JP6519325B2 - Communication device - Google Patents

Description

  The present invention relates to a communication device that receives a communication packet in a predetermined format, which is wirelessly transmitted from another device.

  In recent years, an inter-vehicle communication system in which each of a plurality of vehicles transmits, to another vehicle, a communication packet indicating vehicle information such as the current position of the host vehicle and the traveling direction, and sequentially receives communication packets transmitted from the other vehicle. Has been proposed. In this inter-vehicle communication system, the communication device mounted on the own vehicle may not normally receive the communication packet transmitted by the other vehicle due to various causes such as propagation loss and packet collision.

  As one measure to solve this problem, a continuous transmission system has been proposed in which the same information is transmitted multiple times. Further, Patent Document 1 discloses an error correction method of a received packet in the case where a continuous transmission method is adopted as a communication method of an inter-vehicle communication system.

JP 2007-104423 A

  By adopting the continuous transmission method, it is possible to increase the probability of success in packet reception (referred to as a reception success rate) on the receiving side. However, in the case of the continuous transmission system, the same communication packet is transmitted a plurality of times, which results in an increase in communication traffic.

  Further, according to the method disclosed in Patent Document 1, since errors in the received packet can be corrected based on a plurality of received packets, it is possible to improve the reception success rate, but it is necessary for error correction. A waiting time until receiving the continuous transmission packet is required. Furthermore, since the error correction method of Patent Document 1 is a method based on the continuous transmission method, it can not be applied when the continuous transmission method is not employed. That is, there is a need for a mechanism for increasing the reception success rate of communication packets, which is applicable even if it is not the continuous transmission method.

  The present invention has been made based on the above circumstances, and an object of the present invention is to increase the reception success rate of communication packets wirelessly transmitted from other devices without using a continuous transmission method. To provide a communication device.

A first invention for achieving the object is a communication device for receiving a communication packet in a predetermined format, which is wirelessly transmitted from another device, the communication packet comprising at least the communication packet. A transmission source information area including a type information area in which information indicating the type of communication packet is stored, and transmission source information representing a transmission source that is an apparatus that has transmitted the communication packet is disposed at a predetermined position. The reception unit (1) receives a signal in a frequency band used for wireless communication with another device, and a bit string corresponding to the reception signal by demodulating the signal received by the reception unit. A demodulator (3) that generates a certain received word, and whether or not the type of a communication packet corresponding to the received word generated by the demodulator is a predetermined replacement target type When it is determined by the packet type determination unit (4) and the packet type determination unit that the type of the communication packet corresponding to the received word is a replacement target type, as a replacement target among bit strings constituting the received word A replacement unit (5) that generates a replaced received word in which a replacement target area, which is a preset part, is replaced with a predetermined replacement bit string, and the replaced received word generated by the replacement unit is decoded and replaced Whether or not an error occurs in the received message, which is a bit string generated by decoding the received word by the decoding unit (7) configured to also decode the received word that has not been subjected to replacement by the unit Information indicating the transmission source of the received word, with the received word corresponding to the received message determined to have no error by the error determining unit (10) and the error determining unit as the reception success word And a communication packet corresponding to a new received word which is a newly generated received word, in the case where the received word storage unit (12) stores the received word in association with the received word and the demodulation unit generates a new received word. The received word acquisition unit acquires, from the received word storage unit, the received success word received from the same transmission source as the newly received word when the packet type determination unit determines that the type of the packet is the replacement target type (5 S212 And the replacement bit string is a bit string in the case where no bit error occurs in the replacement target area, and the communication packet as the replacement target type is position information indicating the latitude and longitude as the current position of the transmission source. Is a communication packet having a position information area in which is placed at a predetermined position, and a bit corresponding to the degree and the minute of the position information area in the received word corresponding to the communication packet of the replacement target type. Preparative column, is set as the replacement target area, replacing unit that is configured to the replacement area of the newly received word is replaced with a replacement area of the reception success word received word acquisition unit acquires It features.
A second invention for achieving the above object is a communication device for receiving a communication packet in a predetermined format, which is wirelessly transmitted from another device, and the communication packet is at least A transmission source information area including a type information area in which information indicating the type of communication packet is stored, and transmission source information representing a transmission source that is an apparatus that has transmitted the communication packet is disposed at a predetermined position. The reception unit (1) receives a signal in a frequency band used for wireless communication with another device, and a bit string corresponding to the reception signal by demodulating the signal received by the reception unit. A demodulator (3) that generates a certain received word, and whether or not the type of a communication packet corresponding to the received word generated by the demodulator is a predetermined replacement target type When it is determined by the packet type determination unit (4) and the packet type determination unit that the type of the communication packet corresponding to the received word is a replacement target type, as a replacement target among bit strings constituting the received word A replacement unit (5) that generates a replaced received word in which a replacement target area, which is a preset part, is replaced with a predetermined replacement bit string, and the replaced received word generated by the replacement unit is decoded and replaced Whether or not an error occurs in the received message, which is a bit string generated by decoding the received word by the decoding unit (7) configured to also decode the received word that has not been subjected to replacement by the unit Information indicating the transmission source of the received word, with the received word corresponding to the received message determined to have no error by the error determining unit (10) and the error determining unit as the reception success word And a communication packet corresponding to a new received word which is a newly generated received word, in the case where the received word storage unit (12) stores the received word in association with the received word and the demodulation unit generates a new received word. The received word acquisition unit acquires, from the received word storage unit, the received success word received from the same transmission source as the newly received word when the packet type determination unit determines that the type of the packet is the replacement target type (5 S212 And the replacement bit string is a bit string in the case where a bit error does not occur in the replacement target area, and the replacement part is a new received word and a reception success word stored in the received word storage part. That the source of the newly received word is specified based on the Hamming distance of and the replacement target area of the newly received word is replaced with the replacement target area of the received success word acquired by the received word acquisition unit. To feature
A third invention for achieving the above object is a communication device for receiving a communication packet in a predetermined format, which is wirelessly transmitted from another device, and the communication packet is at least A transmission source information area including a type information area in which information indicating the type of communication packet is stored, and transmission source information representing a transmission source that is an apparatus that has transmitted the communication packet is disposed at a predetermined position. The reception unit (1) receives a signal in a frequency band used for wireless communication with another device, and a bit string corresponding to the reception signal by demodulating the signal received by the reception unit. A demodulator (3) that generates a certain received word, and whether or not the type of a communication packet corresponding to the received word generated by the demodulator is a predetermined replacement target type When it is determined by the packet type determination unit (4) and the packet type determination unit that the type of the communication packet corresponding to the received word is a replacement target type, as a replacement target among bit strings constituting the received word A replacement unit (5) that generates a replaced received word in which a replacement target area, which is a preset part, is replaced with a predetermined replacement bit string, and the replaced received word generated by the replacement unit is decoded and replaced Whether or not an error occurs in the received message, which is a bit string generated by decoding the received word by the decoding unit (7) configured to also decode the received word that has not been subjected to replacement by the unit Information indicating the transmission source of the received word, with the received word corresponding to the received message determined to have no error by the error determining unit (10) and the error determining unit as the reception success word And a communication packet corresponding to a new received word which is a newly generated received word, in the case where the received word storage unit (12) stores the received word in association with the received word and the demodulation unit generates a new received word. The received word acquisition unit acquires, from the received word storage unit, the received success word received from the same transmission source as the newly received word when the packet type determination unit determines that the type of the packet is the replacement target type (5 S212 And the replacement bit string is a bit string in the case where no bit error occurs in the replacement target area, and the reception success word is stored separately for each transmission source in the reception word storage unit. Together with the time when the reception success word is received, the substitution unit stores the reception time of the new reception word and the reception success word for each transmission source stored in the reception word storage unit. Based on time Te, identifies the newly received word source, characterized in that it is configured to be replaced area of newly received word, as replaced with replacement region of the reception success word received word acquisition unit has acquired.
A fourth invention for achieving the above object is a communication device for receiving a communication packet in a predetermined format, which is wirelessly transmitted from another device, and the communication packet is at least A transmission source information area including a type information area in which information indicating the type of communication packet is stored, and transmission source information representing a transmission source that is an apparatus that has transmitted the communication packet is disposed at a predetermined position. The reception unit (1) receives a signal in a frequency band used for wireless communication with another device, and a bit string corresponding to the reception signal by demodulating the signal received by the reception unit. A demodulator (3) that generates a certain received word, and whether or not the type of a communication packet corresponding to the received word generated by the demodulator is a predetermined replacement target type When it is determined by the packet type determination unit (4) and the packet type determination unit that the type of the communication packet corresponding to the received word is a replacement target type, as a replacement target among bit strings constituting the received word A replacement unit (5) that generates a replaced received word in which a replacement target area, which is a preset part, is replaced with a predetermined replacement bit string, and the replaced received word generated by the replacement unit is decoded and replaced Whether or not an error occurs in the received message, which is a bit string generated by decoding the received word by the decoding unit (7) configured to also decode the received word that has not been subjected to replacement by the unit Information indicating the transmission source of the received word, with the received word corresponding to the received message determined to have no error by the error determining unit (10) and the error determining unit as the reception success word And a communication packet corresponding to a new received word which is a newly generated received word, in the case where the received word storage unit (12) stores the received word in association with the received word and the demodulation unit generates a new received word. The received word acquisition unit acquires, from the received word storage unit, the received success word received from the same transmission source as the newly received word when the packet type determination unit determines that the type of the packet is the replacement target type (5 S212 And the replacement bit string is a bit string in the case where no bit error occurs in the replacement target area, and the reception success word is stored separately for each transmission source in the reception word storage unit. Together with the received signal strength of the received signal that is the source of the successful word, the substitution unit stores the received signal strength of the new received word and the reception word stored in the received word storage unit. Success word received It is characterized in that the transmission source of the newly received word is specified based on the signal strength, and the replacement target area of the new received word is replaced with the replacement target area of the reception success word acquired by the received word acquisition unit. I assume.

