JP2011205350A - Terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for detecting a faulty base station device.SOLUTION: A terminal 14 performs inter-terminal communication. An RF part 52 and a modulation/demodulation part 54 receive a signal from the base station device in a first period concerning a frame including the first period for the base station device to announce a signal and a second period for the terminal 14 to announce a signal. A storage part 74 stores position information of the base station device to announce the signal to be received. An estimation part 72 estimates the fault of the base station device when the signal from the base station device is not received in the circumference of the position information stored in the storage part 74.

Description

  The present invention relates to a communication technique, and more particularly to a terminal device that transmits and receives a signal including predetermined information.

  Road-to-vehicle communication is being studied to prevent collisions at intersections. In the road-to-vehicle communication, information on the situation of the intersection is communicated between the roadside device and the vehicle-mounted device. Road-to-vehicle communication requires the installation of roadside equipment, which increases labor and cost. On the other hand, if it is the form which communicates information between vehicle-to-vehicle communication, ie, vehicle equipment, installation of a roadside machine will become unnecessary. In that case, for example, the current position information is detected in real time by GPS (Global Positioning System), etc., and the position information is exchanged between the vehicle-mounted devices so that the own vehicle and the other vehicle enter the intersection respectively. (See, for example, Patent Document 1).

JP 2005-202913 A

  In a wireless LAN (Local Area Network) compliant with a standard such as IEEE 802.11, an access control function called CSMA / CA (Carrier Sense Multiple Access Collision Aviation) is used. Therefore, in the wireless LAN, the same wireless channel is shared by a plurality of terminal devices. In such CSMA / CA, due to the distance between terminal devices and the influence of obstacles that attenuate radio waves, a situation occurs in which radio signals do not reach each other, that is, a situation where carrier sense does not function. When carrier sense does not function, packet signals transmitted from a plurality of terminal devices collide.

  On the other hand, when a wireless LAN is applied to vehicle-to-vehicle communication, it is necessary to transmit information to an unspecified number of terminal devices, so it is desirable that the signal be transmitted by broadcast. However, at an intersection or the like, an increase in the number of vehicles, that is, an increase in the number of terminal devices increases traffic, and therefore, an increase in packet signal collision is assumed. As a result, data included in the packet signal is not transmitted to other terminal devices. If such a situation occurs in vehicle-to-vehicle communication, the objective of preventing a collision accident at the intersection encounter will not be achieved. Furthermore, if the road-to-vehicle communication is executed in addition to the vehicle-to-vehicle communication, the communication forms are various. In that case, reduction of the mutual influence between vehicle-to-vehicle communication and road-to-vehicle communication is requested | required.

  Here, it is assumed that a base station apparatus installed on the road fails. When a base station device fails in the mobile phone system, the failure is notified if the failed base station device itself can notify the failure. Moreover, even if the base station apparatus itself that has failed is not in a situation in which the failure can be notified, the failure is detected by making a complaint by a user who cannot receive the cellular phone service. On the other hand, since the base station apparatus used for vehicle-to-vehicle communication or road-to-vehicle communication is highly likely to be installed only at a specific intersection, the user does not recognize whether the user is receiving a service. Therefore, even if such a base station apparatus breaks down, there is a high possibility that the user will not make a claim. In order to provide the service stably, the failed base station apparatus should be detected.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for detecting a failed base station apparatus.

  In order to solve the above problems, a terminal device according to an aspect of the present invention is a terminal device that performs communication between terminal devices, and includes a first period in which a signal can be reported from a base station device, and a signal from the terminal device. Among the frames including the second period in which the signal can be broadcasted, the position of the receiving unit that receives the signal from the base station device in the first period and the position of the base station device that can report the signal to be received in the receiving unit A storage unit that stores information, and an estimation unit that estimates a failure of the base station device when the reception unit has not received a signal from the base station device around the location information stored in the storage unit, Prepare.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, a failed base station device can be detected.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the structure of the base station apparatus of FIG. FIGS. 3A to 3D are diagrams showing frame formats defined in the communication system of FIG. FIG. 4 is a diagram illustrating a configuration of a subframe in FIG. 3. FIGS. 5A and 5B are diagrams showing a format of a MAC frame stored in a packet signal defined in the communication system of FIG. It is a figure which shows the structure of the terminal device mounted in the vehicle of FIG. It is a flowchart which shows the certification | authentication procedure of the communication state in the terminal device of FIG. It is a flowchart which shows the notification procedure of the failure in the terminal device of FIG. It is a flowchart which shows the update procedure of the database in the terminal device which concerns on the modification of this invention. It is a flowchart which shows the deletion procedure of the database in the terminal device which concerns on the modification of this invention. It is a flowchart which shows the notification procedure of the failure information in the terminal device which concerns on another modification of this invention.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a communication system that performs vehicle-to-vehicle communication between terminal devices mounted on a vehicle, and also executes road-to-vehicle communication from a base station device installed at an intersection or the like to a terminal device. As inter-vehicle communication, the terminal device broadcasts and transmits a packet signal storing information such as the speed and position of the vehicle (hereinafter referred to as “data”). Further, the other terminal device receives the packet signal and recognizes the approach of the vehicle based on the data. Further, as road-to-vehicle communication, the base station apparatus repeatedly defines a frame including a plurality of subframes. The base station apparatus selects any one of the plurality of subframes, and broadcasts a packet signal in which control information and the like are stored in the period of the head portion of the selected subframe.

