WO2020100941A1

WO2020100941A1 - Position determination system and position determination method

Info

Publication number: WO2020100941A1
Application number: PCT/JP2019/044518
Authority: WO
Inventors: 正則小杉; 剛士木村
Original assignee: 株式会社東海理化電機製作所
Priority date: 2018-11-16
Filing date: 2019-11-13
Publication date: 2020-05-22

Abstract

This position determination system (30) comprises a position determination unit (31) which determines the position of a mobile terminal (2) with respect to a communication partner (1). For a plurality of radio waves respectively communicated at different frequencies between each of a plurality of antennas (16, 17) provided in the communication partner (1) and the mobile terminal (2), the position determination unit (31) calculates the characteristic value of each antenna (16; 17) from the reception intensity measured for each radio wave of each frequency, and compares the magnitudes of the characteristic values of the antennas (16, 17) to determine the position of the mobile terminal (2).

Description

Position determination system and position determination method

The present invention relates to a position determination system and a position determination method for determining the position of a mobile terminal with respect to a communication partner when the mobile terminal communicates with the communication partner.

In the past, for example, in a vehicle, an authentication system is known that controls the vehicle through wireless communication between a mobile terminal carried by the user and an in-vehicle device mounted in the vehicle. As an authentication system, a smart verification system is known in which a mobile terminal automatically responds to a radio wave transmitted from a vehicle-mounted device and performs ID verification (smart verification) by wireless communication.

Patent Document 1 discloses a smart matching system including a position determination system that determines the position of a mobile terminal with respect to a vehicle. In this position determination system, the reception intensity when the radio wave transmitted from the vehicle is received by the mobile terminal is measured, and the position where the reception intensity matches is determined as the position of the mobile terminal. When the position determination of the mobile terminal by the position determination system is imposed on the authentication in addition to the ID verification, the security of the smart verification system can be improved.

Japanese Patent Laid-Open No. 2018-12933

By the way, even if the mobile terminal is at the same position, the reception strength may change if, for example, the transmitted radio waves are blocked by obstacles or interfere with other radio waves. When the reception intensity changes, there is a problem that the position of the mobile terminal cannot be accurately determined.

An object of the present invention is to provide a position determination system and a position determination method capable of improving the position determination accuracy of a mobile terminal.

A position determination system according to one embodiment includes a position determination unit that determines a position of the mobile terminal with respect to the communication partner when the mobile terminal and a communication partner communicate with each other wirelessly, and the position determination unit is configured to perform the communication. For a plurality of radio waves communicated at different frequencies between each of a plurality of antennas provided to the other party and the mobile terminal, a characteristic value for each antenna is calculated from the reception intensity measured for each radio wave of each frequency. Then, the position of the mobile terminal is determined by comparing the magnitudes of the characteristic values between the antennas.

In the position determination method according to one embodiment, when a mobile terminal and a communication partner communicate wirelessly, each of a plurality of antennas provided to the communication partner and the mobile terminal communicate at different frequencies. For the plurality of radio waves, the characteristic value for each antenna is calculated from the reception intensity measured for each radio wave of each frequency, and the size of the characteristic value between the antennas is compared to determine whether the mobile phone for the communication partner is used. Determining the location of the terminal.

The position determination system and the position determination method of the present invention can improve the accuracy of position determination of a mobile terminal.

The block diagram which shows the structure of the position determination system provided in the authentication system of 1st Embodiment. The flowchart which shows the flow of authentication through communication between the vehicle and a portable terminal in an authentication system. The figure which shows a radio wave propagation path when a portable terminal is located outside the vehicle. The graph which shows the reception strength of the position detection signal transmitted from the (a) outdoor antenna when the portable terminal is located outdoors of the vehicle, and the graph which shows the reception strength of the position detection signal transmitted from the indoor antenna. The figure which shows a radio wave propagation path when a portable terminal is located in the vehicle interior. The graph which shows the reception intensity of the position detection signal transmitted from the (a) outdoor antenna when the portable terminal is located in the vehicle interior, and the graph which shows the reception intensity of the position detection signal transmitted from the indoor antenna (b). The block diagram which shows the structure of the position determination system provided in the authentication system of 2nd Embodiment. The graph which shows the receiving strength from each antenna when a portable terminal is located outdoors of a vehicle. The graph which shows the reception strength from each antenna when a portable terminal is located in the vehicle interior. The figure which shows the antenna provided in the vehicle in 4th Embodiment. In 5th Embodiment, the graph which shows correction | amendment of average value Pr1 'at the time of performing the outdoor determination. The graph which shows correction | amendment of average value Pr1 'at the time of making an indoor determination in 5th Embodiment. The graph which showed an example of change of the difference of average value Pr1 'and average value Pr2' in a 5th embodiment.

<First Embodiment>
Hereinafter, a first embodiment of a position determination system and a position determination method will be described with reference to FIGS.

As shown in FIG. 1, the vehicle 1 as a communication partner includes an authentication system 3 that authenticates whether the mobile terminal 2 is correct or not through wireless communication. The mobile terminal 2 can be, for example, a high-performance mobile phone that has a telephone function and can communicate with the vehicle 1 using short-range wireless communication. The authentication system 3 of this example is a short-range wireless verification system that executes ID verification by short-range wireless communication triggered by communication from the vehicle 1. The short-range wireless communication may be Bluetooth (registered trademark) communication, for example.

The vehicle 1 includes a verification ECU (Electronic Control Unit) 4 that performs ID verification, a body ECU 5 that manages the power supply of in-vehicle electrical components, and an engine ECU 7 that controls the engine 6. These ECUs are connected through a communication line 8 inside the vehicle. The communication line 8 is composed of, for example, a CAN (Controller Area network) or a LIN (Local Interconnect network).

The electronic key ID and the key unique key of the portable terminal 2 registered in the vehicle 1 are written and stored in the memory 9 of the verification ECU 4. In the authentication system 3, a series of ID verification is automatically executed by mutual communication between the verification ECU 4 and the mobile terminal 2, and the door lock and unlock and engine start are performed on condition that the ID verification is established. Is allowed.