  In the above configuration, when the type of the communication packet corresponding to the received word is the replacement target type by the packet type determination unit, the replacement unit 5 separately prepares the bit string arranged in the replacement target area of the received word. Generate a replaced received word replaced with the replacement bit string. Then, the decoding unit 7 decodes the replaced received word.

  The replacement bit string used here is a bit string that should be originally observed in the replacement target area (that is, it does not contain bit errors), and the original reception is performed by replacing the replacement target area with the replacement bit string. It is generated so that there is no fear of rewriting the information provided in the word.

  Therefore, according to the above configuration, the bit string arranged in the replacement target area is replaced with the bit string that should be present. Therefore, even if a bit error occurs in the replacement target area of the received word at the time of demodulation, the bit error is corrected at the time of decoding, so the bit generated in the replacement target area It is possible to suppress the possibility of discarding a received packet due to an error. That is, according to the above configuration, the reception success rate can be increased.

  Further, in the above configuration, the continuous feeding method is not assumed. Therefore, while being able to suppress the increase in communication traffic, it is applicable also to the system which does not employ | adopt a continuous transmission system. Of course, the above configuration may be applied to a system adopting a continuous delivery system.

  In addition, the code | symbol in the parentheses described in the claim shows correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited. is not.

FIG. 1 is a block diagram showing an example of a schematic configuration of a communication apparatus 100 according to a first embodiment. It is a figure which shows an example of a rough structure of a communication packet. It is a figure which shows an example of a data structure of the communication packet of substitution object type. It is a figure which shows the rough structure of the data which encoded the communication packet of substitution object type shown in FIG. FIG. 10 is a conceptual diagram for explaining the operation of replacement unit 5; It is a flowchart for demonstrating the operation | movement of the communication apparatus 100 which concerns on 1st Embodiment. It is a block diagram showing an example of rough composition of communication apparatus 100 concerning a 2nd embodiment. It is a conceptual diagram for demonstrating the action | operation of the substitution part 5 which concerns on 2nd Embodiment. It is a block diagram which shows an example of a rough structure of the communication apparatus 100 which concerns on 3rd Embodiment. It is a conceptual diagram which shows the rough structure of the data stored in received word DB12. It is a flowchart for demonstrating the operation | movement of the communication apparatus 100 which concerns on 3rd Embodiment. It is a flowchart for demonstrating the transmission source identification process which the substituted part 5 in 4th Embodiment implements.

First Embodiment
Hereinafter, a first embodiment of the present invention will be described using the drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a communication apparatus 100 according to the present embodiment. As shown in FIG. 1, the communication apparatus 100 according to the present embodiment includes an RF (Radio Frequency) unit 1, an analog-to-digital converter (hereinafter referred to as an A / D converter) 2, a demodulator 3, a packet type determination unit 4, A replacing unit 5, a selecting unit 6, a decoding unit 7, and a memory M1 which is a non-volatile storage medium are provided. Note that each unit included in the communication apparatus 100 excluding the memory M1 may be realized as software (that is, as a function provided by the CPU), or may be realized as hardware using an IC, a circuit element, or the like. Good.

  The communication device 100 is a device for receiving a communication packet in a predetermined format, which is transmitted from another device. Here, as an example, the communication device 100 is mounted on a vehicle and used as a communication device for performing wireless communication (so-called inter-vehicle communication) without passing through a wide area communication network with other vehicles. Of course, the application of the communication device 100 is not limited to inter-vehicle communication, and may be used for road-to-vehicle communication, or may be used for applications other than inter-vehicle communication and road-to-vehicle communication.

<About schematic configuration of communication packet>
Before describing the specific configuration of the communication device 100, first, the configuration of a communication packet transmitted and received in inter-vehicle communication will be described. A packet transmitted and received in inter-vehicle communication includes a header H and a payload P as shown in FIG. The header portion H is a packet type area H1 in which information indicating the type of the communication packet is stored, a destination address area H2 in which a destination address indicating a communication apparatus as a destination is stored, and a transmission indicating a communication apparatus of a transmission source. And a source address area H3 in which the source address is stored. The packet type area H1 corresponds to the type information area described in the claims. The transmission source address corresponds to transmission source information described in the claims, and the transmission source address area H3 corresponds to the transmission source information area described in the claims.

  The type of packet here is one in which various communication packets transmitted and received in inter-vehicle communication are classified according to the type of information contained in the communication packet, and are preset when configuring the communication architecture. It is a thing. For example, as a communication packet, a vehicle information packet representing a predetermined type of information such as a current position (referred to as vehicle information) of a vehicle equipped with a communication apparatus of a transmission source, and notification of approach of emergency vehicles An emergency vehicle notification packet etc. are assumed. The type of communication packet may be designed appropriately.

  The payload portion P stores information according to the packet type. For example, as shown in FIG. 3, the payload portion P of the vehicle information packet includes a reservation area P1, a latitude area P2, a longitude area P3 and a time stamp area P4. The reserved area P1 is an area in which a bit string of a preset (= fixed) pattern is stored. The latitude area P2 is an area in which information indicating the latitude (degree, minute, second) of the current position of the transmission source is stored, and the longitude area P3 is the longitude (degree, minute, second) of the current position of the transmission source It is an area where the information to be shown is stored. Note that bit strings corresponding to degrees, minutes, and seconds are stored in the latitude area P2 and the longitude area P3 from the upper bits, respectively. The latitude area P2 and the longitude area P3 correspond to the position information area described in the claims.

  The time stamp area P4 is an area in which information representing the time when the communication packet is generated is stored. The type of information included in the vehicle information packet may be appropriately designed, and may include, for example, traveling speed and acceleration, the state of a direction indicator switch, and the like, in addition to the items described above.

  Further, the communication packet illustrated in FIG. 2 is not transmitted as it is, but is encoded by a predetermined encoding method and transmitted. As a coding method, a well-known method such as convolutional code, turbo code, low density parity check (LDPC) code, or the like may be adopted.

