JP4869131B2 - Communication device - Google Patents

Description

  The present invention relates to a communication device applied to ITS (Intelligent Transport System), and more particularly to a communication device that realizes road-to-vehicle communication and vehicle-to-vehicle communication that do not interfere with each other in the same frequency band.

  In ITS (Intelligent Transport Systems), 5.775 GHz to 5.845 GHz is allocated as a use frequency, and road-to-vehicle communication is currently performed using this frequency band. Further, for the future, studies are underway to use this frequency band in inter-vehicle communication.

  For example, ETC (Electronic Toll Collection Systems) / DSRC (Dedicated Short Range Communications) is widely used as current road-to-vehicle communication using the above frequency band. Since this ETC / DSRC is used for a billing service, high communication quality is required. As an example, in automatic toll collection on a highway, measures such as using different frequencies are taken to avoid interference with adjacent (or nearby) toll gates.

  Here, in the case of realizing road-to-vehicle communication and inter-vehicle communication using the same frequency band, as a method for avoiding interference between road-to-vehicle communication and inter-vehicle communication, for example, a method described in Patent Document 1 below is used. Exists. In this method, the length of the data packet in inter-vehicle communication is less than the slot length specified in the road-to-vehicle communication method, and interference avoidance is realized by using unused slots that are not used for road-to-vehicle communication. Yes.

  As another method, there is a method described in Patent Document 2 below. In this method, inter-vehicle communication is performed using a channel that is not used for road-to-vehicle communication among a plurality of channels defined for road-to-vehicle communication, and a frame control slot (FCMC) used for road-to-vehicle communication is set. By detecting it, it is discriminated whether it is a road-vehicle communication area. And when it is judged that it is a road-vehicle communication area, interference is avoided by changing the channel used for vehicle-to-vehicle communication as needed.

  Since inter-vehicle communication requires transmission at an arbitrary timing, unlike road-to-vehicle communication, CSMA / CA (Carrier Sense Multiplex) is used to detect an empty channel by carrier sense and perform transmission when the channel is free. It has been studied based on a method called “Access with Collision Avoidance”. In this case, since there is leakage power to the adjacent channel, it may be erroneously determined as a used channel in carrier sense even though it is actually an empty channel. As a conventional technique for avoiding this erroneous determination, for example, there is a technique described in Patent Document 3 below. In the technique described in Patent Document 3 below, a used channel number is also transmitted at the time of transmission, and a false detection is determined by collating the used channel number with an empty channel number on the receiving side.

  Furthermore, in the following Patent Document 4, in a system that performs spread spectrum in which a plurality of communications are multiplexed at the same frequency using a spread code, there is a method for determining whether or not confidence transmission is possible by combining a carrier sense signal and a synchronization signal. Proposed. This method uses the fact that different systems have different spreading codes and cannot synchronize. If there is a signal that exceeds the carrier sense, it is determined that it is being used by another system and communication is performed. I am trying not to.

JP 2000-165313 A JP 2000-201103 A JP-A-5-110522 Japanese Patent Laid-Open No. 11-112469

  However, the conventional techniques described above have the following problems. In other words, the method described in Patent Document 1 has a problem in that only a free portion of road-to-vehicle communication can be used, so that the line capacity cannot be increased and vehicle-to-vehicle communication cannot be performed at an arbitrary timing. .

  Further, in the method described in Patent Document 2, since the determination is performed only by the FCMC, it is not possible to determine the road-to-vehicle communication area during the period in which the FCMC is transmitted, and until the FCMC is received. Had the problem of being unable to communicate between cars.

  Further, the method described in Patent Document 3 has a problem that it is necessary to insert a use channel number into a transmission signal, and it cannot be applied to a system that cannot have such a frame configuration.

  In addition, the method described in Patent Document 4 has a problem that, even though the channel is actually an empty channel, carrier sense is activated by the leakage power to the adjacent channel, and the channel is erroneously determined. It was.

  The present invention has been made in view of the above, and in a wireless communication system that performs road-to-vehicle communication and vehicle-to-vehicle communication using the same frequency band, road-to-vehicle communication requires higher communication quality than vehicle-to-vehicle communication. In this case, an object of the present invention is to obtain a communication device that starts vehicle-to-vehicle communication in a shorter time than before while avoiding interference with road-to-vehicle communication.

  It is another object of the present invention to provide a communication device that avoids interference with inter-vehicle communication when inter-vehicle communication requires higher communication quality than road-to-vehicle communication.

