JP2016029812A - Communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for generating a timing synchronized with a base station device while excluding illegal base station devices.SOLUTION: Plural sub frames which are time-divisionally multiplexed with a super frame are prescribed, and it is also prescribed that a base station device is capable of notifying a packet signal in a section of a head portion of a sub frame. A modulation/demodulation unit 54 receives a packet signal. A synchronizing unit 56 executes timing synchronization on the base station device based on the packet signal to generate a super frame. The synchronizing unit 56 specifies a packet signal from an illegal base station device and excludes the specified packet signal from timing synchronization targets. The modulation/demodulation unit 54 notifies a packet signal in a section different from the section of the head portion which the base station device has notifies the packet signal out of plural sub frames which are time-divisionally multiplexed with the generated super frame.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a communication technique, and more particularly to a communication apparatus 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, onboard 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. Furthermore, if road-to-vehicle communication is executed in addition to vehicle-to-vehicle communication, the communication forms will be diversified. Therefore, it is required to reduce the mutual influence between vehicle-to-vehicle communication and road-to-vehicle communication.

  In order to solve such a request, it is desirable to synchronize another wireless device such as the vehicle-mounted device with a frame generated in a predetermined wireless device such as a roadside device. However, when the roadside device is an unauthorized device such as impersonation, there is a high possibility that such a roadside device has not generated a frame that can serve as a reference. Therefore, it is necessary for the terminal device to classify roadside devices that should be the reference for timing synchronization. In the following, the roadside device is referred to as a base station device in correspondence with the terminal device.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for generating a timing synchronized with a base station apparatus while excluding an unauthorized base station apparatus.

  In order to solve the above-described problem, a terminal device according to an aspect of the present invention defines a plurality of subframes time-division-multiplexed in a superframe, and a base station device transmits a packet signal in a section of a head portion of the subframe. Is generated, and a superframe is generated by performing timing synchronization with the base station apparatus based on the packet signal received by the reception unit that receives the packet signal and the packet signal received by the reception unit. Of the subframes time-division-multiplexed to the synchronization unit and the superframe generated by the synchronization unit, the packet signal is broadcast in a section different from the section of the head part where the base station apparatus broadcasts the packet signal. A notification unit. The synchronization unit identifies a packet signal from an unauthorized base station apparatus among the packet signals received by the reception unit, and excludes the identified packet signal from timing synchronization.

  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.

  ADVANTAGE OF THE INVENTION According to this invention, the timing synchronized with the base station apparatus is generable, excluding an unauthorized base station apparatus.

It is a figure which shows the structure of the communication system which concerns on the Example of this invention. FIGS. 2A to 2D are diagrams showing the format of a superframe defined in the communication system of FIG. FIGS. 3A to 3B are diagrams illustrating the configuration of the subframes of FIGS. 2A to 2D. FIGS. 4A to 4F are diagrams showing the frame format of each layer defined in the communication system of FIG. It is a figure which shows the data structure of the security frame of FIG.4 (e). It is a figure which shows the data structure of the message type of FIG. It is a figure which shows the structure of the base station apparatus of FIG. FIGS. 8A to 8E are diagrams illustrating an outline of signature generation processing performed in the base station apparatus of FIG. FIGS. 9A to 9D are diagrams showing an outline of the encryption process performed in the base station apparatus of FIG. FIGS. 10A to 10D are diagrams showing a format of a security frame generated in the base station apparatus of FIG. It is a figure which shows the structure of the terminal device mounted in the vehicle of FIG. 12A to 12C are diagrams showing an outline of MAC generation performed in the terminal device of FIG. FIGS. 13A to 13D are diagrams showing an outline of the encryption process performed in the terminal device of FIG. FIGS. 14A to 14B are diagrams showing a format of a security frame generated in the terminal device of FIG. It is a flowchart which shows the production | generation procedure of the super frame in the terminal device of FIG. It is a flowchart which shows the production | generation procedure of the super frame which concerns on the modification of this invention. It is a flowchart which shows the production | generation procedure of the super frame which concerns on another modification of this invention. It is a figure which shows the format of the IR control field which concerns on another modification of this invention. It is a figure which shows the structure of a base station apparatus. It is a figure which shows the structure of the terminal device mounted in the vehicle. It is a figure which shows the basic composition of an analysis update part. It is a figure which shows the structure of the internal time update part which makes a part of analysis update part. It is a figure which shows the structure of the RVC period information update part which makes a part of analysis update part. It is a flowchart for demonstrating the process of an identification information analysis part. It is a flowchart for demonstrating the process of the analysis mode of the packet received from the base station apparatus. It is a flowchart for demonstrating the process of the analysis mode of the packet received from the terminal device. It is a flowchart for demonstrating the update process of the internal time in a base station apparatus, and RVC period information (the 1). It is a flowchart for demonstrating the update process of the internal time and RVC period information in a base station apparatus (the 2). It is a flowchart for demonstrating the update process of the internal time and RVC period information in a terminal device (the 1). It is a flowchart for demonstrating the update process of the internal time and RVC period information in a terminal device (the 2). It is a figure which shows the structure of the internal time update part which makes a part of analysis update part which concerns on the modification 1. FIG. It is a figure which shows the structure of the RVC period information update part which makes a part of analysis analysis part which concerns on the modification 1. FIG. It is a figure which shows the structure of a difference time holding part. It is a figure which shows the structure of a RVC period information holding part. It is a flowchart for demonstrating the update process of the internal time and RVC period information which concerns on the modification 1 (the 1). It is a flowchart for demonstrating the update process of the internal time and RVC period information which concerns on the modification 1 (the 2). It is a figure which shows the structure of the analysis update part which concerns on the modification 2. It is a flowchart for demonstrating the process of the base station apparatus analysis extraction part which concerns on the modification 2, and a terminal device analysis extraction part. 14 is a flowchart for explaining processing of an updating unit according to Modification 2.

  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. In addition, as road-to-vehicle communication, the base station device broadcasts a packet signal in which intersection information, traffic jam information, and the like are stored. In order to reduce the collision probability of packet signals between such road-to-vehicle communication and vehicle-to-vehicle communication, this embodiment repeatedly defines a superframe 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 generates a super frame that is synchronized in timing with the base station device based on the packet signal from the base station device. Further, the terminal device specifies a road and vehicle transmission period based on the control information, and transmits a packet signal by the CSMA method in a period other than the road and vehicle transmission period (hereinafter referred to as “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.

  In such communications, integrity, authenticity, and confidentiality are desired. Integrity is that no tampering has occurred, authenticity is that the other party is authenticated in addition to integrity, and confidentiality is that the data is not known to others. For example, MAC is used for integrity, electronic signatures are used for authenticity, and data encryption is used for confidentiality. These throughputs are different from each other and should be applied as needed. Since the traffic of inter-vehicle communication is greater than the traffic of road-to-vehicle communication, it is more desirable to reduce the processing amount for inter-vehicle communication. On the other hand, in road-to-vehicle communication, transmission from a genuine base station device is desired. Therefore, in the communication system according to the present embodiment, MAC is used for vehicle-to-vehicle communication, and an electronic signature is used for road-to-vehicle communication. Furthermore, data encryption is used depending on the type of data.

  Under the above situation, when an illegal base station device such as impersonation is broadcasting a packet signal, the terminal device receives the packet signal from the base station device, and receives the received packet signal. It may occur that a super frame is generated based on the above. It is unlikely that such a base station device generates a superframe for a certain period as prescribed. For this reason, even a terminal device that is synchronized in timing with such a base station device cannot generate a superframe at a constant interval. As a result, the road-to-vehicle communication and the vehicle-to-vehicle communication are not time-division multiplexed, and the packet signal collision probability between the two is not reduced. To cope with this, when receiving the packet signal from the base station apparatus, the terminal apparatus according to the present embodiment requests the security layer to verify the public key certificate and the electronic signature included in the packet signal. The terminal device uses the packet signal that has passed the verification as a synchronization target, and excludes the packet signal that has not passed the verification from the synchronization target.

  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). An area 212 is formed around the base station apparatus 10, and an outside area 214 is formed outside the area 212.

  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 apparatus 10 repeatedly generates a superframe including a plurality of subframes based on a signal received from a GPS satellite (not shown) or a superframe formed by another base station apparatus 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. The packet signal includes, for example, control information in which a road and vehicle transmission period is set, and data such as traffic jam information and construction information. This corresponds to the road-to-vehicle communication described above.

  When the terminal apparatus receives the packet signal from the base station apparatus 10, the terminal apparatus generates a super frame based on the control information included in the packet signal. As a result, the super frame generated in each of the plurality of terminal apparatuses is synchronized with the super frame generated in the base station apparatus 10. Here, if the terminal device can receive the packet signal from the base station device 10, it can be said that the terminal device exists in the area 212. When the terminal device exists in the area 212, the terminal device notifies the packet signal by carrier sense during the vehicle transmission period. This corresponds to the aforementioned inter-vehicle communication. 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 it is estimated that the terminal exists outside the area 214, the terminal device broadcasts the packet signal by executing CSMA / CA regardless of the superframe configuration.

  In road-to-vehicle communication, a packet signal to which an electronic signature generated by a secret key in a public key cryptosystem and a public key certificate are attached is notified. The electronic signature is an electronic signature to be given to electromagnetic records such as data included in the packet signal. This is equivalent to a stamp or signature on a paper document, and is mainly used for identity verification and prevention of counterfeiting and anxiety. More specifically, if there is a person listed in the document as the creator of a document, the document is actually created by the creator of the document. It is proved by the signature and mark of its creator. However, since an electronic document cannot be directly stamped or signed, an electronic signature is used to prove this. Cryptography is used to generate the electronic signature.

  As an electronic signature, a digital signature based on a public key cryptosystem is prominent. Specifically, RSA, DSA, ECDSA, or the like is used as a method based on the public key cryptosystem. The electronic signature scheme is composed of a key generation algorithm, a signature algorithm, and a verification algorithm. The key generation algorithm is equivalent to advance preparation of an electronic signature. The key generation algorithm outputs the user's public key and secret key. Since a different random number is selected every time the key generation algorithm is executed, a different public / private key pair is allocated for each user. Each user stores the private key and publishes the public key.

  A user who creates a signature is called a signer for the signature text. The signer inputs his / her private key along with the message when creating a signature sentence by the signature algorithm. Since only the signer himself knows the signer's private key, this is the basis for identifying the creator of the electronic document with the electronic signature. The verifier who is the user who received the message and the signature text verifies whether the signature text is correct by executing a verification algorithm. At that time, the verifier inputs the signer's public key to the verification algorithm. The verification algorithm determines whether or not the signature sentence was really created by the user and outputs the result.

