcasts a scheduling UE message periodically or aperiodically when the scheduling function is effective. The scheduling UE message includes identification information indicating that the UE 100 that transmits the message is a scheduling UE that allocates radio resources. The identification information is a unique identifier of the UE 100 that is the scheduling UE 100.

  The scheduling UE 100 may periodically broadcast a synchronization signal for the other UE 100 to establish synchronization with the scheduling UE 100 in addition to the scheduling UE message. The synchronization signal includes identification information that is a unique identifier of UE 100 that is scheduling UE 100.

  In addition, the scheduling UE 100 assigns radio resources to the UE 100 that has established a connection. That is, the scheduling UE 100 manages radio resources of the UE 100 that has established a connection.

  For example, as illustrated in FIG. 8, the scheduling UE 100 receives a buffer status report (BSR) indicating the amount of untransmitted data from each of the UE 100 a and the UE 100 b that have established a connection. The scheduling UE 100 allocates radio resources to each of the UE 100a and the UE 100b according to the received buffer status report.

  Each UE 100 (UE 100a and UE 100b) may classify untransmitted data into a plurality of logical channel groups (for example, LCG # 0-3) having different priorities. Each UE 100 classifies untransmitted data into logical channel groups whose use is defined in advance according to the type of untransmitted data. For example, unsent data may be classified by associating usage (ie, application) with a logical channel group. Specifically, for example, untransmitted data for real-time communication (voice) is transmitted to LCG # 0, untransmitted data for real-time communication (image) is transferred to LCG # 1, and untransmitted data for data communication (text) is transferred to LCG # 0. 2, untransmitted data for data communication (others) may be classified as LCG # 3.

  A priority is defined in advance for each logical channel group. For example, as shown in FIG. 9, LCG # 0 has the highest priority, and LCG # 1, LCG # 2, and LCG # 3 have lower priorities.

  As shown in FIG. 9, each UE 100 creates a buffer status report indicating the amount of untransmitted data for each of a plurality of logical channel groups. The buffer status report in this case indicates the amount of untransmitted data (Buffer Size # 0-3) corresponding to each logical channel group.

  The scheduling UE 100 allocates radio resources for the UE 100 that has transmitted the buffer status report to transmit untransmitted data according to the priority based on the buffer status report. The scheduling UE 100 transmits band allocation indicating the allocated radio resource to each UE 100. The scheduling UE 100 may transmit the band allocation by unicast or broadcast, or may transmit the group UE by a group cast to a group including the UE 100 to which the scheduling UE 100 allocates radio resources.

  Note that the scheduling UE 100 may transmit band allocation using a modulation scheme and channel coding rate (MCS) defined in advance.

  Further, the scheduling UE 100 may not perform a retransmission process (that is, a HARQ retransmission process in the MAC layer) for retransmitting the band allocation based on a retransmission request from the UE 100 (that is, a negative acknowledgment (NAK) in reception of the band allocation). . Instead of performing retransmission processing, the scheduling UE 100 may repeatedly transmit band allocation according to the request from the UE 100 or the type of communication method with the UE 100 in order to improve error tolerance. For example, the scheduling UE 100 may repeatedly transmit band allocation without a request from the UE 100 when the communication method is a broadcast method or a group cast method.

(Search for scheduling UE 100)
Next, searching for a scheduling UE (Scheduling UE) 100 according to the present embodiment will be described with reference to FIGS. FIG. 10 is a flowchart for explaining the operation of the UE 100 according to the present embodiment. FIG. 11 is a sequence diagram illustrating an operation example in which the UE 100 according to the present embodiment connects to the scheduling UE 100.

  As illustrated in FIG. 10, in step S101, the UE 100 searches for the scheduling UE 100. Specifically, the UE 100 searches for a signal including the above-described scheduling UE message.

  In addition, UE100 starts the search of scheduling UE100, when it determines with it being the situation of the public safety (public safety) which UE100 can allocate a radio | wireless resource instead of a network.

  For example, when the UE 100 does not receive a signal from the eNB 200 for a predetermined period, receives a notification from the eNB 200 that it is in the state of public safety, or when a predetermined period has elapsed after receiving an emergency bulletin from the eNB 200, It is determined that the situation is public safety.

  In step S102, the UE 100 determines whether or not the scheduling UE 100 is found. Specifically, when the UE 100 does not detect a signal including a scheduling UE message (hereinafter, appropriately referred to as a broadcast signal) (in the case of “NO”), the UE 100 determines that the scheduling UE 100 has not been found, Execute the process. On the other hand, when the UE 100 detects a signal including a scheduling UE message (in the case of “YES”), the UE 100 determines that the scheduling UE 100 is found, and executes the process of step S107.

  In step S103, the UE 100 determines whether or not the battery has a margin. Specifically, the UE 100 determines whether or not the remaining battery capacity exceeds a threshold value. UE100 performs the process of step S104, when a battery remaining charge is below a threshold value, ie, when a battery remaining charge is low (in the case of "NO"). On the other hand, when the remaining battery level exceeds the threshold, that is, when the remaining battery level is high (in the case of “YES”), the UE 100 executes the process of step S105.

  In step S104, the UE 100 enters a sleep mode. Specifically, UE100 performs the intermittent reception which starts the radio | wireless transmitter / receiver 110 intermittently. That is, the UE 100 periodically stops the power supply to the radio transceiver 110.

  On the other hand, in step S105, the UE 100 activates the scheduling function when the battery remaining amount exceeds the threshold value in step S103. Thereby, the scheduling function of UE100 becomes effective.

  In addition, since UE100 cannot perform the process of step S105, when not having a scheduling function, operation | movement is complete | finished.

  In step S106, the UE 100 starts transmission of a notification signal.