  In order to solve the above-described problems and achieve the object, the present invention performs inter-vehicle communication using an unused channel among a plurality of communication channels mounted on a vehicle and assigned for road-to-vehicle communication. A communication device that compares candidate selection means for selecting a communication channel candidate to be used for inter-vehicle communication from a plurality of usable communication channels, and compares a received signal level in the communication channel candidate with a predetermined threshold value. , Carrier sense means for determining whether or not the communication channel candidate is unused, and determination for demodulating a received signal in the communication channel candidate and determining whether or not the communication channel candidate is used in road-to-vehicle communication Demodulation means for outputting a demodulated signal including information, and determining whether confirmation processing of the determination information is necessary based on the carrier sense result and confirming Determining means for determining whether it is possible to the inter-vehicle communication using the communication channel candidates when management is determined to be necessary, characterized in that it comprises a.

  According to the present invention, UW used in road-to-vehicle communication is detected while performing carrier sense of a channel selected as a candidate for inter-vehicle communication, and the candidate channel is used for road-to-vehicle communication using the UW detection result. Therefore, it can be determined at high speed whether the candidate channel is used in road-to-vehicle communication, and communication between vehicles is avoided while avoiding interference with the road-to-vehicle communication system. There is an effect that it is possible to shorten the time until start of transmission (until transmission is started).

  Embodiments of a communication apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a first embodiment of a communication device according to the present invention. This communication device includes a transmission antenna 1, a reception antenna 2, a road-to-vehicle communication unit 3, an inter-vehicle communication unit 4, a CS unit (carrier sense unit) 5, a communication determination unit 6, a data processing unit 7, Further, the road-vehicle communication unit 3 includes a modulation unit 31 and a demodulation unit 32, and the vehicle-to-vehicle communication unit 4 includes a modulation unit 41 and a demodulation unit 42. The communication device according to the present invention is mounted on a vehicle such as an automobile (used as an on-vehicle device).

  The road-to-vehicle communication unit 3 modulates the received transmission signal in the modulation unit 31 in accordance with an instruction from the data processing unit 7 and transmits it to the communication device installed on the road serving as the destination via the transmission antenna 1. . The modulated signal received via the receiving antenna 2 is demodulated by the demodulator 32 and output to the communication discriminator 6 and the data processor 7.

  The inter-vehicle communication unit 4 modulates the received transmission signal in the modulation unit 41 in accordance with an instruction from the data processing unit 7 and transmits it to the communication device (on-vehicle device) serving as the destination via the transmission antenna 1. Also, the modulation signal received via the receiving antenna 2 is demodulated by the demodulation unit 42 and output to the data processing unit 7.

  The CS unit 5 obtains the level of the signal (channel) received via the receiving antenna 2 and compares the obtained received signal level with a predetermined threshold value to determine whether the channel can be used (others Whether the communication is in use or not) and outputs a determination result (carrier sense result) to the communication determination unit 6 at the subsequent stage.

  The communication determination unit 6 corresponding to the determination unit selects and determines a channel to be used for inter-vehicle communication based on input signals from the demodulation unit 4 and the CS unit 5. Specifically, it is confirmed whether or not the carrier sense result received from the CS unit 5 indicates carrier detection (channel in use). If it is not carrier detection (when no carrier is detected), the channel further performs road-to-vehicle communication. It is determined based on the input signal from the demodulator 32 whether or not it is used. If the channel is not used for road-to-vehicle communication, the channel is selected and determined as a channel to be used for vehicle-to-vehicle communication.

  The data processing unit 7 corresponding to the candidate selection unit controls the road-to-vehicle communication unit 3 and the vehicle-to-vehicle communication unit 4 and performs processing for realizing various applications.

  FIG. 2 is a channel layout diagram showing the current channel usage status in the 5.8 GHz band allocated for ITS. In FIG. 2, “bus location” is an abbreviation for bus location service. D1 and U1 represent downlink channel number 1 and uplink channel number 1, respectively. Currently, 7 channels are assigned to both uplink and downlink. Moreover, the channel (D6, U6) with the number 6 is unused in both the downlink and the uplink.

  FIG. 3 shows a frame format used in ETC / DSRC. In FIG. 3, PR is a preamble part used for initial acquisition in a demodulator (corresponding to demodulator 32 of the communication apparatus according to the present invention), and a unique word (UW) is a known pattern for finding the head of data. UW is also used to identify a communication channel. DATA is a data portion for road-to-vehicle communication.

