JP6055265B2 - Mobile station, computer program, and data structure of communication packet - Google Patents

Description

The present invention also relates the mobile station, the data structure of a computer program, and a communication packet.

In recent years, road-to-vehicle communication and intelligent road traffic system (ITS) by vehicle-to-vehicle communication have been studied. Road-to-vehicle communication is communication between a roadside communication device (base station) and an in-vehicle communication device (mobile station), and inter-vehicle communication is communication between in-vehicle communication devices (mobile stations).
Standards and guidelines have been established for such communication systems for intelligent transportation systems (see Non-Patent Documents 1 and 2).

  In Non-Patent Document 1, a maximum of 16 road-to-vehicle communication periods that arrive every predetermined transmission cycle (100 ms) are discretely provided, and a time zone other than the road-to-vehicle communication period is set as the vehicle-to-vehicle communication period.

The Japan Radio Industry Association, "700MHz band Intelligent Transport System ARIB-STDT109 Version 1.0", [online], February 14, 2012, [Search September 18, 2012], Internet <http: //www.arib.or.jp/tyosakenkyu/kikaku_tushin/tsushin_kikaku_number.html> ITS Information Communication System Promotion Conference, “700 MHz Band Intelligent Transport System Extended Function Guidelines ITS FORUM RC-010 1.0 Edition”, [online], March 26, 2012, [Search September 18, 2012], Internet <http://www.itsforum.gr.jp/>

  It is effective that the roadside communication device notifies the emergency information to surrounding vehicles so that the driver can quickly grasp the emergency information. Here, the emergency information is, for example, disaster information or traffic information of emergency vehicles (special vehicles). The disaster information is, for example, information on fire, earthquake, or tsunami.

  When transmitting emergency information using the systems specified in Non-Patent Documents 1 and 2, the roadside communication device transmits emergency information to nearby in-vehicle communication devices or pedestrian communication devices during the road-to-vehicle communication period. It is possible to do.

  And if it is going to transmit emergency information between roadside communication devices in order to transmit a wide range, a period (communication period between roadside devices) for performing communication between roadside communication devices is provided, and emergency information by road-to-vehicle communication is provided. Apart from the transmission, it is also conceivable to transmit emergency information by road-to-road communication.

  However, transmitting similar emergency information in both road-to-vehicle communication and road-to-road communication consumes a communication period as a communication resource.

  Therefore, an object of the present invention is to prevent the communication period from being wasted in the above case.

From one viewpoint, the present invention is capable of transmitting a communication packet in a first communication period for communication for a mobile station , and is a second communication period different from the first communication period and is intended for other base stations. A mobile station comprising: a receiving unit capable of receiving a communication packet from a base station capable of transmitting a communication packet in a second communication period for communication; and a communication processing unit, wherein the communication packet is Management information, identification information, and application data. The identification information is information indicating whether the application data is emergency information, and the management information is transmitted from the base station in the first communication period. If the application data included in the communication packet is normal information other than emergency information, it indicates that the communication packet is received by the mobile station, and from the base station during the first communication period. When the application data included in the transmitted communication packet is emergency information, it indicates that the communication packet is received by the base station and the mobile station, and the communication processing unit adds the communication packet received from the base station to the communication packet. Management indicating that the communication packet including the management information indicating reception by the mobile station with reference to the included management information is received as the first information for the mobile station and received by the base station and the mobile station A communication packet including information is also determined as the first information for the mobile station. From another point of view, the present invention is a communication packet structure or information structure.

(1) The present invention from another viewpoint includes a first base station and a second base station, and the first base station can transmit first information for a mobile station in a first communication period. And the second information for the second base station can be transmitted in a second communication period different from the first communication period, and the first information includes application data and identification information, and the identification The information is information indicating whether or not the application data is emergency information. The first base station transmits the emergency information and the identification information to the mobile station in the first communication period. The second base station is capable of receiving the first information and the second information, and includes a discarding unit that discards the received application data, and the discarding unit includes the second base station Included in the first information received by Whether the application data is emergency information is determined based on the identification information. If the application data is not emergency information, the application data is discarded. If the application data is emergency information, the application data is The communication system is characterized in that it is not discarded.
According to the communication system, the first base station transmits the emergency information as the first information for the mobile station in the first communication period. The second base station can receive the first information for the mobile station.
Therefore, the emergency information can be received even if it is included in the first information for the mobile station.
As a result, the first base station does not need to transmit the emergency information as the second information transmitted to the second base station in the second communication period. That is, even if the second communication period is not used for transmitting emergency information, the emergency information can be notified to the second base station, and communication time can be prevented from being wasted.
Here, the first information is originally information for a mobile station and is unnecessary for the second base station. Accordingly, when the second base station reads all the received first information, the processing load increases. In this regard, the second base station of the present invention discards the application data when the application data included in the received first information is not emergency information.
An increase in processing load at the second base station can be prevented by discarding application data other than emergency information.

(2) Preferably, the second base station further includes a retransmission processing unit that retransmits the emergency information and the identification information included in the received first information as the first information for a mobile station. .
In this case, the second base station can retransmit the received emergency information as the first information for the mobile station. Accordingly, mobile stations around the second base station can receive the emergency information transmitted from the first base station via the second base station. When there is another base station (third base station) having the same function as the second base station, the third base station receives the first information retransmitted by the second base station. Can also be expected.

(3) The retransmission processing unit determines whether or not the emergency information and the identification information included in the first information received by the second base station should be retransmitted as first information for a mobile station, When it is determined that retransmission is to be performed, the emergency information and the identification information included in the first information received by the second base station are preferably retransmitted as the first information for the mobile station.
In this case, since the retransmission processing unit performs retransmission after determining whether or not to retransmit, retransmission is optimized.

(4) The first information includes validity information regarding validity of the first information, and the retransmission processing unit adds the first information received by the second base station based on the validity information. It is preferable to determine whether the emergency information and the identification information included should be retransmitted as the first information for the mobile station.
In this case, whether or not to retransmit is determined based on the validity of the first information.

(5) The retransmission processing unit, based on the transmission source of the first information, transmits the emergency information and the identification information included in the first information received by the second base station to the mobile station. It is preferable to determine whether or not to retransmit as one information.
In this case, whether or not to retransmit is determined based on the transmission source of the first information.

(6) It is preferable that the identification information is stored in the first information so that the second base station on the receiving side is recognized before the application data.
In this case, the identification information is recognized before the process for recognizing the application data is performed. Therefore, the discard unit can discard the application data based on the identification information recognized at a relatively early stage. Therefore, it is possible to avoid the process of recognizing unnecessary application information.

(7) The identification information is stored in the first information so that the second base station on the receiving side can recognize the application data before the process of making the application data unsecured. It is preferable.
In this case, the identification information is recognized before the process of unsecuring the application data is performed. Therefore, the unnecessary application data can be discarded before the process of unsecureing the unnecessary application data is performed.

(8) The second base station can receive the third information transmitted by the mobile station, the third information includes the application data and the identification information, and the retransmission processing unit includes the second base station If the identification information indicates that the application data included in the third information received by the station is the emergency information, the emergency information included in the third information received by the second base station and It is preferable that the identification information can be retransmitted as the first information for the mobile station.
In this case, the second base station can receive emergency information via the mobile station. The received emergency information can be retransmitted as the first information for the mobile station.

(9) The present invention viewed from another viewpoint includes a receiving unit that receives information transmitted from a base station or another mobile station, and a retransmission processing unit that performs retransmission processing of information received by the receiving unit, The information received by the receiving unit includes application data and identification information, the identification information is information indicating whether the application data is emergency information, and the retransmission processing unit is configured by the receiving unit. If the identification information indicates that the application data included in the received information is the emergency information, the emergency information and the identification information included in the information received by the receiving unit may be transferred to another It is a mobile station characterized in that it can be retransmitted as information for the station.
According to the mobile station, if the application data transmitted from the base station or another mobile station is emergency information, the emergency information can be retransmitted as information for other mobile stations.

(10) The information received by the receiving unit further includes request information indicating whether or not retransmission by a mobile station is requested, and the retransmission processing unit is received by the receiving unit based on the request information. It is preferable to determine whether or not the emergency information and the identification information included in the information to be retransmitted as information for other mobile stations.
In this case, whether or not to retransmit is determined based on request information indicating whether or not retransmission is requested.

(11) The information received by the receiving unit includes validity information regarding validity of the information received by the receiving unit, and the retransmission processing unit is received by the receiving unit based on the validity information. It is preferable to determine whether or not the emergency information and the identification information included in the information to be retransmitted as information for other mobile stations.
In this case, whether or not to retransmit is determined based on the validity of the received information.

(12) The present invention viewed from another viewpoint is a computer program for causing a computer to function as the retransmission processing unit of the mobile station according to any one of (9) to (11).

(13) From another viewpoint, the present invention can transmit the first information for the mobile station in the first communication period, and the other base station in the second communication period different from the first communication period. Second information can be transmitted, and the first information includes application data, identification information, and request information, and the identification information is information indicating whether or not the application data is emergency information. The base station is characterized in that the request information is information indicating whether or not retransmission of the first information is requested by the mobile station that has received the first information.
According to the base station, since the first information includes information indicating whether or not retransmission by the mobile station that has received the first information is requested, retransmission by the mobile station is optimized.

(14) The present invention viewed from another viewpoint is a computer program that causes a computer mounted on the base station according to (13) to execute processing for transmitting the first information and the second information.

(15) The present invention from another viewpoint is a base station capable of receiving the first information and the second information, and the first information is transmitted to the mobile station by the other base station in the first communication period. The second information is information transmitted to the base station by the other base station in a second communication period different from the first communication period, and the first information is an application Data and identification information, the identification information is information indicating whether or not the application data is emergency information, and includes a discarding unit that discards the received application data, and the discarding unit includes the second base Whether the application data included in the first information received by the station is emergency information is determined based on the identification information. If the application data is not emergency information, the application data is determined. Discard over data, the application data is a base station which is characterized not to discard the application data if emergency information.