  The control information includes information related to a period for the base station apparatus to broadcast the packet signal (hereinafter referred to as “road vehicle transmission period”). The terminal device specifies a road and vehicle transmission period based on the control information, and transmits a packet signal in a period other than the road and vehicle transmission period. Thus, since the road-to-vehicle communication and the vehicle-to-vehicle communication are time-division multiplexed, the collision probability of packet signals between them is reduced. That is, when the terminal device recognizes the content of the control information, interference between road-vehicle communication and vehicle-to-vehicle communication is reduced. In addition, the area where the terminal device performing inter-vehicle communication is mainly classified into three types.

  One is an area formed around the base station apparatus (hereinafter referred to as “first area”), and the other is an area formed outside the first area (hereinafter referred to as “second area”). Another one is an area formed outside the second area (hereinafter referred to as “outside the second area”). Here, in the first area and the second area, the terminal device can receive the packet signal from the base station apparatus with a certain quality, whereas outside the second area, the packet signal from the base station apparatus is received. The terminal device cannot receive with a certain quality. The first area is formed closer to the center of the intersection than the second area. Since the vehicle existing in the first area is a vehicle existing near the intersection, the packet signal from the terminal device mounted on the vehicle can be said to be important information from the viewpoint of suppressing collision accidents.

  Corresponding to such area regulations, a period for vehicle-to-vehicle communication (hereinafter referred to as “vehicle transmission period”) is formed by time division multiplexing of a priority period and a general period. The priority period is a period for use by a terminal apparatus existing in the first area, and the terminal apparatus transmits a packet signal in any of a plurality of slots forming the priority period. The general period is a period for use by a terminal apparatus existing in the second area, and the terminal apparatus transmits a packet signal by the CSMA method in the general period. In addition, the terminal device existing outside the second area transmits a packet signal by the CSMA method regardless of the frame configuration. Here, it is determined in which area the terminal device mounted on the vehicle is present.

  Here, when there is a failed base station apparatus, the control information as described above is not transmitted, and road-to-vehicle communication is not executed. As a result, inter-vehicle communication is also affected. Therefore, it is desirable that a failed base station apparatus be detected early. In the present embodiment, the terminal device stores information (hereinafter referred to as “position information”) regarding the position where each base station device is located. When the terminal device receives the packet signal broadcast from the base station device, the terminal device acquires position information at that timing. By repeating such processing, if a packet signal from the base station device is not received within a predetermined area from the position where the base station device is arranged, the terminal device causes the base station device to fail. It is estimated that

  FIG. 1 shows a configuration of a communication system 100 according to an embodiment of the present invention. This corresponds to a case where one intersection is viewed from above. The communication system 100 includes a base station device 10, a first vehicle 12a, a second vehicle 12b, a third vehicle 12c, a fourth vehicle 12d, a fifth vehicle 12e, a sixth vehicle 12f, and a seventh vehicle 12g, collectively referred to as a vehicle 12. , The eighth vehicle 12h, and the network 202. Each vehicle 12 is equipped with a terminal device (not shown). The first area 210 is formed around the base station apparatus 10, the second area 212 is formed outside the first area 210, and the second outside area 214 is formed outside the second area 212. ing.

  As shown in the drawing, the road that goes in the horizontal direction of the drawing, that is, the left and right direction, intersects the vertical direction of the drawing, that is, the road that goes in the up and down direction, at the central portion. Here, the upper side of the drawing corresponds to the direction “north”, the left side corresponds to the direction “west”, the lower side corresponds to the direction “south”, and the right side corresponds to the direction “east”. The intersection of the two roads is an “intersection”. The first vehicle 12a and the second vehicle 12b are traveling from left to right, and the third vehicle 12c and the fourth vehicle 12d are traveling from right to left. Further, the fifth vehicle 12e and the sixth vehicle 12f are traveling from the top to the bottom, and the seventh vehicle 12g and the eighth vehicle 12h are traveling from the bottom to the top.

  The communication system 100 arranges the base station device 10 at an intersection. The base station device 10 controls communication between terminal devices. The base station device 10 repeatedly generates a frame including a plurality of subframes based on a signal received from a GPS satellite (not shown) and a frame formed by another base station device 10 (not shown). Here, the road vehicle transmission period can be set at the head of each subframe. The base station apparatus 10 selects a subframe in which the road and vehicle transmission period is not set by another base station apparatus 10 from among the plurality of subframes. The base station apparatus 10 sets a road and vehicle transmission period at the beginning of the selected subframe. The base station apparatus 10 stores control information including information on a road and vehicle transmission period in a packet signal. The base station apparatus 10 also stores predetermined data in the packet signal. The base station apparatus 10 notifies the packet signal in the set road and vehicle transmission period.

  A first area 210 and a second area 212 are formed around the communication system 100 according to the reception status when the terminal apparatus receives a packet signal from the base station apparatus 10. As shown in the figure, a first area 210 is formed in the vicinity of the base station apparatus 10 as an area having a relatively good reception status. It can be said that the first area 210 is formed near the central portion of the intersection. On the other hand, the second area 212 is formed outside the first area 210 as a region where the reception situation is worse than that of the first area 210. Further, outside the second area 212, an area outside the second area 214 is formed as an area where the reception status is worse than that in the second area 212. Note that the packet signal error rate and received power are used as the reception status.