  Here, in the standard “ARIB STD-T75 1.3 edition narrow area communication (DSRC) system” (developed in November 2005) defined by the Japan Radio Industry Association, FCMC ( Four types of communication channels are defined: Frame Control Message Channel), MDC (Message Data Channel), ACCC (Ack Channel), and ACTC (Activation Channel).

  “FCMC” is a channel for channel control, “MDC” is a channel for data communication, “ACKC” is a channel for response confirmation, and “ACTC” is a channel for requesting communication allocation. Regarding UW, three types of “UW1”, “UW2A”, and “UW2B” as shown in FIG. 4 are prepared corresponding to these four types of communication channels. UW1 is a unique word used in FCMC. UW2A is a unique word used in ACTC and ACCC. UW2B is a unique word used in MDC.

  Next, the operation of the communication apparatus according to the present invention will be described with reference to the drawings. Here, in the following description, it is assumed that road-to-vehicle communication operates according to “ARIB STD-T75” and operates by TDMA (Time Division Multiple Access), and further, vehicle-to-vehicle communication operates by CSMA / CA. In addition, for simplicity of explanation, road-to-vehicle communication can use only channels D1 / U1, D2 / U2, D5 / U5, D7 / U7, and vehicle-to-vehicle communication can use all channels. And Further, it is assumed that road-to-vehicle communication is required to have higher communication quality than vehicle-to-vehicle communication.

  FIG. 5 is a diagram illustrating an example of a result of carrier sense executed by a communication device (hereinafter referred to as an onboard device) mounted on a vehicle prior to the start of inter-vehicle communication. FIG. 6 is a diagram illustrating a configuration example of a communication frame used when full-duplex communication is performed in road-to-vehicle communication. FIG. 7 is a diagram illustrating a communication frame used when half-duplex communication is performed in road-to-vehicle communication. It is a figure which shows the example of a structure. The communication frame is composed of three types of slots as shown in FIGS.

  In the communication frames shown in FIGS. 6 and 7, FCMS (Frame Control Message Slot) is a frame control information multiplexing slot, and one exists at the head of the frame. Further, it is composed of the FCMC described above. MDS (Message Data Slot) is a slot for data communication, and is configured by the above-described MDC and ACKC. ACTS (Activation Slot) is a slot for requesting communication allocation, and is composed of the above-described ACTC.

  FIG. 8 is a flowchart showing an example of an operation for selecting and determining a communication channel used by the communication apparatus (vehicle-mounted device) according to the present invention for inter-vehicle communication. FIG. 9 shows the communication channel selection determining operation along the time axis. FIG. Note that “CS” shown in FIG. 9 indicates a state in which carrier sense is being executed. Here, as an example, an operation when searching for an empty channel (used channel) in the order of D4 (5790 MHz) → D5 (5785 MHz) → D6 (5780 MHz) will be described. Each channel is already assigned to the use shown in FIG. 2, and the carrier sense result of each channel is assumed to be the one shown in FIG.

  When there is a request for the start of inter-vehicle communication, the data processing unit 7 uses a channel that can be used for inter-vehicle communication (channel allocated for inter-vehicle communication in the system, etc., hereinafter referred to as “inter-vehicle communication selectable channel”). Is selected as a candidate channel for the inter-vehicle communication channel (steps S11 and S12). In this example, D4 is selected and set as a candidate channel.

  Next, the CS unit 5 performs carrier sense for the candidate channel (D4 in this example) set in step S12, and notifies the communication determination unit 6 of the result (step S13). The communication determination unit 6 determines whether or not the candidate channel is usable based on the carrier sense result notified from the CS unit 5. Specifically, first, it is determined whether or not the notified carrier sense result indicates that no carrier is detected in the candidate channel, that is, whether or not the candidate channel is in use based on the received signal power (or strength) in the candidate channel. It is confirmed whether or not it is less than or equal to a threshold value for performing (step S14). If the received signal power in the candidate channel is equal to or less than the threshold value (Yes in step S14), it is determined that this candidate channel can be selected. Here, when the received signal power is close to the threshold value, there is a possibility that it is actually in use even if the carrier is not detected. Therefore, in the present invention, in parallel with the carrier sense in the CS unit 5, the signal received by the demodulation unit 32 on the candidate channel is demodulated. If it is determined in step S14 that the received signal power in the candidate channel is less than or equal to the threshold value, the candidate channel is further used for road-to-vehicle communication using the demodulated signal output from the demodulator 32. It is confirmed whether it has been done (step S16). If the candidate channel is not used in road-to-vehicle communication (step S16, No), it is determined that the candidate channel is usable.

