WO2017131112A1 - Wireless communication authenticity determination system - Google Patents

Abstract

In a first communication unit (2), two-way communication with a second communication unit (9) is performed using radio waves of the same frequency, the reception signal strength of a radio wave (24) sent from the second communication unit (9) is calculated as a first reception signal strength, and the first reception signal strength is reported to the second communication unit (9). In the second communication unit (9), the reception signal strength of a radio wave (28) with which the first reception signal strength was reported is calculated as a second reception signal strength, and the difference is calculated between the first reception signal strength and the second reception signal strength. The second communication unit (9) determines the communication authenticity of smart communication by confirming whether the difference is within a reference range.

Description

Wireless communication pass / fail judgment system

The present invention relates to a wireless communication correctness determination system in which a communication terminal and a communication master communicate wirelessly.

Conventionally, many vehicles are equipped with an electronic key system (see Patent Document 1 or the like) that performs ID collation using an electronic key that wirelessly transmits an ID code. In this type of electronic key system, when an electronic key receives a request transmitted from a vehicle, the electronic key automatically returns an ID code to the vehicle in response to the request, and performs an ID verification. There is. In the key operation free system, door lock / unlock is permitted or executed when ID verification is established outside the vehicle, and engine start operation is permitted when ID verification is performed inside the vehicle.

In such an electronic key system, a fraudulent act using a repeater as a fraudulent act to establish ID verification without relying on the user's will ((Refuse of repeater use fraud): Patent Document 2, Patent Document 3, etc.) There is something called. For example, when the electronic key is located at a location far from the vehicle, the repeater use fraudulent act is an act of establishing a communication between these two parties by connecting the electronic key to the vehicle by a plurality of repeaters and relaying radio waves. is there.

In Patent Document 2, when both RSSI (radio wave intensity) of the LF signal from the vehicle to the portable device and RSSI of the RF signal from the portable device to the vehicle are detected, and one of them is extremely small from the correlation between both RSSIs, etc. When the criteria for fraud using a repeater are met, door unlocking and engine starting are not permitted.

In Patent Document 3, when a vehicle transmits a plurality of radio waves, the transmission intensity is changed and each radio wave is transmitted. When the electronic key receives a radio wave from the vehicle, the received signal strength of the received radio wave is calculated by the electronic key. Like to do. Then, based on the calculated received signal strength, it is determined whether or not the communication is regular communication.

JP 2005-262915 A JP 2012-60482 A JP 2011-229061 A

By the way, conventionally, when performing communication with the LF signal from the vehicle to the electronic key and communication with the RF signal from the electronic key to the vehicle, either of them may be null in the antenna direction. Since it is erroneously determined that there has been an illegal act using a repeater, the door cannot be unlocked and the engine cannot be started normally. For this reason, it is necessary to consider the relative difference between the LF signal and the RF signal. As a result, the criteria for determining that there has been a fraudulent act using a repeater may be relaxed, and the fraudulent act using a repeater may not be detected. .

An object of the present invention is to provide a radio communication correct / incorrect determination system that can prevent the occurrence of unauthorized radio communication using a repeater.

One aspect of the present invention is a wireless communication correctness determination system. The wireless communication correctness determination system includes a first communication unit including a first transmission execution unit, and a second communication unit including a second transmission execution unit. The first transmission execution unit and the second transmission execution unit include: Bidirectional communication can be performed using radio waves having the same frequency. The first communication unit includes first received signal strength calculating means for calculating the received signal strength of the radio wave from the second communication unit as the first received signal strength. Transmits received signal strength information. The second communication unit includes second received signal strength calculating means for calculating the received signal strength of the radio wave from the first communication unit as a second received signal strength, the first received signal strength, and the first received signal. Based on a comparison result between the determination value and a reference range, a determination value calculation means for calculating a determination value based on the second received signal strength calculated when receiving the strength information, and the first communication unit And communication correctness determination means for determining whether or not communication with the device is regular communication.

According to this configuration, since bidirectional communication between the second communication unit and the first communication unit is performed at the same frequency, the antenna directivity and the distance between the second communication unit and the first communication unit are reduced. Regardless, the difference between the first received signal strength (radio wave strength) and the second received signal strength (radio wave strength) is within the reference range. On the other hand, when communication is performed between the second communication unit and the first communication unit via a relay (repeater), the difference between the first received signal strength and the second received signal strength is a reference range. Not inside. Therefore, it is possible to determine whether or not the normal communication is performed by comparing the determination value based on the first received signal strength and the second received signal strength with the reference range.

The determination value calculation means may calculate a difference between the first received signal strength and the second received signal strength as the determination value.
According to this configuration, since the determination value is the difference between the first received signal strength and the second received signal strength, it is possible to quickly determine whether the communication is normal communication with a simple calculation.

Further, the second communication unit acquires the first received signal strength for determination based on the plurality of first received signal strengths acquired by the plurality of times of bidirectional communication, and acquired by the plurality of times of bidirectional communication. Auxiliary calculation means for calculating a second received signal strength for determination based on a plurality of second received signal strengths, wherein the determination value calculating means includes the first received signal strength for determination, the second received signal strength for determination, The difference may be calculated as the determination value.

Here, from the time when the first communication unit receives the radio wave from the second communication unit and calculates the first received signal strength, the second communication unit receives the radio wave from the first communication unit and receives the second received signal. It is assumed that, for example, a regular user with an electronic key moves to a null point before calculating the strength. In this case, even if bidirectional communication is performed at the same frequency, the difference between the first received signal strength and the second received signal strength changes, and even a legitimate user may erroneously determine that it is not legitimate communication.

In this regard, according to the above-described configuration, the determination value calculation means calculates the first received signal strength for determination based on the plurality of first received signal strengths and the second received signal strength for determination based on the plurality of second received signal strengths. The difference is calculated as a determination value. Therefore, for example, even if a legitimate user with an electronic key moves to a null point during two-way communication, the change in the difference can be suppressed, and the two-way communication by the legitimate user is erroneously determined not to be legitimate communication. it can.

Further, the auxiliary calculation means determines the estimated value of the first received signal strength at a predetermined time within a period of obtaining the plurality of first received signal strengths based on the plurality of first received signal strengths. And calculating an estimated value of the second received signal strength at the predetermined time point as the second received signal strength for determination based on the plurality of second received signal strengths. Good.

According to this configuration, the first received signal strength for determination and the second received signal strength for determination are acquired when the relative positions of the first communication unit and the second communication unit communicate in the same situation. The values are approximate to the received signal strength and the second received signal strength. Therefore, for example, even when a regular user with an electronic key moves to a null point during two-way communication, the change in the difference can be suitably suppressed, and the two-way communication by the regular user is erroneously determined not to be regular communication. Can be suitably reduced.

Further, the auxiliary calculation means calculates the first received signal strength for determination based on the two first received signal strengths obtained in two bidirectional communications, as follows:
RSSI1_est = (RSSI1_n1 · T2 + RSSI1_n2 · T1) / (T1 + T2)
And the second received signal strength for determination based on the two second received signal strengths acquired in the two-way bidirectional communication is expressed by the following equation:
RSSI2_est = (RSSI2_n1 · T4 + RSSI2_n2 · T3) / (T3 + T4)
You may calculate using. Here, “RSSI1_est” is the first received signal strength for determination, “RSSI1_n1” is the first received signal strength obtained in the above two-way communication, and “RSSI1_n2” is the above two-way communication. The first received signal strength after acquisition at “T1” is a time interval from the time when the previous first received signal strength was acquired to the predetermined time, and “T2” is the first time after the predetermined time. The time interval until the reception signal strength is acquired, “RSSI2_est” is the second received signal strength for determination, “RSSI2_n1” is the second received signal strength of the previous acquired in the two-way bidirectional communication, “RSSI2_n2” "Is the second received signal strength after being acquired in the two-way communication," T3 "is the time interval from when the second received signal strength is acquired to the predetermined time, and" T4 "is The time from the predetermined time point to the time point when the second received signal strength is acquired It is.