  On the other hand, in inter-vehicle communication, a packet signal to which a MAC generated by a common key encryption method is attached is notified. In the common key cryptosystem, the same key as that used for encryption or a value that can be easily derived from the encryption key is used as the decryption key. Since the decryption key is known to the terminal device on the receiving side and no key certificate is required, deterioration of transmission efficiency is suppressed as compared with the public key cryptosystem. Further, the common key cryptosystem has a smaller processing amount than the public key cryptosystem. Typical common key ciphers are DES and AES.

  2A to 2D show a superframe format defined in the communication system 100. FIG. FIG. 2A shows the structure of the super frame. The superframe is formed by N subframes indicated as the first subframe to the Nth subframe. For example, when the length of the superframe is 100 msec and N is 8, a subframe having a length of 12.5 msec is defined. N may be other than 8. FIG. 2B shows a configuration of a super frame generated by the first base station apparatus 10a. The first base station device 10 a corresponds to any one of the base station devices 10. 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 a 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 device 10a can notify the packet signal, and in the subframe, in the vehicle and vehicle transmission period other than the road and vehicle transmission period, the terminal device Is defined such 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. 2C shows a configuration of a super frame generated by the second base station apparatus 10b. The second base station apparatus 10b corresponds to a base station apparatus 10 different from the first base station apparatus 10a. 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. 2D shows a configuration of a super frame generated by the third base station apparatus 10c. The third base station apparatus 10c corresponds to a base station apparatus 10 different from the first base station apparatus 10a and the second base station apparatus 10b. 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.

  FIGS. 3A to 3B show subframe configurations. As shown in the figure, one subframe is configured in the order of road-to-vehicle transmission period and vehicle-to-vehicle transmission. In the road and vehicle transmission period, the base station device 10 notifies the packet signal, the vehicle and vehicle transmission period has a predetermined length, and the terminal device can notify the packet signal. FIG. 3B shows the arrangement of packet signals during the road and vehicle transmission period. As illustrated, 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). Hereinafter, the RSU packet signal may be simply referred to as “packet signal”.

  4A to 4F show the frame formats of the respective layers defined in the communication system 100. FIG. FIG. 4A shows the frame format of the physical layer. As shown in the figure, a PLCP preamble, a PLCP header, a PSDU (Physical Layer Service Data Unit), and a tail are sequentially arranged in the frame. FIG. 4B shows a frame format of the MAC layer. This frame is stored in the PSDU of FIG. As shown in the figure, a MAC header, an MSDU (MAC Layer Service Data Unit), and an FCS are sequentially arranged in the frame. FIG. 4C shows a frame format of the LLC layer. This frame is stored in the MSDU of FIG. As illustrated, an LLC header and an LSDU (LLC Layer Service Data Unit) are sequentially arranged in the frame.

  FIG. 4D shows the frame format of the inter-vehicle / road-vehicle shared communication control information layer. This frame is stored in the LSDU of FIG. As shown in the figure, an RSU control header (IR control field) and an APDU (Application Protocol Data Unit) are sequentially arranged in the frame. FIG. 4E shows the frame format of the security layer. This frame is stored in the APDU of FIG. As illustrated, a security header, an SPDU (Security Protocol Data Unit), and a security footer are sequentially arranged in the frame. FIG. 4F shows the frame format of the application layer. This frame is stored in the SPDU of FIG. 4E and is configured by application data. The above frame may be simply referred to as a “packet signal”.

  In the format shown in FIGS. 4A to 4F, alteration of data in the security layer and the application layer can be detected. On the other hand, it is difficult to detect alteration of data in the IR control field of the inter-vehicle / road-vehicle shared communication control information layer.

  FIG. 5 shows the data structure of the security frame. This is a detailed diagram of the contents of FIG. The payload in the figure corresponds to the SPDU in FIG. Also, the device management in the figure is an option and is not shown in FIG. Here, the transmission source information, payload, and data authentication data length are variable. The sender information is 4 bytes when using the common key method, that is, in the case of vehicle-to-vehicle communication, and 111 bytes when using the public key method, that is, in the case of road-to-vehicle communication. Data authentication is 12 bytes in the case of a message authentication code, that is, in the case of vehicle-to-vehicle communication, and in the case of an electronic signature, it is 56 bytes in the case of road-to-vehicle communication.

  FIG. 6 shows the data structure of the message type. The message type consists of 0.5 bytes. As an authentication method, the common key method is used for vehicle-to-vehicle communication, and the public key method is used for road-to-vehicle communication. When the message format is data with data authentication, an electronic signature or MAC is attached. When the message format is encrypted data with authentication, data encryption is performed in addition to electronic signature and MAC attachment. When the message format is plain text, an electronic signature or MAC is not attached, and data encryption is not performed.

  FIG. 7 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 network communication unit 28, and a control unit 30. The processing unit 26 includes a frame definition unit 40, a selection unit 42, and a communication processing unit 44, and the communication processing unit 44 includes a lower layer processing unit 46 and a security layer processing 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 super frames based on the time information as shown in FIG. For example, the frame defining unit 40 generates ten superframes 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, it is defined that the super frame is repeated. The frame defining unit 40 may detect control information from the demodulation result and generate a super frame based on the detected control information. Such a process corresponds to generating a super frame synchronized with the timing of the super frame formed by another base station apparatus 10.

  The selection part 42 selects the sub-frame which should set a road and vehicle transmission period among several sub-frames contained in the super frame. More specifically, the selection unit 42 receives a super 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 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 The results selected in this way correspond to FIGS. 2 (b)-(d). The selection unit 42 outputs the selected subframe number to the communication processing unit 44.

  The lower layer processing unit 46 extracts a security frame from the MAC frame from the modem unit 24 as a reception process, and outputs the security frame to the security layer processing unit 48. The lower layer processing unit 46 generates a MAC frame by adding a MAC header, an LLC header, and an RSU control header to the security frame from the security layer processing unit 48 as a transmission process. Further, the lower layer processing unit 46 receives the subframe number from the selection unit 42. The communication processing unit 44 sets the road and vehicle transmission period in the subframe of the received subframe number, and arranges the MAC frame at the timing of the RSU packet signal to be notified in the road and vehicle transmission period as shown in FIG. . The lower layer processing unit 46 outputs the MAC frame arranged at the timing of the RSU packet signal to the modem unit 24.

  The security layer processing unit 48 receives application data from the network communication unit 28 as transmission processing. This corresponds to the application data in FIG. The security layer processing unit 48 stores application data in the payload. Further, the security layer processing unit 48 generates the security header shown in FIGS. At that time, a public key certificate is attached, which corresponds to caller authentication. When the message authentication shown in FIG. 6 is data with data authentication or encrypted data with authentication, the security layer processing unit 48 uses the security key and the payload to generate an electronic signature using a secret key. Is generated. Here, it is assumed that the secret key is ECDSA.

  Therefore, the security header that is the target of the electronic signature includes a public key certificate, and a private key corresponding to the public key certificate is used to generate the electronic signature. The security layer processing unit 48 stores the electronic signature in the security footer. When device management is included, the security layer processing unit 48 generates an electronic signature using a secret key based on the security header, device management, and payload. On the other hand, when the message authentication shown in FIG. 6 is plain text, the security layer processing unit 48 does not generate an electronic signature. At that time, the security layer processing unit 48 stores dummy data in the security footer.

  FIGS. 8A to 8E show an outline of signature generation processing performed in the base station apparatus 10. FIG. 8A shows a security header, device management, and payload to be processed by the security layer processing unit 48. FIG. 8B shows SHA-224 operations performed on the security header, device management, and payload in the security layer processing unit 48. SHA-224 (Secure Hash Algorithm) is a group of related hash functions. FIG. 8C shows a hash value that is the result of SHA-224. The hash value has a fixed length of 28 bytes. FIG. 8D shows an ECDSA signature calculation performed on the hash value in the security layer processing unit 48. FIG. 8E shows an electronic signature that is a calculation result of the ECDSA signature. The electronic signature has a fixed length of 56 bytes. Returning to FIG.

  When the message authentication shown in FIG. 6 is encrypted data with authentication, the security layer processing unit 48 performs an encryption process on the payload and the security footer. For example, AES128-CTR is used for encryption. When device management is included, the security layer processing unit 48 performs encryption processing on the device management, payload, and security footer. Here, the security layer processing unit 48 excludes the security header from encryption processing targets.

  FIGS. 9A to 9D show an outline of the encryption process performed in the base station apparatus 10. FIG. 9A shows a configuration of an encryption key used for encryption in the security layer processing unit 48. As illustrated, the encryption key has a fixed length of 16 bytes. FIG. 9B shows an operation for encryption processing in the security layer processing unit 48. As illustrated, encryption is performed in units of 16 bytes with an encryption key. More specifically, the security layer processing unit 48 inserts padding so that the size of the device management and payload is an integer multiple of 16 bytes, and the signature size is also an integer multiple of 16 bytes. 8 bytes of padding are inserted. FIG. 9C shows the result of encryption. As illustrated, encryption device management, an encryption payload, and an encryption signature are generated. FIG. 9D shows an output from the security layer processing unit 48. As shown in the figure, encrypted device management, encrypted payload, and encrypted signature are integrally output. Returning to FIG.

  As shown in FIGS. 4E and 5, the security layer processing unit 48 generates a security frame in which at least a security header, a payload, and a security footer are arranged. May include equipment management. When the message authentication is encrypted data with authentication, the payload and security footer in the security frame are encrypted. If device management is included, device management is also encrypted. FIGS. 10A to 10D show the format of a security frame generated in the base station apparatus 10. FIG. 10A shows a case where device management is not included. FIG. 10B shows a case where only the notification code and the device ID are included in the device management. FIG. 10C shows a case where parameters are included in device management. FIG. 10D shows a case where only device management is included and no payload is included. As shown in these figures, the format of the security frame is common regardless of whether the message format is data with data authentication, encrypted data with authentication, or plain text. Returning to FIG. The security layer processing unit 48 outputs the security frame to the lower layer processing unit 46.

  The security layer processing unit 48 receives a security frame from the lower layer processing unit 46 as a reception process. The security layer processing unit 48 confirms the contents of the security header in the security frame. When the message format is data with data authentication, the security layer processing unit 48 executes message verification processing. When the message format is encrypted data with authentication, the security layer processing unit 48 executes message verification processing, and the security layer processing unit 48 executes decryption processing. If the message format is plain text, these processes are omitted.

  Here, when the transmission source of the security frame is another base station apparatus 10, the security layer processing unit 48 or the security layer processing unit 48 performs message verification processing corresponding to the above-described electronic signature generation processing or encryption processing. Or perform decryption processing. Furthermore, the security layer processing unit 48 also performs device authentication based on the public key certificate included in the security frame. On the other hand, when the transmission source of the security frame is a terminal device, the security layer processing unit 48 or the security layer processing unit 48 performs message verification processing or decryption processing corresponding to electronic signature generation processing or encryption processing performed in the terminal device. Execute the process. Electronic signature generation processing and encryption processing performed in the terminal device will be described later. The security layer processing unit 48 outputs the processing result to the network communication unit 28.