The body ECU 5 controls the operation of the door lock device 11 as a mechanical part that locks and unlocks the vehicle door 10. The vehicle door 10 is provided with an exterior door handle 12 for operating the opening and closing of the vehicle door 10. The exterior door handle 12 is provided with a touch sensor 13 that detects a user's touch operation on the exterior door handle 12 as a trigger for unlocking the door, for example. Further, the vehicle exterior door handle 12 is provided with a lock button 14 that is operated, for example, when locking the door. The body ECU 5 controls the operation of the door lock device 11 based on the detection signal of the touch sensor 13 or the lock button 14 when the ID verification is established and the portable terminal 2 is located outside the vehicle 1. .

The engine ECU 7 controls the operation of the engine 6 of the vehicle 1. The vehicle 1 is provided with an engine switch 15 for operating the power transition of the engine 6. The engine switch 15 can be, for example, a push-type switch. The engine ECU 7 controls the transition of the engine 6 by operating the engine switch 15 under a predetermined condition. The predetermined condition here means that ID verification is established, the portable terminal 2 is located inside the vehicle 1, and the brake pedal (not shown) of the vehicle 1 is stepped on. , The transmission of the vehicle 1 is in the parking range, or a combination thereof.

The vehicle 1 includes an outdoor antenna 16 and an indoor antenna 17 for performing near field communication with the mobile terminal 2. The outdoor antenna 16 is provided outside the vehicle 1. The indoor antenna 17 is provided on the indoor side of the vehicle 1. The outdoor antenna 16 and the indoor antenna 17 of this example perform BLE (Bluetooth Low Energy) communication with the mobile terminal 2. The outdoor antenna 16 and the indoor antenna 17 have their own unique antenna IDs. In the BLE communication of this example, the mobile terminal 2 is a master and the vehicle 1 is a slave. The relationship between the master and the slave is not limited to this, and the vehicle 1 may be the master and the mobile terminal 2 may be the slave. The outdoor antenna 16 and the indoor antenna 17 periodically transmit an advertisement message to an area near the vehicle 1 in a predetermined order.

The mobile terminal 2 includes a terminal control unit 20 that controls the operation of the mobile terminal 2, a network communication module 21 that performs network communication between the mobile terminal 2 and an external device or a communication partner, and the mobile terminal 2 and a communication partner (vehicle). 1) and a terminal communication unit 22 that performs near field communication (BLE communication).

When using the mobile terminal 2 as the electronic key of the vehicle 1, the mobile terminal 2 registers the electronic key ID and the key unique key of the mobile terminal 2 in the vehicle 1 (electronic key registration). For example, the mobile terminal 2 acquires an electronic key ID and a key unique key from a server (not shown) through network communication, writes them in the memory 24, and saves them. Further, the mobile terminal 2 connects (logs in) to the vehicle 1 through BLE communication and registers the electronic key ID and the key unique key of the mobile terminal 2.

When the mobile terminal 2 receives the advertisement message from the vehicle 1 and establishes the BLE communication connection with the vehicle 1, the mobile terminal 2 automatically performs ID verification by mutual communication through the BLE communication with the vehicle 1. For example, when the electronic key registration of the mobile terminal 2 is completed and the BLE communication connection is established between the vehicle 1 and the mobile terminal 2, the electronic key ID is transmitted and received between the verification ECU 4 and the terminal control unit 20. The electronic key ID is verified, and cryptographic authentication such as challenge response authentication using the key unique key is performed. When the verification ECU 4 confirms that the verification and the authentication are established, the verification ECU 4 determines that the ID verification is established. It should be noted that the series of ID collation is automatically executed without the user operating the mobile terminal 2 or the vehicle 1.

The authentication system 3 includes a position determination system 30 that determines the position of the mobile terminal 2 with respect to the vehicle 1 when the vehicle 1 and the mobile terminal 2 communicate with each other. When the vehicle 1 and the mobile terminal 2 perform ID verification, the position determination system 30 of the present example determines whether the mobile terminal 2 is inside or outside the vehicle 1. In addition, this position determination may be performed at any timing during ID collation communication. That is, the position determination may be performed before ID verification, after ID verification, or during ID verification.

The position determination system 30 includes a position determination unit 31 that determines the position of the mobile terminal 2 with respect to the vehicle 1. The position determination unit 31 of this example is provided in the verification ECU 4 of the vehicle 1. The position determination unit 31 causes the outdoor antenna 16 and the indoor antenna 17 to BLE-transmit the position detection signal Sd including the antenna ID. In the series of position determination process, the position detection signal Sd is transmitted from the outdoor antenna 16 and the indoor antenna 17 a plurality of times. Further, the transmission powers of the position detection signals Sd from the outdoor antenna 16 and the indoor antenna 17 are the same.

The position determination system 30 includes a measurement unit 32 that measures the reception intensity of radio waves between the outdoor antenna 16 and the indoor antenna 17 and the mobile terminal 2 for each radio wave of each frequency (each channel). The measurement unit 32 of this example is provided in the terminal control unit 20 of the mobile terminal 2. Upon receiving the position detection signal Sd from the outdoor antenna 16 and the indoor antenna 17 via the terminal communication unit 22, the measurement unit 32 measures the reception intensity (RSSI: Received Signal Strength Indicator) of this position detection signal Sd. Here, the reception intensity of the position detection signal Sd transmitted from the outdoor antenna 16 is defined as the reception intensity Pr1, and the reception intensity of the position detection signal Sd transmitted from the indoor antenna 17 is defined as the reception intensity Pr2. The measurement unit 32 measures the received signal strength for each received position detection signal Sd, and transmits the measured received strength (reception strength data) of the position detection signal Sd to the verification ECU 4.

When receiving the reception intensity (reception intensity data) from the measurement unit 32, the position determination unit 31 determines the reception intensity measured for each radio wave (position detection signal Sd) of each frequency for each of the outdoor antenna 16 and the indoor antenna 17. Calculate the corresponding characteristic value. In the case of this example, the characteristic value is an average value of the reception intensity, and is, for example, a moving average calculated from the reception intensity data received in the latest predetermined period. The position determination unit 31 of the position determination system 30 temporarily stores the received reception intensity Pr1 and reception intensity Pr2 in the memory 9 of the verification ECU 4. The position determination unit 31 calculates an average value Pr1 ′ of the reception intensities Pr1 from the stored plurality of reception intensities Pr1. Further, the position determination unit 31 calculates an average value Pr2 ′ of the reception intensities Pr2 from the stored plurality of reception intensities Pr2.