According to this configuration, it is possible to quickly determine whether or not regular communication is performed by two-way bidirectional communication while suppressing a large calculation load from being applied to the auxiliary calculation unit.
Further, the first transmission execution means and the second transmission execution means perform radio wave communication alternately at the same time interval, and the auxiliary calculation means calculates the ratio between the time interval T1 and the time interval T2. Is set to “3: 1”, the ratio of the time interval T3 to the time interval T4 is set to “1: 3”, and the ratio of the time interval T1 to the time interval T2 is set to “1: 3”. The ratio of the time interval T3 and the time interval T4 may be set to “3: 1”.

According to this configuration, the first transmission execution unit and the second transmission execution unit perform radio wave communication alternately at the same time interval, thereby suitably suppressing an excessive calculation load on the auxiliary calculation unit, It is possible to quickly determine whether or not regular communication is performed by two-way communication.

In addition, the communication correctness determination unit may determine that normal communication is not performed when it is detected a plurality of times that the comparison result between the determination value and the reference range does not indicate normal communication.
In general, when there is an illegal act using a repeater, it is detected multiple times that the comparison result between the judgment value based on the first received signal strength and the second received signal strength and the reference range does not indicate regular communication. Can be done. For this reason, when such a situation is detected a plurality of times, it can be determined that the communication is not regular communication.

The first communication unit includes first comparison means for comparing the first received signal strength with a first threshold value for detecting a received signal strength saturation, and the first received signal strength is less than the first threshold value. If it exceeds, the first transmission execution means may transmit a first attenuation request to the second communication unit. In this case, the second transmission execution means may perform power control based on the first attenuation request so that the transmission output of the radio wave to the first communication unit is attenuated from the previous transmission output. When the second communication unit newly receives a radio wave without receiving the first attenuation request from the first communication unit after the power control is performed, the determination value calculation unit newly adds the determination value calculation unit. The determination value may be calculated based on the second received signal strength of the received radio wave and the first received signal strength notified by the newly received radio wave.

According to this configuration, when the first communication unit and the second communication unit are in close proximity and the first received signal strength may exceed the first threshold value for detecting the received signal strength saturation, the first received signal strength is Judged to be saturated.

In this case, a first attenuation request is sent from the first communication unit to the second communication unit. For this reason, the second communication unit performs power control based on the first attenuation request so that the transmission output of the radio wave to the first communication unit is attenuated from the previous transmission output. Then, the determination value calculation means of the second communication unit is configured to communicate the first received signal strength of the radio wave newly received from the first communication unit after the power control is performed and the first radio wave received by the newly received radio wave. A determination value is calculated based on the received signal strength. As a result, the communication correctness determination means obtains an appropriate determination value calculated based on the first received signal strength and the second received signal strength obtained in a situation where the first received signal strength is not saturated. It is possible to determine whether or not the communication is regular communication.

The second communication unit includes a second comparison unit that compares the second received signal strength with a second threshold value for detecting a received signal strength saturation, and the second received signal strength is less than the second threshold value. If it exceeds, the second transmission execution means may transmit a second attenuation request to the first communication unit. In this case, the first transmission execution unit performs power control based on the second attenuation request so that the transmission output of the radio wave to the second communication unit is attenuated from the previous transmission output. When the second communication unit newly receives a radio wave from the first communication unit after the second transmission execution unit transmits the radio wave not including the second attenuation request, The determination value may be calculated based on the second received signal strength of the newly received radio wave and the first received signal strength notified by the newly received radio wave.

According to this configuration, when the first communication unit and the second communication unit are in close proximity and the second received signal strength may exceed the second threshold value for detecting the received signal strength saturation, the second received signal strength is Judged to be saturated.

In this case, a second attenuation request is sent from the second communication unit to the first communication unit. For this reason, the first communication unit performs power control based on the second attenuation request so that the transmission output of the radio wave to the second communication unit is attenuated from the previous transmission output. Then, the determination value calculation unit of the second communication unit receives a new radio wave from the first communication unit after the second transmission execution unit transmits the radio wave not including the second attenuation request. In addition, a determination value is calculated based on the second received signal strength of the newly received radio wave and the first received signal strength communicated by the newly received radio wave. As a result, the communication correctness determination means obtains an appropriate determination value calculated based on the first received signal strength and the second received signal strength obtained in a situation where the second received signal strength is not saturated. It is possible to determine whether or not the communication is regular communication.

According to the present invention, unauthorized establishment of wireless communication using a repeater can be made difficult to occur.

The block diagram which shows the structure of the communication fraud establishment prevention system of 1st Embodiment. The timing chart which shows the communication sequence of smart communication. Explanatory drawing which shows the outline | summary of the unauthorized communication using a repeater. The flowchart of the right-and-left determination of the radio | wireless communication of the radio | wireless communication correctness determination system in smart communication. Explanatory drawing of the path | route in the radio | wireless communication between a vehicle and an electronic key. Explanatory drawing of the path | route in the radio | wireless communication between the vehicle and electronic key in the case of a one-sided relay. The block diagram which shows the structure of the communication fraud establishment prevention system in 2nd Embodiment. The block diagram which shows the structure of the communication fraud establishment prevention system in 3rd Embodiment. The block diagram which shows the structure of the communication fraud establishment prevention system of 4th Embodiment. The block diagram which shows the structure of the communication fraud establishment prevention system of 5th Embodiment. The schematic diagram which shows an example of transition of 1st received signal strength and 2nd received signal strength. The schematic diagram which shows an example of transition of 1st received signal strength and 2nd received signal strength. The schematic diagram which shows an example of transition of 1st received signal strength and 2nd received signal strength.

(First embodiment)
A first embodiment of a communication fraud prevention system embodying the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the vehicle 1 transmits a wireless inquiry (request signal Srq) from the vehicle 1 to the electronic key 2, and performs ID verification based on a response (ID signal Sid) of the electronic key 2 to this inquiry. A key operation free system 3 is installed. The key operation free system 3 includes an entry function in which door lock locking / unlocking is permitted or executed when ID verification is established outside the vehicle, and a power transition operation of the vehicle 1 and the engine by the engine switch 4 in the vehicle when ID verification is established in the vehicle. There is an engine start function in which the start operation is permitted. The electronic key 2 is an example of a communication terminal and corresponds to the first communication unit.

In this case, the vehicle 1 includes a key verification device 5 that performs ID verification with the electronic key 2, a door lock device 6 that manages a door lock operation, and an engine start device 7 that manages the operation of the engine. These are provided and connected by an in-vehicle bus 8. The key verification device 5 is provided with a verification ECU (Electronic Control Unit) 9 as a control unit of the key verification device 5. In the memory (not shown) of the verification ECU 9, the ID code of the electronic key 2 that forms a pair with the vehicle 1 is registered. The verification ECU 9 is an example of a communication master and corresponds to the second communication unit.

The verification ECU 9 includes an outside transmitter 10 that transmits radio waves in the LF (Low （Frequency) band and UHF (Ultra High Frequency) band outside the vehicle, an in-vehicle transmitter 11 that transmits radio waves in the LF band and the UHF band inside the vehicle, A vehicle tuner 12 that receives radio waves in the UHF (Ultra High Frequency) band is connected.

The vehicle transmitter 10 and the vehicle transmitter 11 transmit a request signal Srq as an ID reply request to the electronic key 2 by UHF band radio waves, and attempt to establish so-called smart communication.
On the other hand, the electronic key 2 is provided with a key control unit 13 that performs overall control of the operation of the electronic key 2. An “ID code” is registered in the memory (not shown) of the key control unit 13 as an ID unique to the key. The key control unit 13 includes a receiver 14 capable of receiving LF and UHF radio waves, and a UHF transmitter capable of transmitting UHF radio waves having the same frequency as the UHF radio waves transmitted from the key verification device 5. 15 is connected.

As shown in FIG. 2, when the vehicle is parked, an LF band wake signal 16 is intermittently transmitted from the vehicle transmitter 10, and the electronic key 2 receives the wake signal 16 to perform smart communication outside the vehicle (external communication). When established, an ACK signal 17 in the UHF band is returned from the electronic key 2.