  On the other hand, in step S107, when the UE 100 detects the notification signal in step S102, the UE 100 establishes at least synchronization with the scheduling UE 100. In the present embodiment, the UE 100 establishes a connection with the scheduling UE 100 in addition to establishing synchronization. The establishment of the connection between the UE 100 and the scheduling UE 100 will be described in detail later.

  In addition, when only establishing synchronization without establishing a connection with the scheduling UE 100, the UE 100 uses the broadcast signal or the synchronization signal transmitted from the scheduling UE 100 to synchronize the radio link in the direction from the scheduling UE 100 to the UE 100. Establish.

  In step S108, the UE 100 transmits battery information indicating the state of the battery to the scheduling UE 100. The battery information is information indicating, for example, a remaining battery level, a battery usage rate, or a used battery amount. As described later, the scheduling UE 100 determines the UE 100 that requests to become the scheduling UE 100 based on the battery information.

  In step S109, UE100 determines whether it has the user data for transmitting to other UE100. UE100 performs the process of step S110, when it does not have the said user data (in the case of "NO"). On the other hand, when the UE 100 has the user data, the UE 100 executes the process of step S111.

  Note that the UE 100 may execute the process of step S110 when there is no user data to be received in addition to user data for transmission.

  In step S110, the UE 100 enters the sleep mode with at least synchronization with the scheduling UE 100 established. The UE 100 may enter a sleep mode while establishing a connection with the scheduling UE 100.

  On the other hand, in step S111, the UE 100 performs a process for transmitting the user data. Specifically, the UE 100 receives band allocation, which is radio resource allocation information, from the scheduling UE 100. Note that the UE 100 may request the scheduling UE 100 to allocate radio resources in order to have the radio resources allocated.

  The UE 100 recognizes radio resources used for transmission of user data allocated to the UE 100 based on the band allocation, and transmits user data to other UEs 100 using the radio resources.

  Note that the UE 100 establishes a connection for each communication group that transmits and receives user data. For connection and D2D communication, the UE 100 may perform connection and D2D communication according to a predetermined setting, or may newly define a setting between the UEs 100 configuring the communication group. Moreover, UE100 which comprises each communication group may prescribe | regulate the protocol (For example, secret techniques, such as an encryption system and an encryption key) unique to a group. Thereby, different communication groups can coexist.

(Connection with scheduling UE100)
Next, the connection of UE 100 with scheduling UE 100 will be described using FIG. FIG. 11 is a sequence diagram for explaining the connection between the UE 100 and the scheduling UE 100 according to the present embodiment.

  As shown in FIG. 11, in step S201, the UE 100 searches for the scheduling UE 100.

  In step S202, the scheduling UE 100 transmits a broadcast signal (broadcast signal) including the scheduling UE message. The UE 100 receives the notification signal. The UE 100 discovers (detects) the scheduling UE 100 by receiving the broadcast signal. Note that the scheduling UE message includes, as identification information, a unique identifier (Scheduling UE unique ID) of the UE 100 that is the scheduling UE 100.

  In step S203, when the UE 100 detects the scheduling UE 100, the UE 100 starts a random access procedure for establishing a connection with the scheduling UE 100. Specifically, UE100 transmits to scheduling UE100 which detected the random access preamble (RACH preamble). The scheduling UE 100 receives a random access preamble. The scheduling UE 100 estimates the transmission timing from the UE 100 based on reception of the random access preamble.

  In step S204, the scheduling UE 100 transmits to the UE 100 a random access response (RACH Response) that is a response to the random access preamble. The UE 100 receives a random access response.

  The random access response includes a random access preamble identifier (RAPID), a temporary identifier (RNTI), a timing correction value (TA), and a scheduling grant (UL Grant).

  The random access preamble identifier (RAPID) is an identifier for specifying the random access preamble received by the scheduling UE 100.

  The temporary identifier (RNTI) is a temporary identifier used for D2D communication between the UE 100 and the scheduling UE 100. The random access response may include a plurality of types of identifiers (Temporary D2D-RNTI) used for D2D communication as temporary identifiers. The plurality of types of identifiers include, for example, a plurality of identifiers according to the type of information to be transmitted, such as a temporary identifier used for transmission of user data and a temporary identifier used for transmission of control information (eg, bandwidth allocation) It may also include a plurality of identifiers according to the type of communication method such as unicast or group cast. For example, the scheduling UE 100 uses a temporary identifier to transmit radio resources allocated to the UE 100.

  The timing correction value (TA) is a correction value for correcting the transmission timing from the UE 100 estimated by the scheduling UE 100 in step S203. The UE 100 corrects the transmission timing based on the timing correction value in order to establish synchronization in the direction from the UE 100 to the scheduling UE 100.

  The scheduling grant (UL Grant) is radio resource allocation information used for transmitting a message (Msg3) transmitted from the UE 100 to the scheduling UE 100 in step S205.

  In step S205, the UE 100 transmits a message (Msg3) for establishing a connection with the scheduling UE 100 to the scheduling UE 100. The scheduling UE 100 establishes a connection with the UE 100 based on the received message. The message includes, for example, a request for connection in the RRC layer (hereinafter referred to as RRC connection as appropriate) and the identifier of the UE 100.

  Note that, when the UE 100 performs RRC connection with the scheduling UE 100 and there is a setting value for RRC connection defined in advance for D2D communication, transmission of information for RRC connection is omitted. May be. The scheduling UE 100 and the UE 100 perform RRC connection setting based on the specified setting value.

  In step S206, the scheduling UE 100 transmits a contention resolution message (Contention Resolution) used for determining success or failure of the random access procedure to the UE 100. The UE 100 receives the contention resolution message. The contention resolution message includes the message transmitted by the UE 100 and the identifier of the UE 100 transmitted in step S205.