  In step S16, it is determined whether or not the candidate channel is usable, for example, using UW as shown in FIG. That is, different UWs are used for road-to-vehicle communication and inter-vehicle communication, and the received signal is demodulated in parallel with the carrier sense in the CS unit 5. If the demodulated signal includes road-to-vehicle communication UW, it is determined that the candidate channel is used in road-to-vehicle communication. Otherwise, it is determined that the candidate channel is not used in road-to-vehicle communication. Since at least one UW exists in the slots shown in FIGS. 6 and 7, it is possible to determine whether or not the communication is road-to-vehicle communication at high speed.

  On the other hand, when it is determined in step S14 that the received signal power in the candidate channel (D4) exceeds the threshold (No in step S14), the communication determination unit 6 determines that the candidate channel is unusable. Judgment is made and the data processor 7 is requested to change the setting of the candidate channel. Receiving this, the data processing unit 7 selects any one of the remaining vehicle-to-vehicle communication selectable channels instead of the candidate channel set in step S12 (D5 is selected in this example), The channel is reset as a candidate channel for the inter-vehicle communication channel (step S15). When step S15 is executed and candidate channels are reset, steps S13 and S14 described above are executed for the reset candidate channel (D5 in this example).

  If it is determined in step S16 that the candidate channel is used in road-to-vehicle communication (step S16, Yes), the communication determination unit 6 determines that the candidate channel is unusable and sets the candidate channel. Is requested to the data processing unit 7 to be changed. The data processing unit 7 that has received the candidate channel setting change request executes step S15 described above. After step S15 is executed, steps S13 and S14 described above are executed for the candidate channel after resetting.

  When it is determined in step S16 that the candidate channel is not used for road-to-vehicle communication (step S16, No), the communication device starts inter-vehicle communication using the candidate channel (step S17).

  In this example, the carrier sense result in step S13 is the one shown in FIG. 5, and the received power in channel D4 is equal to or greater than the threshold (carrier detection). Therefore, in step S14, the communication determination unit 6 It judges that the candidate channel D4 cannot be used, and requests the data processing unit 7 to change the setting of the candidate channel. Upon receiving the candidate channel setting change request, the data processing unit 7 changes the candidate channel setting to D5. Then, steps S13 and S14 for D5 are executed. In the example shown in FIG. 5, the received power at D5 is less than the threshold value (carrier not detected), and step S16 (check whether D5 is used in road-to-vehicle communication) for D5 is executed. The In this example, since D5 is used for the bus location service with road-to-vehicle communication, UW for road-to-vehicle communication is detected in step S16. Therefore, the communication determination unit 6 determines that the candidate channel D5 is unusable, and requests the data processing unit 7 again to change the setting of the candidate channel.

  Upon receiving the candidate channel setting change request, the data processing unit 7 changes the candidate channel setting to D6. Then, steps S13 and S14 for D6 are executed. In the example shown in FIG. 5, the received power at D6 is less than the threshold value (carrier not detected), and UW for road-to-vehicle communication is not detected at step S16 targeting D6. Therefore, the communication determination unit 6 determines that the candidate channel D6 can be used, and notifies the data processing unit 7 to that effect. Receiving the notification that the candidate channel D6 is usable, the data processing unit 7 permits the modulation unit 41 for inter-vehicle communication to transmit using the channel D6.

  In the present embodiment, as an example, a case where interference avoidance of inter-vehicle communication to road-to-vehicle communication has been described has been described, but it is also the same to prevent road-to-vehicle communication from interfering with inter-vehicle communication. This procedure is possible. Further, the case where the communication determination unit 6 determines whether or not the candidate channel is used for road-to-vehicle communication using the demodulated signal output from the demodulation unit 32 for road-to-vehicle communication has been described. It may be determined using the demodulated signal output from the communication demodulator 42 whether the candidate channel is used for road-to-vehicle communication. Further, both road-to-vehicle communication and vehicle-to-vehicle communication are detected using both of the demodulated signals output from the demodulation units 32 and 42, and whether the candidate channel is used for road-to-vehicle communication using the detection results of both. Judgment may be made.