When the verification ECU 9 receives the ACK signal 17 after transmitting the wake signal 16, it subsequently transmits a “vehicle ID 18” in the UHF band. “Vehicle ID 18” is a unique ID of the vehicle 1. When receiving the “vehicle ID 18”, the electronic key 2 performs vehicle ID collation. When the electronic key 2 confirms that the vehicle ID collation is established, the electronic key 2 returns the UHF band acknowledgment signal 19 again.

When the verification ECU 9 receives the ACK signal 19 after transmitting the “vehicle ID 18”, it subsequently transmits a challenge 20. The challenge 20 includes a “challenge code” and a “key number”. The challenge 20 corresponds to the request signal Srq.

When the electronic key 2 receives the challenge 20, it first checks the key number, and if it is confirmed that the verification is established, it passes the “challenge code” through the encryption key registered in the electronic key 2 and the “response code”. Is calculated. Then, the electronic key 2 transmits main data including the “response code” and the “ID code” as a response 21. Here, the response 21 corresponds to the ID signal Sid.

When the verification ECU 9 transmits the challenge 20 to the electronic key 2, the verification ECU 9 also calculates a “response code” through the challenge code using the encryption key registered in the verification ECU 9. When the verification ECU 9 receives the response 21 from the electronic key 2, the verification ECU 9 performs response verification for confirming whether the “response code” is correct and ID code verification for confirming whether the “ID code” of the electronic key 2 is correct. When the verification ECU 9 confirms that both verifications have been established, in principle, the verification ECU 9 processes smart verification (external vehicle verification) as successful, and permits or executes door lock locking / unlocking by the door lock device 6.

Further, when it is detected by the courtesy switch or the like that the driver has boarded, for example, the transmission of the LF band wake signal 16 is started from the in-vehicle transmitter 11 instead of the out-of-vehicle transmitter 10, and the in-vehicle smart communication is started. (In-car communication) is executed. Then, whether or not smart verification (in-vehicle verification) is established in the vehicle is confirmed by the same procedure as that in the vehicle verification, and when the verification in the vehicle is confirmed, power supply transition operation and engine start operation by the engine starting device 7 are permitted. .

In the case of the present embodiment, as shown in FIG. 1, the key operation free system 3 is provided with a communication fraud establishment prevention system 23 for preventing the smart communication fraud establishment using the repeater 22 shown in FIG. . The establishment of unauthorized communication using the repeater 22 means that when a user who possesses the electronic key 2 is far away from the vehicle 1, a third party who attempts the theft relays radio waves using the repeater 22, This is an act of illegally establishing communication (an illegal act using a repeater). The unauthorized communication establishment prevention system 23 of this embodiment is for preventing the establishment of unauthorized communication using the repeater 22.

By the way, with this type of repeater 22, although the data content can be relayed, it is not possible to relay (copy) to the radio field strength. Therefore, if the received signal strength (RSSI: Received Signal Strength Indication) of the radio wave is confirmed in the electronic key 2, whether smart communication is regular communication via the electronic key 2 or unauthorized communication using the repeater 22. I understand. For this reason, the communication fraud establishment prevention system 23 according to the present embodiment executes the communication correctness determination of the smart communication by confirming the received signal strength of the radio wave in the electronic key 2.

In this case, as shown in FIG. 1, the key control unit 13 of the electronic key 2 is provided with a received signal strength calculating unit 26 that calculates the received signal strength of the received radio wave when the radio wave of the UHF band is received from the verification ECU 9. It has been. The received signal strength calculation unit 26 calculates the first received signal strength RSSI1 by detecting the amplitude of the received radio wave when the receiver 14 receives the radio wave. The received signal strength calculation unit 26 corresponds to first received signal strength calculation means.

The key control unit 13 of the electronic key 2 is provided with a reception signal strength notification unit 27 that notifies the vehicle 1 of the first reception signal strength RSSI1 calculated by the reception signal strength calculation unit 26.
When the electronic key 2 transmits various radio waves (hereinafter collectively referred to as UHF radio wave 28) in response to the inquiry from the vehicle 1, the reception signal strength notification unit 27 transmits the UHF radio wave 28 including the main data 29 to the UHF radio wave 28. Received signal strength information 30 representing one received signal strength RSSI1 is placed. In this embodiment, the main data 29 is the “ID code” and the “response code”. The reception signal strength notification unit 27 corresponds to a first transmission execution unit.

On the other hand, as shown in FIG. 1, when the vehicle 1 transmits various radio waves in the UHF band (hereinafter collectively referred to as UHF radio wave 24) to the electronic key 2 during smart communication, the verification ECU 9 transmits this UHF radio wave. A transmission processing unit 25 that transmits 24 at the same frequency is provided. The transmission processing unit 25 corresponds to a second transmission execution unit.

In addition, the verification ECU 9 is provided with a received signal strength calculating unit 9a that calculates a second received signal strength RSSI2 that is a received signal strength of the received radio wave 28 when the UHF radio wave 28 from the electronic key 2 is received. . The received signal strength calculator 9a corresponds to a second received signal strength calculator.

Further, the verification ECU 9 receives the received signal strength information 30 (first received signal strength RSSI1) notified by the UHF radio wave 28 from the electronic key 2 and the second received signal strength RSSI2 when the received signal strength information 30 is received. The calculation part 9b which calculates the difference with these is provided. The calculation unit 9b corresponds to a determination value calculation unit.

In addition, the verification ECU 9 is provided with a communication correctness determination unit 31. The communication correctness determination unit 31 compares the difference with a reference value R registered in advance, and determines whether smart communication with the electronic key 2 is regular communication based on the comparison result. The communication correctness determination unit 31 corresponds to a communication correctness determination unit, and the difference corresponds to a determination value.

(Regarding reference value R)
The reference value R is registered in a memory (not shown) of the verification ECU 9 as follows.
First communication when the electronic key 2 receives a radio wave (received signal) in the UHF band from the vehicle 1 in communication when registering the “ID code” or the “encryption key” of the electronic key 2 in the verification ECU 9 The signal strength RSSI1 is calculated by the reception signal strength calculation unit 26, and the reception signal strength notification unit 27 notifies the vehicle 1 of the first reception signal strength RSSI1. The received signal strength information 30 at this time is notified using a radio wave when notifying the “ID code” and the “encryption key”.

The second received signal strength RSSI2 of the radio wave in the UHF band carrying the received signal strength information 30 is calculated by the received signal strength calculating unit 9a, and the first received signal strength transmitted from the electronic key 2 by the calculating unit 9b. The difference between RSSI1 and the second received signal strength RSSI2 calculated by the received signal strength calculator 9a is calculated. Using this difference as a reference value R, the verification ECU 9 registers it in a memory (not shown).

Note that the frequency of the radio wave in the UHF band when this reference value R is registered is the same as the frequency of the smart communication. Here, when registering the “ID code” and the “encryption key” of the electronic key 2, the electronic key 2 is in a position close to the vehicle 1 or in a vehicle interior, Registered without using.

(Operation of the first embodiment)
Next, the operation of the unauthorized communication establishment prevention system 23 according to the present embodiment will be described with reference to FIGS.

First, as shown in FIG. 4, it is assumed that the vehicle 1 performs smart communication with the electronic key 2. FIG. 4 is a flowchart of the wireless communication correctness determination in the wireless communication correctness determination system in smart communication. For convenience of explanation, the vehicle ID, the encryption key, and the key number of the vehicle 1 will be described on the premise that they are a proper combination. Further, it is assumed that the reception signal strength calculation unit 26 of the key control unit 13 in the electronic key 2 calculates the reception signal strength of the UHF radio wave 24 every time the UHF radio wave 24 is received from the vehicle 1.