  FIG. 4 conceptually shows data (bit string) obtained by encoding a vehicle information packet. As shown in FIG. 4, a bit string obtained by encoding a vehicle information packet includes a bit type corresponding to each of packet type, destination address, transmission source address, reserved area, latitude information, longitude information, and time stamp. . Specifically, the packet type corresponding bit string shown in FIG. 4 is a bit string obtained by encoding packet type information. The other bit strings are also bit strings obtained by encoding the bit strings stored in each area of the communication packet.

Regarding Configuration of Communication Device 100
Next, referring back to FIG. 1, each unit included in the communication apparatus 100 will be described. Hereinafter, for convenience, a vehicle equipped with the communication device 100 is also referred to as a host vehicle.

  The RF unit 1 is connected to an antenna (referred to as an inter-vehicle communication antenna) capable of receiving radio waves in a frequency band (for example, 700 MHz band) used for inter-vehicle communication, and the signal received by the inter-vehicle communication antenna To get Then, the RF unit 1 converts the received signal into a baseband signal by performing predetermined processing such as amplification, quadrature demodulation, etc. on the received signal input from the inter-vehicle communication antenna to convert the received signal into an A / A signal. Output to D conversion unit 2. The RF unit 1 corresponds to the receiving unit described in the claims.

  As a more preferable mode, the RF unit 1 in the present embodiment has a signal strength detection function of detecting the received signal strength of a signal received by the inter-vehicle communication antenna. The signal strength detection function may be realized by a known signal strength detection circuit that outputs a voltage (or current) according to the signal strength of the received signal.

  The A / D conversion unit 2 converts an analog signal in the baseband which is input from the RF unit 1 into a digital signal and outputs the digital signal to the demodulation unit 3. The demodulation unit 3 subjects the signal input from the A / D conversion unit 2 to digital demodulation processing to generate a bit string corresponding to the reception signal. More specifically, the demodulation unit 3 performs various processing such as synchronous detection processing, propagation path estimation processing, equalization processing, and the like on the bit string (a bit string corresponding to the received signal) input from the A / D conversion unit 2. To generate a bit string (referred to as a received word) obtained by demodulating the received signal. This received word is a bit string still encoded.

  Then, the received word generated by the demodulation unit 3 is provided to the packet type determination unit 4, the replacement unit 5, and the selection unit 6. In the present embodiment, although the demodulation unit 3 performs demodulation according to the hard decision method, the demodulation unit 3 may perform demodulation according to the soft decision method as another aspect.

  The packet type determination unit 4 refers to a bit string arranged in a portion (referred to as a packet type corresponding area) corresponding to the packet type information of the received word provided from the demodulation unit 3 and performs communication corresponding to the received word It is determined whether the type of packet is a predetermined type (referred to as a replacement target type). Then, if the type of the communication packet corresponding to the received word is the replacement target type, the replacement unit 5 is notified of that.

  Here, the replacement target type is a type that is the target of processing (referred to as replacement processing) of replacing a part of the bit string constituting the received word with a bit string of the same length separately prepared. The replacement target type is appropriately designed, and here, as an example, a type including a region (that is, a reserved region) in which a bit string of a certain pattern is arranged in the payload portion P is defined as a replacement target type. It is assumed that That is, the vehicle information packet is set as a replacement target type as an example here. Although one type of replacement target type is used in the present embodiment, a plurality of replacement target types may be defined as another aspect.

  Also, the method by which the packet type determination unit 4 determines whether or not the type of the communication packet corresponding to the received word is a replacement target type may be designed as appropriate. Here, as an example, a bit pattern (referred to as a replacement target bit pattern) indicating that it is a replacement target type is registered in advance in the memory M1, and the packet type determination unit 4 arranges the received word in the packet type corresponding area. If the bit string being processed matches the replacement target bit pattern registered in the memory M1, the type of the communication packet corresponding to the received word may be determined to be the replacement target type.

  The replacement target bit pattern corresponds to a bit string obtained by encoding a bit string indicating that the type is a replacement target type in the packet type area H1. In addition to the replacement target bit pattern, the memory M1 stores a reserved area bit string used by the replacing unit 5 described below. The memory M1 corresponds to the storage unit described in the claims. Hereinafter, for simplification of the description, the type of communication packet corresponding to the received word is also described as the type of received word.

  When the packet type determination unit 4 determines that the type of the received word is the replacement target type, the replacement unit 5 corresponds to the reserved area P1 of the communication packet before encoding in the received word, as shown in FIG. The bit string stored in the part (reservation equivalent area) is replaced with the bit string for reservation area.

  The reserved area bit string used here is a bit string observed in the reserved area, for example, when the wireless signal corresponding to the communication packet of the replacement target type can be received without bit errors (that is, normally). That is, the reserved area bit string is a bit string stored in the reserved area when no bit error occurs in the reserved area. The reserved area bit string corresponds to an example of the replacement bit string described in the claims.

  The received word (referred to as a replaced received word) obtained by replacing the bit string stored in the reserved corresponding area by the replacing unit 5 with the reserved area bit string is output to the selecting unit 6. Hereinafter, a received word that has not undergone substitution processing on a replaced received word is also referred to as a non-replaced received word. In addition, when there is no distinction between a non-replaced received word and a replaced received word, it is simply described as a received word.

  When the packet type determination unit 4 determines that the type of the received word is the replacement target type, the selection unit 6 outputs the replaced received word input from the replacement unit 5 to the decoding unit 7. When the packet type determination unit 4 determines that the type of the received word is not the replacement target type, the non-replacement received word output from the demodulation unit 3 is output to the decoding unit 7.

  The decoding unit 7 decodes the received word input from the selection unit 6. The received word subjected to the decoding process is called a received message. The received message is provided to a software module (referred to as a protocol stack unit) that performs processing corresponding to the protocol stack, for example, after being subjected to error detection processing and the like. If an error is detected in the decoded received word, the communication packet may be discarded.

<Operation of Communication Device 100>
Next, a series of operations of the communication device 100 in the case of receiving a wireless signal from another vehicle will be described using the flowchart shown in FIG. The flowchart shown in FIG. 6 may be started, for example, when the RF unit 1 receives a signal whose received signal strength is equal to or higher than a predetermined threshold. The threshold is a threshold for separating a radio signal transmitted from another vehicle by inter-vehicle communication and noise, and may be, for example, -90 dBm.

  First, in step S101, the A / D conversion unit 2 converts the signal received by the RF unit 1 into a digital signal, and the demodulation unit 3 demodulates the reception signal digitized by the A / D conversion unit 2 To generate a received word (ie, a non-replaced received word). Then, the generated non-replacement received word is provided to the packet type determination unit 4, the replacement unit 5, and the selection unit 6, and the process proceeds to step S102.

  In step S102, the packet type determination unit 4 refers to the packet type corresponding area of the non-replacement received word provided from the demodulation unit 3 and determines whether the type of the received word is a replacement target type. If it is determined that the type of the received word is the replacement target type, step S102 becomes YES and the process moves to step S103. On the other hand, when it is determined that the type of the received word is not the replacement target type, step S102 becomes NO and the process moves to step S105.

  In step S103, the replacing unit 5 replaces the bit string arranged in the reservation corresponding area of the received word with the reserved area bit string stored in the memory M1 to generate a replaced received word, and proceeds to step S104. . The reservation corresponding area corresponds to an example of the replacement target area described in the claims.

  In step S104, the replacing unit 5 provides the replaced received word generated in step S103 to the selecting unit 6, and the selecting unit 6 outputs the replaced received word input from the replacing unit 5 to the decoding unit 7 Move to S106.

  In step S105, the selection unit 6 outputs the non-replacement received word input from the demodulation unit 3 to the decoding unit 7, and the process proceeds to step S106. In step S106, the decoding unit 7 decodes the received word input from the selection unit 6 and ends the present flow.

Summary of First Embodiment
In the above configuration, when the type of the communication packet corresponding to the received word is the replacement target type, replacing section 5 replaces the bit string arranged in the reserved corresponding area of the non-replaced received word with the reserved area bit string. The replaced received word is generated, and the decoding unit 7 decodes the replaced received word. The reserved area bit string used here is a bit string that should originally be observed in the reserved equivalent area (that is, a bit string in which no bit error occurs).