  The plurality of terminal apparatuses receive the packet signal broadcasted by the base station apparatus 10 and, based on the reception status of the received packet signal, in any of the first area 210, the second area 212, and the second outside area 214 Estimate if it exists. When it is estimated that the data exists in the first area 210 or the second area 212, the terminal device generates a frame based on the control information included in the received packet signal. As a result, the frame generated in each of the plurality of terminal devices is synchronized with the frame generated in the base station device 10. Further, the terminal device recognizes the road and vehicle transmission period set by each base station device 10 and specifies the vehicle and vehicle transmission period for transmission of the packet signal. Specifically, when it exists in the first area 210, the priority period is specified, and when it exists in the second area 212, the general period is specified. Further, the terminal device transmits a packet signal by executing TDMA in the priority period and executing CSMA / CA in the general period.

  Note that the terminal apparatus also selects subframes having the same relative timing in the next frame. In particular, in the priority period, the terminal device selects slots having the same relative timing in the next frame. Here, the terminal device acquires data and stores the data in a packet signal. The data includes, for example, information related to the location. The terminal device also stores control information in the packet signal. That is, the control information transmitted from the base station device 10 is transferred by the terminal device. On the other hand, when the terminal device is estimated to exist outside the second area 214, the terminal device transmits a packet signal by executing CSMA / CA regardless of the frame configuration.

  FIG. 2 shows the configuration of the base station apparatus 10. The base station apparatus 10 includes an antenna 20, an RF unit 22, a modem unit 24, a processing unit 26, a control unit 30, and a network communication unit 80. The RF unit 22 receives a packet signal from a terminal device (not shown) or another base station device 10 by the antenna 20 as a reception process. The RF unit 22 performs frequency conversion on the received radio frequency packet signal to generate a baseband packet signal. Further, the RF unit 22 outputs a baseband packet signal to the modem unit 24. In general, baseband packet signals are formed by in-phase and quadrature components, so two signal lines should be shown, but here only one signal line is shown for clarity. Shall be shown. The RF unit 22 includes an LNA (Low Noise Amplifier), a mixer, an AGC, and an A / D conversion unit.

  As a transmission process, the RF unit 22 performs frequency conversion on the baseband packet signal input from the modem unit 24 to generate a radio frequency packet signal. Further, the RF unit 22 transmits a radio frequency packet signal from the antenna 20 during the road-vehicle transmission period. The RF unit 22 also includes a PA (Power Amplifier), a mixer, and a D / A conversion unit.

  The modem unit 24 demodulates the baseband packet signal from the RF unit 22 as a reception process. Further, the modem unit 24 outputs the demodulated result to the processing unit 26. The modem unit 24 also modulates the data from the processing unit 26 as a transmission process. Further, the modem unit 24 outputs the modulated result to the RF unit 22 as a baseband packet signal. Here, since the communication system 100 corresponds to an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, the modem unit 24 also performs FFT (Fast Fourier Transform) as reception processing and IFFT (Inverse Fast Forward) as transmission processing. Also execute.

  The processing unit 26 receives a signal from a GPS satellite (not shown), and acquires time information based on the received signal. In addition, since a well-known technique should just be used for acquisition of the information of time, description is abbreviate | omitted here. The processing unit 26 generates a plurality of frames based on the time information. For example, the processing unit 26 generates 10 frames of “100 msec” by dividing the period of “1 sec” into 10 on the basis of the timing indicated by the time information. By repeating such processing, the frame is defined to be repeated. Note that the processing unit 26 may detect control information from the demodulation result. Such processing corresponds to generating a frame synchronized with the timing of the frame formed by another base station apparatus 10. Details of the processing of the processing unit 26 at that time will be described later.

  3A to 3D show frame formats defined in the communication system 100. FIG. FIG. 3A shows the structure of the frame. The frame is formed of N subframes indicated as the first subframe to the Nth subframe. For example, when the frame length is 100 msec and N is 10, a subframe having a length of 10 msec is defined. FIG. 3B shows a configuration of a frame generated by the first base station apparatus 10a. The first base station apparatus 10a sets a road and vehicle transmission period at the beginning of the first subframe. Moreover, the 1st base station apparatus 10a sets a vehicle transmission period following the road and vehicle transmission period in a 1st sub-frame. The vehicle transmission period is a period during which the terminal device can notify the packet signal. That is, in the road and vehicle transmission period which is the head period of the first subframe, the first base station apparatus 10a can notify the packet signal, and in the frame, the terminal apparatus transmits in the vehicle and vehicle transmission period other than the road and vehicle transmission period. It is defined that the packet signal can be broadcast. Furthermore, the first base station apparatus 10a sets only the vehicle transmission period from the second subframe to the Nth subframe.

  FIG. 3C shows a configuration of a frame generated by the second base station apparatus 10b. The second base station apparatus 10b sets a road and vehicle transmission period at the beginning of the second subframe. Also, the second base station apparatus 10b sets the vehicle transmission period from the first stage of the road and vehicle transmission period in the second subframe, from the first subframe and the third subframe to the Nth subframe. FIG. 3D shows a configuration of a frame generated by the third base station apparatus 10c. The third base station apparatus 10c sets a road and vehicle transmission period at the beginning of the third subframe. In addition, the third base station apparatus 10c sets the vehicle transmission period from the first stage of the road and vehicle transmission period in the third subframe, the first subframe, the second subframe, and the fourth subframe to the Nth subframe. As described above, the plurality of base station apparatuses 10 select different subframes, and set the road and vehicle transmission period at the head portion of the selected subframe.