Vehicle 1 (verification ECU 9) first transmits a wake signal 16 of an LF band radio wave during smart communication. When the electronic key 2 receives the wake signal 16, the electronic key 2 transmits an ACK signal 17 of a radio wave in the UHF band to the vehicle 1. Next, the vehicle 1 (verification ECU 9) transmits the vehicle ID 18 using the UHF radio wave 24. The electronic key 2 that has received the vehicle ID 18 confirms the establishment of the vehicle ID verification, and then transmits an ACK signal 19 of a radio wave in the UHF band to the vehicle 1. Upon receipt of the ACK signal 19, the vehicle 1 (verification ECU 9) transmits a challenge 20 as a request signal (UHF radio wave 24) carrying “challenge code” and “key number”. The electronic key 2 that has received the challenge 20 includes UHF including main data 29 (“ID code” and “response code”) and the first received signal strength RSSI1 (received signal strength information 30) when the challenge 20 is received. The radio wave 28 is transmitted as a response 21 to the vehicle 1. When receiving the response 21 from the electronic key 2, the verification ECU 9 of the vehicle 1 performs response verification for confirming whether the “response code” is correct and ID code verification for confirming whether the “ID code” of the electronic key 2 is correct. When the verification ECU 9 confirms that both verifications are established, the verification ECU 9 next determines whether or not the “communication condition” is satisfied in S10.

(Communication conditions)
The communication conditions are
P1crx = P1krx + □
...... (1)
Whether Formula (1) is materialized. Here, P1crx represents the received power of the vehicle, and P1krx represents the received power of the electronic key. □ represents the difference (reception signal strength difference) between the first received signal strength RSSI1 and the second received signal strength RSSI2.

Derivation of the communication condition will be described with reference to FIG. In FIG. 5, r is the distance between both antennas of the vehicle 1 and the electronic key 2.
When communicating from the vehicle 1 to the electronic key 2 using radio waves of the same frequency,
Vehicle transmission power: P1ctx (dBm)
Vehicle transmit / receive antenna gain: Gc (dBm)
Propagation loss in free section: Lr (dBm)
Electronic key transmit / receive antenna gain: Gk (dBm)
Electronic key received power: P1krx (dBm)
Then,
The reception power P1krx of the electronic key is
P1ctx + Gc−Lr + Gk = P1krx (2)
And a value that approximates the first received signal strength RSSI1 at the electronic key 2.

On the other hand, when communicating from the electronic key 2 to the vehicle 1,
Electronic key transmission power: P1ktx (dBm)
Electronic key transmit / receive antenna gain: Gk (dBm)
Propagation loss in free section: Lr (dBm)
Vehicle transmit / receive antenna gain: Gc (dBm)
Vehicle received power: P1crx (dBm)
Then,
The received power P1crx of the vehicle is
P1ktx + Gk−Lr + Gc = P1crx (3)
This is a value that approximates the second received signal strength RSSI2 in the vehicle 1.

Here, the relationship between the transmission / reception antenna gain Gc of the vehicle and the transmission / reception antenna gain Gk of the electronic key is
Gc = Gk + □ (dBm) (4)
It is represented by If the total power P0 at the transmitting and receiving antennas is the same for both the vehicle and the electronic key,
P0 = P1ctx + Gc = P1ktx + Gk (5)
Is satisfied, from equations (4) and (5),
P1ctx = P1ktx− □
...... (6)
Is derived.

Also,
Gc = Gk + □ (dBm) (7)
When using the relationship (that is, the above equation (4)),
P1crx + Gc = P1krx + Gk
...... (8)
Is satisfied, the expression (1) is derived from the expressions (7) and (8).

Here, from the relationship between P1ctx (transmission power of the vehicle) and P1ktx (transmission power of the electronic key), when the frequency is constant, the difference □ of the received signal strength between the vehicle 1 and the electronic key 2 is constant.

Therefore, if the difference □ is always constant, the formula (1) is established.
In the present embodiment, the verification ECU 9 calculates the second received signal strength RSSI2 of the response 21 by the received signal strength calculation unit 9a in order to determine whether or not the expression (1) is satisfied, and the second of the response 21 is calculated. The calculation unit 9b calculates a difference between the received signal strength RSSI2 and the received signal strength information 30 (first received signal strength RSSI1) notified by the response 21. And the communication correctness determination part 31 determines communication correctness by comparing the reference value R and the said difference. In the present embodiment, the fact that the difference matches the reference value R corresponds to the difference being in the reference range.

In addition, in the comparison between the reference value R and the difference □, if the reference value R and the difference □ are the same value, it may be determined that the communication is proper without fraud using the repeater, or When the difference □ is within the range of R−Δ ≦ □ ≦ R + Δ (that is, the reference range), it is determined that the difference is constant, and it is determined that the communication is proper without fraud using the repeater. May be. In addition, Δ is an allowable value that can be determined that there is no fraud using a repeater.

In S10 of FIG. 4, when the expression (1) is satisfied (that is, established), the verification ECU 9 determines that smart communication is regular communication and processes smart verification (external vehicle verification) as established, and S20 The door lock device 6 permits or executes door lock locking / unlocking.

On the other hand, as shown in FIG. 6, when radio waves are relayed by the one-side relay by the repeater 22, the operation range is determined by communication from the vehicle 1 to the electronic key 2, so when communication is performed via the repeater 22, The formula (1) is not satisfied. For this reason, an illegal act using a repeater can be detected.

In FIG. 6, Gr is the gain of the antenna of the repeater 22, P1rtx is the transmission power of the repeater 22, and P1rrx is the received power of the repeater 22. Lx is a propagation loss due to the distance x between the repeater 22 and the vehicle 1, and Ly is a propagation loss due to the distance y between the repeater 22 and the electronic key 2.

When radio waves are relayed by the relay 22 using a bidirectional relay, the antenna gain Gc, Gr, Gk involved in the communication from the vehicle 1 to the electronic key 2 and the antenna communicating from the electronic key 2 to the vehicle 1 If the gains Gc, Gr, and Gk are not equal, the received signal strength difference □ is not constant and does not satisfy the expression (1). That is, when relaying radio waves with such a bidirectional relay, it is difficult to create a repeater that makes the gain involved in the forward path equal to the gain involved in the return path. Therefore, it is possible to easily detect fraud using a repeater.

As described above, when the expression (1) is not satisfied in S10 (that is, when it is not established), the verification ECU 9 determines the smart communication as unauthorized communication, and performs the smart verification (ex-vehicle verification) in S30. Treat as unsuccessful.

As described above, in this embodiment, communication is performed between the vehicle 1 and the electronic key 2 using the UHF radio wave 24 and the UHF radio wave 28 having the same frequency in the smart communication. Then, the electronic key 2 calculates the first received signal strength RSSI1 when the radio wave from the vehicle 1 is received. In the electronic key 2, the calculated first received signal strength RSSI 1 is transmitted to the vehicle 1 as received signal strength information 30. The vehicle 1 calculates the second received signal strength RSSI2 of the radio wave carrying the received signal strength information 30, and the difference between the received signal strength information 30 (first received signal strength RSSI1) and the calculated second received signal strength RSSI2 □ If the difference □ is the same as the reference value R or within the reference range, the smart communication is processed as regular communication, while the difference □ is not the same as the reference value R or not within the reference range. In this case, it is processed as unauthorized communication using the repeater 22. Therefore, since it is possible to identify unauthorized communication using the repeater 22, it is possible to prevent the unauthorized communication from being processed as established.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The vehicle 1 and the electronic key 2 communicate with each other using UHF radio waves having the same frequency, and the electronic key 2 calculates the first received signal strength RSSI1 of the radio waves from the vehicle 1, and the first received signal strength RSSI1. Is transmitted to the vehicle 1 as received signal strength information 30. Then, the vehicle 1 calculates a difference □ between the notified received signal strength information 30 (first received signal strength RSSI1) and the second received signal strength RSSI2 of the radio wave carrying the received signal strength information 30. By checking whether □ is the same as the reference value R (or whether it is within the reference range), the communication correctness of the smart communication is determined. For this reason, since it becomes possible to distinguish whether smart communication is communication using the repeater 22, it is difficult to establish unauthorized communication using the repeater 22. Therefore, security against unauthorized use or theft of the vehicle 1 can be ensured.

