Vehicle communication method and vehicle communication system

Abstract

To reduce power consumption during radio communication performed between a portable terminal and an on-vehicle unit for controlling equipment of a vehicle.SOLUTION: A portable terminal 2 determines whether or not the portable terminal 2 is moving by a motion detection sensor 20 mounted on the portable terminal 2. If the mobile terminal 2 is determined to be moved, the mobile terminal 2 transmits a first radio signal having a first frequency. An on-vehicle device 10 determines whether or not the first radio signal is received. If the on-vehicle device 10 receives the first radio signal, the on-vehicle device 10 transmits a second radio signal having a second frequency lower than the first frequency.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle communication method and a vehicle communication system. [Background technology]

[0002] Patent Document 1 describes a vehicle communication device that communicates with a portable device to control vehicle equipment. The vehicle communication device intermittently transmits a high-frequency signal that has a higher frequency than a low-frequency LF signal to search for a communication partner, and when a communication partner is found by searching using the high-frequency signal, it intermittently transmits an LF signal to search for the communication partner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-22922 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the invention of Patent Document 1 had a problem in that if the portable device was located within range of the high-frequency signal, radio waves would be transmitted and received between the vehicle communication device and the portable device, consuming power even if the user did not intend to use the vehicle. An object of the present invention is to reduce power consumption caused by wireless communication between a mobile terminal and an in-vehicle device for controlling equipment of a vehicle. [Means for solving the problem]

[0005] In the vehicle communication method, a motion detection sensor mounted on the portable terminal determines whether the portable terminal is moving, and if it is determined that the portable terminal is moving, the portable terminal transmits a first wireless signal of a first frequency, an in-vehicle device determines whether it has received the first wireless signal, and if it has received the first wireless signal, the in-vehicle device transmits a second wireless signal of a second frequency lower than the first frequency. Effect of the Invention

[0006] According to the present invention, it is possible to reduce power consumption due to wireless communication between a mobile terminal and an in-vehicle device for controlling equipment in a vehicle. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of a vehicle communication system according to an embodiment; [Diagram 2] 1A is an example of a state transition diagram of an in-vehicle device, and FIG. 1B is an example of a state transition diagram of a portable terminal. [Diagram 3] 6(a) to 6(e) are diagrams illustrating an example of the operation of the in-car device and the mobile terminal. [Figure 4] FIG. 4 is a sequence diagram of an example of the operation of the mobile terminal and the in-car device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same or similar parts are given the same or similar reference numerals, and duplicated explanations are omitted. Each drawing is schematic and may differ from the actual one. The embodiments shown below are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the devices and methods exemplified in the following embodiments. The technical idea of ​​the present invention can be modified in various ways within the technical scope described in the claims.

[0009] (composition) 1 is a diagram showing an example of a schematic configuration of a vehicle communication system 100 according to an embodiment. The vehicle communication system 100 includes an in-vehicle device 10 mounted on a vehicle 1 and a mobile terminal 2 carried by a user of the vehicle 1, and is a system that performs wireless communication between the mobile terminal 2 and the in-vehicle device 10 to control equipment of the vehicle 1. The vehicle 1 transmits a LF (Low Frequency) signal S LFThe LF signal S is transmitted to the outside and inside of the vehicle. LF may be a radio signal having a relatively low frequency. For example, the LF signal S LF The LF signal S may be a radio signal with a frequency of about 125 kHz. LF The communication distance of the LF signal S is relatively short. LF The communication distance may be about 1m.

[0010] The mobile terminal 2 may be, for example, a remote control terminal (such as a KEYFOB) for locking and unlocking the vehicle 1 and for operating the ignition switch. The mobile terminal 2 transmits an LF signal S LF A request signal S HF and LF signal S LF A response signal S transmitted in response to R and an operation signal S for operating the equipment of the vehicle 1. O The response signal S R may include identification information such as the ID code of the mobile terminal 2. request signal S HF , response signal S R and operation signal S O may be a radio signal having a relatively high frequency. For example, the request signal S HF , response signal S R and operation signal S O may be a radio frequency (RF) signal having a frequency of about 300 MHz. request signal S HF , response signal S R and operation signal S O The communication distance is relatively long, for example, about 30 m.