  FIG. 4 shows the structure of a subframe. As illustrated, one subframe is configured in the order of a road and vehicle transmission period, a priority period, and a general period. The priority period and the general period correspond to the vehicle transmission period shown in FIG. When the road and vehicle transmission period is not included in the subframe, the subframe is configured in the order of the priority period and the general period. In the priority period, a plurality of slots are time-division multiplexed. With such a configuration, a frame including at least a plurality of slots is repeated. Returning to FIG.

  The processing unit 26 inputs a demodulation result from another base station device 10 or a terminal device (not shown) via the RF unit 22 and the modem unit 24. Here, the configuration of the MAC frame stored in the packet signal will be described as a demodulation result. The MAC frame input to the processing unit 26 and the MAC frame output from the processing unit 26 have the same configuration. FIGS. 5A and 5B show the formats of MAC frames stored in packet signals defined in the communication system 100. FIG. FIG. 5A shows the format of the MAC frame. In the MAC frame, “MAC header”, “RSU control header”, “application data”, and “CRC” are arranged in order from the top. The RSU control header corresponds to the control information described above. The application data stores data to be notified to the terminal device such as accident information.

  FIG. 5B shows the format of the RSU control header. The RSU control header includes “basic information”, “timer value”, “transfer count”, “subframe number”, “frame period”, “used subframe number”, “start timing & time length” in order from the top. Deploy. Note that the configuration of the RSU control header is not limited to that shown in FIG. 5B, and some elements may be excluded, or other elements may be included. The number of times of transfer indicates the number of times that the control information transmitted from the base station apparatus 10, particularly the content of the RSU control header, has been transferred by a terminal device (not shown). Here, the base station device 10 corresponds to the base station device 10 for the MAC frame output from the processing unit 26, and the base station device 10 corresponds to the MAC frame input to the processing unit 26. Corresponds to another base station apparatus 10. This is common in the following description.

  The MAC frame output from the processing unit 26 has the transfer count set to “0”. In addition, the number of transfers for the MAC frame input to the processing unit 26 is set to “0” or more. The number of subframes indicates the number of subframes forming one frame. The frame period indicates the period of the frame, and is set to, for example, “100 msec” as described above. The used subframe number is a number of a subframe in which the base station device 10 sets a vehicle transmission period. As shown in FIG. 3A, the subframe number is set to “1” at the head of the frame. In the start timing & time length, the start timing of the road and vehicle transmission period at the beginning of the subframe and the time length of the road and vehicle transmission period are indicated. Returning to FIG.

  Here, a procedure for selecting a subframe in which a road and vehicle transmission period is to be set will be described. Processing in which the processing unit 26 generates a frame synchronized with the timing of a frame formed by another base station apparatus 10 will be described. The processing unit 26 extracts a MAC frame whose transfer count is set to “0” from the MAC frames. This corresponds to a packet signal directly transmitted from another base station apparatus 10. The processing unit 26 specifies the value of the used subframe number among the extracted MAC frames. This corresponds to specifying a subframe used by another base station apparatus 10. The processing unit 26 measures the received power of the packet signal arranged at the head of the already identified subframe. This corresponds to measuring the reception power of the packet signal from the other base station apparatus 10.

  The processing unit 26 extracts a MAC frame whose transfer count is set to “1” or more from the MAC frames. This corresponds to a packet signal transmitted from the other base station apparatus 10 and then transferred by the terminal apparatus. The processing unit 26 specifies the value of the used subframe number among the extracted MAC frames. This corresponds to specifying a subframe used by another base station apparatus 10. The terminal device transfers the subframe number when the terminal device receives a packet signal from another base station device 10.

  The processing unit 26 also measures the received power of these packet signals. Further, the processing unit 26 estimates that the acquired received signal is the received power of the packet signal from the other base station apparatus 10 to which the control information is transferred by the packet signal. The processing unit 26 identifies a subframe in which a road and vehicle transmission period is to be set. Specifically, the processing unit 26 checks whether there is an “unused” subframe. If present, the processing unit 26 selects one of the “unused” subframes. Here, when a plurality of subframes are unused, the processing unit 26 selects one subframe at random. When there is no unused subframe, that is, when each of the plurality of subframes is used, the processing unit 26 preferentially specifies a subframe with low reception power.

  The processing unit 26 sets a road and vehicle transmission period at the beginning of the subframe having the specified subframe number. The processing unit 26 generates a MAC frame to be stored in the packet signal. At that time, the processing unit 26 determines the value of the RSU control header of the MAC frame according to the setting of the road and vehicle transmission period. This corresponds to control information related to the frame configuration. The processing unit 26 acquires predetermined information via the network communication unit 80 and includes the predetermined information in the application data. Here, the network communication unit 80 is connected to a network 202 (not shown). The processing unit 26 broadcasts the packet signal to the modem unit 24 and the RF unit 22 during the road and vehicle transmission period. Here, the packet signal includes control information and identification information for identifying the base station apparatus 10. Identification information for identifying the base station apparatus 10 is included in the MAC header of FIG.