(2) Since authentication of smart communication is performed on the vehicle 1 side, there is no need to newly provide this kind of authentication function in the electronic key 2. Therefore, the electronic key 2 used so far can be used as it is, and the electronic key 2 can have a simple structure.

(3) Since the communication correctness is determined using the difference □ between the first received signal strength RSSI1 and the second received signal strength RSSI2, it is possible to quickly determine whether the communication is normal communication with a simple calculation.
(Second Embodiment)
Next, the communication fraud establishment preventing system 23 employed in the key operation free system 3 of the second embodiment will be described with reference to FIG. In the following, the second embodiment will be described with a focus on the configuration different from the first embodiment, and the same or corresponding components as those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. In the second embodiment as well, the UHF radio wave used for communication between the vehicle 1 and the electronic key 2 has the same frequency as in the first embodiment. Further, the type of UHF radio wave in each embodiment including the second embodiment is not limited.

The second embodiment is different from the first embodiment in that a comparison unit 13 a is provided in the key control unit 13 of the electronic key 2.
The comparing unit 13a compares the first received signal strength RSSI1 of the UHF radio wave 24 transmitted from the vehicle 1 calculated by the received signal strength calculating unit 26 with a first threshold value for detecting received signal strength saturation. The first threshold is a value slightly lower than the saturation value (maximum value) of the received signal strength of the UHF radio wave 24 that can be processed by the circuit inside the receiver 14, for example. When the first received signal strength RSSI1 exceeds the first threshold, the comparison unit 13a determines that the first received signal strength RSSI1 of the received UHF radio wave 24 is saturated. When this determination is made, the reception signal strength notification unit 27 notifies the vehicle 1 of the saturated first reception signal strength RSSI1 and the attenuation request with the UHF radio wave 28. Thus, when the first received signal strength RSSI1 of the UHF radio wave 24 from the vehicle 1 is saturated, the electronic key 2 transmits the UHF radio wave 28 in response to the UHF radio wave 24.

Here, the comparison unit 13a corresponds to a first comparison unit, and the attenuation request transmitted from the received signal strength notification unit 27 corresponds to a first attenuation request.
When the verification ECU 9 of the vehicle 1 receives the first received signal strength RSSI1 and the attenuation request exceeding the first threshold value, the transmission processing unit 25 outputs the transmission output of the UHF radio wave 24 to the electronic key 2 based on them. Power control is performed to attenuate the transmission output. In this case, the attenuation α of the transmission output is a preset amount.

The verification ECU 9 of the vehicle 1 performs the same power control as described above every time it receives the first received signal strength RSSI1 and the attenuation request exceeding the first threshold.
If the vehicle 1 newly receives the notification of the first received signal strength RSSI1 as the UHF radio wave 28 without receiving an attenuation request from the electronic key 2 after power control is performed, the calculation unit 9b A difference □ between the second received signal strength RSSI2 of the newly received radio wave 28 not including the attenuation request and the first received signal strength RSSI1 notified by the newly received radio wave 28 is calculated.

In this case, the communication correctness determination unit 31 includes a reference value changed from “R” to “R + n · α” according to the number of times n (ie, the number of attenuation requests) the transmission output is attenuated by the attenuation amount α, and a calculation unit. Whether the communication is correct or not is determined by comparing the difference calculated by 9b.

According to the configuration of the second embodiment, the following effects can be obtained.
(1) When the vehicle 1 and the electronic key 2 are close to each other, the received signal intensity of the radio wave 24 received by the electronic key 2 may be saturated. In this case, in the second embodiment, when the electronic key 2 requests the verification ECU 9 of the vehicle 1 to attenuate the transmission output of the radio wave 24, the received signal strength of the radio wave 24 newly received by the electronic key 2 is increased. Can not be saturated. Therefore, it is possible to determine whether or not the communication of smart communication is correct in a state where such saturation is eliminated. As a result, the same effect as that of the first embodiment can be obtained.

(Third embodiment)
Next, the communication fraud establishment prevention system 23 employed in the key operation free system 3 of the third embodiment will be described with reference to FIG. In the following, the third embodiment will be described with a focus on the configuration different from the first embodiment, and the same or corresponding components as those in the first embodiment will be assigned the same reference numerals and detailed description thereof will be omitted. In the third embodiment, as in the first embodiment, UHF radio waves used for communication between the vehicle 1 and the electronic key 2 have the same frequency.

The third embodiment is different from the first embodiment in that a comparison unit 9 c is provided in the verification ECU 9 of the vehicle 1.
The comparing unit 9c compares the second received signal strength RSSI2 of the UHF radio wave 28 from the electronic key 2 calculated by the received signal strength calculating unit 9a with the second threshold value for detecting the received signal strength saturation, and compares the second received signal. When the intensity RSSI2 exceeds the second threshold value for detecting the received signal intensity saturation, it is determined that the received signal intensity of the received radio wave 28 is saturated. Note that the second threshold value is slightly lower than the saturation value (maximum value) of the received signal strength of the UHF radio wave 28 that can be processed by the circuit inside the vehicle tuner 12, for example.

The transmission processing unit 25 transmits the attenuation request and the second received signal strength RSSI2 exceeding the second threshold to the electronic key 2. Here, the comparison unit 9c corresponds to a second comparison unit, and the attenuation request transmitted from the transmission processing unit 25 corresponds to a second attenuation request.

Based on the attenuation request and the second received signal strength RSSI2 exceeding the second threshold, the received signal strength notification unit 27 of the electronic key 2 attenuates the transmission output of the UHF radio wave 28 to the vehicle 1 from the previous transmission output. Power control as you do. In this case, the attenuation β of the transmission output is a preset amount. The attenuation amount β may be the same as or different from the attenuation amount α of the second embodiment.

The electronic key 2 performs the same power control as described above every time the attenuation request and the second received signal strength RSSI2 exceeding the second threshold are received.
The calculation unit 9b of the verification ECU 9 of the vehicle 1 transmits the radio wave 24 (challenge 20) that does not include an attenuation request immediately after or after the transmission processing unit 25 transmits the second received signal strength RSSI2 exceeding the second threshold. In response to this, when the vehicle 1 newly receives the radio wave 28 transmitted from the electronic key 2, the second received signal strength RSSI2 of the newly received radio wave 28 and the newly received radio wave 28 are notified. A difference □ from the received first received signal strength RSSI1 is calculated. The communication correctness determination unit 31 then changes the reference value changed from “R” to “R + m · β” according to the number m of transmission output attenuation by the attenuation amount β (that is, the number of attenuation requests), and the calculation unit 9b. Is compared with the difference calculated by, to determine whether the communication is correct.

According to the configuration of the third embodiment, the following effects can be obtained.
(1) When the vehicle 1 and the electronic key 2 are close to each other, the radio wave 28 received by the verification ECU 9 may be saturated. In this case, in the third embodiment, when the verification ECU 9 of the vehicle 1 requests the electronic key 2 to attenuate the transmission output of the radio wave 28, the received signal strength of the radio wave 28 newly received by the verification ECU 9 is increased. Saturation can be avoided. Therefore, it is possible to determine whether or not the communication of smart communication is correct in a state where such saturation is eliminated. As a result, the same effect as that of the first embodiment can be obtained.

(Fourth embodiment)
Next, the communication fraud establishment preventing system 23 employed in the key operation free system 3 of the fourth embodiment will be described with reference to FIG. The fourth embodiment is a combination of the second embodiment and the third embodiment. That is, in the fourth embodiment, as shown in FIG. 9, the key operation free system 3 and the communication fraud establishment prevention system 23 are configured by the electronic key 2 having the comparison unit 13a and the verification ECU 9 having the comparison unit 9c. Yes. This unauthorized communication establishment prevention system 23 has the effects described in the second embodiment and the third embodiment.

In the fourth embodiment, when n · α ≠ m · β, the communication correctness determination unit 31 changes the transmission output from “R” to “R” according to the amount of attenuation of the transmission output on the vehicle 1 side and the electronic key 2 side, respectively. By comparing the reference value changed to “R + n · α−m · β” and the difference calculated by the calculation unit 9b, the communication correctness is determined.

