JP2015039089A - Radio device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to improve the convenience of a user by changing communication processing depending on a communication environment.SOLUTION: An extraction unit 66 detects migration from a first area to a second area in an area where the first area and the second area are defined as areas having priority different from each other. If the extraction unit 66 has detected migration, it changes communication processing from first communication processing defined in the first area to second communication processing defined in the second area. Here, a transmission frequency in the second communication processing is lower than that in the first communication processing. A notification unit 70 gives notice of area change if migration has been detected.

Description

  The present invention relates to communication technology, and more particularly, to a wireless 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, a packet signal is transmitted after confirming that no other packet signal is transmitted by carrier sense.

  On the other hand, when a wireless LAN is applied to inter-vehicle communication such as ITS (Intelligent Transport Systems), 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. In addition, since various communication environments are assumed, it is desired to execute communication processing according to the communication environment.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a wireless device suitable for a communication environment.

  In order to solve the above problems, a radio apparatus according to an aspect of the present invention defines a first area and a second area as areas having different priorities, and moves from the first area to the second area. The detection unit to detect, and the movement in the detection unit when the detection unit detects movement, the communication unit that changes the first communication process defined in the first area to the second communication process defined in the second area And a notification unit for notifying the change of the area. The transmission frequency in the second communication process in the communication unit is lower than the transmission frequency in the first communication process.

  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 wireless device suitable for a communication environment can be provided.

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. FIGS. 4A to 4B are diagrams illustrating the configuration of the priority area and the general area. FIGS. 5A to 5B are diagrams illustrating the configuration of the subframes of FIGS. 3A to 3D. FIGS. 6A and 6B are diagrams showing the format of the MAC frame stored in the 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 selection procedure of the priority period or the general period in the terminal device of FIG. It is a flowchart which shows the display procedure in the terminal device of FIG. It is a figure which shows the structure of the terminal device which concerns on the modification of this invention. It is a flowchart which shows the process sequence in the terminal device of FIG. It is a flowchart which shows the process sequence in the terminal device which concerns on another modification of this invention. It is a figure which shows the structure of the communication system which concerns on another modification of this invention. It is a figure which shows the structure of the communication system which concerns on another modification of this invention. It is a figure which shows the data structure of the table memorize | stored in the extraction part of FIG. It is a flowchart which shows the process sequence in the terminal device of FIG.

  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. Here, the base station apparatus repeatedly defines a frame including a plurality of subframes. The base station apparatus selects any of a plurality of subframes for road-to-vehicle communication, and broadcasts a packet signal in which control information and the like are stored during 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. Here, the following two situations are assumed depending on the shape of the intersection.

  In the first situation, since the vehicle in the second area will enter the intersection from now on, 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. Is the case. The second situation is that the vehicle in the first area exists near the intersection, so the packet signal from the terminal device mounted on the vehicle is important information from the point of suppression of collision accidents. This is the case. Thus, it is required to set the priority according to the position where the packet signal should be transmitted. If the driver can recognize what priority is set in the area, it can be reflected in the driving. For example, if it is known that the vehicle is located in a high priority area, the possibility of a collision accident increases, so the driver can drive more carefully. For this reason, it is desired that the driver recognize what kind of priority exists in the set area.

  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 formed by a plurality of slots, and the terminal device broadcasts the packet signal by any of the plurality of slots. The general period has a predetermined period, and the terminal apparatus broadcasts a packet signal by the CSMA method during the general period. The terminal device existing outside the second area transmits a packet signal by the CSMA method regardless of the frame configuration. For the first situation described above, the terminal apparatus existing in the second area uses the priority period, and the terminal apparatus existing in the first area uses the general period. In addition, for the second situation described above, the terminal apparatus existing in the first area uses the priority period, and the terminal apparatus existing in the second area uses the general period.

  Here, it is determined in which area the terminal device mounted on the vehicle is present. It is preferable for the driver to be able to recognize which area is present. When the risk of a collision accident is higher in the priority area than in the general area, the driver can drive more carefully than before, if he / she recognizes that it is in the priority area. That is, the driver can be alerted. In order to cope with this, the terminal device notifies the driver of the area that currently exists, thereby allowing the driver to recognize that the area has changed.

  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 notifies the packet signal in the set road and vehicle transmission period.

  A plurality of types of data are assumed as data to be included in the packet signal. One is data such as traffic jam information and construction information, and the other is data relating to each slot included in the priority period. The latter includes slots that are not used in any terminal device (hereinafter referred to as “empty slots”), slots that are used in one terminal device (hereinafter referred to as “used slots”), and used in multiple terminal devices. Slot (hereinafter referred to as “collision slot”). A packet signal containing data such as traffic jam information and construction information (hereinafter referred to as “RSU packet signal”) and a packet signal including data relating to each slot (hereinafter referred to as “control packet signal”) are separately provided. Is generated. The RSU packet signal and the control packet signal are collectively referred to as “packet signal”.