  The UE 100 compares the identifier of the UE 100 included in the contention resolution message with the identifier of the UE 100 transmitted in step S205. Also, the UE 100 compares other information included in the message included in the conflict resolution message with other information included in the message transmitted in step S205. As a result of the comparison, the UE 100 determines that the random access procedure is successful when the identifier of the UE 100 and other information match. On the other hand, if these pieces of information do not match, the UE 100 determines that the random access procedure has failed. If the UE 100 determines that the random access procedure has failed, the UE 100 starts the random access procedure again.

  Note that the scheduling UE 100 may omit the transmission of the contention resolution message. For example, the scheduling UE 100 can omit the transmission of the contention resolution message according to the number of UEs 100 that perform radio resource allocation. The scheduling UE 100 omits the transmission of the contention resolution message to the UE 100 that has newly started the random access procedure when the number of the UEs 100 exceeds the threshold.

  Note that the UE 100 may establish only a connection in the PHY layer without establishing a connection in the MAC layer and the RRC layer with the scheduling UE 100. After establishing the connection in the PHY layer, the UE 100 starts waiting for a message in the PHY layer from the scheduling UE 100. When the scheduling UE 100 transmits a message in PHY by broadcast or group cast, the UE 100 that has started standby can receive the message in PHY.

(Reception of signals from other UEs 100)
Next, a case where the scheduling UE 100 or the UE 100 to which radio resources are allocated from the scheduling UE 100 receives a signal from another UE 100 will be described with reference to FIGS.

(1) Case 1A
Case 1A is a case where the scheduling UE 100 or the UE 100 to which radio resources are allocated from the scheduling UE 100 receives a broadcast signal from another scheduling UE 100. Case 1A will be described with reference to FIGS. FIG. 12 is an explanatory diagram for describing an operating environment of case 1A in the mobile communication system according to the embodiment. 13 and 14 are sequence diagrams for explaining the operation of case 1A in the mobile communication system according to the embodiment. FIG. 15 is an explanatory diagram for explaining the synchronization correction operation according to the embodiment.

  As illustrated in FIG. 12, there is a UE 100c to which radio resources are allocated from the scheduling UE 100a, the scheduling UE 100b, and the scheduling UE 100a. The scheduling UE 100b is adjacent to the UE 100c, and the scheduling UE 100b does not manage the allocation of radio resources from the scheduling UE 100a.

  The UE 100c stops searching for the scheduling UE 100 after establishing the connection with the scheduling UE 100a.

  In such an operating environment, each UE 100 performs the following operations.

  First, as shown in FIG. 13, in step S301, the UE 100c transmits a buffer status report to the scheduling UE 100a. The scheduling UE 100a receives the buffer status report.

  In step S302, the scheduling UE 100a transmits band allocation to the UE 100c based on the buffer status report. The UE 100c receives the band allocation.

  In step S303, the scheduling UE 100a transmits a broadcast signal including a unique identifier (Scheduling UE unique ID # 1) of the scheduling UE 100a.

  In step S304, the scheduling UE 100b transmits a broadcast signal including a unique identifier (Scheduling UE unique ID # 2) of the scheduling UE 100b, similarly to step S303. The UE 100c determines that interference has been detected based on the notification signal from the scheduling UE 100b. For example, the UE 100c determines that the interference is detected when the user data from the scheduling UE 100a cannot be received.

  In step S305, when the UE 100c detects interference, the UE 100c restarts the search for the scheduling UE 100.

  In step S306, the scheduling UE 100b transmits a broadcast signal including a unique identifier (Scheduling UE unique ID # 2) of the scheduling UE 100b, similarly to step S304. The UE 100c receives the notification signal from the scheduling UE 100b by searching for the scheduling UE 100.

  When the UE 100c detects the scheduling UE 100 that has not been notified to the scheduling UE 100a, the UE 100c executes the process of step S307. On the other hand, when the UE 100c detects the scheduling UE 100 notified to the scheduling UE 100a, the UE 100c ends the process. The UE 100c also ends the process when receiving a notification signal from the scheduling UE 100a.

  When the UE 100c detects the scheduling UE 100 that is an interference source, the UE 100c may stop searching for the scheduling UE 100 again.

  As illustrated in FIG. 12 and FIG. 13, in step S307, when the UE 100c detects a scheduling UE 100 that has not been notified to the scheduling UE 100a, the UE 100c notifies the scheduling UE 100a of neighboring scheduling UE information. The scheduling UE 100a receives neighboring scheduling UE information.

  The adjacent scheduling UE information is information indicating that a broadcast signal from the scheduling UE 100 to which no radio resource is allocated is detected. The adjacent scheduling UE information includes a unique identifier (Scheduling UE unique ID # 2) of the scheduling UE 100c included in the received broadcast signal.

  When the scheduling UE 100a determines that the scheduling UE 100b notified from the UE 100c is an undetected scheduling UE 100, the scheduling UE 100a performs the process of step S311. On the other hand, when determining that the scheduling UE 100a is the scheduling UE 100 detected by the scheduling UE 100b, the scheduling UE 100a executes the process of step S321. Note that the scheduling UE 100a performs the determination based on the identifier included in the adjacent scheduling UE information.

  In step S311, the scheduling UE 100a transmits an adjacent scheduling UE information response including an undetected flag indicating that the scheduling UE 100b has not been detected to the UE 100c. The UE 100c receives the adjacent scheduling UE information response.

  In step S312, the UE 100c activates the scheduling function when receiving the neighboring scheduling UE information including the undetected flag.

  In step S313, the UE 100c transmits scheduling activation information indicating that the scheduling function is activated to the scheduling UE 100a. The scheduling UE 100a receives the scheduling activation information.