When n · α = m · β, the communication correctness determination unit 31 sets the reference value to “R”, and compares the reference value R with the difference calculated by the calculation unit 9b. Judgment of communication correctness is performed.

(Fifth embodiment)
Next, the communication fraud establishment prevention system 23 employed in the key operation free system 3 of the fifth embodiment will be described with reference to FIGS. In the following, the fifth embodiment will be described with a focus on the configuration different from the first embodiment, and the same or corresponding components as those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted. In the fifth embodiment, as in the first embodiment, UHF radio waves used for communication between the vehicle 1 and the electronic key 2 have the same frequency.

FIG. 11 shows a case where a legitimate user having the electronic key 2 moves through a null point of the radio wave when the transmission / reception antenna gain Gc of the vehicle 1 and the transmission / reception antenna gain Gk of the electronic key 2 are substantially equal. The transition of the first received signal strength RSSI1 (open circle in FIG. 11) and the second received signal strength RSSI2 (open triangle in FIG. 11) is shown. Since the antenna gain Gc · Gk is substantially equal, if the relative positions of the vehicle 1 and the electronic key 2 are the same, the values of the first received signal strength RSSI1 and the second received signal strength RSSI2 are substantially constant. When the electronic key 2 enters the null point, the values are lowered as shown in FIG.

Here, when the electronic key 2 receives the radio wave from the verification ECU 9 and calculates the first received signal strength RSSI1, the verification ECU 9 receives the radio wave from the electronic key 2 and calculates the second received signal strength RSSI2. In the meantime, for example, a case where a regular user having the electronic key 2 moves to the null point is assumed. In this case, even when bidirectional communication is performed at the same frequency, the difference between the first received signal strength RSSI1 and the second received signal strength RSSI2 acquired sequentially changes as shown in FIG. That is, if the value does not move to the null point, the values of the first received signal strength RSSI1 and the second received signal strength RSSI2 are substantially constant, so the difference should be substantially zero, but the first received signal strength RSSI1 The difference from the second received signal strength RSSI2 increases, for example, as indicated by the difference □ x in FIG. As a result, there is a risk that communication by an authorized user is erroneously determined not to be authorized communication. Although it is conceivable to set a large reference range for comparison with the difference, in this case, there is a risk that unauthorized communication via the repeater 22 may be erroneously set as regular communication.

In consideration of this point, in the fifth embodiment, the electronic key 2 and the verification ECU 9 perform bidirectional communication over a plurality of times to determine whether the smart communication is correct or not.
Specifically, the reception signal strength notification unit 27 and the transmission processing unit 25 perform radio wave communication alternately at the same time interval based on the unit time T. In this example, the received signal strength notification unit 27 transmits the UHF radio wave 28 after a predetermined time interval (for example, a time “2T” that is twice the unit time T) after the electronic key 2 receives the UHF radio wave 24 from the verification ECU 9. To do. Further, the transmission processing unit 25 transmits the UHF radio wave 24 after the predetermined time interval (2T) after the verification ECU 9 receives the UHF radio wave 28 from the electronic key 2. The predetermined time interval is set to be longer than the time required for the calculation processing required for the verification ECU 9 and the key control unit 13 to transmit the UHF radio waves 24 and 28.

As shown in FIG. 10, an auxiliary calculator 41 is provided in the verification ECU 9 of the vehicle 1 of the fifth embodiment. The auxiliary calculation unit 41 uses a plurality of first received signal strengths RSSI1_est for determination based on a plurality of first received signal strengths RSSI1 obtained by a plurality of bidirectional communications, and a plurality of obtained by the plurality of bidirectional communications. The second received signal strength RSSI2_est for determination based on the second received signal strength RSSI2 is calculated. In the fifth embodiment, the auxiliary calculation unit 41 corresponds to auxiliary calculation means.

For example, a case will be described in which the verification ECU 9 obtains two first received signal strengths RSSI1 and two second received signal strengths RSSI2 by two-way communication twice. In this case, the auxiliary calculation unit 41 estimates the received signal strength of the radio wave from the verification ECU 9 at the predetermined time point Px within the period in which the two first received signal strengths RSSI1 are obtained, and uses this estimated value for the first reception for determination. Calculated as signal strength RSSI1_est. The auxiliary calculation unit 41 calculates the first received signal strength for determination RSSI1_est using the following equation (9).

RSSI1_est = (RSSI1_n1 · T2 + RSSI1_n2 · T1) / (T1 + T2) …… (9)
As shown in the enlarged view of FIG. 11, “RSSI1_n1” is the first received signal strength obtained in the two-way communication (first received signal strength RSSI1 at time P1 in FIG. 11). “RSSI1_n2” indicates the first received signal strength (first received signal strength RSSI1 at time point P2 in FIG. 11) after being acquired by two-way bidirectional communication. “T1” indicates a time interval from the time point P1 when the first received signal strength RSSI1_n1 is acquired to the predetermined time point Px, and “T2” is a time point when the first received signal strength RSSI1_n2 after the predetermined time point Px is acquired. The time interval up to P2 is shown. In this example, at the predetermined time point Px, a time (3T) that is three times the unit time T has elapsed since the previous first received signal strength RSSI1_n1 was acquired within the period in which the two first received signal strengths RSSI1 were obtained. Is set at the time. Therefore, the time interval T1 is three times the unit time T, the time interval T2 is equal to the unit time T, and the ratio between the time interval T1 and the time interval T2 is “3: 1”.

Therefore, as indicated by the black circles in FIG. 11, the first reception signal strength RSSI1_est for determination is calculated as an average value obtained by weighting the first reception signal strengths RSSI1_n1 and RSSI1_n2 by the time intervals T1 and T2. (RSSI1_est) is obtained as an estimated value of the received signal strength when the verification ECU 9 transmits the UHF radio wave 24 at the predetermined time point Px.

In addition, the auxiliary calculation unit 41 estimates the received signal strength of the radio wave from the electronic key 2 at a predetermined time point Px based on the two second received signal strengths RSSI2 acquired by the two-way bidirectional communication, This estimated value is calculated as the determination second received signal strength RSSI2_est. The auxiliary calculator 41 calculates the second received signal strength for determination RSSI2_est using the following equation (10).

RSSI2_est = (RSSI2_n1 · T4 + RSSI2_n2 · T3) / (T3 + T4) (10)
“RSSI2_n1” indicates the second received signal strength (second received signal strength RSSI2 at time P3 in FIG. 11) acquired by two bidirectional communications, and “RSSI2_n2” indicates two bidirectional communications. The second received signal strength (second received signal strength RSSI2 at time P4 in FIG. 11) after being acquired by communication is shown. “T3” indicates a time interval from the time point P3 when the previous second received signal strength RSSI2_n1 is acquired to the predetermined time point Px, and “T4” indicates a time point when the second received signal strength RSSI2_n2 after the predetermined time point Px is acquired. The time interval up to P4 is shown. In the present example, as described above, the predetermined time point Px is set to a time point when three times (3T) of the unit time T has elapsed since the previous first received signal strength RSSI1_n1 was acquired, and therefore the time interval T3 is set. It becomes equal to the unit time T, and the time interval T4 is three times the unit time T. That is, the ratio between the time interval T3 and the time interval T4 is “1: 3”.

Therefore, as indicated by black triangles in FIG. 11, the second received signal strength for determination RSSI2_est is calculated as an average value obtained by weighting the second received signal strengths RSSI2_n1 and RSSI2_n2 by the time intervals T3 and T4. (RSSI2_est) is obtained as an estimated value of the received signal strength when the electronic key 2 transmits the UHF radio wave 28 at the predetermined time point Px. In other words, the first received signal strength RSSI1_est for determination and the second received signal strength RSSI2_est for determination are the first received signal strength RSSI1 and the second received when the electronic key 2 and the verification ECU 9 communicate in the same relative position. Each value approximates the received signal strength RSSI2.