  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 packet signal from the base station apparatus 10 includes two types of control information, one is information on the set road and vehicle transmission period (hereinafter referred to as “basic part”), and the other is Information on the set priority period (hereinafter referred to as “extended portion”). The terminal device generates a frame based on the basic part 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 receives the packet signal broadcasted by the base station device 10, and based on the reception status of the received packet signal and the extended portion, the first area 210, the second area 212, and the second area outside It is estimated in which of 214.

  Further, the extended portion included in the packet signal from the base station apparatus 10 includes information indicating the correspondence between the area and the vehicle transmission period (hereinafter referred to as “priority area identifier”). The information indicating the correspondence between the area and the vehicle transmission period can be said to be information indicating whether the priority period should be used in either the first area 210 or the second area 212. Here, the first arrangement and the second arrangement are defined. In the first arrangement, the general period is used in the first area 210 and the priority period is used in the second area 212. On the other hand, in the second arrangement, the priority period is used in the first area 210 and the general period is used in the second area 212. When the priority area identifier indicates the first arrangement and exists in the first area 210, the terminal device broadcasts the packet signal by carrier sense in the general period, and when the priority area identifier exists in the second area 212, priority is given. The packet signal is broadcast in any slot included in the period. When the priority area identifier indicates the second arrangement and exists in the first area 210, the terminal device broadcasts the packet signal in any slot included in the priority period and exists in the second area 212. When doing so, the packet signal is broadcast by carrier sense in the general period.

  As a result, TDMA is executed in the priority period, and CSMA / CA is executed 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 broadcasts the 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 processing unit 26 includes a frame definition unit 40, a selection unit 42, a detection unit 44, a generation unit 46, and a setting unit 48. 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 frame defining unit 40 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 frame defining unit 40 generates a plurality of frames based on the time information. For example, the frame defining unit 40 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 frame defining unit 40 may detect the control information from the demodulation result and generate a frame based on the detected control information. Such processing corresponds to generating a frame synchronized with the timing of the frame formed by another base station apparatus 10. 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 8, a subframe having a length of 12.5 msec is defined. The description of FIGS. 3B to 3D will be described later and returns to FIG.

  The selection part 42 selects the sub-frame which should set a road and vehicle transmission period among several sub-frames contained in the flame | frame. More specifically, the selection unit 42 receives a frame defined by the frame defining unit 40. The selection unit 42 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. The selection unit 42 extracts a demodulation result from another base station apparatus 10 from the input demodulation results. The extraction method will be described later. The selection unit 42 identifies the subframe that has not received the demodulation result by specifying the subframe that has received the demodulation result. This corresponds to specifying a subframe in which the road and vehicle transmission period is not set by another base station apparatus 10, that is, an unused subframe. When there are a plurality of unused subframes, the selection unit 42 selects one subframe at random. When there are no unused subframes, that is, when each of a plurality of subframes is used, the selection unit 42 acquires reception power corresponding to the demodulation result, and gives priority to subframes with low reception power. Select

  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. Returning to FIG. The selection unit 42 outputs the selected subframe number to the detection unit 44 and the generation unit 46.

  The setting unit 48 has an interface for receiving instructions from the business operator, and receives parameter setting instructions via the interface. For example, the interface is a button, and the setting unit 48 receives a parameter setting instruction by inputting to the button. The interface may be a connection terminal with a network communication unit 80 described later. At this time, the setting unit 48 receives a parameter setting instruction via the network communication unit 80, the network 202 (not shown), and the PC. Here, the parameter setting instruction is whether to use the first arrangement or the second arrangement. The setting unit 48 outputs the received setting instruction to the generation unit 46.

  FIGS. 4A to 4B are diagrams illustrating the configuration of the priority area and the general area. The first area 210, the second area 212, and the second outside area 214 shown in these figures are the same as those in FIG. FIG. 4A corresponds to the first arrangement. A first area 210 around the base station device 10 (not shown) is set as a general area. The general area is an area where the general period should be used. Therefore, the terminal device 14 existing in the general area can report the packet signal in the general period. A second area surrounding the first area 210 is set as a priority area. The priority area is an area where the priority period should be used. Therefore, the terminal device 14 existing in the priority area can broadcast the packet signal in each slot forming the priority period. FIG. 4B corresponds to the second arrangement. The first area 210 is set as the priority period, and the second area 212 is set as the general period. Note that the sizes of the first area 210 and the second area 212 may be different between the first arrangement and the second arrangement. Returning to FIG.

  The detection unit 44 identifies whether each of the plurality of slots included in the priority period is unused, in use, or has a collision. Before describing the processing of the detection unit 44, the configuration of the subframe will be described here. Fig.5 (a)-(b) shows the structure of a sub-frame. As illustrated, one subframe is configured in the order of a road and vehicle transmission period, a priority period, and a general period. In the road and vehicle transmission period, the base station device 10 broadcasts the packet signal, the priority period is formed by time division multiplexing of a plurality of slots, and the terminal device 14 can broadcast the packet signal in each slot, The general period has a predetermined length, and the terminal device 14 can broadcast the packet signal. 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. At that time, the road and vehicle transmission period is also a priority period. FIG. 5B will be described later. Returning to FIG.