  Moreover, in this Embodiment, although the case where the communication apparatus (vehicle equipment) was provided with the road-to-vehicle communication part 3 and the vehicle-to-vehicle communication part 4 was demonstrated as an example, road-to-vehicle communication and vehicle-to-vehicle communication are performed simultaneously. When there is not, it is good also as a structure which integrated the road-to-vehicle communication part 3 and the vehicle-to-vehicle communication part 4 into one. In this case, the configuration of the communication device is as shown in FIG. The communication apparatus shown in FIG. 10 includes a transmission antenna 1, a reception antenna 2, a CS unit 5, a communication determination unit 6a, a data processing unit 7a, and a communication unit 8, and the communication unit 8 performs modulation. A unit 81 and a demodulation unit 82 are provided. The CS unit 5 obtains the level of the received signal (channel) and determines whether the channel is in use. The communication determination unit 6a selects and determines a channel to be used for inter-vehicle communication based on input signals from the demodulation unit 4 and the CS unit 5. The data processing unit 7a controls the communication unit 8 and performs processing for realizing various applications. The communication unit 8 integrates the road-to-vehicle communication unit 3 and the vehicle-to-vehicle communication unit 4 of the communication apparatus shown in FIG. 1 and is used in both cases of road-to-vehicle communication and vehicle-to-vehicle communication.

  As described above, in the present embodiment, UW used in road-to-vehicle communication is detected while performing carrier sense of a channel selected as a candidate for inter-vehicle communication, and the UW detection result is used to detect the candidate. It was decided to determine whether the channel is used for road-to-vehicle communication. As a result, it can be determined at high speed whether or not the candidate channel is used in road-to-vehicle communication. In addition to avoiding interference with the road-to-vehicle communication system, until the vehicle-to-vehicle communication is started (transmission is started). Can be shortened, and the system capacity can be increased.

  In addition, since it is determined whether the candidate channel is used for road-to-vehicle communication or vehicle-to-vehicle communication from the detection result of UW, erroneous detection of carrier sense due to leakage power to the adjacent channel can be suppressed.

Embodiment 2. FIG.
In the first embodiment described above, in parallel with the process of obtaining the power (or strength) of the received signal in the processing target (candidate channel) performed by the CS unit 5, the communication determination unit 6 is a demodulating unit for road-to-vehicle communication. Using the demodulated signal output from 32, it is determined whether or not the candidate channel is used for road-to-vehicle communication. In this case, the in-vehicle device determines whether or not the final transmission is possible until the UW is output from the demodulation unit 32 even though the CS unit 5 has determined whether or not transmission is possible by carrier sense. There is a problem that you can not. For this reason, in this embodiment, a communication apparatus that can determine whether transmission is possible or not by preparing a plurality of threshold values will be described. The configuration of the communication apparatus according to the present embodiment is the same as that of the communication apparatus according to the first embodiment described above.

  FIG. 11 is a diagram illustrating an example of a relationship between a carrier sense result in the CS unit 5 and two types of threshold values for determining whether transmission is possible. FIG. 12 is a flowchart showing an example of an operation for selecting and determining a communication channel used for inter-vehicle communication by the communication device (vehicle equipment) according to the second embodiment, and FIG. It is a figure for demonstrating along. In FIG. 12, the same processes as those described in the flowchart (see FIG. 8) showing the operation of the first embodiment are denoted by the same step numbers and the description thereof is omitted. Further, “CS” shown in FIG. 13 indicates a state in which carrier sense is being executed.

  In the present embodiment, it is determined whether or not the candidate channel is used for inter-vehicle communication using the first threshold value (corresponding to threshold value # 1 shown in FIG. 11). Whether or not the channel is used for road-to-vehicle communication is determined using a second threshold value (corresponding to threshold value # 2 shown in FIG. 11) different from the first threshold value. An example of the case will be described. As in the first embodiment, road-to-vehicle communication can use only channels D1 / U1, D2 / U2, D5 / U5, D7 / U7, and vehicle-to-vehicle communication can use all channels. To do. An operation when searching for an empty channel (used channel) in the order of D4 (5790 MHz) → D5 (5785 MHz) → D6 (5780 MHz) will be described. Further, it is assumed that road-to-vehicle communication is required to have higher communication quality than vehicle-to-vehicle communication.

  As in the case of the first embodiment, after executing steps S11 to S13, the communication determination unit 6 of the vehicle-mounted device (communication device) of the present embodiment, based on the carrier sense result notified from the CS unit 5, Determine whether a candidate channel is available. Specifically, first, it is confirmed from the notified carrier sense result whether the candidate channel is used in inter-vehicle communication. Here, the carrier sense result indicates that “the received signal power (or strength) in the candidate channel is equal to or less than threshold value # 1 (threshold value for determining whether or not the candidate channel is used for inter-vehicle communication)”. Is confirmed (step S14a). If the received signal power in the candidate channel is equal to or less than threshold value # 1 (step S14a, Yes), it is determined that the candidate channel is not used for inter-vehicle communication, and the candidate channel is used for road-to-vehicle communication. Check if it is. Here, the carrier sense result is “the received signal power (or strength) in the candidate channel is equal to or less than threshold value # 2 (threshold value for determining whether the candidate channel is used in road-to-vehicle communication)”. It is confirmed whether or not this is indicated (step S21). If the received signal power in the candidate channel is equal to or less than threshold value # 2 (Yes in step S21), it is determined that the candidate channel is not used in road-to-vehicle communication, and the candidate channel is usable. to decide.