  When the packet signal received from the terminal device includes information on another base station device 10 that has failed (hereinafter referred to as “failure information”), the processing unit 26 transmits the failure information to the network communication unit. Output to 80. The network communication unit 80 notifies failure information to a management center (not shown) via the network 202 (not shown). That is, the management center is notified of the failure found. The estimation result may be included in the packet signal and notified from the processing unit 26, the modem unit 24, and the RF unit 22. The control unit 30 controls processing of the entire base station apparatus 10.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 6 shows the configuration of the terminal device 14 mounted on the vehicle 12. The terminal device 14 includes an antenna 50, an RF unit 52, a modem unit 54, a processing unit 56, and a control unit 58. The processing unit 56 includes a generation unit 64, a timing identification unit 60, a transfer determination unit 90, a notification unit 70, an estimation unit 72, a storage unit 74, and a positioning unit 76. The timing specifying unit 60 includes an extraction unit 66, a selection unit 92, and a carrier sense unit 94. The antenna 50, the RF unit 52, and the modem unit 54 execute the same processing as the antenna 20, the RF unit 22, and the modem unit 24 in FIG. Therefore, here, the difference will be mainly described.

  The modem unit 54 and the processing unit 56 receive packet signals from other terminal devices 14 and the base station device 10 (not shown). As described above, a subframe in which the priority period and the general period are time-multiplexed is defined, and the road and vehicle transmission period may be time-multiplexed in the subframe. The road and vehicle transmission period is a period during which a packet signal can be notified from the base station apparatus 10. Here, the modem unit 54 and the processing unit 56 receive the packet signal from the base station apparatus 10 in the road and vehicle transmission period. The packet signal includes identification information for identifying the base station apparatus 10 that is a notification source of the packet signal. The priority period is a period that the terminal apparatus 14 existing in the first area 210 formed around the base station apparatus 10 should use for broadcasting the packet signal. Multiple slots are included in the priority period. The general period is a period that the terminal device 14 existing in the second area formed outside the first area 210 should use for broadcasting the packet signal. Also, a frame in which a plurality of subframes are time-multiplexed is defined.

  The extraction unit 66 measures the received power of the packet signal from the base station device 10. Based on the measured received power, the extraction unit 66 estimates whether it exists in the first area 210, the second area 212, or outside the second area 214. For example, the extraction unit 66 stores a first threshold for area determination and a second threshold for area determination. Here, the first threshold for area determination is defined to be larger than the second threshold for area determination. If the received power is greater than the first threshold value for area determination, the extraction unit 66 determines that it exists in the first area 210. If the received power is equal to or smaller than the first threshold for area determination and is larger than the second threshold for area determination, the extraction unit 66 determines that the second area 212 exists. If the received power is equal to or smaller than the second threshold for area determination, the extraction unit 66 determines that the power is present outside the second area 212. Note that the extraction unit 66 may use an error rate instead of the received power, or may use a combination of the received power and the error rate.

  Based on the estimation result, the extraction unit 66 determines any one of the priority period, the general period, and the timing unrelated to the frame configuration as the transmission period. More specifically, when it is estimated that the extraction unit 66 exists outside the second area 214, the extraction unit 66 selects a timing unrelated to the frame configuration. When it is estimated that the extraction unit 66 exists in the second area 212, the extraction unit 66 selects the general period. When it is estimated that the extraction unit 66 exists in the first area 210, the extraction unit 66 selects a priority period.

  When the demodulation result from the modem unit 54 is a packet signal from the base station apparatus 10 (not shown), the extraction unit 66 specifies the timing of the subframe in which the road-vehicle transmission period is arranged. Further, the extraction unit 66 generates a frame based on the subframe timing and the content of the RSU control header. Note that the generation of the frame may be performed in the same manner as the processing unit 26 described above, and thus the description thereof is omitted here. As a result, the extraction unit 66 generates a frame synchronized with the frame formed in the base station apparatus 10. Moreover, the extraction part 66 specifies a road and vehicle transmission period based on the content of the RSU control header.

  When selecting the priority period, the extraction unit 66 outputs information on the priority period to the selection unit 92. When the general period is selected, the extraction unit 66 outputs information on the frame and subframe timing and the vehicle transmission period to the carrier sense unit 94. When selecting the timing irrelevant to the frame configuration, the extraction unit 66 instructs the carrier sense unit 94 to execute carrier sense. The selection unit 92 receives information on the priority period from the extraction unit 66. In addition, the selection unit 92 selects any slot from the plurality of slots included in the priority period, and determines the selected slot as the transmission timing. Here, received power may be used to select a slot. For example, a slot with a small reception power is selected. The selection unit 92 notifies the generation unit 64 of the determined transmission timing.

  The carrier sense unit 94 receives information about the timing of frames and subframes and the vehicle transmission period from the extraction unit 66. The carrier sense unit 94 measures the interference power by performing carrier sense in the general period. Further, the carrier sense unit 94 determines the transmission timing in the general period based on the interference power. More specifically, the carrier sense unit 94 stores a predetermined threshold value in advance, and compares the interference power with the threshold value. If the interference power is smaller than the threshold value, the carrier sense unit 94 determines the transmission timing. When receiving the carrier sense execution instruction from the extraction unit 66, the carrier sense unit 94 determines the transmission timing by executing the CSMA without considering the frame configuration. The carrier sense unit 94 notifies the generation unit 64 of the determined transmission timing.

  The positioning unit 76 includes a GPS receiver (not shown), a gyroscope, a vehicle speed sensor, and the like. Based on data supplied from the GPS receiver, the position of the vehicle 12 (not shown), that is, the vehicle 12 on which the terminal device 14 is mounted, Get direction, speed, etc. The existence position is indicated by latitude and longitude. Since a known technique may be used for these acquisitions, description thereof is omitted here. The positioning unit 76 outputs the presence position and the like to the generation unit 64.