  The network communication unit 28 is connected to a network 202 (not shown). The network communication unit 28 outputs the processing result in the security layer processing unit 48 to the network 202 (not shown), accumulates it inside, and periodically outputs it to the network 202 (not shown). The network communication unit 28 receives road information (construction, traffic jam, etc.) from the network 202 (not shown). 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. 11 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 synchronization unit 56, a processing unit 58, a data generation unit 60, a notification unit 62, and a control unit 64. The synchronization unit 56 includes an acquisition unit 66, a request unit 68, a selection unit 70, and a generation unit 72, and the processing unit 58 includes a lower layer processing unit 74, a security layer processing unit 76, and a transfer processing unit 78. 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 data generation unit 60 includes a GPS receiver (not shown), a gyroscope, a vehicle speed sensor, and the like, and information on the own vehicle (not shown), that is, the presence of the vehicle 12 on which the terminal device 14 is mounted is provided by information supplied from them. Get position, direction of travel, speed of movement, 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 data generation unit 60 generates data based on the acquired information, and outputs the generated data to the security layer processing unit 76 as application data.

  The security layer processing unit 76 receives application data from the data generation unit 60 as a transmission process. This corresponds to the application data in FIG. The security layer processing unit 76 stores application data in the payload. Further, the security layer processing unit 76 generates the security header shown in FIGS. In addition, when the message authentication shown in FIG. 6 is data with data authentication or encrypted data with authentication, the security layer processing unit 76 determines the MAC by the common key based on the security header and the payload. Generate.

  The security layer processing unit 76 stores the MAC in the security footer. When device management is included, the security layer processing unit 76 generates a MAC with a common key based on the security header, device management, and payload. On the other hand, when the message authentication shown in FIG. 6 is plain text, the security layer processing unit 76 does not generate a MAC. At that time, the security layer processing unit 76 stores dummy data in the security footer.

  FIGS. 12A to 12C show an outline of MAC generation performed in the terminal device 14. FIG. 12A shows a security header, device management, and payload to be processed by the security layer processing unit 76. The security layer processing unit 76 inserts padding so that the size of the security header is 32 bytes, and inserts padding so that the size of the device management and the payload is an integer multiple of 16 bytes. FIG. 12B shows the calculation of AES128 CBC mode encryption processing performed on the security header, device management, and payload in which padding is inserted in the security layer processing unit 76. FIG. 12C shows the encryption result and the MAC generated from the encryption result. The MAC has a fixed length of 12 bytes. Returning to FIG.

  When the message authentication shown in FIG. 6 is encrypted data with authentication, the security layer processing unit 76 performs an encryption process on the payload and the security footer. For example, AES-CTR is used for encryption. When device management is included, the security layer processing unit 76 performs encryption processing on the device management, payload, and security footer. Here, the security layer processing unit 76 excludes the security header from the encryption processing target.

  FIGS. 13A to 13D show an outline of encryption processing performed in the terminal device 14. FIG. 13A shows a configuration of an encryption key used for encryption in the security layer processing unit 76. As illustrated, the encryption key has a fixed length of 16 bytes. FIG. 13B shows computation for encryption processing in the security layer processing unit 76. As illustrated, encryption is performed in units of 16 bytes with an encryption key. More specifically, the security layer processing unit 76 inserts padding so that the size of device management and payload is an integer multiple of 16 bytes, and the MAC size is also an integer multiple of 16 bytes. Inserts 4 bytes of padding. FIG. 13C shows the result of encryption. As shown in the figure, encrypted device management, encrypted payload, and encrypted MAC are generated. FIG. 13D shows the final encryption result. As shown in the figure, the encryption device management, the encryption payload, and the encryption MAC are integrally combined. Returning to FIG.

  As described above, the security layer processing unit 76 generates a security frame in which at least a security header, a payload, and a security footer are arranged as shown in FIGS. May include equipment management. When the message authentication is encrypted data with authentication, the payload and security footer in the security frame are encrypted. If device management is included, device management is also encrypted. FIGS. 14A to 14B show the format of a security frame generated in the terminal device 14. FIG. 14A shows a case where device management is not included. FIG. 14B shows a case where device management is included. Returning to FIG. The security layer processing unit 76 outputs the security frame to the lower layer processing unit 74.

  The security layer processing unit 76 receives a security frame from the lower layer processing unit 46 as a reception process. The security layer processing unit 76 confirms the contents of the security header in the security frame. When the message format is data with data authentication, the security layer processing unit 76 executes message verification processing. When the message format is encrypted data with authentication, the security layer processing unit 76 executes message verification processing, and the security layer processing unit 76 executes decryption processing. If the message format is plain text, these processes are omitted. Here, when the transmission source of the security frame is another terminal device 14, the security layer processing unit 76 and the security layer processing unit 76 perform message verification processing corresponding to the above-described electronic signature generation processing and encryption processing, Perform decryption processing. On the other hand, when the transmission source of the security frame is the base station device 10, the security layer processing unit 76 and the security layer processing unit 76 support the electronic signature generation processing and encryption processing performed in the base station device 10 already described. The verification processing and decryption processing of the received message are executed. The security layer processing unit 76 outputs the processing result to the notification unit 62.

  Based on the data received from the security layer processing unit 76 and the own vehicle information received from the data generation unit 60, the notification unit 62 is provided with a risk of collision, an approach of an emergency vehicle such as an ambulance or a fire engine, a road in a traveling direction, Estimate traffic congestion at intersections. The notification unit 62 includes means for notifying a user such as a monitor, a lamp, and a speaker (not shown). The notification unit 62 notifies the driver of the approach of another vehicle 12 (not shown) via a monitor, a lamp, or a speaker. In addition, traffic information and image information such as intersections are displayed on the monitor.

  The antenna 50, the RF unit 52, and the modem unit 54 receive the packet signal. The acquisition unit 66 receives the packet signal from the modem unit 54. Here, the transmission source of the packet signal is the base station device 10 or another terminal device 14 (not shown). The acquisition unit 66 extracts an identification number, for example, a MAC address, included in the received packet signal. If the MAC address corresponds to the base station device 10, the acquisition unit 66 acquires the packet signal. The acquisition unit 66 outputs the acquired packet signal to the request unit 68 and the selection unit 70.

  The request unit 68 receives the packet signal from the acquisition unit 66. The request unit 68 requests the security layer processing unit 76 to verify the received packet signal. Here, the verification of the packet signal is verification of an electronic signature included in the packet signal and verification of a public key certificate included in the packet signal. The security layer processing unit 76 executes these verification processes, but since a known technique may be used, description thereof is omitted here.

  The selection unit 70 receives the packet signal from the acquisition unit 66 and also receives the verification result from the security layer processing unit 76. If the selection unit 70 passes the verification, the selection unit 70 holds a packet signal corresponding to the verification. On the other hand, when the selection unit 70 does not pass the verification, the selection unit 70 excludes the corresponding packet signal. Note that the exclusion may be limited to a certain period. This is equivalent to identifying a packet signal from an illegal base station apparatus 10 such as spoofing by the verification and excluding the identified packet signal from the target of timing synchronization.

  If there are a plurality of held packet signals, the selection unit 70 selects one of them. For example, the packet signal with the maximum received power is selected. If there is one held packet signal, the selection unit 70 selects it. The selection unit 70 outputs the selected packet signal to the generation unit 72.

  The generation unit 72 receives the packet signal from the selection unit 70 and generates a super frame based on the packet signal. More specifically, the generation unit 72 generates a subframe by specifying the subframe number in which the received packet signal is broadcast, and generates a superframe by combining the subframes. As described above, the synchronization unit 56 generates a superframe by executing timing synchronization with the base station apparatus 10 based on the received packet signal. The generation unit 72 also specifies a subframe in which a road and vehicle transmission period is set in the entire superframe by specifying a subframe number in which a packet signal not selected by the selection unit 70 is broadcast. The generation unit 72 instructs the processing unit 58 to perform operations in the generated superframe, particularly operations outside the road and vehicle transmission period.

  The transfer processing unit 78 extracts information about the base station apparatus 10 that is information included in the packet signal from the modem unit 54. This information corresponds to the aforementioned control information. The transfer processing unit 78 stores the extracted control information in the packet signal to be notified. The control information is stored, for example, in the RSU control header shown in FIG. At that time, the transfer processing unit 78 excludes the control information related to the base station apparatus 10 for which the verification result requested by the requesting unit 68 has failed from the storage target. The processing unit 58, the modulation / demodulation unit 54, the RF unit 52, and the antenna 50 are packets in the CSMA / CA scheme in the vehicle transmission period among a plurality of subframes time-division multiplexed on the superframe generated by the synchronization unit 56. Announce the signal. The control unit 64 controls the operation of the entire terminal device 14.

  The operation of the communication system 100 configured as above will be described. FIG. 15 is a flowchart illustrating a superframe generation procedure in the terminal device 14. The acquisition unit 66 acquires a packet signal from the base station apparatus 10 (S10). The request unit 68 requests the security layer processing unit 76 to verify the certificate (S12). If there is a packet signal that failed to be verified (Y in S14), the selection unit 70 excludes the packet signal (S16). If there is no packet signal that failed to be verified (N in S14), step 16 is skipped. If there is a packet signal (Y in S18) and there are a plurality (Y in S20), the selection unit 70 selects one of the packet signals based on the received power (S22). If there are not more than one (N in S20), step 22 is skipped. The generation unit 72 generates a super frame so as to be synchronized with the packet signal (S24). If there is no packet signal (N in S18), the generation unit 72 does not generate a super frame (S26).

  Next, a modified example of the present invention will be described. The modification of this invention is related with the communication system which performs vehicle-to-vehicle communication and road-to-vehicle communication similarly to an Example. The terminal device according to the embodiment requests the security layer to verify the public key certificate and the electronic signature included in the packet signal in order to suppress synchronization with an unauthorized base station device. On the other hand, the terminal device according to the modification does not make a request to the security layer in order to suppress synchronization with an unjustified base station device. The terminal device generates a super frame based on each of the plurality of packet signals. It is estimated that among those superframes, a superframe that is greatly deviated is based on an illegal base station apparatus. The communication system according to this modification is the same type as in FIG. 1, the base station apparatus according to this modification is the same type as in FIG. 7, and the terminal apparatus according to this modification is the same as in FIG. Of the type. Here, the difference will be mainly described.

  11 does not include the request unit 68 and the generation unit 72. The selection unit 70 receives the packet signal from the acquisition unit 66 and generates a superframe based on each packet signal. The selection unit 70 detects a super frame that is greatly deviated. Specifically, the average superframe is derived by calculating the average of all superframes. In addition, the selection unit 70 detects a super frame whose deviation from the average super frame is larger than a threshold value. The selection unit 70 excludes the detected superframe. Further, the selection unit 70 selects any one of the remaining super frames.