The position determination unit 31 determines whether the mobile terminal 2 is located inside or outside the vehicle 1 by comparing the magnitudes of the average value Pr1 ′ and the average value Pr2 ′. When the average value Pr1 ′ is equal to or larger than the average value Pr2 ′, the position determination unit 31 determines that the mobile terminal 2 is located outside the vehicle 1 (outdoor determination). On the other hand, when the average value Pr1 ′ is less than the average value Pr2 ′, the position determination unit 31 determines that the mobile terminal 2 is located inside the vehicle 1 (indoor determination).

Next, the operation and effect of the position determination system 30 will be described with reference to FIGS. 2 to 6.
As shown in FIG. 2, in step S101, the vehicle 1 (collation ECU 4) sends an advertisement message from the outdoor antenna 16 and the indoor antenna 17 to an area near the vehicle 1 in order to establish a BLE communication connection with the mobile terminal 2. Repeatedly send in order. When the portable terminal 2 (terminal control unit 20) enters the area near the vehicle 1 and receives the advertisement message, it returns a response to the antenna that has transmitted the advertisement message and starts the BLE communication connection with the vehicle 1.

In step S102, the vehicle 1 and the mobile terminal 2 are automatically connected to each other when device authentication (for example, address authentication) is established according to a series of communication connection processes linked to the advertisement message. The communication connection between the two continues until the mobile terminal 2 moves out of the short-range wireless communication range with the vehicle 1.

In step S103, when the vehicle 1 and the mobile terminal 2 are communicatively connected, the vehicle 1 and the mobile terminal 2 start ID verification. ID verification includes verification of electronic key IDs and cryptographic authentication using a key unique key. The verification ECU 4 determines that the ID verification is unsuccessful when either the verification of the electronic key ID or the cryptographic authentication using the key unique key is unsuccessful. If the ID verification is unsuccessful, the operation of the vehicle 1 is prohibited. On the other hand, the verification ECU 4 continues the process if the ID verification is successful.

In step S104, the position determination unit 31 transmits the position detection signal Sd from the outdoor antenna 16 and the indoor antenna 17, causes the measurement unit 32 of the mobile terminal 2 to measure the reception intensity of these radio waves, and the measurement result is received by the vehicle 1 To reply (notify). The position detection signal Sd may include each antenna ID, and the mobile terminal 2 on the receiving side may be able to identify which of the outdoor antenna 16 and the indoor antenna 17 is the radio wave. Further, the position detection signals Sd of the outdoor antenna 16 and the indoor antenna 17 may be transmitted at different timings or frequencies so that the mobile terminal 2 can receive both. Upon receiving the position detection signal Sd, the measuring unit 32 measures the reception intensity (reception intensity Pr1 and reception intensity Pr2) of the position detection signal Sd, and returns the measured reception intensity data to the outdoor antenna 16 and the indoor antenna 17. To notify you.

In the case of the present example, the position determination unit 31 repeats a series of processes of position detection signal transmission, reception intensity measurement, and reception intensity data notification by changing the frequency (channel) in each of the outdoor antenna 16 and the indoor antenna 17. Run (shown only once in Figure 2). As a result, in each of the outdoor antenna 16 and the indoor antenna 17, a data group of the reception intensity Pr1 and the reception intensity Pr2 measured during communication with the mobile terminal 2 is acquired.

As shown in FIG. 3, in this example, one outdoor antenna 16 and one indoor antenna 17 are provided in the vehicle 1. When the mobile terminal 2 is located outside the vehicle 1, the propagation path L1 of the radio wave between the outdoor antenna 16 and the mobile terminal 2, the indoor antenna 17, and the mobile terminal 2 are provided between the vehicle 1 and the mobile terminal 2. There is a radio wave propagation path L2 between and. The propagation path L1 and the propagation path L2 include various propagation paths through which the transmitted position detection signal Sd passes as a direct wave, a diffracted wave, and a reflected wave.

As shown in FIGS. 4A and 4B, the reception intensity Pr1 when passing through the propagation path L1 and the reception intensity Pr2 when passing through the propagation path L2 have variations among a plurality of measurements. is doing. For example, in BLE communication, a frequency hopping method is used to switch between a plurality of channels (frequencies), and variations occur in reception strength between channels. Therefore, if the reception strengths (instantaneous values) at one point of the reception strength Pr1 and the reception strength Pr2 are compared, even when the mobile terminal 2 is located outside the vehicle 1, the reception strength Pr1 is lower than the reception strength Pr1. Pr2 may be larger. Therefore, it is not possible to determine that the mobile terminal 2 is located outside the vehicle 1 by simply comparing the instantaneous values of the reception intensities.

On the other hand, in the case of this example, the average value Pr1 ′ and the average value Pr2 ′ are used for the position determination. When the mobile terminal 2 is located outside the vehicle 1, the average value Pr1 ′ is usually equal to or larger than the average value Pr2 ′. That is, the relationship of “Pr1 ′ ≧ Pr2 ′” is established. The average value Pr1 ′ and the average value Pr2 ′ are as shown by the broken line and the alternate long and short dash line in FIGS. 4A and 4B, for example. Therefore, it can be seen that in the determination of the position of the mobile terminal 2, the use of the average value improves the determination accuracy than the use of the instantaneous value.

Also, the reception intensity of the position detection signal Sd changes due to obstacles that block radio waves and interference with other radio waves. For example, if there is an obstacle (such as a user's bag) that covers the mobile terminal 2, the reception strength is reduced. Therefore, if the method of determining the position of the mobile terminal 2 based on whether or not the reception intensity exceeds the threshold value is adopted, even if the mobile terminal 2 is at the same position, the reception intensity changes, and the determination result is May change. On the other hand, in the case of this example, the position is determined by comparing the magnitudes of the average values of the reception intensities. For example, when there is an obstacle (such as a user's bag) that covers the mobile terminal 2, radio waves are blocked by both the propagation path L1 and the propagation path L2, so that both the average value Pr1 ′ and the average value Pr2 ′ are present. Is reduced. Therefore, the magnitude relationship between the average value Pr1 ′ and the average value Pr2 ′ is not reversed. Therefore, the accuracy of the position determination can be improved by comparing the magnitudes of the average values Pr1 ′ and Pr2 ′ between the

antennas

16 and 17.

As shown in FIG. 5, when the mobile terminal 2 is located inside the vehicle 1, a radio wave propagation path L3 between the outdoor antenna 16 and the mobile terminal 2 is provided between the vehicle 1 and the mobile terminal 2. There is a radio wave propagation path L4 between the indoor antenna 17 and the mobile terminal 2.