Then, the calculation unit 9b calculates the difference between the first received signal strength for determination RSSI1_est and the second received signal strength for determination RSSI2_est. In the fifth embodiment, the difference corresponds to a determination value. Thereafter, the communication correctness determination unit 31 determines the communication correctness of the smart communication as in the first embodiment.

According to the structure of 5th Embodiment, in addition to the effect of (2) of the said 1st Embodiment, the effect as described below can be acquired.
(1) The vehicle 1 and the electronic key 2 perform two-way communication with a UHF radio wave of the same frequency a plurality of times, and the vehicle 1 receives a plurality of first received signals notified from the electronic key 2 by a plurality of two-way communication. Based on the strength RSSI1, the first received signal strength for determination RSSI1_est is calculated. In addition, the vehicle 1 acquires a plurality of second received signal strengths RSSI2 by a plurality of two-way communications, and calculates a determination second received signal strength RSSI2_est based on the plurality of second received signal strengths RSSI2. Then, the vehicle 1 calculates a difference between the determination first received signal strength RSSI1_est and the determination second received signal strength RSSI2_est. Then, by confirming whether or not the difference is the same as the reference value, it is determined whether or not the smart communication is correct. For this reason, since it becomes possible to distinguish whether smart communication is communication using the repeater 22, it is difficult to establish unauthorized communication using the repeater 22. Therefore, security against unauthorized use or theft of the vehicle 1 can be ensured.

(2) The auxiliary calculation unit 41 calculates the estimated value of the first received signal strength RSSI1 at the predetermined time point Px as the first received signal strength RSSI1_est for determination based on the first received signal strength RSSI1_n1 and the first received signal strength RSSI1_n2. did. Further, based on the second received signal strength RSSI2_n1 and the second received signal strength RSSI2_n2, the estimated value of the second received signal strength RSSI2 at the predetermined time point Px is calculated as the second received signal strength for determination RSSI2_est. The first reception signal strength RSSI1_est for determination and the second reception signal strength RSSI2_est for determination calculated in this way are the first reception acquired when communication is performed under the same relative position between the electronic key 2 and the verification ECU 9. The signal strength RSSI1 and the second received signal strength RSSI2 are approximate values. Therefore, even if the first received signal strength RSSI1 and the second received signal strength RSSI2 change, the difference between the first received signal strength for determination RSSI1_est and the second received signal strength for determination RSSI2_est is, for example, the difference in FIG. As shown by □ y, it becomes a very small value, and the change is suitably suppressed. For this reason, it is possible to preferably reduce the erroneous determination that the communication by the authorized user is not the authorized communication.

(3) The auxiliary calculation unit 41 calculates the first reception signal strength RSSI1_est for determination based on the two first reception signal strengths RSSI1 using Equation (9), and uses Equation (10) to calculate 2 A second received signal strength for determination RSSI2_est is calculated based on the two second received signal strengths RSSI2. For this reason, it is possible to quickly determine whether or not the communication is regular communication by performing two-way communication while suppressing a large calculation load from being applied to the auxiliary calculation unit 41.

(4) The reception signal strength notification unit 27 and the transmission processing unit 25 perform radio wave communication alternately at the same time interval, and the auxiliary calculation unit 41 sets the ratio of the time interval T1 and the time interval T2 to “3: 1”. At the same time, the ratio of the time interval T3 and the time interval T4 is set to “1: 3”, and the above formulas (9) and (10) are used. For this reason, it is possible to quickly determine whether or not the communication is regular communication through two-way bidirectional communication while suitably suppressing an excessive calculation load from being applied to the auxiliary calculation unit 41.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
In each of the above embodiments, the received signal strength information 30 is put on the response 21, but in the UHF radio wave 28 transmitted from the electronic key 2, the radio wave on which the received signal strength information 30 is put is the ACK signals 17 and 19, the response described above. 21 may be used, and other types of UHF radio waves may be used. Then, the reception signal strength calculation unit 9a of the radio wave carrying the reception signal strength information 30 calculates, and after calculating the difference by the calculation unit 9b, the communication correctness determination unit 31 compares the reference value R with the difference □. It may be.

In each of the above embodiments, the communication correctness determination unit 31 determines that the difference between the second received signal strength RSSI2 of the response 21 and the first received signal strength RSSI1 (received signal strength information 30) of the challenge 20 is different from the reference value R. When it was detected once that it was not within the reference range, it was determined that regular communication was not performed.

Instead, during communication of various radio waves a plurality of times between the vehicle 1 and the electronic key 2, the communication correctness determination unit 31 performs the second received signal strength RSSI2 and the first received signal strength RSSI1 (received signal strength information 30). When it is detected a plurality of times that the difference from the reference value R is different from the reference value R or not within the reference range, it may be determined that the communication is not regular communication. That is, even if it is determined that the difference is different from the reference value R or not within the reference range and the difference becomes constant after being detected a plurality of times, the communication correctness determination unit 31 determines that unauthorized communication is being performed. Good.

In the second embodiment, when the UHF radio wave transmitted from the vehicle 1 is saturated, the electronic key 2 sends the attenuation request (first attenuation request) and the first received signal strength RSSI1 at that time to the vehicle 1. However, only the attenuation request (first attenuation request) may be transmitted to the vehicle 1. In this case, the transmission processing unit 25 in the verification ECU 9 of the vehicle 1 attenuates the transmission output of the UHF radio wave based on this attenuation request (first attenuation request).

In the third embodiment, when the UHF radio wave transmitted from the electronic key 2 is saturated, the vehicle 1 sends the attenuation request (second attenuation request) and the second received signal strength RSSI2 at that time to the electronic key 2. However, only the attenuation request (second attenuation request) may be transmitted to the electronic key 2. In this case, the reception signal strength notification unit 27 of the electronic key 2 attenuates the transmission output of the UHF radio wave based on this attenuation request (second attenuation request).

-In the said 5th Embodiment, you may apply the structure which performs attenuation | damping request | requirement based on the saturation of a UHF electromagnetic wave like the said 2nd-4th embodiment.
In the fifth embodiment, as shown in FIG. 12, the auxiliary calculation unit 41 sets the ratio between the time interval T1 and the time interval T2 to “1: 3” and the ratio between the time interval T3 and the time interval T4. May be set to “3: 1” to calculate the first received signal strength RSSI1_est for determination and the second received signal strength RSSI2_est for determination at a predetermined time Py. Even if comprised in this way, there exists an effect similar to the said 5th Embodiment. In FIG. 12, a black square mark indicates the determination first received signal strength RSSI1_est, and a black star mark indicates the determination second received signal strength RSSI2_est.

In the fifth embodiment, the auxiliary calculation unit 41 calculates the first received signal strength for determination RSSI1_est and the second received signal strength for determination RSSI2_est using the above equations (9) and (10). However, the present invention is not limited to this. Based on two or more first received signal strengths RSSI1 and two or more second received signal strengths RSSI2, for example, a first received signal strength RSSI1_est for determination using an approximate expression such as a quadratic approximation is used. The determination second received signal strength RSSI2_est may be calculated, and the calculation method may be changed as appropriate.

In the fifth embodiment, the reception signal strength notification unit 27 and the transmission processing unit 25 perform radio wave communication alternately at the same time interval. However, the present invention is not limited to this, and radio wave communication is alternately performed at different time intervals. You may make it perform.

In the fifth embodiment, the first received signal strength RSSI1 and the second received signal strength RSSI2 at the same predetermined time point Px are estimated as the first received signal strength RSSI1_est for determination and the second received signal strength RSSI2_est for determination. Calculated. However, the present invention is not limited to this, and the first received signal strength RSSI1 and the second received signal strength RSSI2 at different time points are estimated and calculated for the first received signal strength RSSI1_est for determination and the second received signal strength RSSI2_est for determination. Also good. In this case, as a method of calculating the first received signal strength RSSI1_est for determination and the second received signal strength RSSI2_est for determination, the above formulas (9) and (10), approximate formulas, and the like can be used as appropriate.