[0011] As mentioned above, the LF signal S LF The communication distance of the LF signal S is relatively short. LF The mobile terminal 2 that receives the response signal S RBy authenticating the mobile terminal 2 based on the identification information contained in the mobile terminal 2, operation of the equipment of the vehicle 1 can be permitted only when the user carrying the mobile terminal 2 is inside or near the vehicle 1. request signal S HF is an example of the "first wireless signal" described in the claims, and the LF signal S LF is an example of a "second wireless signal" as defined in the claims.

[0012] The vehicle-mounted device 10 includes a high-frequency receiver 11, a low-frequency transmitter 12, an operation switch 13, and a controller 14. 1, high frequency is indicated as "HF" (i.e., High Frequency), low frequency is indicated as "LF", switch is indicated as "SW", and ignition is indicated as "IGN". The high frequency receiver 11 and the low frequency transmitter 12 are examples of the "receiver" and "second transmitter" respectively described in the claims. The high frequency receiver 11 receives the request signal S transmitted from the mobile terminal 2. HF , response signal S R , operation signal S O Receive. A low frequency transmitter 12 transmits an LF signal S LF is transmitted to both the outside and inside of the vehicle.

[0013] The operation switch 13 is a switch that accepts a user's operation of equipment of the vehicle 1. The equipment of the vehicle 1 may be, for example, a lock device 17 that locks and unlocks the doors of the vehicle 1, or an ignition switch 18. The controller 14 is an electronic control unit (ECU) and outputs an LF signal S LF and controls whether to permit or prohibit the user from operating the equipment of vehicle 1. The controller 14 includes a processor 15 and peripheral components such as a storage device 16. The processor 15 may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).

[0014] The storage device 16 may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device 16 may include memories such as a register, a cache memory, a ROM (Read Only Memory) used as a main storage device, and a RAM (Random Access Memory). The functions of the controller 14 described below are realized by, for example, the processor 15 executing a computer program stored in the storage device 16. The controller 14 may be formed of dedicated hardware for executing each information processing operation described below. For example, the controller 14 may include a functional logic circuit configured in a general-purpose semiconductor integrated circuit, or may include a programmable logic device (PLD) such as a field programmable gate array (FPGA). The processing by the controller 14 will be described later.

[0015] The mobile terminal 2 includes a motion detection sensor 20, a high-frequency transmitter 21, a low-frequency receiver 22, an operation switch 23, and a controller 24. The high frequency transmitter 21 is an example of a "first transmitter" or a "transmitter" as defined in the claims. The motion detection sensor 20 detects the motion of the mobile terminal 2. For example, the motion detection sensor 20 detects acceleration in three axial directions and angular velocity around three axes. For example, the motion detection sensor 20 may be a motion sensor that combines an inertial sensor (a three-axis acceleration sensor and a three-axis gyro sensor) and a three-axis geomagnetic sensor. By detecting the movement of the portable terminal 2, it is possible to determine whether the user is carrying the portable terminal 2 and moving in order to use the vehicle 1, or whether the user has no intention of using the vehicle 1 and the portable terminal 2 is simply left there.

[0016] The high frequency transmitter 21 transmits a request signal S HF , response signal SR and operation signal S O Send. The low frequency receiver 22 receives the LF signal S LF Receive. The operation switch 23 is a switch that accepts an operation of the equipment of the vehicle 1 by a user. When the operation switch 23 is operated by a user, the controller 24 outputs an operation signal S O is transmitted to the high frequency transmitter 21. The controller 24 receives a request signal S HF , response signal S R and operation signal S O This is an electronic control unit that controls the transmission. The controller 24 includes a processor 25 and peripheral components such as a storage device 26. The processor 25 may be, for example, a CPU or an MPU.

[0017] The storage device 26 may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The storage device 26 may include memories such as a register, a cache memory, and a ROM and a RAM used as a main storage device. The functions of the controller 24 described below are realized by, for example, the processor 25 executing a computer program stored in the storage device 26. The controller 24 may be formed of dedicated hardware for executing each of the information processes described below. For example, the controller 24 may include a functional logic circuit implemented in a general-purpose semiconductor integrated circuit, or may include a PLD such as an FPGA. The processing by the controller 24 will be described later.

[0018] Next, a description will be given of the processing by the controllers 14 and 24. Fig. 2(a) is an example of a state transition diagram of the in-vehicle device 10. When control by the controller 14 starts, the controller 14 first transitions the operation state of the in-vehicle device 10 to an operating state ST11. In the operating state ST11, the controller 14 transmits the LF signal S to the low frequency transmitter 12. LFis transmitted intermittently. LF signal S LF When a mobile terminal 2 is present within the communication range of the LF signal S LF A response signal S transmitted from the mobile terminal 2 in response to R When the high frequency receiver 11 receives the signal S, the controller 14 outputs a response signal S R The response signal S is then compared to the identification information stored in the storage device 16. R If the identification information included in the authentication information matches the identification information stored in the storage device 16, the mobile terminal 2 is authenticated.