As shown in FIGS. 6A and 6B, the reception intensity Pr1 when passing through the propagation path L3 and the reception intensity Pr2 when passing through the propagation path L4 also have variations among a plurality of measurements. is there. When the mobile terminal 2 is located inside the vehicle 1, the average value Pr1 'is usually smaller than the average value Pr2'. That is, the relationship of “Pr1 ′ <Pr2 ′” is established. The average value Pr1 ′ and the average value Pr2 ′ are as shown by the broken line and the alternate long and short dash line in FIGS. 6A and 6B, for example. Therefore, even when the mobile terminal 2 is located inside the vehicle 1, it is understood that the position of the mobile terminal 2 can be accurately determined by comparing the magnitudes of the average values of the reception intensities.

Returning to FIG. 2, in step S105, the position determination unit 31 calculates an average value Pr1 ′ and an average value Pr2 ′ from the stored plurality of reception intensities Pr1 and Pr2. Then, by comparing the magnitudes of the average value Pr1 ′ and the average value Pr2 ′, it is determined whether the portable terminal 2 is located inside or outside the vehicle 1. When the average value Pr1 ′ is equal to or larger than the average value Pr2 ′ (Pr1 ′ ≧ Pr2 ′), the position determination unit 31 determines that the mobile terminal 2 is located outside the vehicle 1 (outdoor determination). On the other hand, when the average value Pr1 ′ is less than the average value Pr2 ′ (Pr1 ′ <Pr2 ′), the position determination unit 31 determines that the mobile terminal 2 is located inside the vehicle 1 (indoor determination). For example, the body ECU 5 controls the operation of the door lock device 11 based on the detection signal of the touch sensor 13 or the lock button 14 when the ID collation is established and the outdoor determination is made. Further, the engine ECU 7 controls the transition of the engine 6 by operating the engine switch 15 on condition that the ID collation is established and the indoor determination is made. As described above, the position determination system 30 determines whether the mobile terminal 2 is located inside or outside the vehicle 1, and thus control according to the position of the mobile terminal 2 becomes possible.

Now, in this example, the position determination system 30 calculates the characteristic value of each antenna from a plurality of reception intensities measured for each antenna, and compares the characteristic value between the antennas to determine whether the vehicle 1 (communication partner The position determining unit 31 for determining the position of the mobile terminal 2 with respect to According to this configuration, by using the characteristic value of each antenna calculated based on a plurality of reception intensities, it is possible to suppress the influence on the position determination due to the variation of the reception intensities. Further, when the mobile terminal 2 is at the same position, the magnitude relationship of the characteristic values between the antennas is unlikely to change even if the radio wave is blocked by an obstacle. Therefore, by performing the position determination by comparing the magnitude relationship of the characteristic values between the antennas, it is possible to suppress the occurrence of a situation in which the determination result changes depending on the presence or absence of an obstacle. Therefore, the accuracy of the position determination of the mobile terminal 2 is improved.

In this example, the average value of multiple reception strengths measured for each antenna was used as the characteristic value. According to this configuration, the accuracy of position determination can be improved without imposing an excessive processing load through a simple process of calculating the average of the reception intensities and determining the position.

In this example, the vehicle 1 includes the outdoor antenna 16 and the indoor antenna 17, and the position determination unit 31 compares the average value Pr1 ′ and the average value Pr2 ′ to determine whether the portable terminal 2 is indoors or outdoors of the vehicle 1. It is configured to determine whether or not it is located at. With this configuration, it is possible to accurately determine whether the portable terminal 2 is located inside or outside the vehicle 1.

<Second Embodiment>
Next, a second embodiment of the position determination system and the position determination method will be described with reference to FIGS. The second embodiment mainly differs from the first embodiment in that the characteristic value is corrected. Therefore, the same reference numerals are given to the same member configurations as those of the first embodiment, detailed description thereof will be omitted, and only different portions will be described in detail.

When the average value Pr1 ′ and the average value Pr2 ′ are used for position determination, the variation in the reception intensity can be suppressed, but the influence of the variation cannot be completely canceled. An error may occur in these average values due to variations in reception strength. If there is an error in the values of the average value Pr1 ′ and the average value Pr2 ′, the magnitude relationship between them may be reversed, and the position determination may not be accurately performed. This example is a countermeasure for suppressing the influence of the error between the average value Pr1 ′ and the average value Pr2 ′.

As shown in FIG. 7, the authentication system 3 includes a correction unit 40 that corrects the characteristic value. In the case of this example, the correction unit 40 is provided in the verification ECU 4. The correction unit 40 of the present example uses the ratio of the average value Pr1 ′ to the average value Pr2 ′, that is, “Pr1”, so that the difference between the average value Pr1 ′ and the average value Pr2 ′ when the mobile terminal 2 is located outdoors is large. The correction is performed so that the value of “/ Pr2 ′” becomes larger after the correction than before the correction. The correction unit 40 of the present example corrects the calculated average value Pr1 ′ by the offset value set in advance so as to be increased by the correction. The correction unit 40 may perform the correction so as to reduce the average value Pr2 ′. The position determination unit 31 determines the position of the mobile terminal 2 by comparing the magnitude of the average value Pr1 ′ corrected by the correction unit 40 and the average value Pr2 ′.

Next, the operation and effect of the authentication system 3 (correction unit 40) of the present embodiment will be described with reference to correction using FIG. 8 and FIG. 9.
As shown in FIG. 8, when the mobile terminal 2 is located outside the vehicle 1, the difference obtained by subtracting the average value Pr2 ′ from the average value Pr1 ′ is defined as the difference D1. Therefore, when the mobile terminal 2 is located outside the vehicle 1, the average value Pr1 ′ is usually larger than the average value Pr2 ′ by the difference D1.

As shown in FIG. 9, the difference D2 is the difference between the average value Pr2 ′ and the average value Pr1 ′ when the mobile terminal 2 is located inside the vehicle 1. Therefore, when the mobile terminal 2 is located inside the vehicle 1, the average value Pr2 'is usually larger than the average value Pr1' by the difference D2.