  The detector 44 measures the received power for each slot and also measures the error rate for each slot. An example of the error rate is BER (Bit Error Rate). If the received power is lower than the received power threshold, the detection unit 44 determines that the slot is unused (hereinafter, such a slot is referred to as an “empty slot”). On the other hand, if the received power is equal to or greater than the received power threshold and the error rate is lower than the error rate threshold, the detection unit 44 is in use of the slot (hereinafter referred to as such a slot). (Referred to as “used slot”). If the received power is equal to or greater than the threshold for received power and the error rate is equal to or greater than the threshold for error rate, the detection unit 44 has a collision in the slot (hereinafter referred to as such a slot). Are referred to as “collision slots”). The detection unit 44 executes such processing for all slots and outputs the results (hereinafter referred to as “detection results”) to the generation unit 46.

  The generation unit 46 receives a setting instruction from the setting unit 48, receives a subframe number from the selection unit 42, and receives a detection result from the detection unit 44. The generation unit 46 sets a road and vehicle transmission period in the subframe of the received subframe number, and generates a control packet signal and an RSU packet signal to be notified during the road and vehicle transmission period. FIG. 5B shows the arrangement of packet signals during the road and vehicle transmission period. As illustrated, one control packet signal and a plurality of RSU packet signals are arranged in the road and vehicle transmission period. Here, the front and rear packet signals are separated by SIFS (Short Interframe Space). Returning to FIG.

  Here, the configuration of the control packet signal and the RSU packet signal will be described. FIGS. 6A and 6B show a format of a MAC frame stored in a packet signal defined in the communication system 100. FIG. FIG. 6A shows the format of the MAC frame. In the MAC frame, “MAC header”, “LLC header”, “message header”, “data payload”, and “FCS” are arranged in order from the top. When the detection result is included in the data payload, the packet signal storing the MAC frame corresponds to the control packet signal. Further, when receiving data such as traffic jam information and construction information from the network communication unit 80, the generation unit 46 includes them in the data payload. A packet signal storing such a MAC frame corresponds to an RSU packet signal. Here, the network communication unit 80 is connected to a network 202 (not shown). The packet signal broadcasted in the priority period and the general period also stores the MAC frame shown in FIG.

  FIG. 6B is a diagram illustrating a configuration of a message header generated by the generation unit 46. The message header includes a basic part and an extended part. As described above, since the control packet signal and the RSU packet signal have the same configuration, they include a basic part and an extended part. The basic part includes “protocol version”, “transmission node type”, “reuse count”, “TSF timer”, “RSU transmission period length”, and the extended part includes “vehicle slot size”, “priority general ratio” "," Priority general threshold value "," priority area identifier ".

  The protocol version indicates the version of the corresponding protocol. The transmission node type indicates the transmission source of the packet signal including the MAC frame. For example, “0” indicates a terminal device, and “1” indicates the base station device 10. When the selection unit 42 extracts a demodulation result from another base station apparatus 10 from among the input demodulation results, the selection unit 42 uses the value of the transmission node type. The reuse count indicates an index of validity when the message header is transferred by the terminal device, and the TSF timer indicates the transmission time. The RSU transmission period length indicates the length of the road and vehicle transmission period, and can be said to be information relating to the road and vehicle transmission period.

  The car slot size indicates the size of the slot included in the priority period, the priority general ratio indicates the ratio between the priority period and the general period, and the priority general threshold indicates whether the priority period is used or the general period is used. It is a threshold value for causing the terminal device 14 to select and a threshold value for the received power. The priority area identifier is an identifier for indicating which one of the first arrangement and the second arrangement is used. Here, when the first arrangement is used, that is, when the arrangement of FIG. 4A is used, the priority area identifier is set to “0”. When the second arrangement is used, that is, when the arrangement shown in FIG. 4B is used, the priority area identifier is set to “1”. Thus, the extended portion corresponds to information on the priority period and the general period. Returning to FIG.

  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. That is, the processing unit 26 broadcasts the control packet signal and the RSU packet signal including the basic part and the extended part in the base station broadcast period. 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 only by hardware, or by a combination of hardware and software.

  FIG. 7 shows a 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, and an acquisition unit 72. 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, the modem unit 54 and the processing unit 56 receive the packet signal from the base station apparatus 10 during the road and vehicle transmission period. As described above, the modem unit 54 and the processing unit 56 receive packet signals from other terminal apparatuses 14 in the priority period and the general 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 basic part in the message header of the packet signal, specifically, the content of the RSU transmission period length. Note that the generation of the frame only needs to be performed in the same manner as the frame defining unit 40 described above, and 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.

  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 an area determination threshold value. The area determination threshold corresponds to the above-described priority general threshold. If the received power is larger than the area determination threshold, the extraction unit 66 determines that the first area 210 exists. If the received power is equal to or less than the area determination threshold, the extraction unit 66 determines that the second area 212 exists. When the packet signal from the base station apparatus 10 has not been received, the extraction unit 66 determines that it exists 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 and the priority area identifier, the extraction unit 66 determines whether the currently existing area is a priority area or a general area. When the priority area identifier is “1”, the extraction unit 66 selects the priority area if it exists in the first area 210, and selects the general area if it exists in the second area 212. On the other hand, when the priority area identifier is “0”, the extraction unit 66 selects the general area if it exists in the first area 210 and selects the priority area if it exists in the second area 212.