  The scheduling activation information includes a temporary identifier (C-RNTI # 3) and a unique identifier (UE unique ID # 3) of the UE 100c. The scheduling UE 100a can be seen that the UE 100c having C-RNTI # 3 and UE unique ID # 3 is activated as an adjacent scheduling UE. The temporary identifier may be used, for example, for scrambling for CRC (Cyclic Redundancy Check) added to the control information.

  In step S314, the scheduling UE 100a transmits a scheduling activation information response to the scheduling UE 100c. The scheduling UE 100c receives the scheduling activation information response.

  When the scheduling UE 100a determines that the UE 100 that allocates radio resources is assigned to the scheduling UE 100c, the scheduling UE 100a divides the radio resources that can be allocated by the scheduling UE 100a. The scheduling UE 100a transmits an identifier (UE unique ID #n) indicating each scheduling UE 100 and radio resource allocation information (band allocation) that can be allocated to each scheduling UE 100 to the scheduling UE 100c. In the present embodiment, the identifier indicating each scheduling UE 100 is UE specific # 1 indicating scheduling UE 100a and UE specific # 3 indicating scheduling UE 100c. Also, the radio resource allocation information is the band allocation of each of the scheduling UE 100a and the scheduling UE 100c. Note that the scheduling UE 100a may transmit only the bandwidth allocation of the scheduling UE 100c instead of the identifier indicating each scheduling UE 100 and the radio resource allocation information. In step S315, each scheduling UE100 (UE100a, UE100b, and UE100c) performs a synchronization correction operation. The synchronization correction operation will be described later.

  On the other hand, if the scheduling UE 100a determines in step S321 that the scheduling UE 100b has detected the scheduling UE 100b, the scheduling UE 100a transmits an adjacent scheduling UE information response including a detected flag indicating that the scheduling UE 100b has been detected to the UE 100c. To do. The UE 100c receives the adjacent scheduling UE information response.

  When the scheduling UE 100c receives the adjacent scheduling UE information response including the detected flag, the scheduling UE 100c may stop searching for the scheduling UE 100 again.

  Next, the synchronization correction operation in step S315 described above will be described with reference to FIG.

  As shown in FIG. 14, steps S351 to S355 correspond to steps S202 to S206 of FIG.

  The scheduling UE 100c determines that the synchronization timing between the scheduling UE 100b and the D2D communication is shifted by the random access procedure from Steps S352 to S355. If the scheduling UE 100c determines that the synchronization timing is shifted, the scheduling UE 100c executes the process of step S356 to perform correction for matching the synchronization timing.

  In step S356, the scheduling UE 100c transmits a synchronization correction request for matching the synchronization timing to the scheduling UE 100b. The scheduling UE 100b receives the synchronization correction request.

  The synchronization correction request includes a timing correction value (TA) in the direction from the scheduling UE 100b to the scheduling UE 100c and the number of UEs under the scheduling UE 100 having the same synchronization timing as an index for determining a target to be synchronized.

  Note that the number of UEs serving as the index may be the number of scheduling UEs 100 having the same synchronization timing, or the number of UEs under the control of the scheduling UE 100 that transmits the synchronization correction request. The target for synchronization correction is determined according to the number of UEs serving as indices. Further, the index may be a unique ID of the scheduling UE 100. In this case, a target to be subjected to synchronization correction is determined depending on the size of the unique ID.

  In addition, you may determine the object which performs synchronous correction | amendment with the combination of the said parameter | index.

  In addition, when each scheduling UE 100 synchronization correction request is made, information serving as the above-described index may be requested to other scheduling UEs 100, or information serving as the index may be received periodically. Further, when the index is updated, the scheduling UE 100 may transmit information serving as an index.

  In the present embodiment, synchronization correction is performed when the number of UEs serving as indices is smaller. Further, in the present embodiment, description will be made assuming that the synchronization timing of the scheduling UE 100a and the scheduling UE 100c is the same.

  The number under the scheduling UE 100a is A, the number under the scheduling UE 100c is C, and the total number of UEs is N (= A + C). On the other hand, the number under the scheduling UE 100b is M.

  In step S357, the scheduling UE 100b transmits a synchronization correction response to the scheduling UE 100c as a response to the synchronization correction request. The scheduling UE 100c receives the synchronization correction response.

  The synchronization correction response includes the timing correction value (TA) in the direction from the scheduling UE 100c to the scheduling UE 100b and the number of UEs under the scheduling UE 100 having the same synchronization timing as in step S356.

  In the present embodiment, the scheduling UE 100b does not establish synchronization with other scheduling UEs 100, and the number of UEs under the scheduling UE 100b is M.

  If M is greater than N (N <M), the process of step S361 is executed. On the other hand, if M is N or less (N ≧ M), the process of step S381 is executed.

  In step S361, the number of UEs under the scheduling UE 100 having the same synchronization timing is smaller in the scheduling UE 100c than in the scheduling UE 100b. Make corrections.

  As shown in FIG. 15, the scheduling UE 100c does not set the subframe # m2, which is a predetermined subframe of the scheduling UE 100c, and sets the head of the next subframe # m3 to match the synchronization timing. The scheduling UE 100b may be made to coincide with the beginning of the subframe # n3.

  In addition, the scheduling UE 100c may transmit to the subordinate UE 100 that the synchronization timing is synchronized. The scheduling UE 100c may transmit a timing correction value together with the notification.

  In step S362, the scheduling UE 100c transmits a synchronization correction request to the scheduling UE 100a as in step S356. The scheduling UE 100a receives the synchronization correction request. Note that the number of UEs under the scheduling UE 100 having the same synchronization timing in the scheduling UE 100c is M + C.