In the fifth embodiment, the calculation unit 9b uses the difference between the determination first received signal strength RSSI1_est and the determination second received signal strength RSSI2_est as the determination value. However, the present invention is not limited to this. For example, the difference between the first received signal strength RSSI1_est for determination and the second received signal strength RSSI2 or the difference between the first received signal strength RSSI1 and the second received signal strength RSSI2_est for determination may be used as the determination value. Good.

For example, as shown in FIG. 13, an average value of the first received signal strength RSSI1_n1 acquired at the time point P1 and the first received signal strength RSSI1_n2 acquired at the time point P2 is calculated as the first received signal strength RSSI1_est for determination. The difference between the first received signal strength RSSI1_est for use and the second received signal strength RSSI2 acquired at time P3 may be calculated as a determination value. According to this configuration, even if a legitimate user having an electronic key moves to a null point during two-way communication and the first received signal strength RSSI1 and the second received signal strength RSSI2 change, for determination The difference between the first received signal strength RSSI1_est and the second received signal strength RSSI2 is a small value, for example, as indicated by the difference □ y in FIG. Thus, the change of the difference can be suppressed, and it can be reduced that the communication by the authorized user is erroneously determined not to be the regular communication. In this case, needless to say, for example, the difference between the first received signal strength for determination RSSI1_est and the second received signal strength for determination RSSI2_est may be used as the determination value.

In each of the above embodiments, the electronic key system is not limited to the key operation free system 3, and may be an immobilizer system, for example.
In the above embodiments, the frequency used for bidirectional communication is not limited to UHF, and other frequencies such as LF (Low Frequency) and HF (High Frequency) may be used.

In each of the above embodiments, the communication master is not limited to the verification ECU 9, and may be another ECU that manages communication.
In each of the above embodiments, the communication terminal is not limited to the electronic key 2 and may be any terminal capable of wireless communication.

In the above embodiments, the inquiry is not limited to the request signal Srq, and other signals can be employed. Further, the response is not limited to the ID signal Sid, but may be any signal that the electronic key 2 returns to the vehicle 1.

In each of the above embodiments, the communication fraud establishment prevention system 23 is not limited to being used for the vehicle 1 but can be applied to other devices and apparatuses.
In each of the above embodiments, the first communication unit is a communication terminal (electronic key 2) and the second communication unit is a communication master (verification ECU 9). Conversely, the first communication unit is a communication master (verification ECU 9). The second communication unit may be a communication terminal (electronic key 2). That is, the configuration of the verification ECU 9 of each of the embodiments that performs communication correctness determination may be provided on the electronic key side.

In each of the above embodiments, the communication correctness determination is performed in either the first communication unit or the second communication unit. However, the configuration of the verification ECU 9 in each of the embodiments that performs the communication correctness determination is You may provide in both 1 communication part and 2nd communication part.

Claims (9)

1. A first communication unit including a first transmission execution unit; and a second communication unit including a second transmission execution unit. The first transmission execution unit and the second transmission execution unit use radio waves having the same frequency. Wireless communication correctness determination system capable of performing bidirectional communication,
   The first communication unit includes first received signal strength calculating means for calculating the received signal strength of the radio wave from the second communication unit as the first received signal strength. Send received signal strength information,
   The second communication unit is
   Second received signal strength calculating means for calculating the received signal strength of the radio wave from the first communication unit as the second received signal strength;
   Determination value calculating means for calculating a determination value based on the first received signal strength and the second received signal strength calculated when the information on the first received signal strength is received;
   A wireless communication correctness determination system comprising: communication correctness determination means for determining whether communication with the first communication unit is a normal communication based on a comparison result between the determination value and a reference range.
2. The wireless communication correctness determination system according to claim 1, wherein the determination value calculation means calculates a difference between the first received signal strength and the second received signal strength as the determination value.
3. The second communication unit includes a plurality of first received signal strengths for determination based on a plurality of first received signal strengths obtained in a plurality of bidirectional communications, and a plurality of obtained in the plurality of bidirectional communications. Auxiliary calculation means for calculating the second received signal strength for determination based on the second received signal strength is provided,
   2. The wireless communication correctness determination system according to claim 1, wherein the determination value calculation unit calculates a difference between the determination first received signal strength and the determination second received signal strength as the determination value.
4. The auxiliary calculation means includes
   Based on the plurality of first received signal strengths, an estimated value of the first received signal strength at a predetermined point in time during which the plurality of first received signal strengths are obtained is calculated as the first received signal strength for determination. And
   The wireless communication correctness determination system according to claim 3, wherein an estimated value of the second received signal strength at the predetermined time point is calculated as the second received signal strength for determination based on the plurality of second received signal strengths. .
5. The auxiliary calculation means includes
   Based on the two first received signal strengths obtained by two-way communication, the first received signal strength for determination is expressed by the following equation:
   RSSI1_est = (RSSI1_n1 · T2 + RSSI1_n2 · T1) / (T1 + T2)
   Is calculated using
   Based on the two second received signal strengths acquired in the two-way bidirectional communication, the determination second received signal strength is expressed by the following equation:
   RSSI2_est = (RSSI2_n1 · T4 + RSSI2_n2 · T3) / (T3 + T4)
   Is calculated using
   here,
   “RSSI1_est” is the first received signal strength for determination,
   “RSSI1_n1” is the first received signal strength obtained in the above two-way communication,
   “RSSI1_n2” is the first received signal strength obtained after the two-way communication,
   “T1” is a time interval from the time when the first received signal strength is acquired to the predetermined time,
   “T2” is a time interval from the predetermined time point to the time point when the subsequent first received signal strength is acquired,
   “RSSI2_est” is the second received signal strength for determination,
   “RSSI2_n1” is the second received signal strength obtained in the previous two-way communication,
   “RSSI2_n2” is the second received signal strength obtained after the two-way communication,
   “T3” is a time interval from the time when the second received signal strength is acquired to the predetermined time,
   The wireless communication correctness determination system according to claim 3 or 4, wherein "T4" is a time interval from the predetermined time point to a time point when the second received signal strength is acquired.
6. The first transmission execution means and the second transmission execution means perform radio wave communication alternately at the same time interval,
   The auxiliary calculation means includes
   When the ratio of the time interval T1 and the time interval T2 is set to “3: 1”, the ratio of the time interval T3 and the time interval T4 is set to “1: 3”;
   The ratio of the time interval T3 and the time interval T4 is set to "3: 1" when the ratio of the time interval T1 and the time interval T2 is set to "1: 3". Wireless communication correctness determination system.
7. The communication correctness determination unit determines that normal communication is not performed when it is detected that the comparison result between the determination value and the reference range does not indicate normal communication a plurality of times. The wireless communication correctness determination system according to any one of the above.
8. The first communication unit includes a first comparison unit that compares the first received signal strength with a first threshold value for detecting a received signal strength saturation, and the first received signal strength exceeds the first threshold value. The first transmission execution unit transmits a first attenuation request to the second communication unit;
   The second transmission execution means performs power control based on the first attenuation request so that the transmission output of the radio wave to the first communication unit is attenuated from the previous transmission output,
   The determination value calculating means receives a new radio wave when the second communication unit newly receives a radio wave without receiving the first attenuation request from the first communication unit after the power control is performed. 8. The determination value according to claim 1, wherein the determination value is calculated based on the second received signal strength of radio waves and the first received signal strength notified by the newly received radio waves. The wireless communication correctness determination system described.
9. The second communication unit includes second comparing means for comparing the second received signal strength with a second threshold value for detecting a received signal strength saturation, and the second received signal strength exceeds the second threshold value. The second transmission execution means transmits a second attenuation request to the first communication unit;
   The first transmission execution means performs power control based on the second attenuation request so that the transmission output of the radio wave to the second communication unit is attenuated from the previous transmission output,
   When the second communication unit newly receives a radio wave from the first communication unit after the second transmission execution unit transmits a radio wave not including the second attenuation request, the determination value calculation unit The determination value is calculated on the basis of the second received signal strength of the radio wave received at the first time and the first received signal strength notified by the newly received radio wave. The wireless communication correctness determination system according to item 1.

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