(16) The present invention viewed from another viewpoint is a computer program for causing a computer to function as the discard unit of the base station described in (15).

(17) The present invention from another viewpoint is a base station capable of transmitting information for mobile stations and receiving mobile station transmission information transmitted by the mobile station, wherein the information for mobile stations is mobile The mobile station transmission information includes application data and identification information, and the identification information indicates whether the application data is emergency information. A retransmission processing unit that retransmits the emergency information and the identification information included in the received mobile station transmission information as information for the mobile station,
The retransmission processing unit, if the identification information indicates that the application data included in the received mobile station transmission information is the emergency information, the emergency information included in the received mobile station transmission information and The base station is characterized in that the identification information can be retransmitted as information for the mobile station.

(18) The present invention from another viewpoint is a computer program for causing a computer to function as the retransmission processing unit of the base station described in (17).

(19) The present invention viewed from another viewpoint is a communication method of the first information and the second information, wherein the first information is information transmitted to the mobile station in the first communication period, Application data and identification information, wherein the identification information is information indicating whether or not the application data is emergency information, and the second information is in a second communication period different from the first communication period. Information transmitted to a base station, wherein the first base station uses the emergency information as the application data and the identification information as the first information in the first communication period. Transmitting, the first base station transmitting the second information in the second communication period, receiving the first information and the second information, and discarding the received first information Possible second The ground station determines whether the application data included in the received first information is emergency information based on the identification information. If the application data is emergency information, the application data is not discarded. Reading.

It is a schematic perspective view which shows one Embodiment of an intelligent road traffic system. It is a block diagram of a roadside communication apparatus and a vehicle-mounted communication apparatus. (A) is a figure which shows a radio | wireless frame (super frame), (b) is a figure which shows the transmission period and transmission prohibition period in a radio | wireless frame. It is a figure which shows the protocol stack of a communication apparatus. It is a figure which shows a packet structure. It is a structural diagram of a layer 7 header. It is a structure figure of an application header. It is a figure which shows the communication method of a 1st comparative example. It is a figure which shows the information transmission in a 1st comparative example. It is a figure which shows the communication method of a 2nd comparative example. It is a figure which shows the information transmission in a 2nd comparative example. It is a figure which shows the communication method of 1st Example. It is a figure which shows the information transmission in 1st Example. It is a figure which shows the communication method of 2nd Example. It is a figure which shows the information transmission in 2nd Example. It is a figure which shows the communication method of 3rd Example. It is a figure which shows the information transmission in 3rd Example. It is a flowchart of a process of a roadside communication apparatus. It is a flowchart of a process of a vehicle-mounted communication apparatus. It is a figure which shows the transmission range of a roadside communication apparatus. It is a communication topology diagram between roadside communication devices. It is a figure which shows the example of the value of the setting information for implement | achieving a communication topology.

[1. Communications system]
FIG. 1 is a schematic perspective view showing an overall configuration of an intelligent road traffic system (ITS) according to an embodiment of the present invention. In this embodiment, as an example of the road structure, a grid structure in which a plurality of roads in the north-south direction and the east-west direction intersect with each other is assumed.
As shown in FIG. 1, the intelligent transportation system of this embodiment includes a traffic signal 1, a roadside communication device (base station) 2, an in-vehicle communication device (mobile station) 3 (see FIG. 2), a central device 4, and in-vehicle communication. A vehicle 5 on which the machine 3 is mounted, and a roadside sensor 6 including a vehicle detector, a monitoring camera, and the like are included. The mobile station is not limited to the in-vehicle communication device 3 and may be, for example, a pedestrian communication device possessed by a pedestrian.
Note that points that are not particularly described in the present embodiment are based on Non-Patent Documents 1 and 2.

Traffic signal machine 1 and roadside communication machine 2 (2A, 2B) are installed in each of a plurality of intersections A1-A5, B1-B5, C1-C5, D1-D5, E1-E5. Some roadside communication devices 2A among the plurality of roadside communication devices 2 are connected to the router 8 via a wired communication line 7 such as a telephone line. This router 8 is connected to the central device 4 in the traffic control center. The plurality of roadside communication devices 2 include a roadside communication device 2 </ b> B that is not connected to the router 8.
The central device 4 constitutes a local area network (LAN) with the traffic signal device 1 and the roadside communication device 2 in the area that it is in charge of. The central device 4 may be installed on the road instead of the traffic control center.

The roadside communication device 2A (online roadside communication device) connected to the central device 4 via the wired communication line 7 is a part of all roadside communication devices included in the area controlled by the central device 4, and the central device There is also a roadside communication device 2 </ b> B (stand-alone roadside communication device) that is not connected to 4 by a wired communication line 7.
In FIG. 1, the roadside communication device 2A installed at the intersections A1 to A5 is an online roadside communication device, and the roadside communication devices installed at the other intersections B1 to B5, C1 to C5, D1 to D5, and E1 to E5. 2B is a stand-alone roadside communication device. Thus, the installation / maintenance cost of the wired communication line 7 can be reduced by not using all roadside communication devices as online roadside communication devices.
In the case where the online roadside communication device 2A and the stand-alone roadside communication device 2B are not distinguished, they are referred to as “roadside communication device 2”.

The roadside sensor 6 is installed in various places on the road in the jurisdiction area for the purpose of counting the number of vehicles flowing into each intersection. The roadside sensor 6 is composed of a vehicle sensor for ultrasonically sensing the vehicle 5 passing underneath, or a monitoring camera for photographing road traffic conditions in time series, and the sensing information and image data are transmitted via the communication line 7. To the central device 4.
In FIG. 1, for simplification of illustration, only one signal lamp is depicted at each intersection. However, at each actual intersection, at least four signal lamps are used for ascending and descending roads that intersect each other. Is installed.

In an intelligent road traffic system, a plurality of roadside communication devices (base stations) 2 installed at each of a plurality of intersections constituting a wireless communication system are connected to an in-vehicle communication device (mobile station) 3 of a vehicle traveling around the roadside communication devices. Wireless communication (road-to-vehicle communication) is possible.
Each roadside communication device 2 is also capable of wireless communication (inter-road communication) with other roadside communication devices 2 that are located within a predetermined range within which their transmission waves reach.
An in-vehicle communication device (mobile station) 3 that also constitutes a wireless communication system performs wireless communication with the roadside communication device 2 and also wirelessly communicates with other in-vehicle communication devices 3 (vehicle-to-vehicle communication) using a carrier sense method. Is possible.

As shown in FIG. 2A, the online roadside communication device (base station) 2A includes a wireless communication unit (RF unit; PHY unit) 21 to which an antenna 20 for wireless communication is connected, and a wired communication line 7. And a communication processing device 25 for performing communication control processing.
The communication processing device 25 includes a control unit 23 and a storage unit 24 that stores necessary information. The control unit 23 performs communication control processing for wireless communication and wired communication. The storage unit 24 stores information necessary for wireless communication and wired communication.

  A part or all of the functions of the communication processing device 25 may be configured by a hardware circuit, or a part or all of the functions may be realized by a computer program. When some or all of the functions of the communication processing device 25 are realized by a computer program, the communication processing device 25 (control unit 23) includes a computer, and the computer program executed by the computer is stored in the storage unit 24. The

  As shown in FIG. 2B, the stand-alone roadside communication device (base station) 2B corresponds to a device in which the wired communication unit 22 is omitted from the online roadside communication device 2A.

The in-vehicle communication device (mobile station) 3 includes a wireless communication unit (RF unit; PHY unit; receiving unit) 31 to which an antenna 30 for wireless communication is connected, and a communication processing device 35 that performs communication control processing. ing.
A part or all of the functions of the communication processing device 35 of the in-vehicle communication device 3 may be configured by a hardware circuit, or a part or all of the functions may be realized by a computer program. . When a part or all of the functions of the communication processing device 35 are realized by a computer program, the communication processing device 35 (control unit 33) includes a computer, and the computer program executed by the computer is stored in the storage unit 34. The

FIG. 3A shows a radio frame (super frame) used in the radio communication system. This radio frame is set to have a length (frame length) in the time axis direction of 100 ms. That is, 10 frames are generated per second.
The frame is generated based on, for example, 1 PPS (signal with a period of 1 second) included in a GPS signal received by a GPS receiver (not shown) included in the roadside communication device 2.

One radio frame (100 ms) includes a plurality of road-to-vehicle communication periods SL1 and a plurality of vehicle-to-vehicle communication periods SL2.
The road-to-vehicle communication period SL1 is a time slot for road-to-vehicle communication assigned to the roadside communication device 2 (transmission period for roadside communication device), and wireless transmission by the roadside communication device 2 is allowed in this time zone SL1. . Up to 16 road-to-vehicle communication periods SL1 can be set in one radio frame (100 ms).

  The inter-vehicle communication period SL2 is a time slot (vehicle communication period) for the in-vehicle communication device 3, and this time zone SL2 is released as a radio transmission time by the CSMA method by the in-vehicle communication device 3, so that the roadside communication device 2 Wireless transmission is not performed in the inter-vehicle communication period SL2.

The road-to-vehicle communication period SL1 and the vehicle-to-vehicle communication period SL2 included in the wireless frame are alternately arranged in the time axis direction.
Slot numbers n (= 1 to 16) are assigned to the road-to-vehicle communication period SL1.

In each roadside communication device 2, one or a plurality of road-to-vehicle communication periods SL1 among a plurality of road-to-vehicle communication periods SL1 included in the radio frame is set as a transmission period, and the other road-to-vehicle communication periods SL1 are Transmission is prohibited. That is, for the roadside communication device 2, the vehicle-to-vehicle communication period SL2 and the road-to-vehicle communication period SL1 not assigned to the own device 2 are transmission prohibited periods.
FIG. 3B shows a transmission prohibition period when three road-to-vehicle communication periods SL1 of n = 4, 5, and 6 are assigned to the roadside communication device 2 as transmission periods. The roadside communication device 2 performs data transmission in a period (transmission period) other than the transmission prohibition period.