[0019] When the mobile terminal 2 is authenticated, the controller 14 permits the user to operate the equipment of the vehicle 1. For example, the controller 14 permits the user to operate the lock device 17 and the ignition switch 18 using the operation switch 13. In addition, the controller 14 permits the user to operate the operation signal S transmitted from the mobile terminal 2 by operating the operation switch 23. O When the high frequency receiver 11 receives the operation signal S O The device controls the equipment of vehicle 1 according to the request. On the other hand, if the mobile terminal 2 is not authenticated, the controller 14 prohibits the user from operating the equipment of the vehicle 1.

[0020] Further, in the operating state ST11, the controller 14 detects whether the high frequency receiver 11 receives a request signal S HF The time duration during which no signal is received is measured. Before the predetermined time T has elapsed, the high frequency receiver 11 receives a request signal S HF When the controller 14 receives the command, the controller 14 maintains the operation state of the in-vehicle device 10 in the operating state ST11. request signal S HF If the state where the vehicle-mounted device 10 does not receive the signal continues for a predetermined time T or more, the controller 14 transitions the operation state of the vehicle-mounted device 10 to the power-saving state ST12. If the ignition switch 18 is switched on, the controller 14 also transitions the operation state of the vehicle-mounted device 10 to the power-saving state ST12.

[0021] In the power saving state ST12, the controller 14 transmits the LF signal SLF This stops the intermittent transmission of the LF signal S LF This reduces power consumption for transmitting the signal. The controller 14 also detects whether the high frequency receiver 11 receives a request signal S HF It monitors whether the request signal S HF If the controller 14 does not receive the request signal S, the controller 14 maintains the operation state of the in-vehicle device 10 in the power saving state ST12. HF When the signal is received, the operation state of the in-vehicle device 10 is transitioned to the operating state ST11.

[0022] When the in-vehicle device 10 operates in this manner, even if the user has no intention of using the vehicle, the request signal S HF When the LF signal S reaches the in-vehicle device 10, the in-vehicle device 10 outputs the LF signal S LF By transmitting the LF signal S LF It consumes power for transmission. For example, as in the above-mentioned Patent Document 1, even if a configuration is adopted in which a high-frequency signal is transmitted from the vehicle side in advance to search for a portable unit, and an LF signal is transmitted when the portable unit is found, power is consumed for transmitting the high-frequency signal. Also, if the high-frequency signal reaches the portable unit, the LF signal S is transmitted even if the user does not intend to use the vehicle. LF It consumes power for transmission.

[0023] Therefore, the portable terminal 2 of the embodiment determines whether the portable terminal 2 is moving by the motion detection sensor 20, and when it is determined that the portable terminal 2 is moving, it outputs a request signal S HF By transmitting the LF signal S LF to send the 2(b) is an example of a state transition diagram of the portable terminal 2. When control by the controller 24 starts, the controller 24 first transitions the operation state of the portable terminal 2 to an operating state ST21. In the operating state ST21, the controller 24 transmits a request signal S HF is transmitted intermittently.

[0024] request signal S HF When the in-vehicle device 10 is within the communication range of the HF In response to the LF signal S LF Send. Then, the mobile terminal 2 transmits the LF signal S LF and a low frequency receiver 22 receives an LF signal S LF Upon receiving the signal, the controller 24 transmits a response signal S to the high frequency transmitter 21. R to be transmitted. When the user operates the operation switch 23, the controller 24 transmits an operation signal S O to be transmitted.

[0025] Furthermore, in the operating state ST21, the controller 24 monitors the movement of the portable terminal 2 by the movement detection sensor 20. When the movement detection sensor 20 detects the movement of the portable terminal 2 (i.e., when it detects that the portable terminal 2 is moving), the controller 24 maintains the operating state of the portable terminal 2 in the operating state ST21. When the motion detection sensor 20 does not detect the motion of the portable terminal 2 (that is, when it detects that the portable terminal 2 is not moving), the controller 24 transitions the operation state of the portable terminal 2 to the power saving state ST22.