  Therefore, according to the above configuration, if there is a bit error in the reservation corresponding area of the received word, the reservation corresponding area is corrected to a normal bit string by performing the replacement process.

  Therefore, according to the above configuration, the received packet will not be discarded due to at least a bit error occurring in the reservation equivalent area. That is, focusing on the fact that the same bit string as another packet is present in part of the received packet, the reception success rate can be increased by replacing the bit string.

  Since the reserved area is an area which is a bit string of a fixed pattern, the reserved equivalent area should also be a bit string of a fixed pattern. Therefore, by replacing the bit string in the reserved corresponding area with the reserved area bit string, the information originally contained in the non-replaced received word is not rewritten.

  Further, in the above configuration, the continuous feeding method is not assumed. Therefore, the increase in communication traffic can be suppressed, and the present invention can be applied to a system that does not adopt the continuous transmission method. That is, according to the above configuration, it is possible to increase the reception success rate of communication packets transmitted from other vehicles without using the continuous transmission method. Of course, the above configuration may be applied to a system adopting a continuous feeding system.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following embodiment is also included in the technical scope of this invention, Furthermore, a summary is described in addition to the following. Various modifications can be made without departing from the scope of the invention.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings. In addition, about the member which has the function same as the member of a structure of above-mentioned 1st Embodiment in the following, the same code | symbol is attached | subjected and the description is abbreviate | omitted. In addition, when only a part of the configuration is mentioned, the first embodiment described above and various modified examples can be applied to the other parts.

  The communication device 100 according to the second embodiment is, as shown in FIG. 7, a state acquisition unit 8 communicably connected to the clock 81 and the GNSS receiver 82 in addition to the components included in the communication device 100 according to the first embodiment. And a partial encoding unit 9.

  The clock 81 measures the current time, and sequentially provides time information indicating the current time to the state acquisition unit 8. The GNSS receiver 82 acquires current position information indicating the current position of the GNSS receiver 82 by receiving radio waves from satellites (referred to as GNSS satellites) used in Global Navigation Satellite System (GNSS). The current position may be represented by, for example, latitude and longitude. It is assumed that the current position of the GNSS receiver 82 can be regarded as the current position of the host vehicle. The current position information acquired by the GNSS receiver 82 is sequentially provided to the state acquisition unit 8.

  The state acquisition unit 8 acquires time information and current position information provided from the clock 81 and the GNSS receiver 82, and provides them to the partial encoding unit 9. The partial encoding unit 9 generates a bit string (hour-minute bit string) obtained by encoding data corresponding to hours and minutes, which is included in time information provided from the state acquisition unit 8. Further, the partial encoding unit 9 corresponds to a bit string (latitude minute bit string) obtained by encoding data corresponding to the degree / minute of the latitude information included in the current position information, and the degree / minute of longitude included in the current position information. And generate a bit string (longitude divided bit string) obtained by encoding the data to be encoded. The latitude minute bit string, the longitude minute bit string, and the time minute bit string are sequentially generated and updated to a bit string corresponding to the current position or time.

  The degree / minute value indicated by the latitude minute bit string sequentially generated by the partial encoding unit 9 substantially matches the degree / minute value indicating the current position of the transmission source of the vehicle information packet received by the vehicle. This is because, generally, the reach of the communication packet in inter-vehicle communication is about several hundred meters to 1 km, the other vehicle corresponding to the transmission source of the vehicle information packet received by the own vehicle is within 1 km from the own vehicle It will exist. Therefore, it is possible to expect that the degree / minute of the latitude indicating the current position of the other vehicle as the transmission source matches the degree / minute of the latitude indicating the current position of the own vehicle. It should be noted that at a level finer than the minute (ie, the second level), it is not considered identical because the value is likely to be different from the current position of the vehicle.

  For the same reason, the degree / minute indicated by the longitude division bit string sequentially generated by the partial encoding unit 9 also coincides with the degree / minute of the longitude indicating the current position of the transmission source of the vehicle information packet received by the own vehicle Can be regarded as

  Furthermore, it can be considered that the hour and minute bit strings sequentially generated by the partial encoding unit 9 indicate that the minute value matches the hour and minute value of the time stamp included in the vehicle information packet received by the vehicle. This is because it can be expected that the error of the clock 81 provided in each communication device 100 falls within 60 seconds or less.

  When the packet type determination unit 4 determines that the type of the received word is the replacement target type (here, the vehicle information packet) by the packet type determination unit 4 in the present embodiment, as shown in FIG. The bit string arranged in the area is replaced with the reserved area bit string stored in the memory M1. In addition, the substitution unit 5 is a latitude minute bit sequence in which the partial encoding unit 9 generates a bit sequence corresponding to degrees and minutes in a portion (latitude equivalent region) corresponding to the latitude region P2 in the communication packet before encoding. In the communication packet before encoding, in the portion (longitude equivalent region) corresponding to the longitude region P3, the bit string corresponding to degree and minute is replaced with the longitude minute bit string. Furthermore, the replacing unit 5 replaces the bit string corresponding to hour / minute with the hour / minute bit string in a portion (time stamp corresponding region) corresponding to the time stamp region P4 in the communication packet before encoding.

Summary of Second Embodiment
In the above configuration, when the communication device 100 acquires the received word corresponding to the communication packet (here, the vehicle information packet) that is the replacement target type, the replacing unit 5 determines the reservation equivalent area included in the received word, the latitude Each of the upper bits (degrees and minutes) of the equivalent area, the upper bits (degrees and minutes) of the longitude equivalent area, and the upper bits (hours and minutes) of the time stamp equivalent area is a reserved area bit string, Replace with latitude minute bit string, longitude minute bit string, time minute bit string.

  According to the above configuration, since the bit string arranged in the reservation corresponding area is replaced with the reservation area bit string to be originally observed in the reservation corresponding area, the bits generated in the reservation corresponding area as in the first embodiment It can be suppressed that the received communication packet is discarded due to an error.

  In addition, since the reservation corresponding area should be a fixed bit string, the content of the received vehicle information packet can be rewritten or damaged by replacing the bit string of the reservation corresponding area of the received word with the bit string for the reservation area. There is no risk of

  In addition, it is expected that the latitude and longitude of the current position of the communication device present in the range where inter-vehicle communication is performed and the latitude and longitude of the own vehicle coincide at the level of degree / minute. Therefore, by replacing the upper bits of the latitude equivalent area and the upper bits of the longitude equivalent area with the latitude and longitude degrees indicating the current position of the vehicle and the latitude and longitude bit strings generated based on the minutes, respectively. The risk of the content of the received vehicle information packet being rewritten or damaged is relatively small. In addition, since the latitude part bit string and the longitude part bit string are bit strings generated by the communication device 100 itself, the possibility that these bit strings include bit errors can be regarded as zero.

  Therefore, according to the above configuration, if a bit error occurs in the upper bits of the latitude equivalent region of the received word or the upper bits of the longitude equivalent region, the portion is corrected to a normal (no bit error) bit string It will be

  Furthermore, it is expected that the error of the time held by each communication device is within 60 seconds. Therefore, in the received vehicle information packet, the upper bits (bit strings corresponding to hours and minutes) of the area corresponding to the time stamp are replaced with the hour / minute bit string generated based on the current time obtained from the clock 81 of the own device. There is relatively little risk that information will be rewritten or lost. In addition, since the time-division bit string is a bit string generated by the communication device 100 itself, the possibility that this bit string contains a bit error can be regarded as zero.

  Therefore, according to the above configuration, when a bit error occurs in the upper bits of the time stamp corresponding area of the received word, the part is corrected to a normal bit string.

  That is, according to the configuration of the second embodiment, even if a bit error occurs not only in the reservation equivalent area of the received word but also in the high order bits of the latitude equivalent area, the longitude equivalent area, and the time stamp equivalent area, It is corrected (specifically, replaced) to a bit string assumed to be correct. Therefore, it is possible to further suppress the possibility that the communication packet is discarded due to a bit error occurring in the received word, as compared with the first embodiment.