  The number of transmission periods allocated to one roadside communication device 2 in one radio frame is arbitrary. Further, the period length of one transmission period may be equal to the period length of the road-vehicle communication period or may be shorter than the road-vehicle communication period. A plurality of transmission periods may be set within one road-vehicle communication period.

  FIG. 4 shows a communication protocol stack shown in the standard of Non-Patent Document 1 plus an extended layer EL shown in the guidelines of Non-Patent Document 2.

  The protocol stack defined in Non-Patent Document 1 includes Layer 1 (L1, Physical Layer), Layer 2 (L2, Data Link Layer), Inter-Vehicle / Road-Vehicle Shared Communication Control Information Layer (IVC). -RVC layer: Inter-Vehicle Communication-Road to Vehicle Communication Layer) and Layer 7 (L7, Application Layer: Application Layer). Each layer and application AP can access system management with information for system management.

Layer 1 operates in accordance with a physical layer defined in IEEE 802.11.
Layer 2 includes a MAC sublayer (Medium Access Control sublayer) and an LLC sublayer (Logical Link Control sublayer). The MAC sublayer is also simply referred to as a MAC layer (Medium Access Control layer), and the LLC sublayer (Logical Link Control sublayer) is also simply referred to as an LLC layer (Logical Link Control layer).

The MAC layer performs frame control and broadcast communication (broadcast) as wireless channel communication management.
The LLC layer provides a connectionless communication service without confirmation in order to perform packet transmission between higher-layer entities.

  The inter-vehicle / road-vehicle shared communication control information layer (IVC-RVC layer) generates and manages information necessary for inter-vehicle / road-vehicle shared communication control. In Non-Patent Document 1, road-to-road communication is not defined, so when performing road-to-road communication in the road-to-vehicle communication period SL1 as in this embodiment, the inter-vehicle / road-to-vehicle shared communication control information layer (IVC) -RVC layer), road-to-road communication is handled as a kind of road-to-vehicle communication.

  Layer 7 is for providing communication control means to the application AP. The application AP gives the application data (traffic information, vehicle information, etc.) stored in the transmitted communication packet to the layer 7 and acquires the application data stored in the received communication packet from the layer 7.

The enhancement layer EL defined in Non-Patent Document 2 exists as an upper layer of the layer 7, and is for extending the communication function between the application AP and the layer 7.
The enhancement layer EL provides a data transmission service to the application AP. The application AP gives application data (traffic information, vehicle information, etc.) stored in the transmitted communication packet to the enhancement layer EL. In order to provide the data transmission service, the enhancement layer EL issues a data transmission request to the lower layer below the layer 7.

Further, the enhancement layer EL can divide the application data given from the application AP and give the divided data to the layer 7. That is, the enhancement layer EL functions as a division processing unit that divides application data and generates a plurality of pieces of divided data.
Further, the divided data received from the layer 7 can be combined and given to the application AP.
The enhancement layer EL can access security management together with the layer 7.

  Functions corresponding to the extension layer EL, layer 7, IVC-RVC layer, layer 2, application AP, security management SEC, and system management shown in FIG. 4 are the functions of the communication processing device 25 of the roadside communication device 2 and the in-vehicle communication device 3. It is executed by each communication processing device 35. Further, the layer 1 function is executed by the wireless communication unit 21 of the roadside communication device 2 and the wireless communication unit 31 of the in-vehicle communication device 3.

In the communication processing device 25, a function corresponding to the application AP in FIG. 4 is referred to as an “application device 25a”, and functions lower than the application AP in FIG. 4 (extended layer EL, layer 7, IVC-RVC layer). , Layer 2, security management SEC and system management) are referred to as “communication processing unit 25b”.
Also, in the communication processing device 35, the function corresponding to the application AP of FIG. 4 is referred to as “application device 35a”, and functions lower than the application AP of FIG. 4 (extended layer EL, layer 7, IVC-RVC layer). , Layer 2, security management SEC and system management) are referred to as “communication processing unit 35b”. The extension layer EL may be omitted.

  The function of the application device 25a can be realized by a computer program, and the function of the communication processing unit 25b can be configured by hardware. Further, the function of the communication processing unit 25b may be realized by a computer program.

FIG. 5 shows a configuration of communication packets transmitted by the roadside communication device 2 and the in-vehicle communication device 3. The configuration of the communication packet shown in FIG. 5 is based on Non-Patent Documents 1 and 2.
The road-to-vehicle communication data (first information; information for mobile stations), road-to-road communication data (second information), and vehicle-to-vehicle communication data (third information; mobile station transmission information) described later are all shown in FIG. It is transmitted in the format of the communication packet shown.

The communication packet has a PHY header (physical header) at the head. The PHY header is placed before the MAC frame (MPDU; MAC Protocol Data Unit) acquired from the MAC layer by layer 1 (physical layer) of the communication devices 2 and 3 (roadside communication device 2 or in-vehicle communication device 3) on the transmission side. Added.
The PHY header is read in layer 1 (physical layer) in the communication devices 2 and 3 on the reception side and used for communication control processing in layer 1 on the reception side. Note that the entire communication packet including the PHY header is a PPDU (PHY Protocol Data Unit). The MAC frame (MPDU) on the rear side of the PHY header is also a PSDU (PHY Service Data Unit).

  The configuration of the PHY header conforms to IEEE 802.11. Therefore, the PHY header includes a preamble and the like.

Subsequent to the PHY header, a MAC control field (MAC header) and an LLC control field (LLC header) are provided. The MAC control field is added before the LLC frame (LPDU; LLC Protocol Data Unit) acquired from the LLC layer by the MAC layer of the layer 2 of the communication devices 2 and 3 on the transmission side.
The MAC control field is read by the MAC layer of the layer 2 of the communication devices 2 and 3 on the reception side and used for communication control processing in the MAC layer on the reception side.
The LLC frame (LPDU) on the rear side of the MAC control field is also an MSDU (MAC Service Data Unit).

The LLC control field following the MAC control field is added in front of the IR frame (IPDU; IVC-RVC Protocol Data Unit) acquired from the IVC-RVC layer by the LLC layer of the layer 2 of the transmitters 2 and 3 on the transmission side. The
The LLC control field is read by the LLC layer of the layer 2 of the communication devices 2 and 3 on the reception side, and used for communication control processing in the LLC layer on the reception side.
The IR frame (IPDU) on the rear side of the LLC control field is also an LSDU (LLC Service Data Unit).

Following the LLC control field, an IR control field (IR header) is provided. The IR control field is added before the AP frame (APDU; Application Protocol Data Unit) by the IVC-RVC layer of the communication devices 2 and 3 on the transmission side.
The IR control field is read in the IVC-RVC layer of the receiving side communication devices 2 and 3 and used for the communication control processing in the receiving side IVC-RVC layer.
An AP frame (APDU; Application Protocol Data Unit) behind the IR control field is also an ISDU (IVC-RVC Service Data Unit).

Following the IR control field, an L7 header is provided. The L7 header is added before the ASDU (Application Service Data Unit) by the layer 7 of the communication devices 2 and 3 on the transmission side.
The L7 header is read by the layer 7 of the receiving side communication devices 2 and 3 and used for communication control processing in the receiving side layer 7.
An EL frame (EL-PDU; EL-Protocol Data Unit) behind the layer 7 header is also an ASDU (Application Service Data Unit).

Subsequent to the L7 header, an EL header (EL base station header) is provided. The EL header is added before EL-SDU (EL-Service Data Unit) by the enhancement layer EL of the communication devices 2 and 3 on the transmission side.
The EL header is read by the enhancement layer EL of the reception side communication devices 2 and 3 and used for processing in the reception side enhancement layer EL.

The EL-SDU has a security header, an application header, and application data. The application data is given from the application AP to the communication processing units 25b and 35b. Application data includes normal information (traffic information, signal information, etc.) and emergency information (emergency vehicle information, disaster information, etc.), which will be described later.
The application header is added in front of the application data by the application AP of the communication devices 2 and 3 on the transmission side.

The application data and the application header are read by the application AP of the receiving side communication devices 2 and 3 and used for processing in the receiving side application AP.
The application AP can generate data to be transmitted, read the received data and use it for its own processing, or retransmit (transfer) the received data.

The security header is added by the security management (security processing unit) SEC. When receiving the application data (with the application header added) from the application AP, the enhancement layer EL of the communication devices 2 and 3 on the transmission side causes the security management SEC to execute security processing as necessary.
In the security management SEC, security processing is performed on unsecured application data received from the enhancement layer EL to generate secure application data. The security management SEC also adds a security header.

In security management SEC, processing (security processing) for converting unsecured application data to secure application data includes processing such as encryption processing and signature processing (however, it is defined in Non-Patent Documents 1 and 2). Absent).
The security management returns secure application data subjected to security processing to the enhancement layer EL. Thereafter, the extension layer EL adds an EL header as described above.

When receiving the secure application data from the lower layer (layer 7), the enhancement layer EL of the communication devices 2 and 3 on the receiving side passes the secure application data to the security management SEC. The security management SEC performs security processing on secure application data and returns it to unsecure application data.
When the extension layer EL receives the unsecure application data from the security management SEC, the extension layer EL passes the unsecure application data to the application AP.

  Note that, when the extension layer EL does not exist, the layer 7 exchanges with the security management SEC.

FIG. 6 shows the structure of the L7 header shown in FIG. As shown in FIG. 6, the L7 header has a “version” field, a “security classification information” field, a “reservation” field, and an “application related information” field. In Non-Patent Document 1, the content of the “application related information” field (8 bits) is not defined. However, in this embodiment, as shown in FIG. 6, the “application related information” field (b7-b0) is a 3-bit “management information” field (b7-b5), a 2-bit “data type” field (b4, b4). b3) A 1-bit “retransmission request to mobile station” field (b2) and a 2-bit “required number of retransmissions by mobile station” field (or “retransmission period” field) (b1, b0) are provided.
Each field is set by the communication devices 2 and 3 that transmit communication packets (application data).

