JP6949582B2 - Wireless communication system for vehicles - Google Patents

Description

The present invention relates to a wireless communication system for vehicles.

For example, in a communication system mounted on a vehicle and performing wireless data communication between various in-vehicle devices, there are restrictions on available frequency resources, and there are also restrictions on the installation location of each communication device. Even under such restrictions, it is necessary for a large number of communication systems to coexist, and it is also necessary to avoid the influence of unnecessary radio wave interference coming from the inside of the own vehicle or the outside of the own vehicle.

As prior art related to the present invention, for example, Patent Document 1, Patent Document 2, and Non-Patent Document 1 are known.

In the technique of Patent Document 1, when interference occurs in the channel allocated for data transmission, a transmission path is established by searching for an alternative channel having a different frequency and no interference. In addition, while transmitting data through this alternative channel, the presence or absence of interference in each channel is inspected.

In the technique of Patent Document 2, each radio on the vehicle is linked with the adjacent vehicle detecting means for detecting another vehicle adjacent to the own vehicle, and when the adjacent vehicle is detected, the radio wave interference determining means is the same wireless system. Determine the radio wave interference caused by the in-vehicle wireless communication system. Then, when radio wave interference is detected, radio wave interference is avoided by changing the frequency channel used.

In the paper of Non-Patent Document 1, it is shown that a device is devised so that a plurality of frequencies can be switched to obtain a more accurate radio wave propagation time.

Japanese Patent Application Laid-Open No. 2005-539431 International Publication No. 2009/147777

Deepak Vasisht, Swarun Kumar, Dina Katabi, “Decimeter-Level Location with a Single WiFi Access Point”, 13th USENIX Symposium on Networked Systems Design and Implementation (NSDI'16), March 16-18, 2016, ISBN 978-1-931971 -29-4.

As shown in Patent Document 1, when interference occurs in a wireless communication channel, it is possible to avoid the interference by searching for an alternative channel having a different frequency and no interference. However, since the frequency resources that can actually be used are limited, it may not be possible to find an alternative channel without interference even if an alternative channel is searched. Therefore, for example, in a state where a large number of independent wireless communication systems exist in a narrow space on the same vehicle, it may not be possible to operate the system so as not to cause interference.

Further, when the method as shown in Patent Document 2 is used, a delay time occurs when searching for a usable frequency. Further, when various control signals are added immediately before the frame and transmitted / received, a data delay of the added amount occurs. Therefore, such a method cannot be adopted in a wireless communication system having a large delay time constraint. Moreover, since it is necessary to equip the technique of Patent Document 2 with a special adjacent vehicle detecting means, it is inevitable that the cost of the system will increase.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an environment in which a plurality of wireless systems exist in a limited narrow space and the available frequency resources are severely restricted. It is an object of the present invention to provide a wireless communication system for vehicles capable of reducing the influence of radio wave interference without switching radio channels or increasing the delay time.

In order to achieve the above-mentioned object, the vehicle wireless communication system according to the present invention is characterized by the following (1) to (6).
(1) The own terminal installed in the vehicle and capable of transmitting and receiving wireless signals,
With other terminals installed in the vehicle and capable of transmitting at least wireless signals,
With
The own terminal includes a own terminal control unit that controls transmission / reception of wireless signals.
The other terminal includes at least another terminal control unit that controls transmission of a wireless signal.
When the own terminal control unit acquires a wireless signal transmission request, it detects the transmission of the wireless signal by the other terminal, and when it is determined that the other terminal is interfering with the other terminal, the other terminal control unit is notified. To reduce the transmission power of the other terminal,
A wireless communication system for vehicles characterized by this.

(2) A distance storage unit that stores the distance between the own terminal and the other terminal,
A distance calculation unit for calculating the distance from the transmission source of the signal received by the own terminal is further provided.
When the distance of the transmission source of the radio signal received by the own terminal and the distance stored in the distance storage unit are different from each other, the own terminal control unit increases the transmission power of the own terminal.
The vehicle wireless communication system according to (1) above.

(3) The own terminal control unit has a fluctuation of the distance of the transmission source calculated by the distance calculation unit of a predetermined value or more, or a fluctuation of the received power of a signal received from the transmission source of a predetermined value or more. In this case, it is determined that the transmission source is outside the vehicle, and the transmission power of the own terminal is increased .
The vehicle wireless communication system according to (2) above.

(4) The distance calculation unit calculates the position where the transmission source exists, and then
The own terminal control unit compares the position of the transmission source calculated by the distance calculation unit with the distance of the other terminal included in the predetermined directivity range of the directional antenna existing on the vehicle. Depending on the result, it is determined whether or not the transmission source is outside the vehicle.
The vehicle wireless communication system according to (2) or (3) above.

(5) The radio signal includes a priority signal indicating the priority of transmission.
When the transmission source of the received signal is the other terminal and the priority represented by the received signal is lower than the priority represented by the radio signal for which the transmission request has been made, the own terminal control unit has a lower priority. Increases the transmission power of the own terminal,
The vehicle wireless communication system according to (2) above.

(6) The own terminal control unit automatically adjusts the amount of increase / decrease in the transmission power of at least one of the own terminal and the other terminal according to the power strength of the radio signal received by the own terminal.
The vehicle wireless communication system according to any one of (2) to (5) above.