  Further, when estimating that the extraction unit 66 exists outside the second area 214, the extraction unit 66 selects a timing unrelated to the frame configuration. The extraction unit 66 selects a general period when a general area is selected. When selecting the priority area, the extraction unit 66 selects a priority period. When selecting the priority period, the extraction unit 66 outputs the detection result included in the data payload of the control packet signal 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 the detection result from the extraction unit 66. As described above, the detection result indicates whether each of the plurality of slots included in the priority period is an empty slot, a used slot, or a collision slot. The selection unit 92 selects one of the empty slots. If a slot has already been selected, the selection unit 92 continues to select the same slot if the slot is a used slot. On the other hand, when the slot has already been selected, the selection unit 92 newly selects an empty slot if the slot is a collision slot. The selection unit 92 notifies the generation unit 64 of information related to the selected slot as a 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 acquisition unit 72 includes a GPS receiver (not shown), a gyroscope, a vehicle speed sensor, and the like. Based on data supplied from these, the location of the vehicle 12 (not shown), that is, the position of the vehicle 12 on which the terminal device 14 is mounted, the progress The direction, the moving speed, etc. (hereinafter collectively referred to as “position information”) are acquired. 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 acquisition unit 72 outputs the position information to the generation unit 64.

  The transfer determining unit 90 controls message header transfer. The transfer determining unit 90 extracts a message header from the packet signal. When the packet signal is directly transmitted from the base station apparatus 10, the reuse count is set to “0”. However, when the packet signal is transmitted from another terminal apparatus 14, the reuse is performed. The number of times is set to a value of “1 or more”. The transfer determining unit 90 selects a message header to be transferred from the extracted message header. Here, for example, the message header with the smallest number of reuses is selected. Further, the transfer determination unit 90 may generate a new message header by combining the contents included in the plurality of message headers. The transfer determination unit 90 outputs the message header to be selected to the generation unit 64. At that time, the transfer determining unit 90 increases the number of reuses by “1”.

  The generation unit 64 receives position information from the acquisition unit 72 and receives a message header from the transfer determination unit 90. The generation unit 64 stores the position information in the data payload using the MAC frame shown in FIGS. 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 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. As a process for the acquired packet signal, the notification unit 70 notifies the driver of the approach of another vehicle 12 (not shown) or the like via a monitor or a speaker in accordance with the content of data stored in the packet signal.

  As described above, the extraction unit 66 specifies whether the extraction unit 66 exists in the first area 210, the second area 212, or the second area 214. Here, the first area 210, the second area 212, and the second outside area 214 can be said to be areas having different priorities. In the case of the second arrangement, since the first area 210 corresponds to the priority area and the second area 212 corresponds to the general area, the priority of the first area 210 is the highest, and the priority of the second area 212 is the next. High and the priority outside 214 in the second area is low. In this case, it can be said that the priority of each area is defined according to the importance of the signal to be notified. On the other hand, in the first arrangement, since the first area 210 corresponds to the general area and the second area 212 corresponds to the priority area, the second area 212 has the highest priority, and the first area 210 has the highest priority. Next, the priority of 214 outside the second area is low.

  Moreover, it can be said that the priority with respect to the 1st area 210 and the 2nd area 212 is defined according to the quality of the received signal. In the second arrangement, the first area 210 with higher reception quality has a higher priority than the second area 212 with lower reception quality. In the first arrangement, the second area 212 having a lower reception quality has a higher priority than the first area 210 having a higher reception quality. Furthermore, it can be said that the priority for the first area 210 and the second area 212 is determined according to the distance to the base station apparatus 10. In the case of the second arrangement, the first area 210 with a shorter distance has a higher priority than the second area 212 with a longer distance. In the case of the first arrangement, the second area 212 having a longer distance has a higher priority than the first area 210 having a shorter distance.

  The extraction unit 66 detects movement to different areas by monitoring existing areas. For example, movement from a priority area to a general area. The reverse movement may be used. Furthermore, the movement may be between the second area 212 and the second area 214, such as between the general area and the second area 214, or between the priority area and the second area 214. . When detecting the movement, the extraction unit 66 changes the instruction to the selection unit 92 and the carrier sense unit 94. For example, when the movement from the priority area to the general area is detected, the extraction unit 66 changes the communication process defined in the priority area to the communication process defined in the general area. Specifically, the instruction to the selection unit 92 is changed to an instruction to the carrier sense unit 94.

  When the extraction unit 66 detects a movement between the second area 212 and the second area 214, the extraction unit 66 performs a communication process between the communication process in the second area 212 and the communication process in the second area 214. change. The communication processing in the second area 212 is the use of the priority period by the selection unit 92 or the general period by the carrier sense unit 94. Since these are operations constrained by the frame configuration, it can be said that the operations correspond to the operation timing of the base station apparatus 10. On the other hand, the communication processing outside the second area 214 is an operation that does not depend on the frame configuration by the carrier sense unit 94. This can be said to be an operation unrelated to the operation timing of the base station apparatus 10. The extraction unit 66 notifies the notification unit 70 of the area change by notifying the notification unit 70 of the existing area.