  The generation unit 64 receives the presence position and the like from the positioning unit 76. The generation unit 64 uses the MAC frame shown in FIGS. 5A to 5B and stores the presence position in the application data. Further, the generation unit 64 receives identification information from the extraction unit 66, and also stores the most recently received identification information in the application data. The generation unit 64 generates a packet signal including a MAC frame, and generates the packet signal via the modulation / demodulation unit 54, the RF unit 52, and the antenna 50 at the transmission timing determined by the selection unit 92 or the carrier sense unit 94. Broadcast packet signals. The transmission timing is included in the vehicle transmission period.

  The transfer determination unit 90 controls transfer of the RSU control header. The extraction unit 66 extracts an RSU control header from a packet signal for which the base station device 10 is an information source. As described above, when the packet signal is directly transmitted from the base station apparatus 10, the number of transfers is set to “0”, but when the packet signal is transmitted from another terminal apparatus 14. The number of transfers is set to a value of “1 or more”. Here, since the used subframe number is not changed when transferred by the terminal apparatus 14, the subframe used in the base station apparatus 10 serving as the information source is specified by referring to the used subframe number. The

  The transfer determination unit 90 acquires information on the number of transfers for each base station apparatus 10 that is an information source. More specifically, the transfer determining unit 90 sequentially acquires the number of transfers corresponding to the subframe number “1”, and then executes the same processing for the number of transfers corresponding to other subframe numbers. . Further, the transfer determination unit 90 acquires, for each base station device 10 serving as an information source, the smaller transfer number, for example, the value of the minimum transfer number, from the information related to the transfer number related to the base station device 10. To do. That is, the transfer count acquisition unit 110 acquires the minimum transfer count corresponding to the subframe number “1”, the minimum transfer count corresponding to the subframe number “2”, and the like.

  The transfer determination unit 90 measures the RSU control header, that is, the number of extractions of control information, for each base station apparatus 10 that is an information source. Moreover, the transfer determination part 90 selects the frequency | count of extraction of the control information containing the value of the frequency | count of transfer acquired in the transfer determination part 90 for every base station apparatus 10 used as an information source. More specifically, the transfer determination unit 90 measures the number of times control information is extracted for each transfer number for one subframe number. As a result, for example, for the subframe number “1”, the number of times control information is extracted is “0”, and the number of times control information is extracted is “4”. ", And the number of times control information is extracted is" 6 "times. If the acquired transfer count is “1”, the transfer determination unit 90 selects the control information extraction count “4” including the transfer count.

  The transfer determination unit 90 stores the subframe number, the transfer count, and the extraction count in association with each other. In addition, the transfer determination unit 90 updates the stored content when the number of transfers and the number of extractions are updated. The transfer determination unit 90 acquires the number of transfers and the number of extractions for each base station device 10. The transfer determination unit 90 selects control information corresponding to at least one base station apparatus 10 as control information to be transferred based on the number of transfers and the number of extractions. More specifically, the transfer determination unit 90 compares the number of transfers with the plurality of base station devices 10 and then compares the number of extractions. That is, after selecting the control information with the smaller number of transfers, for example, the control information with the minimum number of transfers, the control information with the larger number of extractions and the maximum number of extractions are selected from the selected control information. Selected control information is selected.

  In this way, control information having the minimum number of transfers and control information having the maximum number of extractions corresponding to the number of transfers is selected by the transfer determination unit 90. It can be said that control information is received near the base station apparatus 10 which becomes an information source, so that the frequency | count of transfer is small. In addition, it can be said that the control information is received in a situation where the variation in the wireless environment is smaller as the number of extractions is larger. Therefore, it can be said that the terminal device 14 has selected the control information from the base station apparatus 10 installed as close as possible by selecting the control information that satisfies the above-described situation.

  The transfer determination unit 90 instructs the generation unit 64 to generate an RSU control header based on the selected control information. The transfer determination unit 90 increases the number of transfers in the information related to the number of transfers when storing the control information in the RSU control header. In response to such an instruction, the generation unit 64 generates an RSU control header based on the control information selected by the transfer determination unit 90 and increases the number of transfers at that time.

  The storage unit 74 stores position information of the base station apparatus 10 that can broadcast a packet signal to be received by the RF unit 52, the modem unit 54, and the processing unit 56. Since a plurality of base station devices 10 are installed, the storage unit 74 stores a plurality of pieces of position information. The position information is indicated by latitude and longitude so as to be associated with the road map. Further, since the position information is shown as digital data, the storage unit 74 is configured as a storage medium such as a hard disk capable of storing digital data. Here, in order to simplify the description, it is assumed that the position information is stored in the storage unit 74 in advance. For example, it is preset when the terminal device 14 is purchased.

  The estimation unit 72 sequentially receives the positioning presence positions from the positioning unit 76. The estimation unit 72 assumes a circular area having a predetermined radius with the position information stored in the storage unit 74 as the center. Such a region corresponds to, for example, the first area 210 and the second area 212 in FIG. 1, but here corresponds to the second area. A circular area is assumed for each of the plurality of base station apparatuses 10. The estimation unit 72 is present in the vicinity of the base station apparatus 10 installed at the center of the circular area by detecting that the consecutively received existence positions have entered from the outside to the inside of the circular area. Detect that. Moreover, the estimation part 72 detects whether the packet signal from the base station apparatus 10 is received while existing in the circular area. When the packet signal is received, the estimation unit 72 estimates that the base station apparatus 10 is operating normally. On the other hand, when the packet signal is not received, the estimation unit 72 estimates a failure of the base station device 10. When the estimation unit 72 estimates a failure, the estimation unit 72 outputs the fact to the generation unit 64 and the notification unit 70.