  FIG. 16 is a flowchart showing a procedure for generating a superframe according to a modification of the present invention. The selection unit 70 generates a super frame from each of the plurality of packet signals (S40). If there is a greatly deviated super frame (Y in S42), the selection unit 70 excludes the super frame deviated greatly (S44). If there is no greatly deviated superframe (N in S42), step 44 is skipped. If there are a plurality of super frames (Y in S46), the selection unit 70 selects any one of the super frames (S48). If there are not a plurality of superframes (N in S46), step 48 is skipped.

  Next, another modification of the present invention will be described. Another modified example of the present invention also relates to a communication system that performs vehicle-to-vehicle communication and road-to-vehicle communication as before. Similarly to the modified example, the terminal device according to another modified example does not make a request to the security layer in order to suppress synchronization with an inappropriate base station apparatus. A terminal apparatus according to another modification sequentially generates superframes based on packet signals from the base station apparatus, and derives an error for each superframe. The terminal apparatus estimates that a super frame with a large error is based on an invalid base station apparatus. A communication system according to another modification is of the same type as in FIG. 1, a base station apparatus according to another modification is of the same type as in FIG. 7, and a terminal apparatus according to another modification is illustrated in FIG. 11 is the same type. Here, the difference will be mainly described.

  11 does not include the request unit 68 and the generation unit 72. The selection unit 70 receives the packet signal from the acquisition unit 66. The selection unit 70 sequentially generates superframes based on packet signals from the same base station apparatus 10. The selection unit 70 derives an error for each super frame. More specifically, the selection unit 70 estimates the timing of the current superframe from the previous superframe, and derives an error between the estimated timing of the superframe and the actual timing of the current superframe. The selection unit 70 detects a super frame whose error is larger than a threshold value. The selection unit 70 excludes the detected superframe. Further, the selection unit 70 selects any one of the remaining super frames.

  FIG. 17 is a flowchart showing a procedure for generating a superframe according to another modification of the present invention. The selection unit 70 acquires a superframe history (S60). If the error of the super frame is larger than the threshold (Y in S62), the selection unit 70 excludes the super frame (S64). If the error of the super frame is not larger than the threshold value (N in S62), step 64 is skipped.

  According to the embodiment of the present invention, when a packet signal is received from an unauthorized base station device, the packet signal is excluded from the target of timing synchronization. Generation can be suppressed. In addition, since the generation of a superframe synchronized with an unauthorized base station apparatus is suppressed, it is possible to operate at a timing according to a uniform superframe according to a regulation. Further, since the operation is performed at the timing according to the uniform superframe according to the regulation, the collision probability between the road-to-vehicle transmission packet signal and the vehicle-to-vehicle transmission packet signal can be reduced. In addition, since the packet signal collision probability is reduced, the communication quality can be improved. Further, since the packet signal is verified in the security layer, an invalid base station device can be detected. In addition, since a superframe whose timing is greatly shifted is selected from among a plurality of superframes, an invalid base station apparatus can be detected. In addition, since a super frame having a large time variation is selected, an unreasonable base station apparatus can be detected.

  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 synchronization unit 56 detects an invalid base station apparatus 10 based on the detection result in the security layer. However, the present invention is not limited to this. For example, the synchronization unit 56 holds the position information of each intersection, and is invalid based on the position information included in the packet signal from the base station apparatus 10 and the held position information. The base station apparatus 10 may be detected. Specifically, the selection unit 70 derives the distance between the position information included in the packet signal from the base station apparatus 10 and the held position information, and if the distance is larger than the threshold, The station device 10 is detected as an illegal base station device 10. As a premise, it is assumed that the base station apparatus 10 stores its own position information in the packet signal. According to this modification, the base station apparatus 10 that is not installed at the intersection can be detected.

  Further, when the vehicle 12 equipped with the terminal device 14 is moving, if the packet signal is received from the same base station device 10 over a period longer than the predetermined period, the selection unit 70 The base station device 10 may be detected as an invalid base station device 10. According to this modification, the moving base station apparatus 10 can be detected. In addition, when there is a base station device 10 that broadcasts data exceeding the capacity that can be transmitted by the packet signal in the road and vehicle transmission period, the selection unit 70 sets the base station device 10 as an illegal base station device. It may be detected as 10. According to this modification, it is possible to detect the base station apparatus 10 that transmits data exceeding the regulation.

  Next, still another modification will be described. Currently, communication systems such as ITS (Intelligent Transport Systems) using road-to-vehicle communication (hereinafter referred to as RVC; Road-to-Vehicle Communication) and vehicle-to-vehicle communication (hereinafter referred to as IVC; Inter-Vehicle Communication) are being studied. ing. In ITS, the use of a wireless LAN compliant with a standard such as IEEE802.11 is under consideration. In such a wireless LAN, an access control function called CSMA / CA (Carrier Sense Multiple Access with Collision Avidance) is used. Therefore, in the wireless LAN, the same wireless channel is shared by the base station device and the plurality of terminal devices. In such CSMA / CA, after confirming that no other packet signal is transmitted by carrier sense, the packet signal is transmitted by broadcast (hereinafter, transmission of the packet signal by broadcast is referred to as “notification”).

  As a communication protocol of such RVC and IVC, a model composed of a physical layer, a MAC (Media Access Control) layer, an LLC (Logical Lind Control) layer, a communication control information layer, a security layer, and an application layer has been proposed. .

  In the above model, security layer and application layer data are subject to authentication and encryption. Therefore, even if those data are falsified, the falsification can be detected. In contrast, communication control information layer data is not subject to authentication or encryption. Therefore, if data in a vehicle-to-vehicle / road-vehicle shared communication control field (hereinafter referred to as an IR control field) arranged in the header of the communication control information layer is falsified, it is difficult to detect the falsification.

  If the IR control field is falsified and synchronization processing is performed based on the data, the NAV (Network Allocation Vector) setting of the RSU (Load Side Unit) packet will be shifted, and the terminal device will be in the transmission time of the base station device. There is a possibility that problems such as transmission of packets and loss of transmission opportunities of terminal devices may occur.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for improving the accuracy of synchronization processing between communication apparatuses.

  FIG. 18 shows the format of the IR control field. As illustrated, in the IR control field, version, identification information, synchronization information, reservation, transmission time, road-to-vehicle communication period information, and extension area are arranged in this order. In the example shown in FIG. 18, the version has 4 bits, the identification information has 4 bits, the synchronization information has 3 bits, the reservation has 1 bit, the transmission time has 20 bits, the road-to-vehicle communication period information has 128 bits, and the extension area has 16 bits. Each is allocated and consists of a total of 176 bits (22 octets).

  FIG. 19 shows the configuration of base station apparatus 1020. The base station apparatus 1020 includes an antenna 1021, an RF unit 1022, a modem unit 1023, a processing unit 1030, a data generation unit 1026, a network communication unit 1027, and a control unit 1029. The processing unit 1030 includes a frame detection unit 1031, a communication control header detection unit 1032, and an analysis update unit 1033.

  The RF unit 1022 and the modem unit 1023 are the same as the RF unit 22 and the modem unit 24 shown in FIG. The processing unit 1030 processes a frame in a layer higher than the MAC layer. The frame detection unit 1031 detects a frame of the vehicle-to-vehicle / road-to-vehicle shared communication control information layer. The communication control header detection unit 1032 detects an IR control field that is a communication control header of the inter-vehicle / road-vehicle shared communication control information layer from the frame. The analysis update unit 1033 analyzes the IR control field and updates its own internal communication control information. Details of the analysis update unit 1033 will be described later.

  The network communication unit 1027 is connected to the external network 1200. The network communication unit 1027 receives road information related to construction and traffic jams from the external network 1200. Further, the network communication unit 1027 outputs the processing result of the processing unit 1030 to the external network 1200. The data generation unit 1026 generates application data. For example, road information is set in application data. Then, the protection format is designated according to the contents of the application data, and the generated application data and its data length are output to the processing unit 1030. The control unit 1029 controls processing of the entire base station apparatus 1020.

  FIG. 20 shows a configuration of terminal apparatus 1010 mounted on vehicle 1100. The terminal device 1010 includes an antenna 1011, an RF unit 1012, a modem unit 1013, a processing unit 1030, a reception processing unit 1016, a notification unit 1017, a data generation unit 1018, and a control unit 1019. The processing unit 1030 includes a frame detection unit 1031, a communication control header detection unit 1032, and an analysis update unit 1033.

  The antenna 1011, the RF unit 1012, the modem unit 1013, and the processing unit 1030 are basically the same in configuration and operation as the antenna 1021, the RF unit 1022, the modem unit 1023, and the processing unit 1030 in FIG.

  The reception processing unit 1016 is based on the data received from the processing unit 1030 and the vehicle information of the host vehicle received from the data generation unit 1018, the risk of collision, the approach of emergency vehicles such as ambulances and fire engines, Estimate traffic congestion at intersections. Further, if the data is image information, it is processed to be displayed on the notification unit 1017.

  The notification unit 1017 includes notification means for the user such as a monitor, a lamp, and a speaker (not shown). In accordance with an instruction from the reception processing unit 1016, the driver is notified of the approach of another vehicle (not shown) via the notification means. In addition, traffic information, image information such as intersections, and the like are displayed on the monitor.

  The data generation unit 1018 identifies a current position, a traveling direction, a moving speed, and the like of the vehicle 1100 on which the terminal device 1010 is mounted based on information supplied from a GPS receiver, a gyroscope, a vehicle speed sensor, and the like (not shown). The current position is indicated by latitude / longitude. Since the method for identifying these pieces of information can be realized by a generally known technique, description thereof is omitted here. The data generation unit 1018 generates data to be notified to other terminal apparatuses 1010 and the base station apparatus 1020 based on the specified information, and outputs the generated data (hereinafter referred to as application data) to the processing unit 1030. Further, the generated information is output to the reception processing unit 1016 as vehicle information of the own vehicle. The control unit 1019 controls processing of the entire terminal device 1010.

  FIG. 21 shows a basic configuration of the analysis update unit 1033. The configuration of the analysis update unit 1033 is basically the same in both the base station device 1020 and the terminal device 1010. The analysis update unit 1033 includes an identification information analysis unit 1331, a base station device analysis update unit 1332, and a terminal device analysis update unit 1333.

  The identification information analysis unit 1331 acquires IR control field data (see FIG. 18) and analyzes the identification information included in the data. In the example shown in FIG. 18, the identification information is composed of 4 bits. Bit number 3 (b3), which is the most significant bit, is used to identify the transmission source. The base station device is “1”, and the “terminal device” is “0”. The other bit numbers 2 to 0 (b2 to b0) are reserved and are set to “0”. The identification information analysis unit 1331 outputs the data from the base station device 1020 to the base station device analysis update unit 1332 as a result of the analysis of the identification information, and the terminal device analysis update if the data is from the terminal device 1010. Output to the unit 1333.