The “management information” field indicates the relationship between the transmission side and the reception side.
In “1: mobile station → base station, mobile station”, a packet is transmitted from the mobile station (vehicle communication device 3) and received by the base station (roadside communication device 2) and the mobile station (vehicle communication device 3). Is shown.
“2: base station → base station, mobile station” indicates that the packet is transmitted from the base station and received by the base station and the mobile station.
“3: mobile station → mobile station” indicates that the packet is transmitted from the mobile station and received by the mobile station (corresponding to normal vehicle-to-vehicle communication).
“4: Base station → mobile station” indicates that the packet is transmitted from the base station and received by the mobile station (corresponding to normal road-to-vehicle communication).
“5: mobile station → base station” indicates that the packet is transmitted from the mobile station and received by the base station.
“6: base station → base station” indicates that the packet is transmitted from the base station and received by the base station (corresponding to normal communication between roads).

The “data type” field indicates the type of application data (whether or not the application data is emergency information). That is, the information stored in the “data type” field is identification information indicating whether the application data is emergency information.
“0: Normal” indicates that the application data is normal data, that is, data other than emergency information.
“1: Emergency (emergency vehicle)” indicates that the application data is emergency information. “1: Emergency (emergency vehicle)” indicates that the emergency information is information (emergency vehicle information) indicating the presence of the emergency vehicle. The emergency vehicle is, for example, a fire fighting car, an emergency car, or a police car. The definition of emergency vehicles can follow the definition of “emergency car” in the Japanese Road Traffic Act.
“2: Emergency (disaster)” indicates that the application data is emergency information. “2: Emergency (disaster)” indicates that the emergency information is information (disaster information) indicating a disaster (fire, earthquake, tsunami, etc.).

  Depending on the content of the emergency information, it may be better to vary the way of transmitting emergency information (transmission range). Therefore, as described above, the emergency information is divided into a plurality of types (emergency (emergency vehicle) and emergency (disaster)), so that the emergency information transmission method (transmission range) varies depending on the content of the emergency information. be able to.

The “retransmission request to mobile station” field indicates whether or not to request retransmission to the mobile station on the receiving side. That is, the information stored in the “retransmission request to mobile station” field is request information indicating whether or not retransmission by the mobile station 3 is requested. When retransmission is requested, the mobile station 3 on the receiving side must retransmit the received application data. “0: No request” indicates that retransmission by the mobile station 3 is not requested, and “1: Request” indicates that retransmission by the mobile station 3 is requested.
The “retransmission request to mobile station” field is set by the roadside communication device 2 that transmits emergency information. When the emergency information needs to be retransmitted by inter-vehicle communication, the roadside communication device 2 sets the “Retransmission request to mobile station” field to “1: Requested”. When the in-vehicle communication device 3 retransmits the application data, the value of the “retransmission request to mobile station” field set by the roadside communication device 2 is used as the “retransmission request to mobile station” of the communication packet of the application data to be retransmitted. Store in the field.

The “required number of retransmissions of mobile station” field indicates the number of retransmissions requested by the transmission side roadside communication device 2 to the mobile station (vehicle communication device or the like) 3. The application data may be retransmitted by the number of mobile stations 3 shown in the “number of required retransmissions of mobile station” field at the maximum.
“0: 0 times” indicates that the requested number of retransmissions is 0 (no retransmission by the mobile station 3), and “0: no request” is set in the “retransmission request to mobile station” field. If set.
“1: 5 times”, “2:10 times”, and “3:15 times” indicate that the required number of retransmissions is 5, 10 times, and 15 times, respectively.
The “required number of retransmissions of mobile station” field is set by the roadside communication device 2 (the roadside communication device 2 that has issued the retransmission request) in which the “retransmission request to mobile station” field is set to “1: requested”. The in-vehicle communication device 3 stores the value of the “required number of retransmissions of mobile station” field set by the roadside communication device 2 in the “required number of retransmissions of mobile station” field of the communication packet of the application data to be retransmitted.

  The “number of required retransmissions of the mobile station” field may be a “retransmission period” field indicating a period of retransmission.

FIG. 7 shows the structure of the application header shown in FIG. As shown in FIG. 7, the application header of this embodiment (not defined in Non-Patent Document 1) includes a “management information” field (3 bits), a “data type” field (2 bits), and a “data version” field ( 3 bits), an “increment counter” field (1 Byte), and a “number of retransmissions” field (1 Byte).
Each field is set by the communication devices 2 and 3 that transmit communication packets (application data).

  The “management information” field and the “data type” field shown in FIG. 7 are the same as the “management information” field and the “data type” field shown in FIG.

The “retransmission request to mobile station” field indicates whether or not to request retransmission to the mobile station on the receiving side, as in the description of the field in the layer 7.
The “number of required retransmissions of the mobile station” field indicates the number of retransmissions requested by the transmission side roadside communication device 2 to the mobile station 3, as in the description of the field in the layer 7.
The “increment counter” field indicates a transmission number that is incremented by one when application data is transmitted. Based on the “increment counter” field, it is possible to determine whether the application data is new or old (whether a plurality of application data are the same or different).

  The “number of retransmissions” field indicates the number of times application data has been retransmitted by the mobile station. When the roadside communication device 2 transmits, the application AP of the roadside communication device 2 sets the “number of retransmissions” field to “0”. The application AP of the in-vehicle communication device 3 that retransmits the packet (application data; the number of retransmissions = 0) transmitted by the roadside communication device 2 through inter-vehicle communication sets the “number of retransmissions” field to “1”. The application AP of another in-vehicle communication device 3 that has received the packet in which the “number of retransmissions” field is set to “1” increments the number of retransmissions and sets the “number of retransmissions” field to “2”. In this way, retransmission is repeated until the number of retransmissions reaches the number indicated in the “required number of retransmissions of mobile station” field.

  The value of the “number of retransmissions” field is validity information indicating the validity of the communication packet (application data). As the number of retransmissions increases, it indicates that the data is old, and the validity of the data decreases. The validity information may be a time after data is generated, or an index indicating the validity of the data.

"2. Communication method"
[2.1 First Comparative Example]
8 and 9 show a communication method according to the first comparative example. FIG. 8 shows a first super frame (100 ms) and a second super frame (100 ms) following the first super frame. When information is transmitted as shown in FIG. 8, the information is transmitted as shown in FIG.
In the first comparative example, the emergency information transmitted from the central device 4 is directly or indirectly transmitted to the first roadside communication device 2A and the second roadside communication device 2B, and is mounted on the vehicle from each roadside communication device 2A, 2B. Emergency information is notified to the communication device 3.

In FIG. 8, the first superframe and the second superframe include a road-to-vehicle communication period SL1-A assigned to the first roadside communication device (online roadside communication device) 2A shown in FIG. A road-to-vehicle communication period SL1-B assigned to the second roadside communication device (stand-alone roadside communication device) 2B shown is provided.
As shown in FIG. 3, the inter-vehicle communication period SL2 is between the plurality of road-vehicle communication periods SL1.

  In FIG. 8, road-to-vehicle communication data (first information) for the in-vehicle communication device and the pedestrian communication device (mobile station) 3 is included in the road-to-vehicle communication period (base station transmission period) SL1-A and SL1-B. 1st communication period TA-1 and TB-1 for transmitting, and 2nd communication period TA-2 for transmitting the roadside communication data (2nd information) for other roadside communication apparatuses (base station) 2 , TB-2.

  For example, as shown in FIG. 8, when emergency information is transmitted from the central device 4 to the first roadside communication device 2A before the start of the first superframe, the first roadside communication device 2A The emergency information is transmitted as road-to-vehicle communication data (first information) in order to notify the emergency information to the in-vehicle communication device (or pedestrian communication device) 3 around the roadside communication device 2A. The first roadside communication device 2A allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TA-1 (first roadside communication device 2A) in the period SL1-A of the first superframe. Transmitted in the first communication period). In the first communication period TA-1, normal information other than emergency information can also be transmitted.

  Further, the first roadside communication device 2A transmits the emergency information to the roadside communication data (second information) in order to transmit the emergency information to the second roadside communication device 2B that is not wiredly connected to the central device 4. ). The first roadside communication device 2A sends the roadside communication data (second information) including emergency information to the second communication period TA-2 (to the first roadside communication device 2A) within the period SL1-A of the first superframe. (Assigned second communication period). In the second communication period TA-2, normal information other than emergency information can also be transmitted.

  When the emergency information is also transmitted to the second roadside communication device 2B that is a stand-alone type by the road-to-road communication, the second roadside communication device 2B is connected to the in-vehicle communication device (or the walking) around the second roadside communication device 2B. The emergency information is transmitted as road-to-vehicle communication data (first information) in order to notify the emergency information to the communication apparatus 3). The second roadside communication device 2A allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TB-1 (second roadside communication device 2B) within the period SL1-B of the second superframe. Transmitted in the first communication period). In the first communication period TB-1, normal information other than emergency information can also be transmitted.

  Further, the first roadside communication device 2B uses the emergency information as roadside communication data (second information) in order to transmit emergency information to another roadside communication device 2 (not shown). Send. The second roadside communication device 2B sends the roadside communication data (second information) including emergency information to the second communication period TB-2 (to the second roadside communication device 2B) in the period SL1-B of the second superframe. (Assigned second communication period). In the second communication period TB-2, normal information other than emergency information can also be transmitted.

[2.2 Second Comparative Example]
10 and 11 show a communication method according to the second comparative example. FIG. 10 shows a first super frame (100 ms) and a second super frame (100 ms) following the first super frame. When information is transmitted as shown in FIG. 10, the information is transmitted as shown in FIG.
In the second comparative example, the emergency information transmitted from the in-vehicle communication device 3 is transmitted directly or indirectly to the first roadside communication device 2A and the second roadside communication device 2B, and from each roadside communication device 2A, 2B. Emergency information is notified to the in-vehicle communication device 3.