Third Embodiment
Next, a third embodiment of the present invention will be described using the drawings. In addition, about the member which has the function same as the member of a structure of above-mentioned 1st Embodiment in the following, the same code | symbol is attached | subjected and the description is abbreviate | omitted. In addition, when only a part of the configuration is mentioned, the first embodiment described above and various modified examples can be applied to the other parts.

  The communication device 100 according to the third embodiment, as shown in FIG. 9, includes an error detection unit 10, an encoding unit 11, and a received word database (hereinafter referred to as “reception word” in addition to the respective units included in the communication device 100 according Word DB 12 is provided. The error detection unit 10 and the encoding unit 11 may be realized in software (that is, as a function provided by the CPU) or may be realized in hardware using circuit elements such as an IC. The received word DB 12 may be realized by a rewritable storage medium such as a RAM or a flash memory. Hereinafter, the configuration of the present embodiment will be described in more detail.

  First, the decoding unit 7 in the present embodiment provides the error detection unit 10 with a bit string obtained by decoding the received word provided from the selection unit 6 (that is, a received message). The error detection unit 10 determines whether the received message provided from the decoding unit 7 contains an error. The process performed by the error detection unit 10 may be included as part of the decoding process performed by the decoding unit 7.

  For example, if the error detection unit 10 detects a bit error using a known method such as a CRC (Cyclic Redundancy Check) method or a parity check method, for example, it determines that the received message contains an error. Good. Also, whether or not an error has occurred may be determined based on whether or not the bit pattern constituting the received message conforms to a predetermined format. In the case where it is determined that the predetermined format is not met, for example, the number of bits of the received message does not match the specified number of bits, or a state where a bit at a predetermined position should be observed (1/0 And so on. The error detection unit 10 corresponds to an error determination unit described in the claims.

  If it is determined that the received message contains an error as a result of the determination as to whether the received message contains an error, the received message is discarded. If it is determined that no error is included, the received message is provided to the encoding unit 11 and a protocol stack unit (not shown).

  The encoding unit 11 re-encodes the received message provided from the error detection unit 10 and stores it in the received word DB 12. For convenience, the bit string obtained by re-encoding the received message is referred to as a checked received word. This is because error correction is performed at the time of decoding, and the error detection unit 10 checks for the presence or absence of an error.

  The checked received word in the received word DB 12 is stored separately for each communication device corresponding to the transmission source of the received word. Specifically, as shown in FIG. 10, the bit string corresponding to the transmission source address (which is a transmission source address equivalent bit string) included in the checked received word is stored separately. Since the transmission source address equivalent bit string has a one-to-one correspondence with the communication device as the transmission source, storing the received word in association with the transmission source address equivalent bit string means that the communication device uses the received word as the transmission source It corresponds to storing in association with Further, consecutive numbers (referred to as item numbers) according to the order of arrangement of data are assigned to each communication device. In the present embodiment, each communication apparatus is identified by using a transmission source address equivalent bit string, but may be identified using a transmission source address obtained by decoding a received word.

  In addition, when storing each received word in the received word DB 12, in addition to the transmission source address corresponding bit string, the reception time and the received signal strength are also linked and stored. Note that data related to a communication apparatus that has not received a new received word for a predetermined time (for example, 30 seconds) may be deleted. The received word DB 12 corresponds to the received word storage unit described in the claims, and the checked received word corresponds to the received success word described in the claims.

  When the type of the non-replacement received word is not the replacement target type, the selection unit 6 in the present embodiment outputs the non-replaced received word to the decoding unit 7. In addition, even if the type of the non-replacement received word is the replacement target type, it is output to the decoding unit 7 once as it is. That is, when the demodulator 3 generates a received word, the received word is temporarily output to the decoder 7 to be decoded.

  Then, when an error is detected in the received message obtained by decoding the received word corresponding to the communication packet of the replacement target type, the replaced received word generated by the replacing unit 5 is output to the decoding unit 7.

  When an error is detected in the received message obtained by decoding the non-replacement received word corresponding to the communication packet of the replacement target type, the replacement unit 5 in the present embodiment is a transmission source address equivalent bit string of the non-replacement received word Using the received word DB 12 as a search key, the checked received word having the latest received time is extracted from the checked received words associated with the same transmission source.

  Then, among the bit strings constituting the non-replacement received word, the bit string arranged in the reserved corresponding area is replaced with the bit string arranged in the reserved corresponding area of the extracted checked received word. Further, among the bit strings constituting the non-replacement received word, the bit string corresponding to the degree / minute of the latitude equivalent area and the longitude equivalent area corresponds to the degree / minute of the latitude equivalent area and the longitude equivalent area of the extracted checked word Replace with a bit string

  Generally, in vehicle-to-vehicle communication, a vehicle information packet is transmitted every several hundreds of milliseconds, so it can be expected that the value for the degree of latitude and longitude remains the previous value. Therefore, a bit string corresponding to the degree / minute of the extracted checked latitude equivalent area functions as a latitude minute bit string in the second embodiment described above, and a bit string corresponding to the degree / minute of the checked checked longitude corresponding area Functions as a longitude minute bit.

  When a checked received word associated with the same transmission source is not stored in the received word DB 12, a series of processes for replacing and decoding the non-replaced received word is ended. In addition, when the substitution process is performed on the non-replacement received word, the fact that the substitution process has been performed is held in the internal state. For example, the replacing unit 5 holds the received word that is currently being handled using a flag (referred to as a replaced flag) or the like indicating whether the received word is a replaced received word.

<Operation of Communication Device 100 in Third Embodiment>
Next, a series of operations of the communication device 100 when a wireless signal from another vehicle is received will be described using the flowchart shown in FIG. Similar to the flowchart shown in FIG. 6, the flowchart shown in FIG. 11 may be started, for example, when the RF unit 1 receives a signal whose received signal strength is equal to or higher than a predetermined threshold. Note that at the start of this flow, it is assumed that the replacement flag is in a state (off state) indicating that the replacement process has not been performed.

  First, in step S201, the A / D converter 2 converts the signal received by the RF unit 1 into a digital signal, and the demodulator 3 demodulates the received signal digitized by the A / D converter 2. To generate a non-replaced received word. Then, the generated non-replacement received word is provided to the packet type determination unit 4, the replacement unit 5, and the selection unit 6, and the process proceeds to step S202.

  In step S202, the packet type determination unit 4 determines whether the type of the non-replacement received word is a replacement target type. If it is determined in step S202 that the type of the non-replacement received word is not the replacement target type, step S202 becomes NO and the process moves to step S203. On the other hand, if it is determined that the type of the non-replacement received word is the replacement target type, step S202 becomes YES and the process moves to step S205.

  In step S203, the decoding unit 7 generates a received message by decoding the non-replaced received word, and the process proceeds to step S204. In step S204, the error detection unit 10 determines whether the received message generated in step S203 includes an error. If it is determined that there is no error, the received message is output to the protocol stack unit. Finish. When an error is detected, the received message may be discarded.

  In step S205, the decoding unit 7 decodes the received word, generates a received message, and proceeds to step S206. Note that the received word handled in step S205 is a non-replaced received word or a replaced received word that corresponds to the communication packet of the replacement target type.

  In step S206, the error detection unit 10 determines whether an error exists in the received message generated in step S205. Then, when it is determined that there is no error, step S206 becomes NO and the process moves to step S207. On the other hand, if it is determined that there is an error, step S206 becomes YES and the process moves to step S210.

  In step S207, the error detection unit 10 outputs the received message to the protocol stack unit, and proceeds to step S208. In step S208, the encoding unit 11 generates a checked received word obtained by encoding the received message again, and proceeds to step S209. In step S209, the encoding unit 11 stores the checked received word generated in step S208 in association with the transmission source in the received word DB 12, and ends the present flow.

  In step S210, the substitution unit 5 determines whether or not the received word currently handled is a replaced received word. This determination may be made by the replacement completion flag. If it is determined based on the replaced flag that the received word currently being handled is a replaced received word, step S210 is YES and the present flow is ended. Moreover, when the received word currently handled is not a replaced received word, step S210 becomes NO and the process moves to step S211.