  When the generation unit 64 receives a failure estimation result from the estimation unit 72, the generation unit 64 stores the failure estimation result in the application data. As a result, the failure estimation result is notified during the vehicle transmission period. The notification unit 70 acquires a packet signal from the base station device 10 (not shown) in the road and vehicle transmission period, and acquires a packet signal from another terminal device 14 (not shown) in the vehicle and vehicle transmission period. The notification unit 70 notifies the driver of the approach of another vehicle 12 (not shown) to the driver via a monitor or a speaker in accordance with the content of data stored in the packet signal. Furthermore, when the notification unit 70 receives the estimation result of the failure from the estimation unit 72, the notification unit 70 also notifies the driver of the estimation result. When the notification is made via the monitor, the notification unit 70 displays the display color of the part where the base station apparatus 10 that has failed is installed in red. Moreover, the notification part 70 may output that the base station apparatus 10 is out of order from a speaker. The control unit 58 controls the operation of the entire terminal device 14.

  The operation of the communication system 100 configured as above will be described. FIG. 7 is a flowchart showing a communication status authorization procedure in the terminal device 14. The positioning unit 76 acquires the presence position (S10). If it does not exist in the second area (N in S12), the process returns to Step 10. When it exists in the second area (Y in S12), if the RF unit 52 and the modem unit 54 receive a packet signal in the second area (Y in S14), the estimation unit 72 determines that it is normal (Y) S16). On the other hand, if the RF unit 52 and the modem unit 54 do not receive a packet signal in the second area (N in S14), the skip 16 is skipped.

  FIG. 8 is a flowchart illustrating a failure notification procedure in the terminal device 14. The estimation part 72 detects having moved out of the second area (S20). If the estimation unit 72 does not recognize that it is normal (N in S22), the notification unit 70 notifies a failure (S24). If the estimation unit 72 recognizes that it is normal (Y in S22), step 24 is skipped.

  Next, a modified example of the present invention will be described. The modification also relates to the communication system 100 including the base station device 10 and the terminal device 14 as in the embodiment. In the embodiment, the location information of the base station device 10 is preset in the storage unit 74. On the other hand, in the modification, the location information of the base station device 10 is not preset in the storage unit 74, and the storage unit 74 stores the location information based on the location information included in the received packet signal. That is, in the modification, the position information is updated autonomously. The communication system 100 according to the modified example is the same type as that in FIG. 1, the base station device 10 is the same type as that in FIG. 2, and the terminal device 14 is the same type as that in FIG. Below, it demonstrates focusing on a difference.

  Here, the processing unit 26 of the base station apparatus 10 includes the position information of the base station apparatus 10 in the packet signal. The location information may be included in the RSU control header or may be included in application data. The extraction unit 66 of the terminal device 14 extracts position information from the packet signal. The extraction unit 66 outputs the position information to the estimation unit 72. The estimation unit 72 confirms whether the received position information is already stored in the storage unit 74. When the position information is not stored, the estimation unit 72 causes the storage unit 74 to store the position information. At that time, the reception date and time may be stored in the storage unit 74 in association with the position information. On the other hand, when the position information is already stored, the estimation unit 72 does not store the newly received position information in the storage unit 74. Note that the estimation unit 72 may update only the reception date and time. Further, the estimation unit 72 may delete the position information corresponding to the recording date and time before the predetermined period from the storage unit 74.

  FIG. 9 is a flowchart showing a database update procedure in the terminal device 14 according to the modification of the present invention. The RF unit 52 and the modem unit 54 receive the packet signal (S30). If the information of the base station apparatus 10 has been registered (Y in S32), the storage unit 74 updates the reception date and time (S34). If the information of the base station device 10 has not been registered (N in S32), the storage unit 74 updates the information of the terminal device 14 (S36).

  FIG. 10 is a flowchart showing a database erasing procedure in the terminal device 14 according to the modification of the present invention. If there is expiration information (Y in S40), the storage unit 74 deletes the information (S42). If there is no expiration information (N in S40), step 42 is skipped.

  Next, another modification of the present invention will be described. Another modification also relates to the communication system 100 including the base station device 10 and the terminal device 14 as in the embodiment. The estimation unit 72 of the terminal device 14 in the embodiment estimates the failure of the base station device 10 by itself. On the other hand, in another modified example, the packet signal broadcast from the other terminal device 14 includes the failure estimation result, and based on this, the presence of the failed base station device 10 is notified. The communication system 100 according to the modified example is the same type as that in FIG. 1, the base station device 10 is the same type as that in FIG. 2, and the terminal device 14 is the same type as that in FIG. Below, it demonstrates focusing on a difference.

  As described in the embodiment, the packet signal broadcast from the other terminal device 14 includes a failure estimation result. Also, the packet signal broadcast from the base station apparatus 10 may include a failure estimation result. If the packet signal includes a failure estimation result, the extraction unit 66 of the terminal device 14 extracts this. The extraction unit 66 outputs the extracted failure estimation result to the notification unit 70. When the notification unit 70 receives the estimation result of the failure from the estimation unit 72, the notification unit 70 also notifies the driver of the estimation result.

  FIG. 11 is a flowchart showing a failure information notification procedure in the terminal device 14 according to another modification of the present invention. The RF unit 52 and the modem unit 54 receive the packet signal (S50). When failure information is stored (Y in S52), the notification unit 70 notifies the failure information (S54). If failure information is not stored (N in S52), step 54 is skipped.