For example, as shown in FIG. 10, it is assumed that emergency information is transmitted from the in-vehicle communication device 3A in the vicinity of the first roadside communication device 2A by the inter-vehicle communication TC-0 before the start of the first super frame. In this case, the first roadside communication device 2A receives emergency information (vehicle-to-vehicle communication data; third information) transmitted as the vehicle-to-vehicle communication TC-0.
Then, as in the first comparative example, the first roadside communication device 2A transmits emergency information during the road-to-vehicle communication period TA-1 and the road-to-roadway communication period TA-2, and the second roadside communication device 2B Emergency information is transmitted in each road-to-vehicle communication period TB-1 and road-to-road communication period TB-2.

When the emergency information is transmitted in each of the first communication period TA-1, TB-1 and the second communication period TA-2, TB-2 as in the first comparative example and the second comparative example, the first communication period It is necessary to secure a period for transmitting emergency information to each of TA-1 and TB-1 and second communication periods TA-2 and TB-2. In other words, in order to transmit the same emergency information, it is necessary to secure a double period.
For this reason, when it is going to transmit emergency information, the period which transmits normal information becomes short, or the vehicle-to-vehicle communication period SL2 becomes short because road-to-vehicle communication periods SL1-A and SL1-B become long. Arise.

[2.3 First Example]
12 and 13 show a communication method according to the first embodiment.
In the first example, as in the first comparative example, the emergency information transmitted from the central device 4 is directly or indirectly transmitted to the first roadside communication device 2A and the second roadside communication device 2B, Emergency information is notified to the in-vehicle communication device 3 from the roadside communication devices 2A and 2B. However, the method of transmitting emergency information from the first roadside communication device 2A to the second roadside communication device 2B is different from the first comparative example.

  As shown in FIG. 12, when emergency information is transmitted from the central device 4 to the first roadside communication device (first base station) 2A before the start of the first superframe, the first roadside communication device 2A Transmits the emergency information as road-vehicle communication data (first information) in order to notify the emergency information to the in-vehicle communication device (or pedestrian communication device) 3 around the first roadside communication device 2A. . The first roadside communication device 2A allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TA-1 (first roadside communication device 2A) in the period SL1-A of the first superframe. Transmitted in the first communication period). In the first communication period TA-1, normal information other than the emergency information can be transmitted, but the emergency information is transmitted with priority over the normal information (first).

However, in the first embodiment, the first roadside communication device 2A does not transmit emergency information and transmits normal information during the second communication period TA-2 for transmitting roadway communication data (second information). Send.
Instead, the second roadside communication device (second base station) 2B receives emergency information transmitted from the first roadside communication device 2A as road-to-vehicle communication data (first information) in the first communication period TA-1. . Thereby, even if the first roadside communication device 2A does not transmit emergency information as roadside communication data (second information), the second roadside communication device 2B can acquire the emergency information.
Thus, road-to-vehicle communication to which emergency information is transmitted is not only road-to-vehicle communication but also road-to-road communication.

When the emergency information is acquired from the first roadside communication device 2A, the second roadside communication device 2B that is a stand-alone type, like the first comparative example, the in-vehicle communication devices (or pedestrians) around the second roadside communication device 2B. The emergency information is transmitted as road-to-vehicle communication data (first information) in order to notify the emergency information to the communication device 3). The second roadside communication device 2B allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TB-1 (second roadside communication device 2B) within the period SL1-B of the second superframe. Transmitted in the first communication period). In the first communication period TB-1, normal information other than the emergency information can be transmitted, but the emergency information is transmitted with priority over the normal information (first).
The transmission of emergency information as road-to-vehicle communication data (first information) in the first communication period TB-1 is also the transmission of emergency information to another roadside communication device 2 (not shown).

The in-vehicle communication devices 3A and 3C that have acquired emergency information as road-to-vehicle communication data (first information) from the roadside communication devices 2A and 2B, the timing TC-2 at which the emergency information can be transmitted within the vehicle-to-vehicle communication period SL2, In TC-4, it is retransmitted as inter-vehicle communication data (third information). Thereby, the vehicle-mounted communication devices 3B and 3D can also acquire emergency information. When the in-vehicle communication device 3 retransmits the emergency information, even if the in-vehicle communication device 3 cannot receive the emergency information directly from the roadside communication device 2, the emergency information can be acquired.
The in-vehicle communication device 3 can retransmit not only the emergency information received from the roadside communication device 2 but also the emergency information received from other in-vehicle communication devices 3.
In FIG. 12, normal information and emergency information are transmitted as individual communication packets as inter-vehicle communication data, but the in-vehicle communication devices 3A and 3C that have acquired the emergency information receive the emergency information. The normal information and the emergency information may be stored and transmitted in one communication packet at the timing of transmitting (eg, TC-1, TC-3 in FIG. 12).

[2.4 Second Example]
14 and 15 show a communication method according to the second embodiment. In the second example, as in the second comparative example, the emergency information transmitted from the in-vehicle communication device 3A is directly or indirectly transmitted to the first roadside communication device 2A and the second roadside communication device 2B, Emergency information is notified to the in-vehicle communication device 3 from each of the roadside communication devices 2A and 2B. However, the method of transmitting emergency information from the first roadside communication device 2A to the second roadside communication device 2B is different from the second comparative example.

  That is, when the first roadside communication device 2A acquires emergency information transmitted from the in-vehicle communication device 3A in the vicinity of the first roadside communication device 2A by the inter-vehicle communication TC-0, the first roadside communication device 2A The emergency information is transmitted as road-to-vehicle communication data (first information) in order to notify the emergency information to the in-vehicle communication device (or pedestrian communication device) 3 around the communication device 2A. The first roadside communication device 2A allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TA-1 (first roadside communication device 2A) in the period SL1-A of the first superframe. Transmitted in the first communication period). In the first communication period TA-1, normal information other than the emergency information can be transmitted, but the emergency information is transmitted with priority over the normal information (first).

Also in the second embodiment, as in the first embodiment, the first roadside communication device 2A transmits emergency information in the second communication period TA-2 for transmitting roadway communication data (second information). Without sending normal information.
Instead, as in the first embodiment, the second roadside communication device 2B receives the emergency information transmitted as road-to-vehicle communication data (first information) from the first roadside communication device 2A in the first communication period TA-1. Receive. Thereby, even if the first roadside communication device 2A does not transmit emergency information as roadside communication data (second information), the second roadside communication device 2B can acquire the emergency information.
Thus, road-to-vehicle communication to which emergency information is transmitted is not only road-to-vehicle communication but also road-to-road communication.

When the emergency information is acquired from the first roadside communication device 2A, the second roadside communication device 2B that is a stand-alone type, like the first embodiment, has an onboard communication device (or a pedestrian) around the second roadside communication device 2B. The emergency information is transmitted as road-to-vehicle communication data (first information) in order to notify the emergency information to the communication device 3). The second roadside communication device 2B allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TB-1 (second roadside communication device 2B) within the period SL1-B of the second superframe. Transmitted in the first communication period). In the first communication period TB-1, normal information other than the emergency information can be transmitted, but the emergency information is transmitted with priority over the normal information (first).
The transmission of emergency information as road-to-vehicle communication data (first information) in the first communication period TB-1 is also the transmission of emergency information to another roadside communication device 2 (not shown).

The vehicle-mounted communication device 3C that has acquired emergency information as road-to-vehicle communication data (first information) from the roadside communication devices 2A and 2B, at the timing TC-4 at which the emergency information can be transmitted within the vehicle-to-vehicle communication period SL2, Retransmission as inter-vehicle communication data (third information). Thereby, in-vehicle communication machine 3D can also acquire emergency information. When the in-vehicle communication device 3 retransmits the emergency information, even if the in-vehicle communication device 3 cannot receive the emergency information directly from the roadside communication device 2, the emergency information can be acquired.
The in-vehicle communication device 3 can retransmit not only the emergency information received from the roadside communication device 2 but also the emergency information received from other in-vehicle communication devices 3.

[2.5 Third Example]
16 and 17 show a communication method according to the third embodiment. In the third embodiment, as in the second embodiment, the emergency information transmitted from the in-vehicle communication device 3A is directly or indirectly transmitted to the first roadside communication device 2A and the second roadside communication device 2B-1. And emergency information is alert | reported with respect to the vehicle-mounted communication apparatus 3 from each roadside communication apparatus 2A, 2B-1. However, between the first roadside communication device 2A and the second roadside communication device 2B-1, road-to-vehicle communication data (first information) transmitted from the first roadside communication device 2A is used as the second roadside communication device 2B-1. Is too far away to receive.
In the third embodiment, the emergency information is transmitted from the first roadside communication device 2A to the second roadside communication device 2B-1 using not only road-to-vehicle communication but also vehicle-to-vehicle communication.

  That is, when the first roadside communication device 2A acquires emergency information transmitted from the in-vehicle communication device 3A in the vicinity of the first roadside communication device 2A by the inter-vehicle communication TC-0, the first roadside communication device 2A The emergency information is transmitted as road-to-vehicle communication data (first information) in order to notify the emergency information to the in-vehicle communication device (or pedestrian communication device) 3 around the communication device 2A. The first roadside communication device 2A allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TA-1 (first roadside communication device 2A) in the period SL1-A of the first superframe. Transmitted in the first communication period). In the first communication period TA-1, normal information other than the emergency information can be transmitted, but the emergency information is transmitted with priority over the normal information (first).

  In the third embodiment, as in the first and second embodiments, the first roadside communication device 2A is in the second communication period TA-2 for transmitting the roadside communication data (second information). Send normal information without sending. This road-to-road communication data (second information) is received by the third roadside communication device 2B-2 or the like.