  In step S211, the substitution unit 5 searches the received word DB 12 using the bit string corresponding to the transmission source address included in the non-replaced received word as a search key, and there is a checked received word associated with the same transmission source It is determined whether or not. If there is a checked received word associated with the same transmission source, step S211 becomes YES and the process moves to step S212. On the other hand, if there is no checked received word associated with the same transmission source, step S211 is NO and the present flow ends.

  In step S212, the replacing unit 5 extracts, from the received word DB 12 among the checked received words associated with the same transmission source, the checked received word having the latest reception time, and proceeds to step S213. The replacement unit 5 that implements this step S212 corresponds to the received word acquisition unit described in the claims.

  In step S213, among the bit strings constituting the non-replacement received word, the replacing unit 5 extracts the bit string arranged in the reservation corresponding area and the bit string corresponding to the degree / minute of latitude and longitude, Is generated, and a replaced received word is generated by replacing the received received word with a bit string corresponding to degrees and minutes of latitude and longitude, and the process proceeds to step S214. In step S214, the replaced flag is set to a state (on state) indicating that the received word currently being handled is a replaced received word, and the process returns to step S205.

Summary of Third Embodiment
In the above configuration, the received word generated by the demodulator (that is, the non-replaced received word) is a received word corresponding to the communication packet (here, the vehicle information packet) that is the replacement target type (step S202 YES) If the received message obtained by decoding the non-replaced received word contains an error (YES in step S206), the latest checked received word received from the same source as the received word is used Perform replacement processing. Note that the case where an error is included in the received message obtained by decoding the non-replacement received word means that an uncorrectable bit error has occurred in the non-replacement received word.

  According to such a configuration, as in the second embodiment, not only the reservation corresponding area but also the part corresponding to the degree / minute of the latitude corresponding area or the part corresponding to the degree / minute of the longitude corresponding area It is possible to replace with an error-free bit string. As a result, it is possible to suppress the possibility that the received packet may be discarded due to bit errors occurring in each of the reservation corresponding area and the area corresponding to the degree of latitude and longitude. In other words, the reception success rate can be increased.

  Further, according to the above configuration, even if the type of the received word is the replacement target type, it is decoded once to generate the received message, and only when an error is detected in the received message (YES in step S206), In this embodiment, replacement processing is performed. Thereby, the processing load on the communication apparatus 100 can be reduced.

  Of course, as another aspect, in the case where the type of the received word is the substitution target type, the method may move to step S211 to try replacement processing. In such an aspect, if step S211 is YES and a replaced received word can be generated, the replaced received word is provided to the decoding unit 7, while step S211 is NO and the replacement process is performed. If it can not be applied, the received word may be provided to the decoding unit 7.

  Furthermore, in the above description, since the received word checked in the received word DB 12 is stored in association with the transmission source address equivalent bit string, the transmission source address equivalent bit string is used as a search key from the same transmission source as the received word received this time Although the aspect which extracts the received checked received word from received word DB12 was made, it does not restrict to this. In the case of storing the checked received word in the received word DB 12 in association with the transmission source address, from the same transmission source, using the transmission source address indicated in the received message obtained by decoding the non-replacement received word What is necessary is just to extract the checked completed received word.

Modified Example of Third Embodiment
In the third embodiment, among the latitude equivalent region and the longitude equivalent region of the non-replacement received word, an aspect in which a bit string corresponding to degree and minute is a target of replacement is illustrated, but the present invention is not limited thereto. For example, in the case where the communication apparatus 100 is provided with a traveling speed estimation unit that estimates the traveling speed of the transmission source of the non-replacement received word, based on the traveling speed (estimated speed) estimated by the traveling speed estimation unit. The area to be replaced may be expanded to a portion corresponding to seconds.

  Specifically, when the estimated speed is less than a predetermined threshold and can be regarded as 0 km / h (that is, while the vehicle is stopped), the area to be replaced in the area corresponding to the latitude and longitude is the degree, minute, and second. Do. This is because, since the transmission source is not moving, it is presumed that the second level should also match the information indicated in the previous received word in the latitude and longitude indicating the current position.

  When the estimated speed is equal to or higher than a predetermined threshold (for example, 3 km / h) and can be regarded as traveling, a bit string corresponding to degrees and minutes in the latitude equivalent area and the longitude equivalent area as in the second embodiment. As the target of substitution.

  The method for the traveling speed estimation unit to estimate the traveling speed of the transmission source may be, for example, from the time change of the position information included in the communication packet received from the transmission source until then. When the vehicle information packet is configured to include the traveling speed and the acceleration, the traveling speed of the transmission source may be estimated based on the traveling speed and the acceleration indicated in the latest received packet. Furthermore, as another aspect, the traveling speed estimation unit may regard the current traveling speed of the host vehicle as the traveling speed of the transmission source. Note that the traveling speed estimation unit does not have to estimate a specific traveling speed, as long as it can determine at least whether the transmission source is at a stop. The traveling speed estimation unit described above has a function of the replacement unit 5.

  According to the configuration of this modification, for example, at the time of traffic jam where the change of the position of the transmission source is small, the area to be replaced can be expanded, so the reception success rate can be further improved compared to the third embodiment. it can. In addition, since many vehicles exist in a relatively narrow area at the time of traffic congestion, it is predicted that packet interference will occur frequently and the reception success rate will decrease.

Fourth Embodiment
In the third embodiment and the variation thereof, the aspect of specifying the transmission source of the received word using the transmission source address equivalent bit string (or transmission source address) has been illustrated, but the present invention is not limited thereto. The device corresponding to the source may be identified by another method.

  The process (sender identification process) for identifying the sender of the received word corresponding to the newly received signal performed by the communication apparatus 100 in the fourth embodiment will be described below using the flowchart shown in FIG. explain. The flowchart shown in FIG. 12 is started when it is necessary to specify the same transmission source as the received word received this time to perform the substitution process described in the third embodiment, such as step S211 in FIG. 11, for example. Just do it.

  The configuration of the communication apparatus 100 in the present embodiment is the same as that of the third embodiment, and includes, for example, a received word DB 12 that stores data shown in FIG. Also, hereinafter, the received word corresponding to the newly received signal will be described as a new received word in order to distinguish it from the checked received word stored in the received word DB 12.

  First, in step S301, the integer i indicating the item number of the data to be referred to is set to 1, and the process proceeds to step S302. The integer i is a variable used to scan data for each communication device stored in the received word DB 12. In step S302, among the checked received words received from the communication apparatus of item number i, the checked received word having the latest reception time is read out, and the process proceeds to step S303.

  In step S303, the Hamming distance Ham (i) between the checked received word read out in step S302 and the newly received word is calculated, and the process proceeds to step S304. Here, the Hamming distance is a Hamming distance used in so-called information theory, and the calculation method may be a well-known method.

  In step S304, it is determined whether the Hamming distance Ham (i) calculated in step S303 is less than a predetermined threshold (referred to as a Hamming distance threshold) THham. The Hamming distance threshold THham is a threshold for determining whether or not the checked received word read out in step S302 is similar to the newly received word, and may be designed as appropriate. If the communication apparatus of item number i is the transmission source of the new received word, the checked received word read out in step S302 and the new received word have high similarity, and the Hamming distance Ham (i ) Is a relatively small value. That is, the Hamming distance Ham (i) can be used as a determination index as to whether or not the communication device of item number i is a source of a new received word.

  Then, if the Hamming distance Ham (i) is less than the Hamming distance threshold THham, step S304 becomes YES and the process proceeds to step S305, while if it is the Hamming distance threshold THham or more, step S304 is It becomes NO and moves to step S310.

  In step S305, from the history of the reception time of the checked received word stored in association with the communication apparatus of item number i, the time when the communication packet is next transmitted from the communication apparatus is predicted. Then, the reception time error ΔCyc (i), which is an error between the time when the new received word is received and the time when the new reception word is received, is calculated, and the process proceeds to step S306.