  The notification unit 70 notifies the driver of the existing area based on the area information received from the extraction unit 66. For example, when the notification unit 70 exists in the priority area, the vehicle in the navigation system is displayed in red. The notification part 70 displays the own vehicle in a navigation system in yellow, when it exists in a general area. When the notification unit 70 exists outside the second area 214, the notification unit 70 displays the host vehicle in the navigation system in blue. In this way, the display color of the host vehicle is changed according to the existing area, which corresponds to changing the notification mode according to the existing area. As a result, the notification unit 70 notifies the area change when the movement is detected. The notification unit 70 may output a warning sound when entering the priority area, or may output a warning by voice. That is, it is only necessary for the driver to be informed that the vehicle has entered the priority area. A similar process may be performed in the movement between the second area 212 and the second area outside 214. 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. 8 is a flowchart showing a procedure for selecting a priority period or a general period in the terminal device 14. If the priority area identifier is “1” (Y in S30) and the received power is larger than the threshold (Y in S32), the extraction unit 66 determines the use of the priority period (S34). If the received power is not greater than the threshold value (N in S32), the extraction unit 66 determines the use of the general period (S36). If the priority area identifier is not “1” (N in S30) and the received power is larger than the threshold value (Y in S38), the extraction unit 66 determines the use of the general period (S40). If the received power is not greater than the threshold (N in S38), the extraction unit 66 determines the use of the priority period (S42).

  FIG. 9 is a flowchart showing a display procedure in the terminal device 14. When it exists in a priority area (Y of S60), the notification part 70 displays the vehicle 12 in red (S62). On the other hand, when it does not exist in the priority area (N in S60) and exists in the general area (Y in S64), the notification unit 70 displays the vehicle 12 in yellow (S66). When it does not exist in the general area (N in S64), the notification unit 70 displays the vehicle 12 in blue (S68).

  Next, a modification of the present invention will be described. The modification of the present invention also relates to a terminal device that broadcasts a packet signal in which position information and the like are stored. In the embodiment, the terminal device is mounted on a vehicle. On the other hand, in the modification, the terminal device is carried by the user and moved. Since such a terminal device is operated by a built-in battery, low power consumption is desired. On the other hand, in order to ensure the safety of the user, the terminal device is required to inform the vehicle of the location of the user by transmitting a packet signal. Furthermore, when the user gets on the vehicle while carrying the terminal device, the terminal device is also desired to operate similarly to the terminal device mounted on the vehicle.

  In order to cope with this, when the terminal device according to the modification is present outside the vehicle, only the packet signal transmission process is executed, and the packet signal reception process is stopped. On the other hand, when the terminal device is present in the vehicle, the terminal device performs a packet signal transmission process and a reception process. Here, the terminal device is estimated to exist outside the vehicle when operating with the built-in battery, and is estimated to exist within the vehicle when operating with the external power source. The communication system 100 according to the modification is the same type as that in FIG. 1, and the base station apparatus 10 is the same type as that in FIG. Below, it demonstrates focusing on a difference.

  FIG. 10 shows a configuration of the terminal device 14 according to a modification of the present invention. The terminal device 14 includes an antenna 50, an RF unit 52, a modem unit 54, a processing unit 56, a control unit 58, and a connection unit 88. The processing unit 56 includes a transmission processing unit 82, a reception processing unit 84, and an estimation unit 86. Since the antenna 50, the RF unit 52, and the modem unit 54 perform the same operations as those in FIG. 7, the description thereof is omitted here. The transmission processing unit 82 corresponds to a part of the processing unit 56 in FIG. 7 that executes a process for informing a packet signal, and the reception processing unit 84 includes the packet signal in the processing unit 56 in FIG. This corresponds to the part that executes the process for receiving. Here, the terminal device 14 is configured to be portable by the user, for example, like a mobile phone terminal.

  Connection portion 88 is connected to a power supply terminal provided in vehicle 12 (not shown). The connection unit 88 receives power supply from the power supply terminal and drives the terminal device 14. On the other hand, when the terminal device 14 exists outside the vehicle 12, the connection unit 88 is not connected to the power supply terminal and does not accept supply of power. At that time, the terminal device 14 is driven by an internal battery (not shown).

  The estimation unit 86 detects whether or not the connection unit 88 is connected to the power supply terminal. Since a known technique may be used for the detection, description thereof is omitted here. When the estimation unit 86 detects that it is connected to the power supply terminal, the estimation unit 86 estimates that it exists in the vehicle 12. When the estimation unit 86 detects that it is not connected to the power supply terminal, the estimation unit 86 estimates that it exists outside the vehicle 12. That is, the estimation unit 86 estimates whether the terminal device 14 exists in the vehicle 12 or outside the vehicle 12. When estimating that the vehicle is present in the vehicle 12, the estimation unit 86 operates the transmission processing unit 82 and the reception processing unit 84 to perform transmission processing and reception processing. On the other hand, when the estimation unit 86 estimates that the vehicle exists outside the vehicle 12, the estimation unit 86 stops one of the transmission processing and the reception processing by stopping one of the transmission processing unit 82 and the reception processing unit 84. For example, the estimation unit 86 operates only the transmission processing unit 82 and stops the reception processing unit 84. Note that the reverse may be possible.