  In step S363, the scheduling UE 100a transmits a synchronization correction response to the scheduling UE 100c in the same manner as in step S357. The scheduling UE 100c receives the synchronization correction response. The scheduling UE 100c receives the synchronization correction response. Note that the number of UEs under the scheduling UE 100 having the same synchronization timing in the scheduling UE 100a is A.

  In step S364, since the number of UEs M + C is larger than the number of UEs A, the scheduling UE 100a performs synchronization correction based on the timing correction values in steps S362 and S363, similarly to step S361.

  Note that the scheduling UE 100c may omit transmission of the number of UEs when it is determined in advance that the number of UEs M + C is larger than the number of UEs A. In this case, the scheduling UE 100c may transmit a synchronization correction instruction for performing synchronization correction.

  Returning to FIG. 14, in step S381, the number of UEs under the scheduling UE 100 having the same synchronization timing is smaller in the scheduling UE 100b than in the scheduling UE 100c. Therefore, the scheduling UE 100c is similar to step S361 in step S356. And the synchronization correction is performed based on the timing correction value of S357.

(2) Case 2A
Case 2A is a case where the scheduling UE 100 receives specific information from another UE 100 that does not manage radio resources. Case 2A will be described with reference to FIGS. 16 and 17. FIG. 16 is an explanatory diagram for describing an operating environment of case 2A in the mobile communication system according to the embodiment. FIG. 17 is an explanatory diagram for describing radio resources used when transmitting specific information in Case 2A in the mobile communication system according to the embodiment.

  As shown in FIG. 16, there are a scheduling UE 100a, a scheduling UE 100b, a UE 100c, a UE 100d, and a UE 100e. The scheduling UE 100a manages radio resources of the UE 100c. On the other hand, the scheduling UE 100b adjacent to the scheduling UE 100a manages radio resources of the UE 100d and the UE 100e.

  First, the UE 100c determines to broadcast specific information directed to the specific UE 100. The specific information is information classified into a specific logical channel group (for example, LCG ID = 0), for example, information indicating emergency data. The specific information is information that is transferred until the specific UE 100 receives the specific information.

  In the present embodiment, the scheduling UE 100a reserves a dedicated radio resource for transmitting specific information (information with LCG ID = 0). Specifically, as shown in FIG. 17, the scheduling UE 100a reserves a predetermined region in a frequency band to which radio resources can be allocated. The scheduling UE 100a periodically broadcasts information indicating the dedicated radio resource.

  The UE 100c transmits a buffer status report indicating the amount of untransmitted data classified as LCG ID = 0 to the scheduling UE 100a. The scheduling UE 100a allocates a dedicated radio resource when the untransmitted data is classified as LCG ID = 0 by the buffer status report from the UE 100c. In this case, the scheduling UE 100a allocates radio resources in an amount used only for transmission of untransmitted data classified as LCG ID = 0. The scheduling UE 100a transmits the allocated radio resource allocation information (band allocation) to the UE 100c. The UE 100c transmits specific information using dedicated radio resources based on band allocation.

  The scheduling UE 100b receives specific information from the UE 100c that does not manage radio resources. The scheduling UE 100b recognizes that the frequency information dedicated to the received information is used by receiving the information indicating the dedicated radio resource from the scheduling UE 100a. For this reason, scheduling UE100b determines with the information received from UE100c being specific information.

  Information indicating dedicated radio resources may be defined in advance. In this case, the scheduling UE 100b may determine that the information received from the UE 100c is specific information without receiving the information indicating the dedicated radio resource.

  Further, in order to determine whether or not the scheduling UE 100b is specific information, the UE 100c is data classified into a specific logical channel group (for example, LCG ID = 0) in the header portion of the specific information. A flag to that effect may be set. The scheduling UE 100b can determine whether the information is specific information based on the presence or absence of the flag in the header portion.

  If the scheduling UE 100b determines that the specific information is not information directed to the scheduling UE 100b, the scheduling UE 100b determines to transfer the specific information.

  In addition, in order to determine whether scheduling UE100b transfers, UE100c may set a unique numerical value to the header part of specific information. When the scheduling UE 100b has not received the specific information having the same numerical value as the unique numerical value set in the header portion of the received specific information (or has not been received for a certain period of time), the scheduling UE 100b You may determine to transfer.

  For example, the scheduling UE 100b determines that the information is not intended for the scheduling UE 100b when the specific information does not include an identifier addressed to the scheduling UE 100b or when the specific information cannot be combined in an upper layer.

  As illustrated in FIG. 17, the scheduling UE 100b broadcasts specific information using a dedicated radio resource, similarly to the scheduling UE 100b.

  Further, when the UE 100d that has received the specific information determines that the received information is the specific information, the UE 100d broadcasts the specific information using a dedicated radio resource, as described above. In this way, specific information is transferred one after another.

  In addition, in order to prevent retention of specific information, each scheduling UE 100 may determine not to broadcast the specific information when receiving specific information from the UE 100 under its control. Moreover, when each scheduling UE100 receives the specific information from the same UE100 within a predetermined period, you may determine with not broadcasting the said specific information. Moreover, when specific information is addressed to the UE 100 under the scheduling UE 100, the scheduling UE 100 may transmit the information by unicast or group cast without broadcasting.

(Activation of scheduling function)
Next, the case where UE100 starts a scheduling function is demonstrated using FIGS. 18-22. Note that the description of the case described above (search for scheduling UE 100) is omitted.