The larger the difference D1 and the difference D2, the more difficult it is to reverse the magnitude relationship between the average value Pr1 ′ and the average value Pr2 ′. That is, the difference D1 and the difference D2 correspond to the permissible amount for the error between the average value Pr1 ′ and the average value Pr2 ′. Here, it is known from the results of experiments conducted by the present inventors that the difference D2 is larger than the difference D1 (D2> D1). When the correction for increasing the average value Pr1 ′ is performed regardless of the position of the mobile terminal 2, the value of the difference D1 increases, but the value of the difference D2 decreases as a trade-off. However, since the difference D2 is sufficiently large in advance, the correction processing by the correction unit 40 of this example is performed on the assumption that the required difference D2 is secured even if the difference D1 is increased. As a result, it is possible to secure a sufficient allowance for the error between the average value Pr1 ′ and the average value Pr2 ′ regardless of whether the mobile terminal 2 is inside or outside the vehicle 1.

In the case of this example, the average value Pr1 ′ is corrected according to the above concept. The correction unit 40 corrects the average value Pr1 ′ calculated by the position determination unit 31 with an offset value set in advance so as to be increased by the correction. This correction is realized by the arithmetic processing of the correction unit 40 (controller). Then, the position determination unit 31 determines the position of the vehicle 1 of the mobile terminal 2 by comparing the magnitudes of the corrected average value Pr1 ′ and the average value Pr2 ′. As a result, regardless of whether the mobile terminal 2 is located inside or outside the vehicle 1, the determination can be performed with a sufficient allowable amount.

In this example, the correction unit 40 is provided to perform correction so that the average value Pr1 ′ becomes large. According to this configuration, the correction can be performed according to the magnitude relationship between the average value Pr1 ′ and the average value Pr2 ′. Accordingly, when an error occurs in the average value Pr1 ′ and the average value Pr2 ′, for example, when determining the position of the mobile terminal 2, it is possible to secure a sufficient allowance for the error in these average values. This contributes to improving the accuracy of the position determination of the mobile terminal 2.

<Third Embodiment>
Next, a third embodiment of the position determination system and the position determination method will be described with reference to FIGS. 8 and 9. The third embodiment is different from the second embodiment only in the correction method of the correction unit 40. Therefore, also in this example, only the parts different from the second embodiment will be described in detail.

The position determination unit 31 of this example calculates the standard deviation together with the average value of the reception intensity of the position detection signal Sd as the characteristic value. Here, the standard deviation calculated from the reception intensity Pr1 is the standard deviation Dv1, and the standard deviation calculated from the reception intensity Pr2 is the standard deviation Dv2. The correction unit 40 corrects the average value Pr1 ′ with the offset value according to the value of the standard deviation Dv1. Further, the correction unit 40 corrects the average value Pr2 ′ with the offset value according to the value of the standard deviation Dv2. The correction unit 40 corrects the average value by using a larger offset value as the standard deviation is smaller.

Next, the operation and effect of the authentication system 3 (correction unit 40) of this embodiment will be described with reference to FIGS. 8 and 9.
The standard deviation of the reception intensity of the position detection signal Sd depends on the propagation path of the position detection signal Sd. That is, the standard deviation changes depending on propagation modes such as direct waves, diffracted waves, and reflected waves, the presence or absence of obstacles, and interference with other radio waves.

As shown in FIGS. 8 and 9, the present inventors have found that the variation in the reception intensity of the position detection signal Sd passing through the propagation path L1 is smaller than that when passing through the other propagation paths (L2 to L4). I found that. That is, it is known that the propagation path L1 has a small standard deviation, and the propagation path L2, the propagation path L3, and the propagation path L4 have no large difference in standard deviation. That is, even with the position detection signal Sd transmitted from the same outdoor antenna 16, there is a difference in the standard deviation of the reception intensity between the propagation path L1 and the propagation path L3. It was expected that this difference could be applied to correction for increasing the difference D1.

In the case of this example, based on the above idea, the correction unit 40 corrects the average value Pr1 ′ and the average value Pr2 ′ by the offset value that changes according to the standard deviation. When the portable terminal 2 is located outside the vehicle 1, the average value Pr1 ′ is corrected more than the average value Pr2 ′ because the standard deviation of the mobile terminal 2 passing through the propagation path L1 is smaller than that of the propagation path L2. As a result, the difference D1 becomes large, so that the allowable amount for the error of the average value becomes large. Further, when the mobile terminal 2 is located inside the vehicle 1, there is no large difference in standard deviation between the propagation path L3 and the propagation path L4. Therefore, the average value Pr1 ′ and the average value Pr2 ′ should be corrected to the same degree. receive. As a result, the difference D2 is maintained as it is before the correction. As a result, the permissible amount for the error of the average value when the mobile terminal 2 is located outside the vehicle 1 is increased, while the permissible amount for the error of the average value when the mobile terminal 2 is located inside the vehicle 1 is maintained. can do.

By the way, in this example, the correction unit 40 is configured to correct the average value by the offset value that changes based on the standard deviation of the reception intensity of the position detection signal Sd. According to this configuration, when the standard deviation is characterized by the radio wave propagation path between each antenna and the mobile terminal 2, if the average value is corrected based on the standard deviation, the correction according to each radio wave propagation path is performed. It can be performed. This further contributes to improving the accuracy of the position determination of the mobile terminal 2.

<Fourth Embodiment>
Next, a fourth embodiment of the position determination system and the position determination method will be described with reference to FIG. The fourth embodiment is different from the first embodiment in the number of antennas. Therefore, also in this example, only the parts different from the first embodiment will be described in detail.

As shown in FIG. 10, the outdoor antenna 16 of this example includes an outdoor antenna 16a provided on the driver side of the vehicle 1 and an outdoor antenna 16b provided on the passenger side of the vehicle 1. The indoor antenna 17 includes an indoor antenna 17a provided on the driver side of the vehicle 1 and an indoor antenna 17b provided on the passenger side of the vehicle 1. Therefore, in this example, the vehicle 1 is provided with four antennas. The reception intensity of the position detection signal Sd transmitted from the outdoor antenna 16a is the reception intensity Pr1a, the reception intensity of the position detection signal Sd transmitted from the outdoor antenna 16b is the reception intensity Pr1b, and the position detection signal Sd transmitted from the indoor antenna 17a. The reception strength is defined as reception strength Pr2a, and the reception strength of the position detection signal Sd transmitted from the indoor antenna 17b is defined as reception strength Pr2b. Further, these average values are referred to as an average value Pr1a ', an average value Pr1b', an average value Pr2a ', and an average value Pr2b'.