  FIG. 11 is a flowchart showing a processing procedure in the terminal device 14. If it is battery driven (Y of S80), the estimation part 86 will perform a transmission process and will stop a reception process (S82). On the other hand, if not battery driven (N of S80), the estimation part 86 will perform a transmission process and a reception process (S84).

  Next, another modification of the present invention will be described. Another modified example of the present invention also relates to a terminal device configured to be carried and moved by a user, similarly to the modified example. Another modification of the present invention is directed to a case where the terminal device exists outside the vehicle. In the modification, when the terminal device exists outside the vehicle, one of the transmission process and the reception process is stopped for the purpose of reducing power consumption. On the other hand, even when the terminal device exists outside the vehicle, it may be desired to operate the transmission process and the reception process. In order to cope with this, a terminal apparatus according to another modification of the present invention executes a transmission process and a reception process when approaching the base station apparatus. The communication system 100 according to another modification 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 FIGS. is there. Below, it demonstrates focusing on a difference.

  When the extraction unit 66 does not receive the packet signal from the base station apparatus 10, that is, when it exists outside the second area 214 in FIG. 1, the estimation unit 86 is one of the transmission processing unit 82 and the reception processing unit 84. Is stopped, one of the transmission process and the reception process is stopped. On the other hand, when the extraction unit 66 receives the packet signal from the base station apparatus 10, that is, when the extraction unit 66 exists in the first area 210 and the second area 212 in FIG. The transmission process and the reception process are executed by operating the unit 84.

  Note that the connection unit 88 may switch the operation depending on whether or not the packet signal is present in the first area 210 instead of switching whether the packet signal is received from the base station apparatus 10 or not. For example, when it exists in the 1st area 210, the estimation part 86 operates the transmission process part 82 and the reception process part 84. FIG. On the other hand, when it exists in the 2nd area 212 and the 2nd outside area 214, the estimation part 86 stops one of the transmission process part 82 and the reception process part 84. FIG.

  FIG. 12 is a flowchart showing a processing procedure in the terminal device 14 according to another modification of the present invention. If the packet signal from the base station apparatus 10 is not received (N in S90), the estimation unit 86 executes the transmission process and stops the reception process (S92). On the other hand, if the packet signal from the base station apparatus 10 is received (Y in S90), the estimation unit 86 causes transmission processing and reception processing to be executed (S94).

  Next, another modification will be described. Until now, a priority area and a general area, that is, two types of areas have been defined, and a priority period and a general period are used in each area. On the other hand, in another modified example, one of the priority area and the general area, that is, one type of area is defined, and one of the priority period and the general period is used so as to correspond thereto. . FIG. 13 shows a configuration of a communication system 100 according to yet another modification of the present invention. This corresponds to the case where one intersection is viewed from above, as in FIG. Compared with FIG. 1, FIG. 13 does not form the first area 210 but forms only the second area 212. In order to correspond to this, in the subframe configuration shown in FIG. 5A, only one of the priority period and the general period is included. Here, it is assumed that only the general period is included. Therefore, the vehicle transmission period in FIGS. 3B to 3D corresponds to the general period.

  A base station apparatus 10 according to another modification is the same type as that in FIG. 2, but does not execute processing related to the priority period. For this reason, the priority period is not included in the configuration of subframes and frames defined by the frame defining unit 40. The setting unit 48 may be omitted. A terminal device 14 according to another modification is the same type as that shown in FIGS. Similarly to the base station apparatus 10, the terminal apparatus 14 does not execute processing related to the priority period. In particular, the extraction unit 66 identifies whether it exists in the second area 212 or outside the second area 214. This specification is made based on whether or not a packet signal from the base station apparatus 10 is received. Specifically, when receiving a packet signal from the base station apparatus 10, the extraction unit 66 identifies the presence in the second area 212 and has not received the packet signal from the base station apparatus 10. In this case, the extraction unit 66 identifies the presence outside the second area 214. Further, the extraction unit 66 detects a movement from the second area outside 214 to the second area 212 and a movement from the second area outside 214 to the second area 212.

  Next, another modification will be described. Further, the terminal device according to another modification is carried and moved by the user in the same manner as the modification and another modification. Here, the terminal device executes a packet signal transmission process and a reception process. In general, the number of users who are pedestrians increases at intersections. Therefore, the traffic amount of the packet signal notified from the terminal device carried by the user increases. Accordingly, the collision probability of the packet signal notified from the terminal device mounted on the vehicle increases, so that the communication system is adversely affected. In yet another modification, an object is to suppress an increase in the traffic amount of a packet signal broadcast from a terminal device carried by a user near an intersection.