(1) Case 1B
Case 1B is a case in which the UE 100 under the scheduling UE 100 activates the scheduling function when the reception strength, which is the signal strength of the broadcast signal from the scheduling UE 100, is equal to or less than the threshold. Case 1B will be described with reference to FIGS. FIG. 18 is an explanatory diagram for describing an operating environment of case 1B in the mobile communication system according to the embodiment. FIG. 19 is a sequence diagram for explaining the operation of case 1B in the mobile communication system according to the embodiment. FIG. 20 is a flowchart for explaining the operation of case 1B in the mobile communication system according to the embodiment.

  As shown in FIG. 18, there are scheduling UEs 100a, 100b, and 100c. The scheduling UE 100a manages radio resources of the UE 100b and the UE 100c.

  In such an operating environment, each UE 100 performs the following operations.

  As shown in FIG. 19, in step S401, the scheduling UE 100a transmits a notification signal in the same manner as in step S202 of FIG. The UE 100b detects the notification signal again.

  As shown in FIGS. 19 and 20, in step S402 (that is, step S402-1), the UE 100b measures the reception strength Pr of the notification signal again.

  In step S402-2, the UE 100b determines whether the reception strength Pr of the notification signal is equal to or less than the threshold value Pthresh. UE100b complete | finishes a process, when reception intensity | strength Pr is larger than threshold value Pthresh (in the case of "NO"). On the other hand, when the reception intensity Pr is equal to or less than the threshold value Pthresh (in the case of “YES”), the UE 100b executes the process of step S403.

  Step S403 corresponds to step S312 in FIG. Specifically, the UE 100b is activated as a scheduling UE. That is, the UE 100b activates the scheduling function by activating the scheduling function.

  Steps S404 and S405 correspond to steps S313 and S314 in FIG.

  In step S406, the scheduling UE 100b transmits a broadcast signal including a unique identifier (Scheduling UE unique ID # 2) of the scheduling UE 100b.

(2) Case 2B
Case 2B is a case in which the UE 100 activates the scheduling function by receiving a transfer request from the scheduling UE 100. The case 2B will be described with reference to FIGS. FIG. 21 is a sequence diagram for explaining the operation of case 2B in the mobile communication system according to the embodiment. FIG. 22 is a flowchart for explaining the operation of case 2B in the mobile communication system according to the embodiment.

  The operating environment in case 2B is the same operating environment as in case 1B described above.

  As shown in FIG. 21, in step S501, the scheduling UE 100a transmits a notification signal in the same manner as in step S202 of FIG.

  In step S502, the scheduling UE 100a performs assignment determination. Specifically, the scheduling UE 100a determines whether or not to assign the role of radio resource allocation (hereinafter referred to as a scheduling role as appropriate) to another UE 100.

  As illustrated in FIG. 22, in step S502-1, the scheduling UE 100a determines whether or not its own battery remaining amount is equal to or less than a threshold value. The scheduling UE 100a continues to allocate radio resources when the remaining battery level is not less than or equal to the threshold (in the case of “NO”). On the other hand, when the remaining battery level is equal to or less than the threshold (when “YES”), the scheduling UE 100a executes the process of step S502-2.

  In step S502-2, the scheduling UE 100a selects a candidate for the UE 100 to which the scheduling role is assigned based on the battery list of the UE 100.

  The scheduling UE 100a receives the battery information as described in step S108 of FIG. The scheduling UE 100a creates a battery list based on the received battery information. The battery list includes, for example, information such as identification information of the UE 100, a remaining battery level indicated in the battery information, a registration time in the battery list, and a predicted value of the remaining battery level. For example, the scheduling UE 100a determines the predicted value of the remaining battery level based on the radio resource allocation status.

  For example, the scheduling UE 100a selects, as candidate UE 100, the UE 100 having the largest remaining battery level after a predetermined time based on the predicted value of the remaining battery level. In the present embodiment, the description will be made assuming that the UE 100b is selected as a candidate request.

  As shown in FIGS. 21 and 22, in step S503, the scheduling UE 100a transmits a transfer request to the candidate UE 100b. The UE 100b receives the transfer request. The UE 100b that has received the transfer request activates the scheduling function.

  The assignment request is for requesting the candidate UE 100b to become a scheduling UE instead of the scheduling UE 100a. The scheduling UE 100a may transmit information related to the UE 100 whose radio resources are managed by the scheduling UE 100a together with the transfer request. Moreover, scheduling UE100a may transmit the information which shows the timing which switches the transmission destination of the below-mentioned alerting signal with a transfer request.

  In step S504, the UE 100b determines to start transmission of the notification signal from the subframe next to the subframe that has received the transfer request.

  In step S505, the scheduling UE 100a determines to stop transmitting the broadcast signal from the subframe next to the subframe in which the UE 100b has received the transfer request.

  In step S506, the UE 100b (that is, the current scheduling UE 100b) starts transmitting a broadcast signal. On the other hand, the UE 100a (that is, the original scheduling UE 100a) stops the transmission of the notification signal in accordance with the timing at which the UE 100b starts transmitting the notification signal. As a result, the transmission destination of the notification signal is switched with good timing.

(Summary of embodiment)
In this embodiment, when the scheduling function is valid, the UE 100 broadcasts a scheduling UE message including identification information indicating that it is the scheduling UE 100 periodically or aperiodically. Thereby, UE100 which exists in the periphery of scheduling UE100 can discover scheduling UE100 which allocates a radio | wireless resource. Therefore, duplication of radio resources can be suppressed by the scheduling UE 100 allocating radio resources on behalf of a plurality of UEs 100.

  Further, when the UE 100 detects a broadcast signal including a scheduling UE message by searching for the scheduling UE 100, the UE 100 establishes at least synchronization with the scheduling UE 100 that broadcasts the scheduling UE message. Thereby, it is possible to suppress the occurrence of a reception failure such as broadcast information between the UE 100 and the scheduling UE 100 due to the synchronization timing difference between the UE 100 and the scheduling UE 100.