  The base station apparatus analysis updating unit 1332 receives synchronization information, transmission time, and road-to-vehicle communication period information (hereinafter referred to as RVC period information) included in the IR control field data stored in the packet signal from the base station apparatus 1020. Analyze and update the synchronization information, transmission time, and RVC period information of the device as appropriate. The terminal device analysis update unit 1333 analyzes the synchronization information, transmission time, and RVC period information included in the data of the IR control field stored in the packet signal from the terminal device 1010. Update the RVC period information as appropriate.

  FIG. 22 shows the configuration of an internal time update unit 1033a that forms part of the analysis update unit 1033. The configuration of the internal time update unit 1033a is basically the same in both the base station device 1020 and the terminal device 1010. The internal time update unit 1033a includes a transmission time acquisition unit 3310, a differential time calculation unit 3311, an internal time storage unit 3312, a differential time comparison unit 3313, and a differential time temporary storage unit 3314.

  The transmission time acquisition unit 3310 acquires synchronization information and transmission time included in the data of the IR control field. In the example shown in FIG. 18, the synchronization information is composed of 3 bits. Bit number 2 (b2) which is the most significant bit is used for synchronous or asynchronous identification. The meanings of bit numbers 1 and 0 (b1, b0) are as follows. “00” is time synchronization directly to base station apparatus 1020, “01” is time synchronization for information transferred once by terminal apparatus 1010, and “10” is information for information transferred twice by terminal apparatus 1010. Time synchronization and “11” are time synchronization for the information transferred by the terminal device 1010 three times. Thus, when the transmission source is the base station device 1020, it is “00”.

  In the example shown in FIG. 18, the transmission time is a 20-bit field indicating the transmission time of the frame. This is the value of the 1 second period timer in microseconds, and the range of the value is “0 to 999999”. The transmission time is given a timer value at the timing when the head of the PLCP preamble is transmitted from the antenna end, and is given by the MAC sublayer. The timing of grant is defined by the MAC sublayer. The field value assigned in the inter-vehicle / road-vehicle shared communication control information layer is “0”.

  The internal time holding unit 3312 holds the synchronization information of the own device and the internal time. The difference time calculation unit 3311 calculates a difference time between the transmission time output from the transmission time acquisition unit 3310 and the internal time read from the internal time holding unit 3312 and outputs the difference time to the difference time comparison unit 3313. When the difference time is less than or equal to the first threshold value, the difference time comparison unit 3313 executes synchronization processing, and appropriately updates the synchronization information and the internal time held in the internal time holding unit 3312.

  The difference time comparison unit 3313 stores the difference time in the difference time temporary storage unit 3314 when the difference time is greater than the first threshold and no data is stored in the difference time temporary storage unit 3314. When data is stored in the difference time temporary storage unit 3314, the difference time comparison unit 3313 compares the difference time output from the difference time calculation unit 3311 with the difference time read from the difference time temporary storage unit 3314. When the difference is equal to or smaller than the second threshold value, the difference time comparison unit 3313 executes synchronization processing, and appropriately updates the synchronization information and the internal time held in the internal time holding unit 3312. When the synchronization process is executed, the differential time temporary storage unit 3314 deletes the data stored in the differential time temporary storage unit 3314. The first threshold value and the second threshold value described above can be set to values obtained by the designer based on experiments and simulations.

  FIG. 23 shows the configuration of the RVC period information update unit 1033b that forms part of the analysis update unit 1033. The configuration of the RVC period information update unit 1033b is basically the same in both the base station apparatus 1020 and the terminal apparatus 1010. The RVC period information update unit 1033b includes an RVC period information acquisition unit 3320, an RVC period information comparison unit 3321, an internal RVC period information storage unit 3322, a temporary storage RVC period information comparison unit 3323, and an external RVC period information temporary storage unit 3324.

  The RVC period information acquisition unit 3320 acquires RVC period information included in the data of the IR control field. In the example shown in FIG. 18, the RVC period information is composed of 128 bits. One RVC period is formed by a field of 8 bits in total including a 2-bit transfer count and a 6-bit RVC period length. The number of RVC periods is 16, which is 8 × 16 and the RVC period information is 128 bits (16 octets). The RVC period length indicates the length in units of 3 units (48 us), and “0” indicates that there is no RVC period.

  Bit numbers 7 and 6 (b7 and b6), which are the upper 2 bits, indicate the number of transfers. The meanings of bit numbers 7 and 6 (b7 and b6) are as follows. “00” is not transferred, “01” is transferred once, “10” is transferred twice, and “11” is transferred three times. Bit numbers 5 to 0 (b5 to b0), which are the lower 6 bits, indicate the RVC period length. The meanings of bit numbers 5 to 0 (b5 to b0) are as follows. “000000” has no RVC period, “000001” has an RVC period length of 48 us (3 units), “0000010” has an RVC period length of 96 us (6 units),..., “111111” has an RVC period length. 3024 us (189 units).

  The internal RVC period information holding unit 3322 holds the RVC period information of the own device. The RVC period information comparison unit 3321 compares the RVC period information output from the RVC period information acquisition unit 3320 with the RVC period information read from the internal RVC period information holding unit 3322, and performs a synchronization process according to the comparison result. And the RVC period information held in the internal RVC period information holding unit 3322 is appropriately updated. Furthermore, RVC period information output from the RVC period information acquisition unit 3320 is output to the temporary holding RVC period information comparison unit 3323 according to the comparison result.

  Temporary holding RVC period information comparison section 3323 stores the RVC period information in external RVC period information temporary holding section 3324 when data is not stored in external RVC period information temporary holding section 3324. When data is stored in the external RVC period information temporary storage unit 3324, the temporary storage RVC period information comparison unit 3323 outputs the RVC period information output from the RVC period information comparison unit 3321 and the external RVC period information temporary storage unit 3324. The read RVC period information is compared. In accordance with the comparison result, the temporary holding RVC period information comparison unit 3323 executes a synchronization process and appropriately updates the RVC period information held in the internal RVC period information holding unit 3322. When the synchronization process is executed, the data stored in the external RVC period information temporary holding unit 3324 is deleted.

  FIG. 24 is a flowchart for explaining the processing of the identification information analysis unit 1331. The identification information analysis unit 1331 extracts the version included in the data of the IR control field and determines whether or not the version is 0b “0000” (S1010). If the version is not 0b “0000” (N in S1010), the packet signal storing the IR control field is discarded (S1015). When the version is 0b “0000” (Y in S1010), the identification information analysis unit 1331 extracts the identification information included in the data of the IR control field.

  The identification information analysis unit 1331 determines whether or not the identification information is 0b “1000” (S1011). When the identification information is 0b “1000” (Y in S1011), the mode is shifted to the packet analysis mode from the base station apparatus 1020 (S1012). When the identification information is not 0b “1000” (N in S1011), the identification information analysis unit 1331 determines whether the identification information is 0b “0000” (S1013). When the identification information is 0b “0000” (Y in S1013), the mode is shifted to the analysis mode of the packet from the terminal device 1010 (S1014). When the identification information is not 0b “0000” (N in S1013), the packet signal is discarded (S1015).

  FIG. 25 is a flowchart for explaining processing in the analysis mode of a packet received from base station apparatus 1020. The transmission time acquisition unit 3310 extracts the synchronization information included in the data of the IR control field, and determines whether the synchronization information is 0b “100” (S1020). When the synchronization information is not 0b “100” (N in S1020), the transmission time acquisition unit 3310 discards the packet signal in which the IR control field is stored (S1027). If there is data in a packet transmission time register (not shown) to be described later, that data is also discarded.

  When the synchronization information is 0b “100” (Y in S1020), it indicates that the time is direct time synchronization with respect to the base station apparatus 1020. The transmission time acquisition unit 3310 extracts the transmission time included in the data of the IR control field, and determines whether or not the transmission time is in the range of “0” or more and “999999” or less (S1021). When the transmission time is not within the range (N in S1021), the transmission time acquisition unit 3310 discards the packet signal in which the IR control field is stored (S1027). When the transmission time is within the range (Y in S1021), the transmission time is held in a packet transmission time holding register (not shown) (S1022).

  The RVC period information acquisition unit 3320 extracts the RVC period information included in the data of the IR control field, and extracts all the RVC period length fields that are not “0” from the 16 RVC periods forming the RVC period information. (S1023). The RVC period information acquisition unit 3320 determines whether or not the extraction number N is “1” (S1024). When the extraction number N is not “1” (N in S1024), the RVC period information acquisition unit 3320 discards the packet signal in which the IR control field is stored (S1027). This is because in the case of a packet signal from the base station apparatus 1020, the extraction number N should be “1”. When the extraction number N is “1” (Y in S1024), the RVC period information acquisition unit 3320 determines whether or not the transmission time is in the RVC period (S1025).

  Here, a method for calculating the RVC period and a method for comparing the RVC period and the transmission time will be described more specifically. As described above, the length of the superframe is 100 ms, and since this 100 ms is divided into 16 RSU sections, the RSU section length is 6250 u seconds (1 second / 16 sections). Therefore, the RSU section start time (100 ms cycle) of a certain RSU section N (N is an integer in the range of 1 ≦ N ≦ 16) is (6250 × N) u seconds. The range of the RVC period length specified in the RVC period information of the IR control field is 48 u seconds to 3024 u seconds. Therefore, the range of the RVC period length defined in a certain RSU section N is (6250 × N) u seconds to ((6250 × N) + (48-3024)) u seconds.

  While the range of the RVC period length is 100 ms units, the transmission time is a counter in units of 1 second. Therefore, the transmission time is corrected in units of 100 ms. Specifically, the following calculation is performed. Transmission time-INT (transmission time / 100,000). INT () indicates a function for truncating after the decimal point. The RVC period information acquisition unit 3320 determines whether or not transmission time-INT (transmission time / 100,000) is included in (6250 × N) u seconds to ((6250 × N) + (48 to 3024)) u seconds. judge.

  When the transmission time is in the RVC period in step S1025 (Y in S1025), the RVC period information acquisition unit 3320 does not indicate the number of extracted subframes, the number of transfers in the RVC period, and the RVC period length. It is held in the RVC period information register (S1026). When the transmission time does not enter the RVC period (N in S1025), the RVC period information acquisition unit 3320 discards the packet signal in which the IR control field is stored (S1027).

  FIG. 26 is a flowchart for explaining processing in the analysis mode of a packet received from terminal apparatus 1010. The transmission time acquisition unit 3310 extracts the synchronization information included in the data of the IR control field, and determines whether the synchronization information is any one of 0b “101”, 0b “110”, and 0b “111” ( S1030). When the synchronization information is not 0b “101”, 0b “110”, or 0b “111” (N in S1030), the transmission time acquisition unit 3310 discards the packet signal in which the IR control field is stored. (S1037). If there is data in a packet transmission time register (not shown) to be described later, that data is also discarded.