[0026] In the power saving state ST22, the controller 24 receives a request signal S HF Stop the intermittent transmission of As a result, in a state where the motion detection sensor 20 is not detecting the motion of the portable terminal 2, that is, in a state where the user is not moving while carrying the portable terminal 2 in order to use the vehicle 1 (for example, the portable terminal 2 is simply placed down), the request signal S HF This can reduce the power consumption of the mobile terminal 2 for transmitting the request signal S. HF In response to the LF signal S LF This makes it possible to reduce the power consumption of the in-vehicle device 10 that transmits the signal. Therefore, when the user has no intention of using the vehicle 1, power consumption due to wireless communication between the mobile terminal 2 and the in-vehicle device 10 can be reduced.

[0027] In the power saving state ST22, the controller 24 monitors the movement of the mobile terminal 2 by the movement detection sensor 20. When the motion detection sensor 20 does not detect the motion of the portable terminal 2 (that is, when it detects that the portable terminal 2 is not moving), the controller 24 maintains the operating state of the portable terminal 2 in the power saving state ST22. When the motion detection sensor 20 detects the motion of the portable terminal 2 (i.e., when it detects that the portable terminal 2 is moving), the controller 24 transitions the operation state of the portable terminal 2 to the operating state ST21. As a result, the request signal S HF Transmission will resume.

[0028] Next, an example of the operation of the in-car device 10 and the mobile terminal 2 will be described with reference to Fig. 3(a) to Fig. 3(e). HF The dashed line A2 indicates the communication range of the LF signal S LF This shows the communication range. In the state shown in FIG. 3(a), the user U1 is moving outside the communication range A1 while carrying the portable terminal 2. Therefore, the motion detection sensor 20 detects the motion of the portable terminal 2, and the portable terminal 2 enters the operating state ST21. As a result, the portable terminal 2 transmits a request signal S HF However, the request signal S HF does not reach the in-vehicle device 10, the in-vehicle device 10 enters the power saving state ST12 and the LF signal S LF Stop sending. That is, even if the mobile terminal 2 is moving, when the mobile terminal 2 is away from the vehicle-mounted device 10, the vehicle-mounted device 10 receives the LF signal S LF Stop sending.

[0029] Also, when the user U1 does not have the mobile terminal 2 and it is placed outside the communication range A1, the motion detection sensor 20 does not detect the motion of the mobile terminal 2, so that the mobile terminal 2 enters the power saving state ST22.HF is not transmitted, and the in-vehicle device 10 transmits the LF signal S LF Stop sending. In the state shown in FIG. 3(b), a user U1 carrying the portable terminal 2 approaches the vehicle-mounted device 10 and is within the communication range A1 but outside the communication range A2. In this case, the motion detection sensor 20 detects the motion of the portable terminal 2, and the portable terminal 2 enters the operating state ST21. As a result, the portable terminal 2 transmits a request signal S HF The in-vehicle device 10 receives the request signal S HF In this way, the request signal S HF From a state where no request signal S is received HF When it is detected that the mobile terminal 2 is approaching the vehicle-mounted device 10, the vehicle-mounted device 10 receives the LF signal S LF Send. However, when the mobile terminal 2 receives the LF signal S LF Since the mobile terminal 2 is located outside the communication range A2 of the LF Therefore, the response signal S R is not transmitted and the mobile terminal 2 is not authenticated. Therefore, the equipment of the vehicle 1 cannot be operated yet.

[0030] In the state shown in FIG. 3(c), the user U1 does not carry the portable terminal 2, and the portable terminal 2 is placed within the communication range A1. Therefore, the motion detection sensor 20 does not detect the motion of the portable terminal 2, and the portable terminal 2 enters the power saving state ST22. Then, the request signal S HF Since no request signal S is sent, HF If the state where the LF signal S is not received continues for a predetermined time T or more, the in-vehicle device 10 transitions to the power saving state ST12 and outputs the LF signal S LF Stop sending. In the state shown in Fig. 3(d), the user U1 does not carry the portable terminal 2, and the portable terminal 2 is placed within the communication range A2. This case is also similar to Fig. 3(c).