  In order to cope with this, the base station apparatus sets a sensor area near the center of the intersection in the second area. The base station apparatus stores the position information of the sensor area in the packet signal. When the terminal device receives the packet signal in the second area, the terminal device acquires position information of the sensor area. If the terminal device carried by the user is outside the sensor area, the terminal device performs notification based on CSMA within the general period. When the terminal device carried by the user detects that the terminal device has entered the sensor area, the terminal device notifies the user of the fact and stops the notification of the packet signal.

  FIG. 14 shows a configuration of a communication system 100 according to yet another modification of the present invention. This corresponds to the case where one intersection is viewed from above, as in FIGS. Here, the vehicle 12, the terminal device 14, and the like are omitted. In FIG. 14, the second area 212 is formed as compared with FIG. 13, but the sensor area 216 is formed inside thereof. Here, it can be said that the second area 212 and the sensor area 216 have different priorities. Here, since the sensor area 216 is closer to the center of the intersection than the second area 212, it can be said that the risk in the sensor area 216 is higher than the risk in the second area 212. Therefore, the priority of the sensor area 216 is higher than the priority of the second area 212. The base station apparatus 10 transmits the range information indicating the range of the sensor area 216 included in the packet signal. In addition, the base station apparatus 10 which concerns on another modification is the same type as FIG. In addition, the communication system 100 includes a sensor for the sensor area 216, and stores information on a pedestrian existing in the sensor area 216 in a packet signal for notification.

  The terminal device 14 according to another modification is of the same type as that shown in FIG. 7, but in order to estimate whether the terminal device 14 exists inside the vehicle or outside the vehicle, the estimation unit shown in FIG. 86 and connecting portion 88 are also included. In addition, since the process for estimating whether it exists in a vehicle or exists outside a vehicle should just be made like a modification and another modification, description is abbreviate | omitted here. Below, it demonstrates centering on the case where it is carried by the user.

  As described above, the extraction unit 66 in FIG. 7 detects the movement from the second area 214 to the second area 212 and the movement from the second area 212 to the second area 214. This detection is made, for example, depending on whether a packet signal from the base station apparatus 10 is received or not. The extraction unit 66 acquires the range information of the sensor area 216 included in the packet signal when the packet signal from the base station device 10 can be received. Further, the extraction unit 66 acquires the current position information from the acquisition unit 72. The extraction unit 66 detects that the current position information is changed from a state where the current position information is not included in the sensor area 216 to a state where the current position information is included in the sensor area 216. A movement to the area 216 is detected.

  On the other hand, the extraction unit 66 detects from the sensor area 216 that the current position information is not included in the sensor area 216 by detecting that the current position information is not included in the sensor area 216. A movement to the second area 212 is detected. The extraction unit 66 selects a communication process according to the existing area. FIG. 15 shows the data structure of the table stored in the extraction unit 66. As illustrated, a usage mode field 300, an area field 302, and a communication processing field 304 are included. The usage mode column 300 indicates whether the vehicle is inside the vehicle or outside the vehicle. The area column 302 indicates an area that currently exists. The general area in FIG. 15 corresponds to the second area 212 in FIG. 14, and the outside area corresponds to the outside second area 214 in FIG. The communication processing column 304 shows communication processing corresponding to each area.

  When present in the vehicle, the extraction unit 66 selects CSMA within the general period within the general area, and selects CSMA unrelated to the frame configuration outside the area. This is as described above. On the other hand, when the extraction unit 66 exists outside the vehicle, the extraction unit 66 selects a CSMA that is unrelated to the frame configuration outside the area. The extraction unit 66 selects transmission stop within the sensor area, and selects CSMA within the general area and outside the sensor area within the general period. Returning to FIG.

  For this reason, when the extraction unit 66 detects the movement from the second area 212 to the sensor area 216, the carrier sense unit 94 in FIG. 7 has the second area 212 defined outside the sensor area 216. The first communication process is changed to the second communication process defined in the sensor area 216. As described above, since the communication process defined in the sensor area 216 is to stop transmission, it can be said that the transmission frequency in the second communication process is lower than the transmission frequency in the first communication process. The notification unit 70 notifies the change between the second area 212 and the sensor area 216 in addition to the change between the second area 212 and the second outside area 214.

  FIG. 16 is a flowchart showing a processing procedure in the terminal device 14. This corresponds to an operation outside the vehicle. When present in the general area (Y in S100) and in the sensor area 216 (Y in S102), the terminal device 14 stops existing (S104). When it does not exist in the sensor area 216 (N in S102), the terminal device 14 executes CSMA in the general period (S106). When it does not exist in the general area (N in S100), the terminal device 14 executes CSMA unrelated to the frame configuration (S108).

  According to the embodiment of the present invention, since the change of the area is notified, the importance set for the traveling area can be notified to the driver. In addition, since the driver is informed of the importance set for the traveling area, the driver can be alerted. In addition, since the driver is alerted, the probability of occurrence of a collision accident can be suppressed. Also, since priority is given to the area according to the importance of the packet signal to be notified, important information can be transmitted with priority. In addition, since the priority with respect to the area is defined according to the quality of the received signal, transmission processing according to the quality can be realized. In addition, since the priority with respect to the area is defined according to the distance from the base station apparatus, transmission processing according to the distance can be realized. Moreover, since the notification mode is changed according to the area, the area can be recognized accurately.