  When the synchronization information is any one of 0b “101”, 0b “110”, and 0b “111” (Y in S1030), it indicates that the time is synchronized with the base station apparatus 1020. The transmission time acquisition unit 3310 extracts the transmission time included in the data of the IR control field, and determines whether or not the transmission time is in the range of “0” or more and “999999” or less (S1031). When the transmission time is not within the range (N in S1031), the transmission time acquisition unit 3310 discards the packet signal in which the IR control field is stored (S1037). When the transmission time is within the range (Y in S1031), the transmission time is held in a packet transmission time holding register (not shown) (S1032).

  The RVC period information acquisition unit 3320 extracts the RVC period information included in the data of the IR control field, and extracts all the RVC period length fields that are not “0” from the 16 RVC periods forming the RVC period information. (S1033). The RVC period information acquisition unit 3320 determines whether or not the extraction number N is “0” (S1034). When the extraction number N is “0” (Y in S1034), it is determined that there is no information, and the analysis process is terminated. When the extraction number N is not “0” (N in S1034), the RVC period information acquisition unit 3320 determines whether or not the transmission time is in the RVC period (S1035).

  When the transmission time does not fall within the RVC period (N in S1035), the RVC period information acquisition unit 3320 displays a packet RVC (not shown) indicating the number of extracted N subframes, the number of RVC periods transferred, and the RVC period length. It is held in the period information register (S1036). When the transmission time is in the RVC period (Y in S1035), the RVC period information acquisition unit 3320 discards the packet signal in which the IR control field is stored (S1037).

  FIG. 27 is a flowchart for explaining the update process of internal time and RVC period information in base station apparatus 1020 (part 1). FIG. 28 is a flowchart for explaining an update process of internal time and RVC period information in base station apparatus 1020 (part 2). The difference time calculation unit 3311 determines whether data is stored in the packet transmission time holding register (not shown) (S1040). If no data is stored (N in S1040), the process of steps S1041 to S1047 is skipped, and the process proceeds to step S1048. When data is stored (Y in S1040), the difference time calculation unit 3311 calculates a difference time between the transmission time held in the packet transmission time holding register and the internal time of the own device (base station device 1020). Calculate (S1041).

  The difference time comparison unit 3313 has the synchronization information held by the own device of 0b “100”, the absolute value of the difference time is equal to or smaller than the first-first threshold T1, the synchronization information held by the own device is 0b “101”, and The absolute value of the difference time is equal to or smaller than the first-second threshold T2, the synchronization information held by the own device is 0b “110”, and the absolute value of the difference time is equal to or smaller than the first-3 threshold value T3, or the own device holds. It is determined whether or not any of the conditions in which the synchronization information is 0b “111” and the absolute value of the difference time is equal to or smaller than the first to fourth threshold values T4 is satisfied (S1042). In addition, it is set as the relationship of 1-1 threshold-value T1 <= 1-2 threshold-value T2 <= 1-3 threshold-value T3 <= 1-4 threshold-value T4. That is, the allowed difference time may be increased as the number of transfers increases.

  When the above condition is satisfied (Y in S1042), the difference time comparison unit 3313 reads the internal time held in the internal time holding unit 3312, subtracts the difference time from the internal time, and calculates the internal time after subtraction. Stored in the internal time holding unit 3312. In addition, the synchronization information held in the internal time holding unit 3312 is overwritten with 0b “100” (S1045). That is, the internal time and the synchronization information are corrected. The difference time comparison unit 3313 deletes the data if stored in the difference time temporary storage unit 3314 (S1046). Since the internal time has been corrected, the data is not necessary. Then, the process proceeds to step S1048.

  If the above condition is not satisfied in step S1042 (N in S1042), the difference time comparison unit 3313 determines whether data is stored in the difference time temporary storage unit 3314 (S1043). That is, it is confirmed whether or not the previous difference time data is held. If no data is stored (N in S1043), the difference time calculated this time is stored in the difference time temporary storage unit 3314 (S1047). Then, the process proceeds to step S1048.

  If data is stored in step S1043 (Y in S1043), the difference time comparison unit 3313 calculates the absolute difference between the previous difference time held in the difference time temporary holding unit 3314 and the current difference time. It is determined whether or not the value is less than or equal to the second threshold T5 (S1044). When it is equal to or less than the second threshold T5 (Y in S1044), the above-described processing in steps S1045 and S1046 is executed. When it is not less than or equal to the second threshold T5 (N in S1044), the above-described processing in step S1047 is executed.

  Turning to FIG. The RVC period information comparison unit 3321 determines whether there is RVC period information extracted from the packet signal (S1048). That is, it is determined whether or not data is stored in the packet RVC period information holding register (not shown). If the extracted RVC period information does not exist (N in S1048), steps S1049 to S1058 are skipped, and the update process is terminated. When the extracted RVC period information exists (Y in S1048), the RVC period information comparison unit 3321 receives information corresponding to the subframe number of the extracted RVC period information in the internal RVC period information holding unit 3322 of the own device. It is determined whether it is held (S1049).

  When not held in the internal RVC period information holding unit 3322 (N in S1049), the RVC period information comparing unit 3321 stores the number of RVC period transfers and the RVC period length extracted from the packet signal in the internal RVC period information holding unit 3322. In the corresponding subframe area (S1055). That is, writing or updating in the RVC period is performed. The RVC period information comparison unit 3321 deletes data if data remains in the corresponding subframe area of the external RVC period information temporary storage unit 3324 (S1058).

  When it is held in the internal RVC period information holding unit 3322 in step S1049 (Y in S1049), the RVC period information comparison unit 3321 indicates that the number of subframe transfers extracted from the packet signal indicates that the internal RVC period information is held. It is determined whether or not the number of times of transfer of the corresponding subframe held in the unit 3322 is greater than or equal to (S1050). If the former is not equal to or greater than the latter (N in S1050), the process proceeds to step S1058 without updating the corresponding subframe, and the RVC period information comparison unit 3321 stores data in the corresponding subframe area of the external RVC period information temporary storage unit 3324. If it remains, it is erased (S1058).

  If the former is greater than or equal to the latter in step S1050 (Y in S1050), the RVC period information comparison unit 3321 holds the RVC period length of the subframe extracted from the packet signal in the internal RVC period information holding unit 3322. It is determined whether or not it matches the RVC period length of the corresponding subframe (S1051). If they match (Y in S1051), the RVC period information comparison unit 3321 overwrites the transfer count of the subframe extracted from the packet signal with the transfer count of the corresponding subframe in the internal RVC period information holding unit 3322 (S1052). ). That is, the transfer count is updated. Thereafter, the process proceeds to step S1058, and the RVC period information comparison unit 3321 erases the data if the data remains in the corresponding subframe area of the external RVC period information temporary storage unit 3324 (S1058).

  If they do not match in step S1051 (N in S1051), the update of the number of transfers is suspended, and the temporary holding RVC period information comparison unit 3323 has data in the corresponding subframe area of the external RVC period information temporary holding unit 3324. It is determined whether or not (S1053). If it does not exist in the corresponding subframe area (N in S1053), the temporary holding RVC period information comparison unit 3323 uses the RVC period transfer count and RVC period length extracted from the packet signal as the external RVC period information temporary holding unit 3324. (S1056).

  If there is data in the corresponding subframe area in step S1053 (Y in S1053), the temporary holding RVC period information comparison unit 3323 determines that the RVC period length of the subframe extracted from the packet signal is the external RVC period information temporary. It is determined whether or not it matches the RVC period length of the corresponding subframe held in the holding unit 3324 (S1054). If they match (Y in S1054), the temporary holding RVC period information comparison unit 3323 stores the number of RVC period transfers and the RVC period length extracted from the packet signal in the corresponding subframe area of the internal RVC period information holding unit 3322. (S1055). If data remains in the corresponding subframe area of the external RVC period information temporary holding unit 3324, the data is deleted (S1058).

  If they do not match in step S1054 (N in S1054), the temporary holding RVC period information comparison unit 3323 holds the RVC period length of the subframe extracted from the packet signal in the external RVC period information temporary holding unit 3324. The RVC period length of the corresponding subframe is overwritten (S1057).

  FIG. 29 is a flowchart for explaining the update process of internal time and RVC period information in terminal apparatus 1010 (part 1). FIG. 30 is a flowchart for explaining the update process of the internal time and RVC period information in terminal apparatus 1010 (part 2). The difference time calculation unit 3311 determines whether data is stored in the packet transmission time holding register (not shown) (S1060). When data is not stored (N of S1060), the process of steps S1061 to S1068 is skipped, and the process proceeds to step S1069. When data is stored (Y in S1060), the difference time calculation unit 3311 calculates the difference time between the transmission time held in the packet transmission time holding register and the internal time of the own device (terminal device 1010). (S1061).

  The difference time comparison unit 3313 synchronizes the synchronization information held by the own device and the synchronization information extracted from the packet signal (b3 = 0b “1”), and the transfer count of the own device is the packet signal. It is determined whether or not the condition that the number of transfers is equal to or less than the number of transfers extracted from (S1062). When the condition is not satisfied (N in S1062), the process of steps S1063 to S1068 is skipped and the process proceeds to step S1069. When the condition is satisfied (Y in S1062), the difference time comparison unit 3313 determines whether or not the absolute value of the difference time is equal to or less than the first threshold T1 (S1063).

  When the difference is less than or equal to the first threshold T1 (Y in S1063), the difference time comparison unit 3313 reads the internal time held in the internal time holding unit 3312, subtracts the difference time from the internal time, The internal time is stored in the internal time holding unit 3312. Further, the synchronization information held in the internal time holding unit 3312 is updated to the synchronization information extracted from the packet signal (S1066). That is, the internal time and the synchronization information are corrected. The difference time comparison unit 3313 deletes the data if stored in the difference time temporary storage unit 3314 (S1067). Since the internal time has been corrected, the data is not necessary. Then, the process proceeds to step S1069.

  If it is not less than or equal to the first threshold T1 in step S1063 (N in S1063), the difference time comparison unit 3313 determines whether data is stored in the difference time temporary storage unit 3314 (S1064). That is, it is confirmed whether or not the previous difference time data is held. If no data is stored (N in S1064), the difference time calculated this time is overwritten in the difference time temporary storage unit 3314 (S1068). Then, the process proceeds to step S1069.

  When data is stored in step S1064 (Y in S1064), the difference time comparison unit 3313 calculates the absolute difference between the previous difference time held in the difference time temporary holding unit 3314 and the current difference time. It is determined whether or not the value is less than or equal to the second threshold T5 (S1065). When it is equal to or smaller than the second threshold value T5 (Y in S1065), the processes in steps S1066 and S1067 described above are executed. When it is not less than or equal to the second threshold T5 (N in S1065), the above-described processing in step S1068 is executed.