In the third example, as described above, the second roadside communication device 2B-1 cannot receive the road-vehicle communication data (emergency information) transmitted by the first roadside communication device 2A.
However, in the vehicle-mounted communication device 3C that has acquired the emergency information transmitted by the first roadside communication device 2A, the “retransmission request to the mobile station” in the application header (or layer 7 header) of the emergency information is “1: request”. In this case, the emergency information is retransmitted as vehicle-to-vehicle communication data (third information) at a transmission timing TC-2 within the vehicle-to-vehicle communication period SL2.
The second roadside communication device 2B-1 can acquire the emergency information retransmitted as inter-vehicle communication data (third information).
Thus, the second roadside communication device 2B-1 can receive the emergency information transmitted from the first roadside communication device 2A via one or a plurality of in-vehicle communication devices 3.

When the emergency information is acquired from the in-vehicle communication device 3C, the second road-side communication device 2B-1 that is a stand-alone type, like the first and second embodiments, the in-vehicle communication devices around the second road-side communication device 2B-1 (Or pedestrian communication device) In order to notify the emergency information to 3D, the emergency information is transmitted as road-to-vehicle communication data (first information). The second roadside communication device 2A allocates road-to-vehicle communication data (first information) including emergency information to the first communication period TB-1 (second roadside communication device 2B) within the period SL1-B of the second superframe. Transmitted in the first communication period). In the first communication period TB-1, normal information other than the emergency information can be transmitted, but the emergency information is transmitted with priority over the normal information (first).
Transmission of emergency information as road-to-vehicle communication data (first information) in the first communication period TB-1 can also be transmission of emergency information to another roadside communication device 2 (not shown).

[3. Communication processing]
[3.1 Processing of roadside communication device 2]
FIG. 18 shows communication processing executed by the receiving side roadside communication device 2 in order to implement the communication methods of the first to third embodiments. The roadside communication device 2 can receive not only road-to-road communication data (second information) but also road-to-vehicle communication data (first information) and vehicle-to-vehicle communication data (third information). That is, the roadside communication device 2 can receive communication packets that arrive during a period other than the transmission assigned to the own device 2.

When the roadside communication device 2 receives the communication packet, it is determined whether or not the communication packet is road-to-vehicle communication data (first information) transmitted to the in-vehicle communication device 3 (step S1). Whether or not the communication packet is road-to-vehicle communication data (first information) can be determined by referring to the management information field of the layer 7 header and / or the management information field of the application header of the communication packet.
Therefore, the determination in step S1 can be performed by the layer 7 or the application AP of the roadside communication device 2.
In the case of a communication packet of road-vehicle communication data (first information), the management information field of the layer 7 header and the management information field of the application header include “4: base station → mobile station” (in the case of normal information), Alternatively, “2: base station → base station, mobile station” (in the case of emergency information) is stored by the roadside communication device 2 on the transmission side.

If the communication packet is road-vehicle communication data (first information), it is determined whether the application data included in the road-vehicle communication data is emergency information or normal information (step S2).
Whether the application data is emergency information or normal information can be determined by referring to the data type field of the layer 7 header and / or the data type field of the application header of the communication packet.
Therefore, the determination in step S2 can be performed in the layer 7 or application AP of the roadside communication device 2.
When the application data is emergency information, “1: emergency (emergency vehicle)” or “2: emergency (disaster)” is displayed in the data type field of the layer 7 header and the data type field of the application header. Are stored by the roadside communication device 2.

  If it is determined in step S2 that the application data is emergency information, the application data is given to the application AP without being discarded and read by the application AP (step S3). The application AP (retransmission processing unit) performs appropriate processing based on the read application data, and performs retransmission processing such as application data (emergency information) and data type (identification information) as necessary (step S4). The retransmission process will be described later.

On the other hand, when it is determined in step S2 that the application data is not emergency information but normal information, the application data is discarded (step S5). If the road-to-vehicle communication data (first information) is originally information for the in-vehicle communication device 3 and is normal information other than emergency information, information that is originally unnecessary for the roadside communication device 2 is discarded. That's why.
In the present embodiment, since the data type (identification information) is stored in the layer 7 header and the application header, it is possible to determine whether the application data is necessary and discard it in the layer 7 or the application AP.

Further, the data type (identification information) of the layer 7 header is determined from the application header in the communication packet so that the application data is recognized (read) before the application data is recognized (read) by the higher-order application AP. Is also provided on the front side.
Further, the data type (identification information) of the layer 7 header is recognized (read) before security processing (processing to unsecure secure data) is performed in the upper extension layer EL and security management SEC. As shown, the communication packet is provided on the head side of the EL header.

Therefore, the layer 7 can determine whether or not the application data is necessary (necessity of discarding) relatively early. Therefore, it is possible to avoid unnecessary processing by the layer above the layer 7 for unnecessary normal information.
For example, if normal information unnecessary for layer 7 is not discarded, security processing is performed wastefully by the extension layer EL and the security management SEC. However, in this embodiment, normal information that does not require layer 7 as a discard unit is used. By discarding, it is possible to avoid unnecessary security processing being performed in the upper layer.

  If it is determined in step S1 that the communication packet received by the roadside communication device 2 is not road-to-vehicle communication data (first information), whether or not the communication packet is road-to-road communication data (second information). Is determined (step S6). When the communication packet is road-to-road communication data (second information), for example, when the management information field of the layer 7 header and the management information field of the application header are “6: base station → base station”, the road The application data included in the road-to-road communication data (second information) is given to the application AP without being discarded, and is read by the application AP (step S7-1). The application AP (retransmission processing unit) performs appropriate processing based on the read application data, and performs retransmission processing such as application data (normal information) and data type (identification information) as necessary (step S7-2). ). The retransmission process will be described later.

  If it is determined in step 6 that the packet received by the roadside communication device 2 is inter-vehicle communication data (third information), for example, the management information field of the layer 7 header and the management information field of the application header Is “1: mobile station → base station, mobile station”, “3: mobile station → mobile station” or “5: mobile station → base station”, the application data included in the inter-vehicle communication data is emergency information. It is determined whether there is normal information or not (step S8). The determination in step S8 is performed in the same manner as the determination in step 2. If the application data is normal information, the application information is discarded (step S11). The discarding process in step S11 is performed in the same manner as the discarding process in step S5.

  If it is determined in step S8 that the application data is emergency information, the application data is given to the application AP without being discarded and read by the application AP (step S9). The application AP (retransmission processing unit) performs appropriate processing based on the read application data, and also performs retransmission processing such as application data (emergency information) and data type (identification information) (step S10). The retransmission process will be described later.

[3.2 In-vehicle communication device processing]
FIG. 19 shows communication processing executed by the in-vehicle communication device 3 in order to implement the communication methods of the first to third embodiments. The in-vehicle communication device 3 can receive road-to-vehicle communication data (first information) and vehicle-to-vehicle communication data (third information).

When the in-vehicle communication device 3 receives a communication packet of road-to-vehicle communication data (first information) or vehicle-to-vehicle communication data (third information), the vehicle-mounted communication device 3 recognizes (reads) application data included in the communication packet, and retransmits Is determined (step S21).
In the determination in step S21, when the application data included in the received communication packet is emergency information or normal information, and when the application data is emergency information, the emergency information is: A second determination of whether or not retransmission is required is included.

The first determination is performed in the same manner as the determination in step S2 or step S8.
The second determination is performed by referring to the “retransmission request to mobile station” field (request information) in the L7 header of the received communication packet at the layer 7 of the in-vehicle communication device 3 that has received the communication packet. The layer 7 as the determination unit that performs the second determination determines that the received emergency information requires retransmission when the “retransmission request to mobile station” field is set to “1: requested”. To do. When the “Retransmission request to mobile station” field is set to “0: No request”, retransmission is not performed.

  When the “Retransmission request to mobile station” field is set to “1: Requested”, the application AP (retransmission processing unit) of the in-vehicle communication device 3 performs application data (emergency information) and data type (identification information). ) And the like are performed (step S22). The retransmission process will be described later.

  The in-vehicle communication device 3 of a general vehicle does not have a function of generating inter-vehicle communication data (third information) including emergency information, but the in-vehicle communication device 3 of the emergency vehicle itself has emergency information (emergency vehicle (emergency vehicle)). Vehicle-to-vehicle communication data (third information) including information) can be generated.

[3.3 Transmission range and communication topology of roadside communication equipment]
In the communication system of this embodiment, a communication topology for transmitting application information to another roadside communication device 2 is set.
FIG. 20 illustrates a transmission range of the roadside communication device (roadside communication device C) indicated by C. In FIG. 20, roadside communication devices indicated by W2, W, N, S, E, and E2 are installed around the roadside communication device C.
The roadside communication device C is an online roadside communication device 2A connected to the central device 4, and the other roadside communication devices W2, W, N, S, E, and E2 are stand-alone roadside communication devices 2B.

  In FIG. 20, three types of transmission ranges (sub areas) are set as the transmission range of the roadside communication device C. The three types of transmission ranges are a road transmission range, a road vehicle (emergency / emergency vehicle) transmission range, and a road vehicle (emergency / disaster information) transmission range.

  The road transmission range is a range in which road-to-road communication data (second information; normal information) transmitted by the roadside communication device C is transmitted (retransmitted). In FIG. 20, road-to-road communication data (second information) transmitted by the roadside communication device C is transmitted to the five roadside communication devices W2, W, N, S, E, and E2 around the roadside communication device C ( Resent).

The road vehicle (emergency / emergency vehicle) transmission range is a range in which emergency information (emergency vehicle information) transmitted by the roadside communication device C as road-vehicle communication data (first information) is transmitted (retransmitted). In FIG. 20, emergency vehicle information as road-to-vehicle communication data (second information) transmitted by the roadside communication device C is transmitted to the two roadside communication devices W and E in the immediate vicinity of the roadside communication device C.
The road (emergency / emergency vehicle) transmission range is relatively narrow because the emergency vehicle information that informs the travel of the emergency vehicle only needs to be transmitted to the vehicles in the vicinity of the emergency vehicle and does not need to be transmitted over a wide range. It is.