  Further, the UE 100 establishes synchronization with the scheduling UE 100 using a broadcast signal or a synchronization signal transmitted from the scheduling UE 100. Thus, synchronization can be established even if the network situation is unstable.

  Further, the UE 100 establishes connection with the scheduling UE 100 in addition to establishment of synchronization. Thereby, UE100 can be allocated a radio | wireless resource from scheduling UE100, and it becomes possible to suppress duplication of a radio | wireless resource.

Moreover, UE100 starts a random access procedure, when a notification signal is detected.
The scheduling UE 100 transmits to the UE 100 a temporary identifier used for transmitting the radio resource allocated to the UE 100 based on the random access procedure. Thereby, since scheduling UE100 can manage a radio | wireless resource using the temporary identifier which UE100 designated, management of radio | wireless resources, such as transmission of the allocation information of radio | wireless resource, and radio | wireless resource allocation, becomes easy, The load on the scheduling UE 100 can be reduced.

  Moreover, UE100 abbreviate | omits transmission of the information for RRC connection in a random access procedure, and performs RRC connection using the setting value prescribed | regulated previously for D2D communication. Thereby, UE100 can establish the connection with scheduling UE100 immediately.

  In addition, the scheduling UE 100 omits transmission of the contention resolution message in the random access procedure. Thereby, scheduling UE100 can establish a connection with UE100 immediately. Further, the scheduling UE 100 can suppress battery consumption.

  Also, the UE 100 establishes only a PHY connection with the scheduling UE 100 and starts waiting for a message from the scheduling UE 100 in the PHY layer. Thereby, when scheduling UE100 transmits the message in PHY by broadcast or groupcast, UE100 which started standby can receive the message in PHY.

  Moreover, UE100 performs the intermittent reception which starts the radio | wireless transmitter / receiver 110 intermittently, when there is no data to transmit / receive. Thereby, since UE100 can stop the electric power feeding to the radio | wireless transmitter / receiver 110, it can suppress consumption of a battery.

  Further, when the UE 100 does not detect the notification signal, the UE 100 enables the scheduling function. Thereby, since UE100 which enabled the scheduling function can allocate a radio | wireless resource on behalf of the periphery UE100 when the scheduling UE100 does not exist in the periphery, duplication of a radio | wireless resource can be suppressed.

  Moreover, UE100 validates a scheduling function, when a notification signal is not detected and the battery remaining amount exceeds the threshold value. Thereby, UE100 can suppress that a battery remaining charge runs out immediately after starting the allocation of a radio | wireless resource.

  In addition, the scheduling UE 100 receives a buffer status report from the UE 100. The scheduling UE 100 allocates radio resources to the UE 100 according to the buffer status report. Thereby, since scheduling UE100 can grasp | ascertain the amount of untransmitted data of UE100, it can allocate a radio | wireless resource efficiently.

  Untransmitted data is classified into a plurality of logical channel groups having different priorities. The UE 100 transmits a buffer status report indicating the amount of untransmitted data for each of the plurality of logical channel groups. The scheduling UE 100 assigns radio resources to the UE 100 according to the priority based on the buffer status report. Thereby, UE100 which has unsent data with high priority can transmit unsent data with high priority earlier than other UE100.

  In addition, the scheduling UE 100 repeatedly transmits radio resource allocation information according to a request from the UE 100 or the type of communication method with the UE 100, instead of performing retransmission processing. Thereby, scheduling UE100 can improve error tolerance, without performing complicated processing.

  Further, when the scheduling UE 100 detects a notification signal from another scheduling UE 100 and the synchronization timing of the D2D communication is deviated, correction for adjusting the synchronization timing is performed. Thereby, even if UE100 from which scheduling UE100 differs performs D2D communication, it can suppress that the reception failure by a synchronization gap generate | occur | produces.

  Also, the scheduling UE 100 does not set the predetermined subframe of the scheduling UE 100 to match the synchronization timing, and the head of the subframe next to the predetermined subframe matches the head of the subframe of another scheduling UE 100 Let Thereby, scheduling UE100 can match | combine a synchronization timing easily.

  In addition, when detecting a notification signal from another scheduling UE 100, the UE 100 transmits, to the scheduling UE 100, neighboring scheduling UE information indicating that the notification signal from the other scheduling UE 100 is detected. Thereby, since scheduling UE100 can know the information of the surrounding scheduling UE100, the operation | movement for synchronizing with other scheduling UE100 can be started, for example.

  In addition, after establishing a connection with the scheduling UE 100, the UE 100 stops searching for the scheduling UE, and when detecting interference, resumes searching for the scheduling UE. Thereby, UE100 can suppress search of useless scheduling UE100, and can suppress consumption of a battery.

  In addition, the scheduling UE 100 receives specific information directed to the specific UE 100 from another UE 100, and when the scheduling UE 100 is not the specific UE 100, the scheduling UE 100 broadcasts the specific information in order to transfer the specific information.

  Further, the UE 100 may enable the scheduling function of the UE 100 when the reception strength of the notification signal of the scheduling UE 100 is equal to or less than the threshold value. As a result, even when the transmission power of the notification signal is reduced due to a decrease in the remaining battery power of the scheduling UE 100, the scheduling area in which radio resources are allocated is reduced by the UE 100 becoming a scheduling UE. Can be suppressed.

  Also, the scheduling UE 100 receives battery information from the UE 100. The scheduling UE 100 requests the UE 100 to become the scheduling UE 100 instead of the scheduling UE 100 based on the battery information and its own battery remaining amount. Thereby, it can suppress that the allocation of a radio | wireless resource stops suddenly when the remaining amount of scheduling UE100 runs out.