The position determination unit 31 determines the position of the mobile terminal 2 by comparing the magnitude of each average value. The position determination unit 31 performs outdoor determination when the relationship of “Pr1a ′ ≧ Pr2a ′, Pr2b ′ ≧ Pr1b ′, or Pr1b ′ ≧ Pr2a ′, Pr2b ′ ≧ Pr1a ′” is established. Note that “Pr2a ′, Pr2b ′” indicates that the average value Pr2a ′ and the average value Pr2b ′ may be either large or small (the same applies hereinafter). That is, when there is an average value Pr2a 'and an average value Pr2b' between the average value Pr1a 'and the average value Pr1b' in the magnitude relation of the reception intensity, the outdoor determination is performed. On the other hand, the position determination unit 31 makes an indoor determination when the relationship “Pr1a ′, Pr1b ′ <Pr2a ′, Pr2b ′” holds. That is, when both the average value Pr1a 'and the average value Pr1b' are smaller than both the average value Pr2a 'and the average value Pr2b', the indoor determination is performed. In addition, when the magnitude relation of the reception intensities does not apply to either of the above two relations, the position determination unit 31 determines that the position determination is abnormal and issues an error. If the position determination unit 31 produces an error, the verification ECU 4 does not permit the operation of the vehicle 1 on the condition that the portable terminal 2 is located inside or outside the vehicle 1.

In this way, by increasing the number of antennas, the range that the position detection signal Sd reaches can be expanded or made redundant. In addition, the combinations (orders) of the reception intensities from the respective antennas increase, and there is a possibility that it can be applied to more complex and advanced position determination. The number of antennas may be any number as long as it is at least two.

<Fifth Embodiment>
Next, a fifth embodiment of the position determination system and the position determination method will be described with reference to FIGS. 11 to 13. The fifth embodiment differs from the second and third embodiments only in the correction method of the correction unit 40. Therefore, also in this example, only the parts different from the second embodiment will be described in detail.

The correction unit 40 corrects the average value Pr1 ′ to a value according to the current determination result of the position determination unit 31. The correction unit 40 of this example corrects the average value Pr1 ′ using the offset value as the correction amount according to the determination result of the position determination unit 31. The offset value includes a first offset value α used when the position determination unit 31 makes an outdoor determination, and a second offset value β used when the position determination unit 31 makes an indoor determination. .. In the case of this example, the correction unit 40 performs a positive offset so as to increase the value of the average value Pr1 ′ by the first offset value α and the second offset value β. Further, the first offset value α is larger than the second offset value β.

The position determination unit 31 compares the corrected average value Pr1 ′ and the corrected average value Pr2 ′ to determine the position of the mobile terminal 2. The position determination unit 31 switches the position determination by performing the position determination once and then continuously monitoring the average value Pr1 ′ and the average value Pr2 ′.

Next, the operation and effect of this embodiment will be described.
As illustrated in FIG. 11, when the correction unit 40 corrects the average value Pr1 ′ with the first offset value α (hereinafter referred to as the first correction), the average value Pr1 ′ is equal to the first offset value α. growing. That is, the correction is performed so that the ratio of the average value Pr1 ′ to the average value Pr2 ′ becomes large. By the first correction, the value of the difference D1 between the average value Pr1 ′ and the average value Pr2 ′ becomes larger than that before the correction.

As shown in FIG. 12, when the correction unit 40 corrects the average value Pr1 ′ by the second offset value β (hereinafter referred to as the second correction), the average value Pr1 ′ is equal to the second offset value β. growing. That is, the correction is performed so that the ratio of the average value Pr1 ′ to the average value Pr2 ′ becomes large. By the second correction, the value of the difference D2 between the average value Pr2 ′ and the average value Pr1 ′ becomes smaller than that before the correction.

Next, switching of position determination by the position determination unit 31 will be described.
As shown in FIG. 13, the position determination unit 31 monitors the average value Pr1 ′ and the average value Pr2 ′ that change over time due to the movement of the mobile terminal 2 after once performing the position determination, and switches the determination. To do. In the same figure, a curve C shows an example of changes in the difference between the average value Pr1 ′ and the average value Pr2 ′. When the curve C is "0", the magnitude relationship between the average value Pr1 'and the average value Pr2' is reversed.

By the way, when the magnitudes of the average value Pr1 ′ and the average value Pr2 ′ conflict with each other, it is possible that the curve C changes near “0”. In this case, the magnitude relationship between the average value Pr1 ′ and the average value Pr2 ′ is frequently reversed, and the determination may not be stable.

Based on the above, in this example, the judgments are switched as follows. Here, it is assumed that the position determination unit 31 makes the indoor determination. When the indoor determination is performed, the position determination unit 31 switches the position determination by comparing the magnitude relationship between the second corrected average value Pr1 ′ and the average value Pr2 ′. A change in the difference between the second corrected average value Pr1 ′ and the average value Pr2 ′ is shown by a curve Cβ. The position determination unit 31 switches the determination from the indoor determination to the outdoor determination when the second corrected average value Pr1 ′ is equal to or more than the average value Pr2 ′, that is, when the curve Cβ is “0” or more. . On the other hand, the position determination unit 31 maintains the indoor determination when the second corrected average value Pr1 ′ is smaller than the average value Pr2 ′, that is, when the curve Cβ is smaller than “0”.

In the case of this example, at time t1, the second corrected average value Pr1 ′ becomes equal to or larger than the average value Pr2 ′, and the curve Cβ becomes “0” or larger. The position determination unit 31 switches from indoor determination to outdoor determination at time t1.

When the outdoor determination is performed, the position determination unit 31 switches the position determination by comparing the magnitude relationship between the first corrected average value Pr1 ′ and the average value Pr2 ′. A change in the difference between the first corrected average value Pr1 ′ and the average value Pr2 ′ is shown by a curve Cα. The position determination unit 31 determines from the outdoor determination to the indoor determination when the first corrected average value Pr1 ′ becomes smaller than the average value Pr2 ′, that is, when the curve Cα becomes smaller than “0”. Switch. On the other hand, the position determination unit 31 maintains the outdoor determination when the first corrected average value Pr1 ′ is the average value Pr2 ′ or more, that is, when the curve Cα is “0” or more.

In the case of this example, at time t2, the first corrected average value Pr1 ′ becomes smaller than the average value Pr2 ′, and the curve Cα becomes smaller than “0”. The position determination unit 31 switches from outdoor determination to indoor determination at time t2.