The road vehicle (emergency / disaster information) transmission range is a range in which emergency information (disaster information) transmitted by the roadside communication device C as road-vehicle communication data (first information) is transmitted (retransmitted). In FIG. 20, not only the five roadside communication devices W2, W, N, S, E, and E2 around the roadside communication device C but also the roadside communication devices WW, NN, SS, and EE that are farther away. Disaster information as road-to-vehicle communication data (second information) transmitted by C is transmitted.
The reason why the road and vehicle (emergency / disaster information) transmission range is relatively wide is that disaster information such as fire, earthquake or tsunami should be transmitted over a wide area.

Thus, the emergency information can be appropriately transmitted by making the transmission range of the emergency information transmitted between the roads different from the transmission range of the normal information transmitted between the roads. Further, by changing the transmission range of emergency information according to the type of emergency information (emergency vehicle information / disaster information), appropriate transmission according to the type of emergency information becomes possible.
The type of emergency information can be determined by referring to the data type of the L7 header or the data type of application data.

  FIG. 21 shows an example of a communication topology for setting a transmission range between base stations as shown in FIG. FIG. 21 shows a communication topology among seven roadside communication devices C, W2, W, N, S, E, and E2.

  FIG. 21A shows a communication topology for road-to-road communication (usual information transmission). In FIG. 21 (a), roadside communication devices in which parentheses () are added to the IDs (C, W2, W, N, S, E, E2) of roadside communication devices are used as roadside communication data (application data). ) Transmission source (generation source). In FIG. 21A, the destination is the roadside communication device at the head of the arrow (or the head of the most advanced arrow when connected by a plurality of arrows).

That is, when the roadside communication device W2 is the transmission source, the roadside communication device W retransmits (transfers) the communication packet of the roadside communication data (second information) from the roadside communication device W2, and the roadside communication device C receives the destination. It becomes. When the roadside communication device W is the transmission source, the roadside communication device C is the destination.
When the roadside communication device C is the transmission source, the roadside communication devices W and E are the destinations, and the roadside communication devices W and E receive the communication packet of the roadside communication data (second information) from the roadside communication device C. Retransmit (transfer), and the roadside communication devices W2 and E2 are the destinations. Further, when the roadside communication device C is a transmission source, the roadside communication devices N and S are also destinations.
When the roadside communication device E is the transmission source, the roadside communication device C is the destination. When the roadside communication device E2 is the transmission source, the roadside communication device E retransmits (transfers) the communication packet of the roadside communication data (second information) from the roadside communication device E2, and the roadside communication device C is the destination. .
When the roadside communication device N is the transmission source, the roadside communication device C is the destination. When the roadside communication device S is the transmission source, the roadside communication device C is the destination.

  FIG. 21B shows a communication topology for a road vehicle (emergency / emergency vehicle). In FIG. 21 (b), roadside communication devices in which parentheses () are attached to the IDs (C, W2, W, N, S, E, E2) of roadside communication devices receive emergency information ( When the emergency vehicle information) is acquired, a communication packet of road-to-vehicle communication data (first information) including the emergency information (emergency vehicle information) is transmitted. In FIG. 21B, when the roadside communication device at the head of each arrow receives a communication packet of road-to-vehicle communication data (first information) including emergency information (emergency vehicle information), the emergency information (emergency vehicle) The communication packet of road-to-vehicle communication data (first information) including (information) is retransmitted.

  That is, when the roadside communication device W2 acquires emergency vehicle information from the emergency vehicle, the roadside communication device W2 transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication device W receives the communication packet, the roadside communication device W retransmits the communication packet of road-to-vehicle communication data (first information) including emergency information (emergency vehicle information).

  When the roadside communication device W acquires emergency vehicle information from the emergency vehicle, the roadside communication device W transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication devices W2 and C receive the communication packet, the roadside communication devices W2 and C retransmit the communication packet of road-to-vehicle communication data (first information) including emergency information (emergency vehicle information).

  When the roadside communication device C acquires emergency vehicle information from the emergency vehicle, the roadside communication device C transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication devices W and E receive the communication packet, the roadside communication devices W and E retransmit the communication packet of road-to-vehicle communication data (first information) including emergency information (emergency vehicle information).

  When the roadside communication device E acquires emergency vehicle information from the emergency vehicle, the roadside communication device E transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication devices C and E2 receive the communication packet, the roadside communication devices C and E2 retransmit the communication packet of road-to-vehicle communication data (first information) including emergency information (emergency vehicle information).

  When the roadside communication device E2 acquires emergency vehicle information from the emergency vehicle, the roadside communication device E2 transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication device E receives the communication packet, the roadside communication device E retransmits the communication packet of road-to-vehicle communication data (first information) including emergency information (emergency vehicle information).

  When the roadside communication device N acquires emergency vehicle information from the emergency vehicle, the roadside communication device N transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication device C receives the communication packet, the roadside communication device C retransmits the communication packet of road-vehicle communication data (first information) including emergency information (emergency vehicle information).

  When the roadside communication device S acquires emergency vehicle information from the emergency vehicle, the roadside communication device S transmits a communication packet of road-to-vehicle communication data (first information) including the emergency vehicle information. When the roadside communication device C receives the communication packet, the roadside communication device C retransmits the communication packet of road-vehicle communication data (first information) including emergency information (emergency vehicle information).

FIG. 21C shows a communication topology for road vehicles (emergency / disaster information). In FIG. 21C, the disaster information received from the central unit 4 by the roadside communication device in which parentheses () are attached to the ID (C, W2, W, N, S, E, E2) of the roadside communication device or A communication packet of road-to-vehicle communication data (first information) including disaster information generated by itself is transmitted.
In FIG. 21C, when the roadside communication device at the head of each arrow receives a communication packet of road-to-vehicle communication data (first information) including emergency information (disaster information), the roadside communication device includes the emergency information (disaster information). The communication packet of road-to-vehicle communication data (first information) is retransmitted.

The roadside communication device in which “req [xx]” is attached to the ID (W2, E2, N, S) of the roadside communication device communicates road-to-vehicle communication data (first information) including emergency information (disaster information). When retransmitting a packet, the “retransmission request to mobile station” field of the layer 7 header of the communication packet is set to “1: requested”, and the “required number of retransmissions of mobile station” field of the layer 7 header. Is set to a value corresponding to xx (for example, if xx = 10, “2:10 times” is set).
When a roadside communication device not including “req [xx]” in the roadside communication device ID including FIGS. 21A and 21B transmits a communication packet, the layer of the communication packet is used. The “retransmission request to mobile station” field of 7 header is set to “0: no request”, and “0: 0 times” is set to the “required number of retransmissions of mobile station” field of the layer 7 header. .

  When the roadside communication device C receives the disaster information from the central device 4 or generates the disaster information by itself according to the communication topology of FIG. 21 (c), the roadside communication device C performs the road-to-vehicle communication including the disaster information. A communication packet of data (first information) is transmitted. When the roadside communication devices W and E receive the communication packet transmitted by the roadside communication device C, the roadside communication devices W and E retransmit the communication packet of road-to-vehicle communication data (first information) including disaster information. When the roadside communication devices W2 and E2 receive the communication packets transmitted by the roadside communication devices W and E, the roadside communication devices W2 and E2 retransmit the communication packets of road-to-vehicle communication data (first information) including disaster information. The “Resend to mobile station” field of the communication packet transmitted by the roadside communication devices W2 and E2 is set to “1: Requested”, and the “Number of required retransmissions of mobile station” field is set to “2:10”. The

  When the roadside communication devices N and S receive the communication packet transmitted by the roadside communication device C, the roadside communication devices N and S retransmit the communication packet of road-to-vehicle communication data (first information) including disaster information. The “Retransmission request to mobile station” field of the communication packet transmitted by the roadside communication devices N and S2 is set to “1: Requested”, and the “Required retransmission number of mobile station” field is set to “2:10”. Is done.

As a result, as shown in the road and vehicle (emergency / disaster) transmission range of FIG. 20, the in-vehicle communication device 3 that has received the communication packet transmitted from the roadside communication devices W2, E2, N, and S The communication packet of the inter-vehicle communication data (third information) is retransmitted. The in-vehicle communication device 3 that retransmits the communication packet of the inter-vehicle communication data (third information) including the disaster information increments the value of the “retransmission count” field of the application header of the communication packet to be retransmitted. Therefore, 10 times of retransmissions are performed at the maximum, disaster information can be notified over a wide range, and roadside communication devices WW, EE, NN, SS far away from the roadside communication device C can also be A communication packet of communication data (third information) can be received.
At this time, the value of the “increment counter” field of the application header is not incremented. In this way, different (newly) received disaster information from the in-vehicle communication device 3 transmitted by the in-vehicle communication device 3 that has received the communication packet of the inter-vehicle communication data (third information) including the disaster information or received in the past. It is possible to determine whether the same disaster information is received.

FIG. 22 shows setting information set in the storage unit 24 of each roadside communication device W2, W, C, E, E2, N, S in order to realize the communication topology of FIG.
In the setting information shown in FIG. 22, items [ID], [CONNECTEDTO], [RR-GEN-DEST], [RV-EMERGENCY-GEN], and [RV-DISASTER-GEN] are provided.

[ID] indicates the ID (own station ID) of the roadside communication device 2.
[CONNECTEDTO] is an ID of another roadside communication device (base station) 2 that can directly communicate with the own device (own station) 2.

  [RR-GEN-DEST] is a setting value for the communication topology for the road-to-road communication shown in FIG. [RR-GEN-DEST] is a source side (communication source) roadside communication device ID and destination roadside communication device of the own road (own station) 2 that needs to be retransmitted. In addition to the ID, the priority of the road-to-road communication data is shown. The priority is indicated by a number with parentheses (). The higher the value, the higher the priority.