  Turning to FIG. The RVC period information comparison unit 3321 determines whether there is RVC period information extracted from the packet signal (S1069). That is, it is determined whether or not data is stored in the packet RVC period information holding register (not shown). If the extracted RVC period information does not exist (N in S1069), steps S1070 to S1076 are skipped, and the update process is terminated. When the extracted RVC period information exists (Y in S1069), the RVC period information comparison unit 3321 counts the number n (n is an integer of 1 to 16) of the extracted RVC periods (S1070). The RVC period information comparison unit 3321 counts the number m (m is an integer of 1 to 16) in which the extracted RVC period matches the RVC period held in the internal RVC period information holding unit 3322 (S1071).

  The RVC period information comparison unit 3321 determines whether or not the RVC period lengths match in all the matching RVC periods (S1072). If they match (Y in S1072), steps S1073 and S1074 are skipped, and the process proceeds to step S1075. If they do not match (N in S1072), the temporary storage RVC period information comparison unit 3323 determines whether data exists in the external RVC period information temporary storage unit 3324 (S1073). When there is no data (N in S1073), the temporary holding RVC period information comparison unit 3323 stores all RVC period information extracted from the packet signal in the external RVC period information temporary holding unit 3324 (S1077).

  If data exists in step S1073 (Y in S1073), the RVC period information comparison unit 3321 determines whether or not the RVC period lengths match in all the RVC periods extracted from the packet signal (S1074). That is, it is determined whether n RVC periods coincide. When the RVC period lengths match (Y in S1074), the RVC period information comparison unit 3321 displays the RVC period information (more specifically, the number of transfers of the RVC period and the RVC period length) in the internal RVC period information holding unit 3322. Update (S1075). A new RVC period is added. The RVC period information comparison unit 3321 erases data if it remains in the external RVC period information temporary storage unit 3324 (S1076). If the RVC period lengths do not match in step S1074 (N in S1074), the temporary holding RVC period information comparison unit 3323 overwrites the external RVC period information temporary holding unit 3324 with all the RVC period information extracted from the packet signal. (S1078).

  As described above, according to another modification, when the device synchronizes with the transmission time and RVC period information stored in the received packet signal, it synchronizes immediately if a predetermined condition is satisfied. If the condition is not satisfied, it is determined whether or not to hold and wait for the next packet signal to synchronize. As a result, synchronization based on data that may have been tampered with the transmission time and RVC period information can be avoided, and the accuracy of synchronization processing between communication devices can be improved. Therefore, it is possible to suppress a deviation in the NAV setting of the RSU packet, a situation in which the terminal apparatus transmits a packet during the transmission time of the base station apparatus, and a situation in which tampered data is further transferred and an adverse effect is propagated.

  Although it is conceivable to include the IR control field in the security layer, in CSMA control, since the transmission time is not determined until immediately before transmission, it is difficult to ensure a sufficient calculation time for MAC (Message Authentication Code).

  In the above, it demonstrated based on the Example of this invention. 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. .

  Next, Modification 1 will be described. In Modification 1, it is determined whether or not to perform synchronization processing with reference to a result of statistical processing of information included in an IR control field included in a plurality of subsequent packet signals. In this case, the plurality of packet signals may be packet signals transmitted from the same device, or may be packet signals transmitted from a plurality of devices.

  FIG. 31 shows a configuration of an internal time update unit 1033am that forms part of the analysis update unit 1033 according to the first modification. The configuration of the internal time update unit 1033am is basically the same in both the base station device 1020 and the terminal device 1010. The internal time update unit 1033am includes a transmission time acquisition unit 3310, a differential time calculation unit 3311, an internal time storage unit 3312, a differential time storage unit 3315, and a correction value determination unit 3316.

  The transmission time acquisition unit 3310 acquires synchronization information and transmission time included in the data of the IR control field. The internal time holding unit 3312 holds the synchronization information of the own device and the internal time. The difference time calculation unit 3311 calculates a difference time between the transmission time output from the transmission time acquisition unit 3310 and the internal time output from the internal time holding unit 3312, and outputs the difference time to the difference time holding unit 3315. The difference time holding unit 3315 holds a plurality of difference times. The detailed configuration of the difference time holding unit 3315 will be described later. The correction value determination unit 3316 performs a statistical process on the plurality of difference times output from the difference time holding unit 3315, determines a correction value of the internal time to be set in the internal time holding unit 3312, and the internal time Synchronize.

  FIG. 32 shows a configuration of an RVC period information update unit 1033bm that forms part of the analysis update unit 1033 according to the first modification. The configuration of the RVC period information update unit 1033bm is basically the same in both the base station apparatus 1020 and the terminal apparatus 1010. The RVC period information update unit 1033bm includes an RVC period information acquisition unit 3320, an RVC period information holding unit 3325, an RVC period information synchronization determination unit 3326, and an internal RVC period information holding unit 3322.

  The RVC period information acquisition unit 3320 acquires RVC period information included in the data of the IR control field. The internal RVC period information holding unit 3322 holds the RVC period information of the own device. The RVC period information holding unit 3325 holds a plurality of pieces of RVC period information output from the RVC period information acquisition unit 3320. Details of the RVC period information holding unit 3325 will be described later. The RVC period information synchronization determination unit 3326 determines whether to update the RVC period information held in the RVC period information acquisition unit 3320 based on a plurality of pieces of RVC period information output from the RVC period information holding unit 3325. To do.

  FIG. 33 shows the configuration of the difference time holding unit 3315. The difference time holding unit 3315 includes a difference time holding register selection unit 1150, a first difference time holding register 1151, a second difference time holding register 1152, a third difference time holding register 1153, and a register erasing unit 1154. FIG. 33 shows an example in which three differential time holding registers are provided, but the number is not limited to three.

  The difference time holding register selection unit 1150 outputs the difference times sequentially input from the difference time calculation unit 3311 to the first difference time holding register 1151, the second difference time holding register 1152, and the third difference time holding register 1153, respectively. . The first difference time holding register 1151, the second difference time holding register 1152, and the third difference time holding register 1153 each hold the difference time input from the difference time holding register selection unit 1150, and determine a correction value at a predetermined timing. The data are sequentially output to the unit 3316. The register erasing unit 1154 erases data held in the first difference time holding register 1151, the second difference time holding register 1152, and the third difference time holding register 1153 at a predetermined timing.

  FIG. 34 shows the configuration of the RVC period information holding unit 3325. The RVC period information holding unit 3325 includes an RVC period information holding register selection unit 1250, a first RVC period information holding register 1251, a second RVC period information holding register 1252, a third RVC period information holding register 1253, and a register erasing unit 1254. FIG. 34 shows an example in which three RVC period information holding registers are provided, but the number is not limited to three.

  The RVC period information holding register selection unit 1250 sends the differential times sequentially input from the RVC period information acquisition unit 3320 to the first RVC period information holding register 1251, the second RVC period information holding register 1252, and the third RVC period information holding register 1253, respectively. Output. The first RVC period information holding register 1251, the second RVC period information holding register 1252, and the third RVC period information holding register 1253 hold the RVC period information input from the RVC period information holding register selection unit 1250, respectively, and RVC at a predetermined timing. The information is sequentially output to the period information synchronization determination unit 3326. The register erasing unit 1254 erases data held in the first RVC period information holding register 1251, the second RVC period information holding register 1252, and the third RVC period information holding register 1253 at a predetermined timing.

  FIG. 35 is a flowchart for explaining an internal time and RVC period information update process according to Modification 1 (part 1). FIG. 36 is a flowchart for explaining an update process of internal time and RVC period information according to Modification 1 (part 2). The processes described below are common to the base station apparatus 1020 and the terminal apparatus 1010.

  The difference time calculation unit 3311 determines whether data is stored in the packet transmission time holding register (not shown) (S1080). When data is not stored (N in S1080), the processing in steps S1081 to S1087 is skipped, and the process proceeds to step S1088. When data is stored (Y in S1080), the difference time calculation unit 3311 calculates the difference time between the transmission time held in the packet transmission time holding register and the internal time of the own device (S1081). In the present modification, when data is stored in the packet transmission time holding register, a plurality of data are stored. Therefore, the difference time calculation unit 3311 calculates a plurality of difference times between each of the plurality of transmission times and the internal time of the own device.

  The difference time calculation unit 3311 sequentially stores the difference times in each of the difference time holding registers M (three in this modification) (S1082). The difference time holding register in which the difference time is to be stored is cyclically switched every time the difference time is stored. In addition, when storing the difference time, the synchronization information included in the IR control field including the transmission time on which the difference time calculation is based is also stored.

  The correction value determination unit 3316 determines whether data is stored in all of the differential time holding registers (S1083). When not stored (N of S1083), the process of step S1084-S1087 is skipped and it changes to step S1088. When data is stored (Y in S1083), the correction value determination unit 3316 classifies each register value held in each difference time holding register in a predetermined time unit (for example, 10 us unit), and classifies the most. The category to be specified is specified (S1084).

  The correction value determination unit 3316 determines whether or not the number of data belonging to the category exceeds a majority of the total number of data (S1085). When not exceeding (N of S1085), the process of step S1086 and S1087 is skipped and it changes to step S1088. When the time is exceeded (Y in S1085), the correction value determination unit 3316 reads the internal time held in the internal time holding unit 3312, and subtracts the average value of the difference times belonging to the category from the internal time. The later internal time is stored in the internal time holding unit 3312. Further, the synchronization information held in the internal time holding unit 3312 is overwritten with the minimum synchronization information in the category (S1086). That is, the internal time and the synchronization information are corrected. The correction value determination unit 3316 deletes all data in the difference time holding register (S1087). When the synchronization is completed, the data held in the differential time holding register becomes unnecessary. Then, the process proceeds to step S1088.

  Turning to FIG. The RVC period information acquisition unit 3320 determines whether there is RVC period information extracted from the packet signal (S1088). That is, it is determined whether or not data is stored in the packet RVC period information holding register (not shown). If the extracted RVC period information does not exist (N in S1088), steps S1089 to S1095 are skipped, and the update process is terminated. In the present modification, when data is stored in the RVC period information holding register, a plurality of data are stored. When the extracted RVC period information exists (Y in S1088), the RVC period information acquisition unit 3320 sequentially stores the RVC period information in each of the RVC period information holding registers M (three in this modification) ( S1089). Note that the RVC period information holding register in which the RVC period information is to be stored is cyclically switched every time the RVC period information is stored.

  The RVC period information synchronization determination unit 3326 determines whether data is stored in all the RVC period information holding registers (S1090). If not stored (N in S1090), the process of steps S1090 to S1095 is skipped, and the update process is terminated. When data is stored (Y in S1090), the RVC period information synchronization determination unit 3326 groups matching data among the data held in the RVC period information holding register (S1091). The RVC period information synchronization determination unit 3326 determines whether the number of data belonging to the group to which the most data belongs exceeds a majority of the total number of data (S1092). If not exceeded (N in S1092), the process of steps S1093 and S1094 is skipped, and the update process is terminated. When it exceeds (Y in S1092), the RVC period information synchronization determination unit 3326 synchronizes the RVC period information held in the internal RVC period information holding unit 3322 with the data of the group to which the most data belongs (S1093). . The RVC period information synchronization determination unit 3326 erases all data in the RVC period information holding register (S1094). When synchronization is completed, the data held in the RVC period information holding register becomes unnecessary.