In this way, the value of the curve C is provided with a hysteresis ΔC between the time of switching from the indoor determination to the outdoor determination and the time of switching from the outdoor determination to the indoor determination. As a result, it is possible to suppress frequent determination switching.

Note that when switching the determination from the outdoor determination, the value of the curve C becomes smaller than “0” before the time t2. Therefore, the first correction makes it difficult for the position determination unit 31 to switch the determination from the outdoor determination to the indoor determination. As a result, if there is an area where the average value Pr1 ′ and the average value Pr2 ′ compete with each other outside the vehicle 1, even if the mobile terminal 2 moves so as to pass through the area, the indoor determination is performed based on the outdoor determination. It is possible to prevent the determination from being mistakenly switched to.

Also, when switching the determination from the indoor determination, the value of the curve C is still smaller than "0" at time t1. Therefore, by performing the second correction, the position determination unit 31 can easily switch the determination from the indoor determination to the outdoor determination. This is based on the fact that the difference D2 is sufficiently large in advance when the mobile terminal 2 is indoors. For example, it is easy to switch the determination while securing a sufficient allowable amount, which leads to improvement in convenience.

In this example, the correction unit 40 that corrects the average value Pr1 ′ to a value according to the current determination result of the position determination unit 31 is provided. Further, the position determination unit 31 switches the determination of the position of the mobile terminal based on the corrected average value Pr1 ′ and average value Pr2 ′. According to this configuration, it is possible to correctly switch the determination by the correction according to each determination result.

In this example, in the configuration in which the position determination unit 31 determines whether the vehicle 1 is indoors or outdoors, the correction unit 40 performs correction so as to increase the average value Pr1 ′. Further, the first offset value α and the second offset value β having different values are used for switching from the outdoor determination to the indoor determination and switching from the indoor determination to the outdoor determination, respectively. According to this configuration, in the system for determining whether the indoor or outdoor, the determination can be stabilized by the outdoor determination. This is advantageous for switching the correct judgment.

The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-In 5th Embodiment, although it corrected so that the average value Pr1 'might be increased by the 1st offset value (alpha), it is not limited to this, You may correct so that the average value Pr1' may be made small. That is, the determination may be easily switched from the outdoor determination to the indoor determination.

In the fifth embodiment, the average value Pr1 ′ is corrected to be large by the second offset value β, but the present invention is not limited to this, and the average value Pr1 ′ may be corrected to be small. That is, the ratio of the average value Pr1 ′ to the average value Pr2 ′ may be corrected so as to be smaller after the correction than before the correction. This makes it difficult to switch the determination from the indoor determination to the outdoor determination.

In the fifth embodiment, the first offset value α and the second offset value β may be either large or small.
-In 5th Embodiment, although the correction | amendment part 40 corrected average value Pr1 ', it is not limited to this, You may correct average value Pr2', and both average value Pr1 'and average value Pr2'. May be corrected. Further, the correction may be made not only by the offset but also by a coefficient or a ratio.

-In 5th Embodiment, the position determination part 31 may provide a threshold value for determination of a magnitude relationship, for example, determination may be switched according to whether the difference of average value Pr1 'and average value Pr2' is more than a threshold value. . In this case, the correction unit 40 may correct the characteristic value or the threshold value.

In the third embodiment, the standard deviation of the reception intensity of the position detection signal Sd may be used as it is for the position determination of the position determination unit 31. For example, assuming that only the propagation path L1 has a small standard deviation value, the two standard deviations Dv1 and Dv2 are compared, and the standard deviation Dv1 is smaller than the standard deviation Dv2, and the standard deviations Dv1 and Dv2 are smaller. If the difference is greater than or equal to the specified value, outdoor determination may be performed. Further, the determination may be performed by comparing the standard deviations Dv1 and Dv2 together with the comparison of the average values Pr1 ′ and Pr2 ′. According to this configuration, for example, when the standard deviation of the reception intensity has a characteristic caused by the radio wave propagation path between each antenna and the mobile terminal 2, the position of the mobile terminal 2 is determined based on the standard deviation. You can This contributes to improvement in the accuracy of the position determination of the mobile terminal 2.

In the third embodiment, the correction unit 40 may increase the offset value as the standard deviation increases if the standard deviation is large only in a certain propagation path. For example, if only the propagation path L1 has a large standard deviation, the difference D1 can be increased by increasing the offset value.

-In 3rd Embodiment, the correction part 40 may correct with a negative offset value so that a standard deviation may become large and an average value may become small.
-In 2nd Embodiment, the correction | amendment part 40 may perform correction | amendment so that the value of average value Pr2 'may become small, or may make correction so that average value Pr2' may be made small, making average value Pr1 'large. You may go. Also in this case, the same effect that the difference D1 is increased and the difference D2 is decreased can be obtained.

In the second embodiment, the preset offset value can be changed as appropriate. For example, it can be set based on the values of the difference D1 and the difference D2 measured by experiments.
-In 3rd Embodiment, the relationship between the value of a standard deviation and an offset value can be changed suitably.

In the second and third embodiments, the correction unit 40 may correct the reception intensity received from the measurement unit 32 and then calculate the average value. That is, it is sufficient that the average value can be corrected as a result of the correction.

In each embodiment, the measurement unit 32 may be provided on the vehicle 1 side. For example, even if the position detection signal Sd transmitted from the mobile terminal 2 is received by a plurality of antennas on the vehicle 1 side and the position of the mobile terminal 2 is determined based on the magnitude relationship of the characteristic values calculated from the reception intensities thereof. Good.

-In each embodiment, the position determination part 31 may be provided in the portable terminal 2 side.
-In 2nd Embodiment and 3rd Embodiment, the correction | amendment part 40 may be provided in the portable terminal 2 side.

-In each embodiment, the average value is not limited to a moving average, and may be another arithmetic average, a geometric average, or a harmonic average. Alternatively, a weighted moving average or the like may be used.

-In each embodiment, the characteristic value is not limited to the average value, and may be the median value or the mode value. These can be appropriately changed according to the distribution (variation) of the reception strength. However, it is preferable to use the average value in terms of reliability with a small number of data and considering all data.

In each of the embodiments, the position determination unit 31 is not limited to determining whether the mobile terminal 2 is located inside or outside the vehicle 1, and the mobile terminal 2 may be the driver seat side or the passenger seat side of the vehicle 1. It may be determined which of the two, the front side or the rear side, or the coordinates of the mobile terminal 2 with respect to the vehicle 1.