  [RV-EMERGENCY-GEN] is a setting value for a communication topology for road-vehicle communication (emergency / emergency vehicle information) illustrated in FIG. [RV-EMERGENCY-GEN] indicates the roadside communication device ID of the transmission source (generation source) of emergency information (emergency vehicle information) that the own device (own station) 2 needs to transmit (retransmit) as road-vehicle communication data. And the priority of the emergency information. The priority is indicated by a number with parentheses (). The higher the value, the higher the priority.

[RV-DISASTER-GEN] is a setting value for the communication topology for road-vehicle communication (emergency / disaster information) shown in FIG.
[RV-DISASTER-GEN] indicates a roadside communication device ID of a transmission source (generation source) of emergency information (disaster information) that the own device (own station) 2 needs to transmit (retransmit) as road-vehicle communication data. In addition, the priority of the emergency information is shown. The priority is indicated by a number with parentheses (). The higher the value, the higher the priority.
[RV-DISASTER-GEN] is referred to when the value of the [data type] field of the communication packet of the received road-vehicle communication data is [1: emergency (emergency vehicle)].

In the setting value of [RV-DISASTER-GEN], “req [xx]” that may be attached to the roadside communication device ID is disaster information transmitted from the transmission source (generation source) indicated by the roadside communication device ID. Indicates that “retransmission request to mobile station” needs to be set to “1: requested”, and xx indicates the number of required retransmissions.
[RV-DISASTER-GEN] is referred to when the value of the [data type] field of the communication packet of the received road-vehicle communication data is [2: emergency (disaster)].

22A shows the setting information of the roadside communication device W2, FIG. 22B shows the setting information of the roadside communication device W, FIG. 22C shows the setting information of the roadside communication device C, and FIG. (D) shows the setting information of the roadside communication device E, FIG.22 (e) shows the setting information of the roadside communication device E2, FIG.22 (f) shows the setting information of the roadside communication device N, FIG.22 (g ) Shows setting information of the roadside communication device S.
The setting values shown in FIGS. 22A to 22G correspond to the communication topology shown in FIG.

[3.4 Retransmission processing of roadside communication equipment]

  The retransmission process of the roadside communication device 2 is performed by the application AP.

The roadside communication device 2 that has received the communication packet of the roadside communication data (second information) performs the retransmission process (step S7-2 in FIG. 18) as follows. The roadside communication device 2 refers to the transmission source (generation source) of the received communication packet and refers to the set value of the transmission source (generation source) of [RR-GEN-DEST] of the own device (own station) 2. If they match, the communication packet of the road-to-road communication data (second information) is targeted for retransmission. If they do not match, they are not considered for retransmission.
The destination of the retransmitted communication packet is the destination corresponding to the transmission source (generation source) that matches the transmission source (generation source) of the communication packet in [RR-GEN-DEST] of the own device (own station) 2.
When it is necessary to retransmit a plurality of road-to-road communication data, a destination communication packet having a high priority shown in [RR-GEN-DEST] is preferentially retransmitted.

The roadside communication device 2 that has received the communication packet of road-to-vehicle communication data (first information) including emergency vehicle information performs a retransmission process (step S4 in FIG. 18) as follows. The roadside communication device 2 refers to the transmission source (generation source) of the received communication packet and refers to the set value of the transmission source (generation source) of [RV-EMERGENCY-GEN] of the own device (local station) 2. If they match, the communication packet of road-to-vehicle communication data (first information) including emergency vehicle information is subject to retransmission. If they do not match, they are not subject to retransmission.
When it is necessary to retransmit a plurality of road-vehicle communication data, a high-priority transmission source (generation source) communication packet shown in [RV-EMERGENCY-GEN] is retransmitted with priority.

The roadside communication device 2 that has received the communication packet of road-to-vehicle communication data (first information) including disaster information performs a retransmission process (step S4 in FIG. 18) as follows. The roadside communication device 2 refers to the transmission source (generation source) of the received communication packet and refers to the set value of the transmission source (generation source) of [RV-DISASTER-GEN] of the own device (own station) 2. If they match, the communication packet of road-to-vehicle communication data (first information) including disaster information is set as a retransmission target. If they do not match, they are not subject to retransmission.
When it is necessary to retransmit a plurality of road-to-vehicle communication data, a high-priority transmission source (generation source) communication packet shown in [RV-DISASTER-GEN] is preferentially retransmitted.

The roadside communication device 2 that has received the communication packet of the inter-vehicle communication data (third information) including the emergency information performs a retransmission process (step S10 in FIG. 18) as follows.
The roadside communication device 2 refers to the value of the “required number of retransmissions of mobile station” field of the application header (or layer 7 header) of the received communication packet and the value (validity information) of the “number of retransmissions” field of the application header. The validity of the received inter-vehicle communication data (emergency information) is determined. When it is recognized that the roadside communication device 2 should retransmit the received vehicle-to-vehicle communication data (emergency information), the received emergency information and data type (identification information) are changed to the road-to-vehicle communication data (No. 2 information).
If the validity is not recognized, no retransmission is performed.

  For example, if the value of the “required number of retransmissions of mobile station” field is “10” and the value of the “number of retransmissions” field (validity information) is “4”, the validity determination is relatively It is new effective emergency information and it is determined that it should be retransmitted. The value of the “required number of retransmissions of mobile station” field of the road-to-vehicle communication packet retransmitted by the roadside communication device 2 is obtained by subtracting the “number of retransmissions” of the received packet from the “required number of retransmissions of mobile station” of the received packet. It is preferable to use an approximate value of the number. For example, if the “required number of retransmissions of mobile station” of the received packet is “10” and the “number of retransmissions” of the received packet is “4”, the value of the “required number of retransmissions of mobile station” field in the retransmitted packet Can be set to “1: 5” which is an approximate value of 10−4 = 6.

[3.5 Retransmission processing of in-vehicle communication equipment]
The in-vehicle communication device 3 that has received the communication packet of the vehicle-to-vehicle communication data (third information) that includes the emergency information and is set to have a retransmission request performs the retransmission process (step S22 in FIG. 19) as follows.
The in-vehicle communication device 3 refers to the value of the “required number of retransmissions of mobile station” field of the application header (or layer 7 header) of the received communication packet and the value (validity information) of the “number of retransmissions” field of the application header. The validity of the received inter-vehicle communication data (emergency information) is determined. When it is confirmed that the received vehicle-to-vehicle communication data (emergency information) should be retransmitted by the in-vehicle communication device 3, the received emergency information and data type (identification information), etc. 3 information). At the time of retransmission, a value incremented by 1 in the value of the same field of the received emergency information is stored and transmitted in the “number of retransmissions” field of the application header.
If the validity is not recognized, no retransmission is performed.

  With respect to the present invention, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not meant to be described above, but is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 Traffic signal 2 Roadside communication equipment (base station)
2A First roadside communication device (first base station)
2b Second roadside communication device (second base station)
3 In-vehicle communication device (mobile station)
4 Central device 5 Vehicle 6 Roadside sensor 7 Wired communication line 21 Wireless communication unit 22 Wired communication unit 23 Control unit 24 Storage unit 25 Communication processing device 31 Wireless communication unit (reception unit)
33 control unit 34 storage unit 35 communication processing unit AP application (application device; retransmission processing unit)
L7 Layer 7 (Discard)
SEC security management

Claims (7)

A second communication period in which a communication packet can be transmitted in a first communication period for communication for a mobile station and is different from the first communication period and for communication for another base station A receiving unit capable of receiving communication packets from a base station capable of transmitting communication packets at
A communication processing unit;
A mobile station with
The communication packet includes management information, identification information, and application data,
The identification information is information indicating whether the application data is emergency information,
The management information is
When the application data included in the communication packet transmitted in the first communication period from the base station is normal information other than emergency information, it indicates that the communication packet is received by the mobile station,
When the application data included in the communication packet transmitted in the first communication period from the base station is emergency information, it indicates that the communication packet is received by the base station and the mobile station,
The communication processing unit refers to management information included in a communication packet received from a base station, and determines a communication packet including management information indicating reception by the mobile station as first information for the mobile station. A communication packet including management information indicating reception by the base station and the mobile station is also determined as the first information for the mobile station. A retransmission processing unit that performs retransmission processing of the communication packet received by the receiving unit;
The retransmission processing unit is included in the communication packet received by the receiving unit if the identification information indicates that the application data included in the communication packet received by the receiving unit is the emergency information. The mobile station according to claim 1, wherein the emergency information and the identification information can be retransmitted as information for other mobile stations in a communication period for communication between mobile stations different from the first communication period. The communication packet received by the receiving unit further includes request information indicating whether retransmission by the mobile station is requested,
The retransmission processing unit determines whether or not the emergency information and the identification information included in the communication packet received by the receiving unit should be retransmitted as information for another mobile station based on the request information. The mobile station according to claim 2. The communication packet received by the receiving unit includes validity information regarding the validity of the communication packet received by the receiving unit,
The retransmission processing unit determines whether or not the emergency information and the identification information included in the communication packet received by the receiving unit should be retransmitted as information for another mobile station based on the validity information. The mobile station according to claim 2 or 3.   A computer program for causing a computer to function as the communication processing unit of the mobile station according to claim 1.   The computer program for functioning a computer as the said resending process part of the said mobile station of any one of Claims 2-5. A data structure of a communication packet transmitted from a base station in a first communication period for communication for a mobile station,
The communication packet includes management information, identification information, and application data,
The identification information is information indicating whether the application data is emergency information,
The management information is
When the application data included in the communication packet transmitted in the first communication period from the base station is normal information other than emergency information, it indicates that the communication packet is received by the mobile station,
When the application data included in the communication packet transmitted in the first communication period from the base station is emergency information, it indicates that the communication packet is received by the base station and the mobile station,
The management information is referred to by the mobile station that has received the communication packet, and a communication packet including management information indicating that the management information is received by the mobile station is determined as first information for the mobile station, and the base station and the mobile A data structure of a communication packet used for processing by a mobile station that determines that the communication packet including management information indicating reception by the station is also the first information for the mobile station.

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