  On the other hand, if it is determined in step S14a that the signal power in the candidate channel exceeds the threshold (No in step S14a), the communication determination unit 6 uses the candidate channel because it is used in inter-vehicle communication. It judges that it is impossible, and requests the data processing unit 7 to change the setting of the candidate channel. In response to this, the data processing unit 7 selects any one of the remaining vehicle-to-vehicle communication selectable channels (in this example, D5 is selected) instead of the candidate channel set in step S12. The channel is reset as a candidate channel for communication (step S15). When step S15 is executed and the candidate channel is reset, steps S13 and S14a are executed for the reset candidate channel.

  If it is determined in step S21 that the signal power in the candidate channel (D4) exceeds the threshold value # 2 (step S21, No), is the candidate channel used in road-to-vehicle communication? It is confirmed whether or not (step S16). When the candidate channel is not used in road-to-vehicle communication (step S16, No), it is determined that the candidate channel can be used in vehicle-to-vehicle communication. On the other hand, when the candidate channel is used in road-to-vehicle communication (step S16, Yes), the communication determination unit 6 determines that the candidate channel is not usable because it is used in vehicle-to-vehicle communication. The data processing unit 7 is requested to change the setting. The determination method in step S16 is the same as in the first embodiment.

  In this example, the carrier sense result in step S13 is the one shown in FIG. 11, and the received power in channel D4 is equal to or higher than threshold value # 1 (carrier detection). Therefore, in step S14a, the communication determination unit 6 Determines that the candidate channel D4 is unusable and requests the data processing unit 7 to change the setting of the candidate channel. Upon receiving the candidate channel setting change request, the data processing unit 7 changes the candidate channel setting to D5. Then, Steps S13 and S14a targeting D5 are executed. In the example shown in FIG. 11, the received power at D5 is less than threshold value # 1 and greater than or equal to threshold value # 2, and step S16 for D5 (check whether D5 is used in road-to-vehicle communication) ) Is executed. In this example, since D5 is used for the bus location service, UW for road-to-vehicle communication is detected in step S16. As a result, the communication determination unit 6 determines that the candidate channel D5 is unusable, and requests the data processing unit 7 again to change the setting of the candidate channel.

  Upon receiving the candidate channel setting change request, the data processing unit 7 changes the candidate channel setting to D6. Then, Steps S13 and S14a for D6 are executed. In the example shown in FIG. 11, the received power at D6 is less than threshold value # 2 (carrier not detected), so that communication discrimination unit 6 can use candidate channel D6 without executing step S16. And notifies the data processing unit 7 to that effect. Receiving the notification that the candidate channel D6 is usable, the data processing unit 7 permits the modulation unit 41 for inter-vehicle communication to transmit using the channel D6.

  In the present embodiment, as an example, a case where interference avoidance of inter-vehicle communication to road-to-vehicle communication has been described has been described, but it is also the same to prevent road-to-vehicle communication from interfering with inter-vehicle communication. This procedure is possible. Further, the case where the communication determination unit 6 determines whether or not the candidate channel is used for road-to-vehicle communication using the demodulated signal output from the demodulation unit 32 for road-to-vehicle communication has been described. It may be determined using the demodulated signal output from the communication demodulator 42 whether the candidate channel is used for road-to-vehicle communication. Further, both road-to-vehicle communication and vehicle-to-vehicle communication are detected using both of the demodulated signals output from the demodulation units 32 and 42, and whether the candidate channel is used for road-to-vehicle communication using the detection results of both. Judgment may be made.

  Moreover, in this Embodiment, although the case where the communication apparatus (vehicle equipment) was provided with the road-to-vehicle communication part 3 and the vehicle-to-vehicle communication part 4 was demonstrated as an example, road-to-vehicle communication and vehicle-to-vehicle communication are performed simultaneously. When there is not, it is good also as a structure which integrated the road-to-vehicle communication part 3 and the vehicle-to-vehicle communication part 4 into one. In this case, the configuration of the communication device is as shown in FIG.