  As described above, according to the first modification, it is compared with the basic example by determining whether to perform synchronization processing based on the result of statistical processing of communication control information included in a plurality of packet signals. Thus, the accuracy of the synchronization process can be improved. Note that the above-described statistical processing for determining whether the majority is exceeded is merely an example, and other statistical processing may be employed.

  Next, Modification 2 will be described. In the second modification, the aggregation of packets and the update of communication control information are performed in the superframe cycle. Using the beginning of the superframe at the internal time as a trigger, packet aggregation is performed separately for each base station apparatus 1020 and terminal apparatus 1010. Then, synchronization is performed on the merged packet of the base station apparatus 1020 and the base station apparatus 1020 at the head of the next superframe. The merging of the packet of the base station apparatus 1020 and the packet of the terminal apparatus 1010 is basically the addition of the packet of the terminal apparatus 1010 to the packet of the base station apparatus 1020.

  FIG. 37 shows the configuration of the analysis update unit 1033 according to the second modification. The configuration of the analysis update unit 1033 is basically the same in both the base station device 1020 and the terminal device 1010. The analysis update unit 1033 includes an identification information analysis unit 1331, a base station device analysis extraction unit 1334, a terminal device analysis extraction unit 1335, and an update unit 1336.

  The identification information analysis unit 1331 acquires IR control field data and analyzes the identification information included in the data. As a result of analyzing the identification information, the identification information analysis unit 1331 outputs the data from the base station device 1020 to the base station device analysis extraction unit 1334, and if the data is from the terminal device 1010, the terminal device analysis extraction. Output to the unit 1335.

  Base station apparatus analysis and extraction unit 1334 extracts synchronization information, transmission time, and RVC period information included in the IR control field data stored in the packet signal from base station apparatus 1020, and transmits the transmission time and RVC period information. Generate update information. The terminal device analysis extraction unit 1335 extracts synchronization information, transmission time, and RVC period information included in the IR control field data stored in the packet signal from the terminal device 1010, and updates the transmission time and RVC period information. Is generated. The update unit 1336 merges update information respectively output from the base station device analysis extraction unit 1334 and the terminal device analysis extraction unit 1335, and updates the transmission time and RVC period information of the own device. Note that the configurations of the internal time update unit 1033a and the RVC period information update unit 1033b are basically the same as those of the first modification.

  FIG. 38 is a flowchart for explaining processing of the base station apparatus analysis extraction unit 1334 and the terminal apparatus analysis extraction unit 1335 according to the second modification. The processes described below are common to the base station apparatus 1020 and the terminal apparatus 1010. The base station device analysis extraction unit 1334 and the terminal device analysis extraction unit 1335 determine whether or not the internal time of the own device matches the start timing of the superframe (S1100). If they do not match (N in S1100), the difference time calculation unit 3311 determines whether data is stored in the packet transmission time holding register (not shown) (S1101). When data is not stored (N of S1101), the processing of steps S1102 and S1103 is skipped, and the process proceeds to step S1104. When data is stored (Y in S1101), the difference time calculation unit 3311 calculates the difference time between the transmission time held in the packet transmission time holding register and the internal time of the own device (S1102). In the present modification, when data is stored in the packet transmission time holding register, a plurality of data are stored. Therefore, the difference time calculation unit 3311 calculates a plurality of difference times between each of the plurality of transmission times and the internal time of the own device.

  The difference time calculation unit 3311 sequentially stores the difference times in each of the difference time holding registers M (M is a natural number) (S1103). The difference time holding register M to store the difference time is incremented every time the difference time is stored (here, the initial value of M is 1), and the maximum value (that is, the number of difference time holding registers installed). ), The transmission time is not extracted any further. In addition, when storing the difference time, the synchronization information included in the IR control field including the transmission time on which the difference time calculation is based is also stored.

  The RVC period information acquisition unit 3320 determines whether there is RVC period information extracted from the packet signal (S1104). That is, it is determined whether or not data is stored in the packet RVC period information holding register (not shown). If the extracted RVC period information does not exist (N in S1104), step S1105 is skipped and the process is terminated. If present (Y in S1104), the RVC period information acquisition unit 3320 sequentially stores the RVC period information in each of the RVC period information holding registers M (S1105). Note that the RVC period information holding register in which the RVC period information is to be stored is incremented every time the RVC period information is stored (here, the initial value of M is 1) and the maximum value (that is, the RVC period information register). When the number of installations) is reached, no further extraction or storage of RVC period information is performed.

  If they match in step S1100 (Y in S1100), the correction value determination unit 3316 classifies each register value held in each difference time holding register by a predetermined time unit (for example, 10 us unit), A category into which many register values are classified is extracted (S1106). In addition, when the base station apparatus 1020 does not exist in the surroundings, the category may not be extracted.

  The correction value determination unit 3316 determines an average value of data (difference time value) belonging to the category as an internal time difference value (S1107). The correction value determination unit 3316 determines the minimum synchronization information in the category as the synchronization information to be overwritten in the internal time holding unit 3312 (S1108). The RVC period information synchronization determination unit 3326 extracts the mode value for each RSU of the RVC period information holding register (S1109). In this modification, each mode value from RSU1 to RSU16 is extracted. In steps S1107 to S1109, only determination or extraction is performed, and actual synchronization is not performed. The correction value determination unit 3316 erases all the data in the difference time holding register (S1110), and erases all the data in the RVC period information holding register (S1111).

  FIG. 39 is a flowchart for explaining processing of the update unit 1336 according to the second modification. The processes described below are common to the base station apparatus 1020 and the terminal apparatus 1010. The updating unit 1336 determines whether or not there is difference time data from the base station apparatus 1020 (S1120). When present (Y in S1120), the updating unit 1336 corrects the internal differential time value from the base station device 1020 with the differential time data, and synchronizes the synchronization information of the own device with the synchronization information corresponding to the differential time data. (S1122). Then, the process proceeds to step S1124.

  When the difference time data from the base station apparatus 1020 does not exist in step S1120 (N of S1120), the update unit 1336 determines whether or not the difference time data from the terminal apparatus 1010 exists (S1121). When it does not exist (N of S1121), step S1123 is skipped and the process proceeds to step S1124. If present (Y in S1121), the updating unit 1336 corrects the internal difference time value from the terminal device 1010 with the difference time data, and synchronizes the synchronization information of the own device with the synchronization information corresponding to the difference time data. (S1123). Then, the process proceeds to step S1124.

  The updating unit 1336 determines whether or not the extracted RVC period information (RSU1 to RSU16) from the base station apparatus 1020 exists (S1124). When it exists (Y of S1124), the update part 1336 determines whether the RVC period information (RSU1-RSU16) extracted from the terminal device 1010 exists (S1125). When present (Y in S1125), the updating unit 1336 extracts the RVC period information (RSU1 to RSU16) of the base station apparatus 1020 as the synchronous RVC period information, and sets the region without the RSU information to the base station apparatus of the terminal apparatus 1010. It is supplemented with RVC period information 1020 (RSU1 to RSU16) and synchronized with the internal RVC period information of its own device (S1126).

  When the extracted RVC period information (RSU1 to RSU16) from the terminal apparatus 1010 does not exist in step S1125 (N of S1125), the update unit 1336 uses the RVC period information ( RSU1 to RSU16) are extracted and synchronized with the internal RVC period information of the own device (S1127).

  When the extracted RVC period information (RSU1 to RSU16) from the base station apparatus 1020 does not exist in step S1124 (N of S1124), the update unit 1336 extracts the RVC period information (RSU1 to RSU1) from the terminal apparatus 1010. It is determined whether or not there is an RSU 16) (S1128). When present (Y in S1128), the updating unit 1336 extracts the RVC period information (RSU1 to RSU16) of the terminal apparatus 1010 as the synchronous RVC period information and synchronizes with the internal RVC period information of the own apparatus (S1129). When it does not exist (N of S1128), step S1129 is skipped and the process is terminated.

  As described above, according to the second modification, the accuracy of the synchronization process can be improved as compared with the basic example by performing the statistical process at the superframe period and determining whether to perform the synchronization process.

  10 base station devices, 12 vehicles, 14 terminal devices, 20 antennas, 22 RF units, 24 modulation / demodulation units, 26 processing units, 28 network communication units, 30 control units, 40 frame defining units, 42 selection units, 44 communication processing units, 46 lower layer processing unit, 48 security layer processing unit, 50 antenna, 52 RF unit, 54 modulation / demodulation unit, 56 synchronization unit, 58 processing unit, 60 data generation unit, 62 notification unit, 64 control unit, 66 acquisition unit, 68 request Unit, 70 selection unit, 72 generation unit, 74 lower layer processing unit, 76 security layer processing unit, 78 transfer processing unit, 100 communication system.

Claims (6)

A receiving unit that receives packet signals from other communication devices in the same system;
An extraction unit for extracting a communication control field included in the packet signal;
A synchronization unit for synchronizing with the other communication device using information included in the communication control field,
The synchronization unit determines whether or not to synchronize with the other communication device using information included in a communication control field included in a subsequent packet signal. The communication control field includes the transmission time of the packet signal,
A calculation unit for calculating a difference time between the transmission time of the packet signal and the internal time of the communication device;
A difference time holding unit for temporarily holding the difference time calculated by the calculation unit,
The communication device according to claim 1, wherein the synchronization unit performs time synchronization with the other communication device when the calculated difference time is equal to or less than a first threshold value. The communication control field includes the transmission time of the packet signal,
A calculation unit for calculating a difference time between the transmission time of the packet signal and the internal time of the communication device;
A difference time holding unit for temporarily holding the difference time calculated by the calculation unit,
The synchronization unit is configured such that when the calculated difference time is greater than a first threshold and the difference between the calculated difference time and the difference time held in the difference time holding unit is equal to or less than a second threshold, The communication device according to claim 1, wherein time synchronization with another communication device is executed. The communication control field includes communication period information formed by a plurality of communication period fields each including a transfer count and a communication period length.
The synchronization unit compares the number of transfers in the communication period field extracted from the new packet signal with the number of transfers in the corresponding communication period field held in the communication apparatus, and the extracted communication period field. Whether to update the communication period information internally held in the communication apparatus according to at least one of the comparison results between the communication period length and the communication period length of the corresponding communication period field held in the communication apparatus. The communication device according to claim 1, wherein the communication device is determined.   The synchronization unit refers to a result of statistical processing of information included in a communication control field included in a plurality of subsequent packet signals, and determines whether to synchronize with the other communication device. The communication apparatus according to claim 1.   The communication device according to claim 1, wherein the synchronization unit synchronizes with the other communication device in units of a superframe period.

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