  In the general period, terminal devices existing in the first area around the base station apparatus can broadcast packet signals. In the priority period, terminal apparatuses existing in the second area surrounding the first area broadcast packet signals. Since it is possible, the priority of communication in the second area can be improved. Moreover, since the priority of communication in the second area is improved, it is possible to improve the reception probability of the packet signal broadcast from the terminal device existing in the second area. Further, since the reception probability of the packet signal broadcast from the terminal device existing in the second area is improved, important data can be transmitted with priority. Also, since the first arrangement and the second arrangement can be switched, it is possible to switch between improving the communication priority in the first area and improving the communication priority in the second area. In addition, since the priority of communication in the first area can be switched to the priority of communication in the second area, the area to be prioritized can be selected according to the intersection. In addition, since the selection of the first arrangement or the second arrangement is indicated by the priority area identifier, the processing can be simplified.

  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.

  Moreover, since it is estimated whether it exists in a vehicle by whether it is battery drive, the case where operation | movement of low power consumption is required can be pinpointed correctly. Further, since the transmission process and the reception process are executed when the vehicle is present in the vehicle, the same process as that of the in-vehicle terminal device can be executed. Moreover, when it exists out of a vehicle, since one of a transmission process and a reception process is stopped, power consumption can be reduced. Moreover, since it only performs a transmission process when it exists outside a vehicle, it can notify an existing position, reducing power consumption.

  In addition, since the location is notified, the presence can be informed and safety can be ensured. Further, since the terminal device operates with low power consumption, the function of the terminal device can be installed in a mobile phone terminal or the like. Further, since the function of the terminal device is mounted on a mobile phone terminal or the like, the communication system can be easily spread. Moreover, even if it is battery-powered, if it enters into a predetermined area, since a transmission process and a reception process will be performed, the process similar to the vehicle-mounted terminal device can be performed as needed. Moreover, when it exists outside an area, since one of a transmission process and a reception process is stopped, power consumption can be reduced.

  Moreover, since the inside and outside of the area are only specified, the processing can be simplified. Moreover, since the movement from outside the area to the inside of the area is detected, it is possible to notify the improvement of the risk of a collision accident caused by approaching the intersection. Since the sensor area is defined near the center of the intersection and the packet signal notification is stopped in the sensor area, an increase in traffic near the center of the intersection can be suppressed. Moreover, since the packet signal from the terminal device carried by the user is not notified in the sensor area, an increase in the collision probability of the packet signal notified from the terminal device mounted on the vehicle can be suppressed. In addition, the terminal device carried by the user does not notify the packet signal in the sensor area, but the base station device captures the user's presence state in the sensor area, and includes the information in the packet signal to notify the vehicle. The presence status of the user can be notified to the terminal device mounted on the PC. Moreover, since the terminal device carried by the user notifies the user that the sensor area has entered from the general area, the user can be notified of the stoppage of the notification.

  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 modified example of the present invention or another modified example, when the estimation unit 86 is estimated to exist outside the vehicle 12 or is estimated to exist outside the predetermined area, the transmission processing unit 82 and the reception processing unit 84 One of them is stopped. However, the present invention is not limited thereto, and for example, the estimation unit 86 may stop both the transmission processing unit 82 and the reception processing unit 84 in the above case. According to this modification, power consumption can be reduced.

  In yet another modification of the present invention, the sensor area 216 is provided at the center of the intersection. However, the present invention is not limited to this. For example, the sensor area 216 may be set to other than the intersection, and the base station device 10 may notify the position information thereof. According to this modification, the degree of freedom of setting the sensor area 216 can be improved.

  10 base station device, 12 vehicle, 14 terminal device, 20 antenna, 22 RF unit, 24 modulation / demodulation unit, 26 processing unit, 30 control unit, 40 frame definition unit, 42 selection unit, 44 detection unit, 46 generation unit, 48 setting Unit, 50 antenna, 52 RF unit, 54 modem unit, 56 processing unit, 58 control unit, 60 timing identification unit, 64 generation unit, 66 extraction unit, 70 notification unit, 72 acquisition unit, 80 network communication unit, 90 transfer decision Unit, 92 selection unit, 94 carrier sense unit, 100 communication system.

Claims (3)

As the areas having different priorities, a first area and a second area are defined, and a detection unit that detects movement from the first area to the second area;
A communication unit configured to change the first communication process defined in the first area to the second communication process defined in the second area when movement is detected in the detection unit;
When the movement is detected in the detection unit, a notification unit that notifies the change of the area,
A radio apparatus characterized in that a transmission frequency in the second communication process in the communication unit is lower than a transmission frequency in the first communication process.   The radio apparatus according to claim 1, wherein the communication unit stops transmission as the second communication process.   The radio apparatus according to claim 1, wherein the detection unit detects movement from the first area to the second area based on a signal from the base station apparatus.

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