  Thus, in the present embodiment, the received signal power in the channel selected as the candidate for inter-vehicle communication is determined based on the two threshold values (whether the comparison target channel is used for inter-vehicle communication). The first threshold for the second threshold for determining whether it is used for road-to-vehicle communication) and only when the signal power is between the two thresholds Then, it is decided to determine whether or not the candidate channel is used in road-to-vehicle communication using the detection result of UW executed in parallel. Thereby, in addition to avoiding interference with the road-to-vehicle communication system, the system capacity can be increased, and until the vehicle-to-vehicle communication is started (until transmission is started) as compared with the case of the first embodiment. This time can be further shortened. Furthermore, a more flexible operation can be realized by changing the carrier sense level for road-to-vehicle communication and inter-vehicle communication.

  As described above, the communication device according to the present invention is useful for ITS wireless communication, and is particularly suitable for realizing road-to-vehicle communication and vehicle-to-vehicle communication that do not interfere with each other in the same frequency band. .

It is a figure which shows the structural example of the communication apparatus concerning this invention. It is a figure which shows the channel usage condition in the 5.8 GHz band allocated for ITS. It is a figure which shows the format of the flame | frame currently used in ETC / DSRC. It is a figure which shows the bit pattern of a unique word (UW). It is a figure which shows an example of the carrier sense result performed prior to the start of communication between vehicles by the communication apparatus concerning this invention. It is a figure which shows the structural example of the communication frame used when performing full-duplex communication in road-to-vehicle communication. It is a figure which shows the structural example of the communication frame used when performing half-duplex communication in road-to-vehicle communication. It is a flowchart which shows an example of the operation | movement which the communication apparatus (vehicle equipment) concerning this invention selects and determines the communication channel used by vehicle-to-vehicle communication. It is a figure for demonstrating selection selection operation of a communication channel along a time-axis. It is a figure which shows the other structural example of the communication apparatus concerning this invention. It is a figure which shows an example of the relationship between a carrier sense result and two types of threshold values. It is a flowchart which shows an example of the operation | movement which selects and determines the communication channel which the communication apparatus (vehicle equipment) of Embodiment 2 uses by communication between vehicles. FIG. 10 is a diagram for explaining a communication channel selection determination operation according to the second embodiment along a time axis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission antenna 2 Reception antenna 3 Road-to-vehicle communication part 4 Inter-vehicle communication part 5 CS part 6, 6a Communication discrimination | determination part 7, 7a Data processing part 8 Communication part 31, 41, 81 Modulation part 32, 42, 82 Demodulation part

Claims (12)