The reception time error ΔCyc (i) may be calculated by the following equation 1.
(Formula 1) ΔCyc (i) = (T1-T2)% Tcyc
T1 in the equation is the time when the newly received word is received, and T2 is the received time of the checked received word extracted in step S302. Also,% is a remainder operator, and Tcyc is an average transmission cycle of the vehicle information packet. The transmission cycle Tcyc may use a value (for example, 100 milliseconds) designed in advance as a network architecture for inter-vehicle communication, or the reception time of the checked received word stored in association with the item number i. It may be calculated dynamically from the interval.

  In step S306, it is determined whether the reception time error ΔCyc (i) is less than a predetermined threshold (which is a time error threshold) THcyc. The time error threshold THcyc is a threshold for determining whether or not the communication apparatus of item number i is a source of a new received word from the viewpoint of the transmission cycle Tcyc of the communication packet, and a specific value is appropriately determined. It should be designed. For example, when the transmission cycle Tcyc of the vehicle information packet is 100 milliseconds, the time error threshold THcyc may be set to 20 milliseconds or the like. If the communication device of item number i is the transmission source of a new received word, it can be expected that the reception time error ΔCyc (i) will be less than the time error threshold THcyc.

  If the reception time error ΔCyc (i) is less than the time error threshold THcyc, step S306 is YES and the process proceeds to step S307, while the reception time error ΔCyc (i) is greater than or equal to the time error threshold THcyc In the case, step S306 becomes NO and the process moves to step S310.

  In step S307, a reception strength difference ΔRSSI (i), which is the magnitude of the difference between the received signal strength of the checked received word extracted in step S302 and the received signal strength of the new received word, is calculated, and the process proceeds to step S308. .

  In step S308, it is determined whether the reception intensity difference ΔRSSI (i) is less than a predetermined threshold (referred to as an intensity difference threshold) THrssi. The intensity difference threshold value THrssi is a threshold value for determining whether the communication device of item number i is the transmission source of the received word received this time from the viewpoint of the received signal strength of the communication packet, and a specific value Should be designed appropriately. If the communication device of item number i is the transmission source of a new received word, the received intensity difference ΔRSSI (i) is likely to be less than the intensity difference threshold THrssi. This is because the possibility that the received signal strength of the communication packet transmitted as needed from the same transmission source changes rapidly is assumed to be small.

  If the received strength difference ΔRSSI (i) is less than the strength difference threshold THrssi, step S308 is YES and the process moves to step S309, whereas if the strength difference threshold THrssi is greater than or equal to step S308 is NO. And the process proceeds to step S310.

  In step S309, the communication apparatus of item number i is determined to be a transmission source of a new received word, and the present flow ends. This means that the communication device in which all of the Hamming distance Ham (i), the reception time error ΔCyc (i), and the reception intensity difference ΔRSSI (i) are less than a predetermined threshold is the source of the received word received this time It is because the possibility of being relatively high.

  In step S310, it is determined whether the variable i used as the item number is less than the maximum value N of the item number. The maximum value N of the item number is the number of communication devices registered in the received word DB 12 and is a number that schematically represents the number of other vehicles performing inter-vehicle communication with the own vehicle. When the variable i is less than the maximum value N, step S310 becomes YES and moves to step S311, and when i = N, step S310 becomes NO and the present flow ends. The case where step S310 is NO means that the communication device corresponding to the transmission source of the new received word can not be found among the communication devices registered in the received word DB 12. In step S311, 1 is added to the variable i and the process returns to step S302.

Summary of Fourth Embodiment
In the above configuration, using three indicators such as the Hamming distance Ham (i), the reception time error ΔCyc (i), and the reception intensity difference ΔRSSI (i), the communication device registered in the reception word DB 12 is new. The communication device corresponding to the sender of the received word is identified. That is, according to the above configuration, the communication device corresponding to the transmission source of the new reception word can be specified from the communication devices registered in the reception word DB 12 without using the transmission source address equivalent bit string. . Therefore, even when a bit error occurs in the transmission source address equivalent bit string, the transmission source of the newly received word can be specified.

  In the above configuration, when a communication device satisfying each condition is found before the variable i reaches the maximum value N, the communication device is adopted as a transmission source of the new received word, and the transmission source is selected. Although the aspect of terminating the search for the corresponding communication device is described, the present invention is not limited to this. The Hamming distance Ham (i), the reception time error ΔCyc (i), and the reception strength difference ΔRSSI (i) are calculated for all the communication devices from No. 1 to N, and the Hamming distance Ham (i), the reception time The sum of the error ΔCyc (i) and the reception strength difference ΔRSSI (i) (or the sum of the values obtained by squaring the sums) may be calculated, and the communication device with the smallest value may be adopted as the transmission source.

  Also, here, Hamming distance Ham (i), reception time error ΔCyc (i), reception intensity difference ΔRSSI (i) as an index for specifying a transmission source from various communication devices registered in reception word DB 12 Although the aspect which uses three indices of is illustrated, it does not restrict to this. The transmission source may be identified based on at least one of these three indicators. For example, the transmission source may be identified using two indicators of the Hamming distance Ham (i) and the reception time error ΔCyc (i).

100 communication apparatus, 1 RF unit (reception unit), 2 A / D conversion unit, 3 demodulation unit, 4 packet type determination unit, 5 replacement unit, 6 selection unit, 7 decoding unit, 8 state acquisition unit, 9 partial encoding 10 error detection unit (error determination unit) 11 encoding unit 12 received word database (received word storage unit) M1 memory (storage unit) 81 clock 82 GNSS receiver S212 received word acquisition unit

Claims (10)