[0031] In the state shown in FIG. 3(e), the user U1 carrying the portable terminal 2 approaches the vehicle-mounted device 10 and is within the communication range A2. In this case, the motion detection sensor 20 detects the motion of the portable terminal 2, and the portable terminal 2 enters the operating state ST21. As a result, the portable terminal 2 transmits a request signal S HF The controller 14 of the vehicle-mounted device 10 receives the request signal S HF When it receives the LF signal S, it goes into the operating state ST11. LF Send. Since the mobile terminal 2 is located within the communication range A2, the mobile terminal 2 receives the LF signal S LF As a result, the mobile terminal 2 receives a response signal S R The in-vehicle device 10 then transmits the authentication code and authenticates the in-vehicle device 10. This allows the device in the vehicle 1 to be operated.

[0032] In the state shown in FIG. 3(e), the user U1 blocks the path between the mobile terminal 2 and the in-vehicle device 10, and the request signal S HF When the LF signal S stops reaching the in-vehicle device 10, LF may stop transmitting. However, when the user U1 intends to use the vehicle 1, the user U1 moves his / her body, and the positional relationship between the user U1, the vehicle 1, and the mobile terminal 2 changes, so that the request signal S HF The state in which the signal does not reach the in-vehicle device 10 is immediately resolved.

[0033] FIG. 4 is a sequence diagram of an example of the operation of the in-car device 10 and the mobile terminal 2. In FIG. In step S1, the motion detection sensor 20 detects the motion of the mobile terminal 2. Here, a user U1 holds the mobile terminal 2 and sends a request signal S HF Assume that the mobile station is moving outside the communication range A1. Therefore, in step S2, the mobile terminal 2 receives a request signal S HF However, the request signal S HF does not reach the in-vehicle device 10, and the in-vehicle device 10 receives the LF signal S LF Stop sending.

[0034] Next, the user U1 places the mobile terminal 2 within the communication range A1 and the LF signal S LF In step S3, the motion detection sensor 20 stops detecting the motion of the portable terminal 2. Therefore, the portable terminal 2 does not transmit the request signal S HF The in-vehicle device 10 does not transmit the LF signal S LF Stop sending. Next, a user U1 carries a portable terminal 2 and is within a communication range A1 and receives an LF signal S LF In step S4, the motion detection sensor 20 detects the motion of the mobile terminal 2. Therefore, in step S5, the mobile terminal 2 receives a request signal S HF Since the mobile terminal 2 is within the communication range A1, the request signal S HF reaches the in-vehicle device 10.

[0035] Therefore, in step S6, the in-vehicle device 10 outputs the LF signal S LF However, since the mobile terminal 2 is located outside the communication range A2, the LF signal S LF does not reach the mobile terminal 2. Therefore, the response signal S R is not transmitted and the mobile terminal 2 is not authenticated. Therefore, the equipment of the vehicle 1 cannot be operated yet.

[0036] Next, a user U1 carries a mobile terminal 2 and transmits an LF signal S LF In step S7, the motion detection sensor 20 detects the motion of the portable terminal 2. In step S8, the portable terminal 2 transmits a request signal S HF Send. Since the mobile terminal 2 is within the communication range A1, the request signal S HF reaches the in-vehicle device 10, and in step S9, the in-vehicle device 10 outputs the LF signal S LF Send. Since the mobile terminal 2 is within the communication range A2, the LF signal S LF reaches the mobile terminal 2. Therefore, in step S10, the mobile terminal 2 receives a response signal SR As a result, the mobile terminal 2 is authenticated and becomes able to operate the equipment of the vehicle 1.

[0037] (Modification) In the above description, the mobile terminal 2 is a remote control terminal (such as a KEYFOB) that locks and unlocks the vehicle 1 and operates the ignition switch, but the mobile terminal 2 is not limited to such a remote control terminal. For example, the mobile terminal 2 may be a portable terminal device (such as a smartphone or a PDA (Personal Digital Assistant)) capable of transmitting and receiving information to and from the in-vehicle device 10 of the vehicle 1. In this case, for example, the mobile terminal 2 may receive a request signal S HF , response signal S R , operation signal S O Alternatively, the in-vehicle device 10 may transmit a signal conforming to the Bluetooth (registered trademark) standard as the LF signal S LF Alternatively, a UWB (Ultra Wide Band) signal may be transmitted as the wireless communication signal.