A communication device that is installed in a vehicle and performs inter-vehicle communication using an unused channel among a plurality of communication channels allocated for road-to-vehicle communication,
Candidate selection means for selecting a communication channel candidate to be used for inter-vehicle communication from among a plurality of usable communication channels;
A carrier sense means for comparing a received signal level in the communication channel candidate with a predetermined threshold and determining whether the communication channel candidate is unused;
Demodulating means for demodulating a received signal in the communication channel candidate and outputting a demodulated signal including determination information for determining whether the communication channel candidate is used in road-to-vehicle communication;
Judgment as to whether or not confirmation processing of the determination information is necessary based on the carrier sense result, and determination as to whether or not inter-vehicle communication using the communication channel candidate is possible when it is determined that confirmation processing is necessary Means,
A communication apparatus comprising: The determination means includes
If the carrier sense result indicates that it is in use, the candidate selection means is instructed to reselect a communication channel candidate, and indicates that the carrier sense result is unused. 2. The communication device according to claim 1, further comprising confirming the content of the determination information. The determination means includes
If the determination information includes information indicating that the communication channel candidate is used in road-to-vehicle communication, the candidate selection unit is instructed to reselect the communication channel candidate, When the determination information includes information indicating that the communication channel candidate is not used in road-to-vehicle communication, it is determined that inter-vehicle communication using the communication channel candidate is possible. The communication device according to claim 1 or 2. A communication device that is installed in a vehicle and performs road-to-vehicle communication using an unused channel among a plurality of communication channels allocated for vehicle-to-vehicle communication,
Candidate selection means for selecting communication channel candidates to be used for road-to-vehicle communication from among a plurality of usable communication channels;
A carrier sense means for comparing a received signal level in the communication channel candidate with a predetermined threshold and determining whether the communication channel candidate is unused;
Demodulating means for demodulating a received signal in the communication channel candidate and outputting a demodulated signal including determination information for determining whether the communication channel candidate is used in road-to-vehicle communication;
It is determined whether confirmation processing of the determination information is necessary based on the carrier sense result, and when it is determined that confirmation processing is necessary, it is determined whether road-vehicle communication using the communication channel candidate is possible. Judgment means,
A communication apparatus comprising: The determination means includes
If the carrier sense result indicates that it is in use, the candidate selection means is instructed to reselect a communication channel candidate, and indicates that the carrier sense result is unused. The communication apparatus according to claim 4, further comprising confirming the content of the determination information. The determination means includes
If the determination information includes information indicating that the communication channel candidate is used for inter-vehicle communication, the candidate selection unit is instructed to reselect the communication channel candidate, When the determination information includes information indicating that the communication channel candidate is not used in inter-vehicle communication, it is determined that road-to-vehicle communication using the communication channel candidate is possible. The communication device according to claim 4 or 5. A communication device that is installed in a vehicle and performs inter-vehicle communication using an unused channel among a plurality of communication channels allocated for road-to-vehicle communication,
Candidate selection means for selecting a communication channel candidate to be used for inter-vehicle communication from among a plurality of usable communication channels;
The received signal level in the communication channel candidate is a first threshold value for determining whether the communication channel candidate is used in other vehicle-to-vehicle communication, and the communication channel candidate is used in road-to-vehicle communication. Carrier sense means for comparing with a second threshold value for determining whether or not the communication channel candidate is unused,
Demodulating means for demodulating a received signal in the communication channel candidate and outputting a demodulated signal including determination information for determining whether the communication channel candidate is used in road-to-vehicle communication;
Based on the carrier sense result, it is determined whether confirmation processing of the determination information is necessary. When it is determined that confirmation processing is unnecessary, inter-vehicle communication using the communication channel candidate is possible based on the carrier sense result. On the other hand, if it is determined that the confirmation process is necessary, the confirmation process is executed, and whether or not the inter-vehicle communication using the communication channel candidate is possible based on the confirmation process result. A judging means for judging
A communication apparatus comprising: The determination means includes
If the carrier sense result indicates that the received signal level in the communication channel candidate exceeds a first threshold value, the candidate selection means is instructed to reselect the communication channel candidate. In addition, when the carrier sense result indicates that the received signal level in the communication channel candidate is equal to or lower than a second threshold value, it is determined that inter-vehicle communication using the communication channel candidate is possible. The communication device according to claim 7. The determination means includes
If the determination information includes information indicating that the communication channel candidate is used in road-to-vehicle communication, the candidate selection unit is instructed to reselect the communication channel candidate, When the determination information includes information indicating that the communication channel candidate is not used in road-to-vehicle communication, it is determined that inter-vehicle communication using the communication channel candidate is possible. The communication device according to claim 7 or 8. A communication device that is installed in a vehicle and performs road-to-vehicle communication using an unused channel among a plurality of communication channels allocated for vehicle-to-vehicle communication,
Candidate selection means for selecting communication channel candidates to be used for road-to-vehicle communication from among a plurality of usable communication channels;
The received signal level in the communication channel candidate is a first threshold value for determining whether the communication channel candidate is used in other road-to-vehicle communication, and the communication channel candidate is used in inter-vehicle communication. Carrier sense means for comparing with a second threshold value for determining whether or not the communication channel candidate is unused,
Demodulating means for demodulating a received signal in the communication channel candidate and outputting a demodulated signal including determination information for determining whether the communication channel candidate is used in road-to-vehicle communication;
Based on the carrier sense result, it is determined whether confirmation processing of the determination information is necessary, and when it is determined that confirmation processing is unnecessary, road-to-vehicle communication using the communication channel candidate based on the carrier sense result is performed. On the other hand, if it is determined that the confirmation process is necessary, the confirmation process is executed, and whether road-to-vehicle communication using the communication channel candidate is possible based on the confirmation process result. A determination means for determining whether or not,
A communication apparatus comprising: The determination means includes
If the carrier sense result indicates that the received signal level in the communication channel candidate exceeds a first threshold value, the candidate selection means is instructed to reselect the communication channel candidate. If the carrier sense result indicates that the received signal level in the communication channel candidate is equal to or lower than the second threshold value, it is determined that road-to-vehicle communication using the communication channel candidate is possible. The communication apparatus according to claim 10. The determination means includes
If the determination information includes information indicating that the communication channel candidate is used for inter-vehicle communication, the candidate selection unit is instructed to reselect the communication channel candidate, When the determination information includes information indicating that the communication channel candidate is not used in inter-vehicle communication, it is determined that road-to-vehicle communication using the communication channel candidate is possible. The communication device according to claim 10 or 11.

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