  In addition, when the UE 100 becomes a scheduling UE instead of the scheduling UE 100, the scheduling UE 100 stops the transmission of the notification signal of the scheduling UE 100 in accordance with the timing when the UE 100 starts the transmission of the notification signal. Thereby, since there is no duplication of transmission of broadcast signals, it is possible to suppress the surrounding UE 100 from simultaneously discovering a plurality of scheduling UEs 100 including the scheduling UE 100 that stops allocating radio resources.

[Other embodiments]
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the scheduling UE 100 allocates radio resources when the situation is public safety, but the present invention is not limited to this. For example, when the scheduling UE 100 is within a cell managed by the eNB 200 (when the scheduling UE 100 receives a reference signal from the eNB 200), radio resources are allocated to the UE 100 outside the cell. Also good. In this case, the scheduling UE 100 may allocate the radio resource to the UE 100 outside the service area using the proxy identifier (Substate C-RNTI) as the temporary identifier of the cell allocated to the scheduling UE 100, or the scheduling UE 100 may query the network. The radio resource may be allocated to the UE 100 outside the service area using the temporary identifier obtained in this way. The UE 100 outside the service area to which the radio resource is allocated from the scheduling UE 100 may perform D2D communication with the surrounding UE 100 using the radio resource, or perform cellular communication via the scheduling UE 100 (or the surrounding UE 100). Also good.

  Moreover, in embodiment mentioned above, although UE100 started the scheduling function, when there is room in a battery, it is not restricted to this. The UE 100 may activate the scheduling function even when the battery has no room. Thereby, for example, when there is data to be transmitted urgently, the UE 100 can allocate radio resources to transmit the data.

  Moreover, in embodiment mentioned above, although UE100 started the scheduling function, when not detecting the alerting | reporting signal from scheduling UE100, it is not restricted to this. For example, even when the notification signal is received, the UE 100 may activate the scheduling function if the reception strength of the notification signal is equal to or less than a threshold value.

  Moreover, in embodiment mentioned above, UE100 may transmit battery information not only after connecting battery information to scheduling UE100 but periodically or aperiodically. For example, the UE 100 transmits battery information when the remaining battery level falls below a threshold value indicating that the remaining battery level is low, or when the remaining battery level exceeds a threshold value indicating that the remaining battery level is high. Also good.

  In the above-described embodiment (Case 1A), when the scheduling UE 100 performs synchronization correction, one scheduling UE 100 performs synchronization correction. However, both scheduling UEs 100 having different synchronization timings may perform synchronization correction.

  Further, in the above-described embodiment (Case 2B), the scheduling UE 100 assigns the scheduling role by transmitting the assignment request, but is not limited thereto. For example, the scheduling UE 100 may determine that the assignment of the scheduling role has been established when receiving a transfer request response indicating that the transfer of the scheduling role is permitted from the candidate UE 100 that has received the transfer request. In this case, after receiving the assignment request response, the scheduling UE 100 may transmit information indicating the timing for switching the transmission destination of the notification signal and / or information regarding the UE 100 for which the radio resource is managed by the scheduling UE 100. In addition, when the scheduling UE 100 receives a transfer request response to reject transfer of the scheduling role, the scheduling UE 100 may newly transmit a transfer request to another candidate UE 100.

  In the above-described embodiment, an example in which the present invention is applied to the LTE system has been described. However, the present invention is not limited to the LTE system, and the present invention may be applied to a system other than the LTE system.

  10 ... E-UTRAN, 20 ... EPC, 100, 100-1, 100-2, 100-3, 100a, 100b, 100c, 100d, 100e ... UE scheduling UE (user terminal), 101 ... antenna, 110 ... wireless Transceiver 120, user interface 130, GNSS receiver 140, battery 150, memory 160, 160 ′, processor 200, 200-1, 200-2, 200-3, eNB (radio base station), 300 ... MME / S-GW, 400 ... OAM

Claims (3)

A user terminal in a mobile communication system that supports D2D communication, which is direct inter-terminal communication,
A control unit that performs control to search for another user terminal having a specific function including notification of radio resources used for the D2D communication;
The control unit receives a first message including identification information indicating that the specific function is valid from the first user terminal, and then establishes a connection with the first user terminal. Processing to send the message of 2 to the first user terminal,
The control unit establishes a connection with the first user terminal in response to receiving a third message corresponding to the second message from the first user terminal, and then performs the specific function. Stop searching for other user terminals that have
The said control part restarts the search of the other user terminal which has the said specific function, when the deterioration of the receiving state from the said 1st user terminal is detected. A mobile communication system that supports D2D communication that is direct inter-terminal communication,
A first user terminal having a specific function including notifying a radio resource used for the D2D communication;
A second user terminal that searches for another user terminal having the specific function,
The first user terminal broadcasts a first message including identification information indicating that the specific function is valid;
The second user terminal receives the first message from the first user terminal, and then sends a second message for establishing a connection with the first user terminal to the first user terminal. To
The second user terminal establishes a connection with the first user terminal in response to receiving a third message corresponding to the second message from the first user terminal, and Stop searching for other user terminals with the function of
The mobile communication system, wherein the second user terminal restarts searching for another user terminal having the specific function when detecting a deterioration in a reception state from the first user terminal. A method in a user terminal that supports D2D communication that is direct inter-terminal communication,
Searching for another user terminal having a specific function including notifying a radio resource used for the D2D communication;
After receiving a first message including identification information indicating that the specific function is effective from the first user terminal, a second message for establishing a connection with the first user terminal Transmitting to the first user terminal;
Another user terminal having the specific function after establishing a connection with the first user terminal in response to receiving a third message corresponding to the second message from the first user terminal Stopping the search for
Resuming a search for another user terminal having the specific function when a deterioration in a reception state from the first user terminal is detected.

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