[0038] Also, for example, a combination of a remote control terminal such as the above-mentioned KEYFOB and a portable terminal device such as a smartphone may be used as the mobile terminal 2. In this case, for example, the portable terminal device transmits a request signal S HF The in-vehicle device 10 transmits a signal conforming to the Bluetooth (registered trademark) standard as a LF signal S LF The remote control terminal transmits a response signal S R , operation signal S O The device may transmit a radio frequency (RF) signal as a

[0039] (Effects of the embodiment) (1) The vehicle communication system 100 includes a mobile terminal 2 and an in-vehicle device 10. The mobile terminal 2 includes a motion detection sensor 20 that detects motion of the mobile terminal 2, and a request signal S having a first frequency when the motion detection sensor 20 detects motion of the mobile terminal. HFThe in-vehicle device 10 is equipped with a high-frequency transmitter 21 that transmits a request signal S HF A high frequency receiver 11 receives a request signal S HF When receiving an LF signal S with a second frequency lower than the first frequency, LF and a low frequency transmitter 12 for transmitting a

[0040] As a result, when the user does not intend to use the vehicle 1, the request signal S HF and the LF signal S from the in-vehicle device 10. LF As a result, power consumption due to wireless communication between the portable terminal 2 and the in-car device 10 can be reduced. In addition, the LF signal S LF By starting to transmit the highly accurate LF signal S LF This makes it possible to control the stop of transmission.

[0041] (2) The in-vehicle device 10 judges whether the portable terminal 2 is approaching the in-vehicle device 10, and when it judges that the portable terminal 2 is approaching the in-vehicle device 10, it outputs the LF signal S LF In this way, when the mobile terminal 2 is far away from the in-vehicle device 10, the LF signal S LF To stop the transmission of the LF signal S LF This reduces the power consumption for transmitting.

[0042] (3) Even if the mobile terminal 2 is moving, when the mobile terminal 2 is away from the vehicle-mounted device 10, the vehicle-mounted device 10 receives the LF signal S LF As a result, the mobile terminal 2 stops transmitting the request signal S HF Even if the LF signal S is being transmitted, if the mobile terminal 2 is away from the in-vehicle device 10, the LF signal S LF To stop the transmission of the LF signal S LF This reduces the power consumption for transmitting. [Explanation of symbols]

[0043] 100...vehicle communication system, 1...vehicle, 2...mobile terminal, 10...vehicle-mounted device, 11...high-frequency receiver, 12...low-frequency transmitter, 13, 23...operation switch, 14, 24...controller, 15, 25...processor, 16, 26...storage device, 17...locking device, 18...ignition switch, 20...motion detection sensor, 21...high-frequency transmitter, 22...low-frequency receiver

Claims

1. A motion detection sensor mounted on the mobile terminal determines whether the mobile terminal is moving; When it is determined that the mobile device is moving, the mobile device transmits a first wireless signal of a first frequency; The in-vehicle device determines whether or not the first wireless signal is received; an operating state of the in-vehicle device is switchable between an operating state in which the in-vehicle device intermittently transmits a second wireless signal having a second frequency lower than the first frequency, and a power saving state in which the in-vehicle device stops transmitting the second wireless signal; when the in-vehicle device receives the first wireless signal, transitioning an operation state of the in-vehicle device from the power saving state to the working state, and when a state in which the first wireless signal is not received continues for a predetermined time or more, transitioning the operation state of the in-vehicle device from the working state to the power saving state. A vehicle communication method comprising:

2. The vehicle communication method according to claim 1, characterized in that the in-vehicle device determines whether the portable terminal is approaching the in-vehicle device, and transmits the second wireless signal when it determines that the portable terminal is approaching the in-vehicle device.

3. 3. The vehicle communication method according to claim 1, wherein when the portable terminal is moving but is away from the vehicle-mounted device, the vehicle-mounted device stops transmitting the second wireless signal.

4. A vehicle communication system including a mobile terminal and an in-vehicle device, The mobile terminal includes: A motion detection sensor that detects the motion of the mobile terminal; a first transmitter that transmits a first wireless signal of a first frequency when the motion detection sensor detects motion of the mobile terminal; The in-vehicle device includes: a receiver for receiving the first wireless signal transmitted from the mobile terminal; a second transmitter configured to transmit a second radio signal at a second frequency lower than the first frequency, an operation state of the in-vehicle device is switchable between an operating state in which the in-vehicle device intermittently transmits the second wireless signal and a power saving state in which the in-vehicle device stops transmitting the second wireless signal; A vehicle communication system characterized in that when the in-vehicle device receives the first wireless signal, the operating state of the in-vehicle device is transitioned from the power saving state to the working state, and when a state in which the first wireless signal is not received continues for more than a predetermined time, the operating state of the in-vehicle device is transitioned from the working state to the power saving state.

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