-In each embodiment, the transmission interval of the position detection signal Sd transmitted from the antenna is not particularly limited, and may be appropriately changed according to the specifications of the position determination system 30.
-In each embodiment, the arrangement of the antennas is not particularly limited and can be appropriately changed according to the specifications. For example, it may be arranged on the driver's seat side and the passenger's seat side of the vehicle 1 regardless of whether the vehicle 1 is indoors or outdoors.

In each embodiment, the position detection signal Sd does not have to include the antenna ID of the radio wave transmission source. For example, the position determination unit 31 may control the transmission timing of the position detection signal Sd to identify which antenna has the reception intensity from the timing at which the reception intensity data is received, or may transmit the position detection signal Sd. You may identify by receiving receiving intensity data with an antenna.

In each of the embodiments, the outdoor antenna 16 and the indoor antenna 17 may transmit a group of position detection signals Sd having different channels at one time.
In each of the embodiments, the measurement unit 32 may calculate the average value of a group of the plurality of position detection signals Sd and send back (notify) the vehicle 1 side. That is, the characteristic value may be calculated on either the vehicle 1 side or the mobile terminal 2 side.

-In each embodiment, each frequency of a plurality of position detection signals Sd (radio waves) transmitted is not limited to a channel determined by frequency hopping of BLE communication.
In each of the embodiments, the size relationship serving as a reference for position determination is not limited to this embodiment, and can be changed as appropriate based on, for example, data obtained by performing an experiment with the position determination system 30 mounted on the vehicle 1. is there.

In each embodiment, the communication standard and band of the authentication system 3 and the position determination system 30 are not limited to those in the embodiments, and Wi-Fi may be used, for example. Also, different bands may be used between these systems.

-In each embodiment, a method for performing communication connection (pairing) for near field communication between the vehicle 1 and the mobile terminal 2 is not particularly limited. For example, pairing may be performed only by operating one of the devices. Further, when the operation is performed on the vehicle 1 side at the time of pairing, a device such as a car navigation system mounted on the vehicle 1 can be applied as the input / output device. That is, when performing pairing, the operating device, operating method, authentication method, and the like can be changed as appropriate.

In each embodiment, the method for the mobile terminal 2 to acquire the electronic key ID and the key unique key is to acquire the electronic key ID and the key unique key from the server through Internet communication, but the method is not limited to this. For example, a mode may be adopted in which the electronic key ID and the key unique key registered in the vehicle 1 in advance are given to the mobile terminal 2 by logging in to the vehicle 1 (user ID and password authentication) using BLE communication.

In each embodiment, the ID verification performed by the authentication system 3 is not limited to the electronic key ID verification or the cryptographic authentication of the key unique key, and any method that can confirm the correctness of the mobile terminal 2 may be used.
In each embodiment, the order of ID collation and position detection of the mobile terminal 2 is not particularly limited in a series of authentications. For example, the ID collation may be performed after the position detection, or the ID collation and the position detection may be performed so as to overlap with each other.

-In each embodiment, the mobile terminal 2 is not limited to a high-performance mobile phone, and may be an electronic key tied to the vehicle 1.
-In each embodiment, the authentication system 3 and the position determination system 30 are not limited to being mounted on the vehicle 1 and can be changed to various devices and apparatuses. That is, the communication partner of the mobile terminal 2 is not limited to the vehicle 1, and may be equipment in a building, for example.

Claims

When the mobile terminal and the communication partner communicate wirelessly, a position determination unit that determines the position of the mobile terminal with respect to the communication partner is provided,
The position determination unit, based on the reception intensity measured for each radio wave of each frequency, for a plurality of radio waves communicated at different frequencies between each of the plurality of antennas provided to the communication partner and the mobile terminal. A position determination system for determining the position of the mobile terminal by calculating a characteristic value for each antenna and comparing the magnitudes of the characteristic values between the antennas.
The position determination system according to claim 1, wherein the position determination unit calculates an average value of reception intensities of the plurality of radio waves measured for each antenna as the characteristic value.
The plurality of antennas include an outdoor antenna provided outside the communication partner's room and an indoor antenna provided inside the communication partner's room,
The position determination unit determines whether the portable terminal is located indoors or outdoors of the communication partner by comparing the size of the characteristic value of the outdoor antenna and the size of the characteristic value of the indoor antenna. The position determination system according to Item 1 or 2.
A correction unit that corrects at least one of the characteristic value of the outdoor antenna and the characteristic value of the indoor antenna;
The position determination system according to claim 3, wherein the correction unit performs the correction such that a ratio of the characteristic value of the outdoor antenna to the characteristic value of the indoor antenna is larger after the correction than before the correction.
The position determination unit, the average value of the reception intensity of the plurality of radio waves measured for each antenna, and at least one of the standard deviation of the reception intensity of the plurality of radio waves measured for each antenna, the characteristic Calculated as a value,
The position determination system according to claim 1, wherein the position determination unit determines the position of the mobile terminal with respect to the communication partner based on at least one of the average value and the standard deviation.
A correction unit that corrects the average value based on the standard deviation,
The position determination system according to claim 5, wherein the position determination unit determines the position of the mobile terminal with respect to the communication partner based on the average value corrected by the correction unit.
A correction unit that corrects the characteristic value to a value according to the current determination result of the position determination unit,
The position determination system according to claim 1 or 2, wherein the position determination unit determines the position of the mobile terminal based on a comparison of the corrected characteristic values between the antennas.
The correction unit corrects at least one of the characteristic value of the outdoor antenna provided outside the communication partner's room and the characteristic value of an indoor antenna provided inside the communication partner's room to obtain the characteristic value of the indoor antenna. The ratio of the characteristic value of the outdoor antenna with respect to, so that after correction is larger than before correction, the correction is performed using a correction amount,
The position according to claim 7, wherein the correction unit changes the correction amount based on a determination of switching the position of the mobile terminal from indoors to the outdoors and a determination of switching the position of the mobile terminal from the outdoors to the indoors. Judgment system.
When a mobile terminal and a communication partner communicate wirelessly, a plurality of radio waves communicated at different frequencies between each of the plurality of antennas provided in the communication partner and the mobile terminal Calculating a characteristic value for each antenna from the reception intensity measured for each radio wave,
A position determination method comprising: determining the position of the mobile terminal with respect to the communication partner by comparing the magnitudes of the characteristic values between the antennas.