  According to the embodiment of the present invention, it is monitored whether a packet signal from the base station apparatus is received in the area where the base station apparatus is arranged, so that the base station apparatus in failure can be detected. Also, if the packet signal is received even once in the area, it is estimated that the base station apparatus is normal, so that even if the communication quality is deteriorated, it is erroneously estimated that the base station apparatus is out of order. Probability can be reduced. In addition, since a failed base station apparatus is automatically detected, it is possible to detect a failure early. In addition, since the failure is detected early, the influence on the communication system can be reduced. In addition, since the driver is notified of the failure estimation result, the driver can be alerted. In addition, since the packet signal including the failure estimation result is notified, it is possible to notify the other terminal devices of the presence of the failed base station device.

  In addition, since the position information of the base station apparatus is stored in advance, the processing amount can be reduced. Further, since the position information of the base station apparatus is extracted from the received packet signal, the position information of the base station apparatus can be collected autonomously. Further, since the position information of the base station device is autonomously collected, the processing for presetting the information of the base station device can be omitted. Further, since the position information of the base station apparatus is autonomously collected, the latest position information of the base station apparatus can be acquired. In addition, when a predetermined period has elapsed, an increase in the storage capacity of the location information of the base station device can be suppressed. In addition, since the packet signal from the base station apparatus includes the estimation result of the failure of another base station device, the failure detection process can be facilitated. Further, since the packet signal from the terminal device includes the estimation result of the failure of the base station device, the failure detection process can be facilitated.

  Since received power is used to distinguish between the first area and the second area, a range in which the propagation loss is within a predetermined level can be defined as the first area. In addition, since the range in which the propagation loss is within a predetermined level is defined in the first area, the vicinity of the center of the intersection can be used as the first area. In addition, since the time division multiplexing by slots is executed in the priority period, the error rate can be reduced. Moreover, since CSMA / CA is performed in a general period, the number of terminal devices can be adjusted flexibly.

  Also, since the subframe used by the other base station apparatus is specified based on the packet signal received from the terminal apparatus as well as the packet signal directly received from the other base station apparatus, The frame identification accuracy can be improved. In addition, since the accuracy of identifying subframes in use is improved, the probability of collision between packet signals transmitted from the base station apparatus can be reduced. Moreover, since the collision probability between packet signals transmitted from the base station apparatus is reduced, the terminal apparatus can accurately recognize the control information. Further, since the control information is accurately recognized, the road and vehicle transmission period can be accurately recognized. Further, since the road and vehicle transmission period is accurately recognized, the collision probability of the packet signal can be reduced.

  In addition, since a subframe other than the currently used subframe is used preferentially, it is possible to reduce the possibility of transmitting a packet signal at a timing overlapping with packet signals from other base station apparatuses. Further, when any subframe is used by another base station apparatus, a subframe with low received power is selected, so that the influence of packet signal interference can be suppressed. Further, since the received power of the terminal device is used as the received power from another base station device that is the transmission source of the control information relayed by the terminal device, the received power estimation process can be simplified.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the storage unit 74 stores the position information of the base station device 10 in advance. In the modification of the present invention, the storage unit 74 does not store the position information of the base station device 10 in advance. The position information of the base station apparatus 10 included in the packet signal is stored. However, the present invention is not limited to this. For example, the storage unit 74 may store the position information of the base station apparatus 10 in advance, and may also store the position information of the base station apparatus 10 included in the packet signal. According to this modification, the storage unit 74 can update the previously stored location information of the base station device 10 with the location information of the base station device 10 included in the packet signal.

  In the modification of the present invention, the storage unit 74 stores the position information of the base station device 10 included in the packet signal from the base station device 10. However, the present invention is not limited to this, and for example, the storage unit 74 may store the position information of the base station device 10 included in the packet signal from the terminal device 14. At that time, the terminal device 14 broadcasts a packet signal including the position information of the base station device 10. According to this modification, the reception opportunity of the packet signal including the position information of the base station apparatus 10 can be increased.

  10 base station devices, 12 vehicles, 14 terminal devices, 20 antennas, 22 RF units, 24 modulation / demodulation units, 26 processing units, 30 control units, 50 antennas, 52 RF units, 54 modulation / demodulation units, 56 processing units, 58 control units, 60 timing identification unit, 64 generation unit, 66 extraction unit, 70 notification unit, 72 estimation unit, 74 storage unit, 76 positioning unit, 80 network communication unit, 90 transfer determination unit, 92 selection unit, 94 carrier sense unit, 100 communication System, 202 network, 210 first area, 212 second area, 214 outside second area.

Claims (3)

A terminal device that performs communication between terminal devices,
A receiving unit that receives a signal from the base station apparatus in the first period among frames including a first period in which a signal can be reported from the base station apparatus and a second period in which a signal can be reported from the terminal apparatus. When,
A storage unit for storing position information of a base station apparatus capable of broadcasting a signal to be received by the receiving unit;
In the vicinity of the position information stored in the storage unit, when the reception unit has not received a signal from the base station device, an estimation unit that estimates a failure of the base station device;
A terminal device comprising:   The terminal device according to claim 1, further comprising a notification unit that notifies a user of a result estimated by the estimation unit.   The terminal apparatus according to claim 1, further comprising: a transmission unit that broadcasts a signal including a result estimated by the estimation unit in the second period.

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