A communication device for receiving a communication packet in a predetermined format wirelessly transmitted from another device, the communication device comprising:
The communication packet includes a type information area in which at least information indicating the type of the communication packet is stored, and a transmission source information area in which transmission source information representing a transmission source that is a device that has transmitted the communication packet is arranged. , Has a format to prepare at a predetermined position ,
A receiver (1) for receiving a signal in a frequency band used for wireless communication with the other device;
A demodulator (3) for generating a received word which is a bit string corresponding to the received signal by demodulating the signal received by the receiver;
A packet type determination unit (4) that determines whether or not the type of communication packet corresponding to the received word generated by the demodulation unit is a predetermined replacement target type;
In the case where it is determined by the packet type determination unit that the type of the communication packet corresponding to the received word is the replacement target type, a portion of the bit string constituting the received word that is previously set as the target of replacement A replacing unit (5) that generates a replaced received word in which a certain replacement target area is replaced with a predetermined replacement bit string;
A decoding unit (7) configured to decode the replaced received word generated by the replacement unit and to also decode a received word that has not been replaced by the replacement unit ;
An error determination unit (10) that determines whether or not an error has occurred in a received message that is a bit string generated by decoding the received word by the decoding unit;
A received word storage unit (12) which stores the received word corresponding to the received message determined to have no error by the error judging unit as a reception success word in association with information indicating the transmission source of the received word;
In the case where the demodulation unit generates a new received word, and the type of a communication packet corresponding to a newly received word that is the newly generated received word is the replacement target type by the packet type determination unit And a received word acquisition unit (5S212) for acquiring from the received word storage unit the received success word received from the same transmission source as the newly received word when it is determined that there is a received word .
The replacement bit string is a bit string when no bit error occurs in the replacement target area, and
The communication packet as the replacement target type is a communication packet including a position information area in which position information indicating the latitude and longitude as the current position of the transmission source is arranged at a predetermined position.
A bit string corresponding to the degree and the minute of the position information area in the received word corresponding to the communication packet of the replacement target type is set as the replacement target area,
The communication apparatus , wherein the replacement unit is configured to replace the replacement target area of the new received word with the replacement target area of the reception success word acquired by the received word acquisition unit . A communication device for receiving a communication packet in a predetermined format wirelessly transmitted from another device, the communication device comprising:
The communication packet includes a type information area in which at least information indicating the type of the communication packet is stored, and a transmission source information area in which transmission source information representing a transmission source that is a device that has transmitted the communication packet is arranged. , Has a format to prepare at a predetermined position ,
A receiver (1) for receiving a signal in a frequency band used for wireless communication with the other device;
A demodulator (3) for generating a received word which is a bit string corresponding to the received signal by demodulating the signal received by the receiver;
A packet type determination unit (4) that determines whether or not the type of communication packet corresponding to the received word generated by the demodulation unit is a predetermined replacement target type;
In the case where it is determined by the packet type determination unit that the type of the communication packet corresponding to the received word is the replacement target type, a portion of the bit string constituting the received word that is previously set as the target of replacement A replacing unit (5) that generates a replaced received word in which a certain replacement target area is replaced with a predetermined replacement bit string;
A decoding unit (7) configured to decode the replaced received word generated by the replacement unit and to also decode a received word that has not been replaced by the replacement unit ;
An error determination unit (10) that determines whether or not an error has occurred in a received message that is a bit string generated by decoding the received word by the decoding unit;
A received word storage unit (12) which stores the received word corresponding to the received message determined to have no error by the error judging unit as a reception success word in association with information indicating the transmission source of the received word;
In the case where the demodulation unit generates a new received word, and the type of a communication packet corresponding to a newly received word that is the newly generated received word is the replacement target type by the packet type determination unit And a received word acquisition unit (5S212) for acquiring from the received word storage unit the received success word received from the same transmission source as the newly received word when it is determined that there is a received word .
The replacement bit string is a bit string when no bit error occurs in the replacement target area, and
The substitution unit is
The transmission source of the new received word is specified based on the Hamming distance between the new received word and the received success word stored in the received word storage unit,
A communication apparatus configured to replace the replacement target area of the new received word with the replacement target area of the reception success word acquired by the received word acquisition unit . A communication device for receiving a communication packet in a predetermined format wirelessly transmitted from another device, the communication device comprising:
The communication packet includes a type information area in which at least information indicating the type of the communication packet is stored, and a transmission source information area in which transmission source information representing a transmission source that is a device that has transmitted the communication packet is arranged. , Has a format to prepare at a predetermined position ,
A receiver (1) for receiving a signal in a frequency band used for wireless communication with the other device;
A demodulator (3) for generating a received word which is a bit string corresponding to the received signal by demodulating the signal received by the receiver;
A packet type determination unit (4) that determines whether or not the type of communication packet corresponding to the received word generated by the demodulation unit is a predetermined replacement target type;
In the case where it is determined by the packet type determination unit that the type of the communication packet corresponding to the received word is the replacement target type, a portion of the bit string constituting the received word that is previously set as the target of replacement A replacing unit (5) that generates a replaced received word in which a certain replacement target area is replaced with a predetermined replacement bit string;
A decoding unit (7) configured to decode the replaced received word generated by the replacement unit and to also decode a received word that has not been replaced by the replacement unit ;
An error determination unit (10) that determines whether or not an error has occurred in a received message that is a bit string generated by decoding the received word by the decoding unit;
A received word storage unit (12) which stores the received word corresponding to the received message determined to have no error by the error judging unit as a reception success word in association with information indicating the transmission source of the received word;
In the case where the demodulation unit generates a new received word, and the type of a communication packet corresponding to a newly received word that is the newly generated received word is the replacement target type by the packet type determination unit And a received word acquisition unit (5S212) for acquiring from the received word storage unit the received success word received from the same transmission source as the newly received word when it is determined that there is a received word .
The replacement bit string is a bit string when no bit error occurs in the replacement target area, and
The reception success word is stored separately for each transmission source in the reception word storage unit, and is stored in association with the time when the reception success word is received,
The substitution unit is
The transmission source of the new reception word is specified based on the reception time of the new reception word and the reception time of the reception success word for each transmission source stored in the reception word storage unit,
A communication apparatus configured to replace the replacement target area of the new received word with the replacement target area of the reception success word acquired by the received word acquisition unit . A communication device for receiving a communication packet in a predetermined format wirelessly transmitted from another device, the communication device comprising:
The communication packet includes a type information area in which at least information indicating the type of the communication packet is stored, and a transmission source information area in which transmission source information representing a transmission source that is a device that has transmitted the communication packet is arranged. , Has a format to prepare at a predetermined position ,
A receiver (1) for receiving a signal in a frequency band used for wireless communication with the other device;
A demodulator (3) for generating a received word which is a bit string corresponding to the received signal by demodulating the signal received by the receiver;
A packet type determination unit (4) that determines whether or not the type of communication packet corresponding to the received word generated by the demodulation unit is a predetermined replacement target type;
In the case where it is determined by the packet type determination unit that the type of the communication packet corresponding to the received word is the replacement target type, a portion of the bit string constituting the received word that is previously set as the target of replacement A replacing unit (5) that generates a replaced received word in which a certain replacement target area is replaced with a predetermined replacement bit string;
A decoding unit (7) configured to decode the replaced received word generated by the replacement unit and to also decode a received word that has not been replaced by the replacement unit ;
An error determination unit (10) that determines whether or not an error has occurred in a received message that is a bit string generated by decoding the received word by the decoding unit;
A received word storage unit (12) which stores the received word corresponding to the received message determined to have no error by the error judging unit as a reception success word in association with information indicating the transmission source of the received word;
In the case where the demodulation unit generates a new received word, and the type of a communication packet corresponding to a newly received word that is the newly generated received word is the replacement target type by the packet type determination unit And a received word acquisition unit (5S212) for acquiring from the received word storage unit the received success word received from the same transmission source as the newly received word when it is determined that there is a received word .
The replacement bit string is a bit string when no bit error occurs in the replacement target area, and
The reception success word is stored separately for each transmission source in the reception word storage unit, and is stored in association with the received signal strength of the reception signal that is the source of the reception success word. ,
The substitution unit is
The transmission source of the new received word is specified based on the received signal strength of the new received word and the received signal strength of the received success word stored in the received word storage unit,
A communication apparatus configured to replace the replacement target area of the new received word with the replacement target area of the reception success word acquired by the received word acquisition unit . In any one of claims 2 to 4 ,
The communication packet as the replacement target type has a format including, at a predetermined position, a position information area in which position information indicating the latitude and longitude as the current position of the transmission source is arranged,
A communication apparatus characterized in that a bit string corresponding to the degree and the minute of the position information area in the received word corresponding to the communication packet of the substitution object type is set as the substitution object area. In claim 1 or 5 ,
The substitution unit is
Based on the information indicated in the reception success word stored in the reception word storage unit, it is determined whether the transmission source of the new reception word is moving or not.
When it is determined that the transmission source of the new received word has not moved, the received word acquisition unit acquires a bit string corresponding to the degree, the minute, and the second of the position information area in the new received word. A communication apparatus characterized by replacing the position information area in the reception success word with a bit string corresponding to the degree, minute, and second. In claim 3 or 4 ,
A communication apparatus characterized in that the substitution unit specifies a transmission source of the new reception word based on a Hamming distance between the new reception word and the reception success word stored in the reception word storage unit. . In claim 4 ,
The reception success word is stored separately in the reception word storage unit for each transmission source, and is stored in association with the time when the reception success word is received,
The substitution unit specifies a transmission source of the new reception word based on the reception time of the new reception word and the reception time of the reception success word for each transmission source stored in the reception word storage unit. A communication device characterized by In any one of claims 1 to 8 ,
The communication packet of the replacement target type has a format in which a reserved area in which a bit string of a fixed pattern is arranged is provided at a predetermined position in addition to the type information area,
A portion corresponding to the reserved area in the received word is set as the replacement target area, and
A storage unit (M1) storing a reserved area bit string obtained by encoding a bit string arranged in the reserved area;
When the packet type determination unit determines that the type of the communication packet corresponding to the received word is the replacement target type, the replacement unit corresponds to the reserved area in the bit string constituting the received word. A communication apparatus characterized by replacing the portion to be stored with the reserved area bit string stored in the storage unit. In any one of claims 1 to 9 ,
The communication device is a communication device for performing inter-vehicle communication.

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