According to the vehicle wireless communication system having the configuration of (1) above, the transmission power of the other terminal can be reduced by controlling the own terminal in a situation where the other terminal is an interference source. As a result, it is possible to suppress the interference of the radio waves transmitted by other terminals and deliver the radio waves transmitted by the own terminal to the destination terminal. Moreover, there is no need to search for the frequency of radio waves without interference, and no special delay time occurs.

According to the vehicle wireless communication system having the configuration of (2) above, the transmission source belonging to the own system and the other transmission sources are automatically distinguished based on the distance of the wireless signal transmission source. Can be done. That is, since the positions of the terminals existing on the own vehicle are fixed, the relative distance between them does not change. Therefore, by storing this relative distance in advance in the distance storage unit and comparing the measured distance with the stored distance during actual communication, the transmission source (interference source) of the radio signal is stored in the own system. You can automatically distinguish whether you belong or not. Then, when the radio signal from the terminal outside the own vehicle interferes, the interference from the transmission source can be suppressed by increasing the transmission power of the own terminal inside the own vehicle.

According to the vehicle wireless communication system having the configuration of (3) above, the transmission source belonging to the own system and the other transmission sources can be automatically distinguished with higher accuracy. That is, the relative distance of each terminal existing on the own vehicle does not change, but in the case of a fixed terminal existing outside the own vehicle or a terminal inside another vehicle, it accompanies the traveling of the own vehicle. Or, the relative distance changes as the other vehicle travels. Further, when the relative distance changes, the received power of the signal received from the transmission source also changes accordingly. Therefore, when the fluctuation of the detected distance or the fluctuation of the received power is large, it can be considered that the terminal existing outside the own vehicle is the transmission source. Therefore, even in a situation where it is difficult to distinguish only by the absolute value of the distance, such as interference from a wireless device on another adjacent vehicle, the terminal on the own vehicle and the other terminals can be correctly distinguished. ..

According to the vehicle wireless communication system having the configuration of (4) above, the transmission source belonging to the own system and the other transmission sources can be automatically distinguished with higher accuracy. That is, since the installation position of each terminal existing on the own vehicle is fixed, the directivity of the antenna used for wireless communication by these can also be fixed in advance. Then, a terminal existing within the directivity range of the antenna can be regarded as a transmission source belonging to the own system, and other transmission sources can be regarded as not belonging to the own system. It can also be used to distinguish it from other wireless systems installed on its own vehicle.

According to the vehicle wireless communication system having the configuration of (5) above, when another terminal is transmitting a low priority signal, the radio wave from the other terminal is transmitted by increasing the transmission power of the own terminal. Interference can be suppressed and a wireless communication path can be reliably secured.

According to the vehicle wireless communication system having the configuration of (6) above, it is possible to prevent the transmission power of the own terminal or the other terminal from being increased or decreased more than necessary. Therefore, it is possible to prevent the other terminal from failing to transmit the wireless signal by reducing the transmission power of the other terminal more than necessary. Further, it is possible to prevent the other terminal from being interfered with the radio signal from the own terminal due to an increase in the transmission power of the own terminal more than necessary.

According to the vehicle wireless communication system of the present invention, even in an environment where a plurality of wireless systems exist in a limited narrow space and the available frequency resources are severely restricted, the delay time is not increased. It is possible to reduce the influence of radio wave interference. For example, in a situation where another terminal serving as an interference source and a destination terminal exist, the transmission power of the other terminal can be reduced by controlling the own terminal. As a result, it is possible to suppress the interference of the radio waves transmitted by other terminals and deliver the radio waves transmitted by the own terminal to the destination terminal. Moreover, there is no need to search for the frequency of radio waves without interference, and no special delay time occurs.

The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through the embodiments described below (hereinafter referred to as "embodiments") with reference to the accompanying drawings. ..

FIG. 1 is a plan view showing an example of an arrangement state of each wireless terminal of a vehicle wireless communication system mounted on a vehicle as viewed from above. FIG. 2 is a block diagram showing a configuration example of one wireless terminal included in the vehicle wireless communication system according to the embodiment of the present invention. FIG. 3 is a flowchart showing an operation example-1 of one wireless terminal included in the vehicle wireless communication system according to the embodiment of the present invention. FIG. 4 is a flowchart showing an operation example-2 of one wireless terminal included in the vehicle wireless communication system according to the embodiment of the present invention. FIG. 5 is a flowchart showing a part (first half) of operation example-3 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. FIG. 6 is a flowchart showing a part (second half) of the operation example-3 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. FIG. 7 is a flowchart showing a main part of operation example-4 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. FIG. 8 is a plan view showing an arrangement state of each wireless terminal of the vehicle wireless communication system mounted on the vehicle and an example of a region within the directional range by the directional antenna as viewed from above. FIG. 9 is a flowchart showing an operation example-5 of one wireless terminal included in the vehicle wireless communication system according to the embodiment of the present invention. FIG. 10 is a flowchart showing a main part of an operation example-6 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. FIG. 11 is a flowchart showing an operation example-7 of one wireless terminal included in the vehicle wireless communication system according to the embodiment of the present invention.

Specific embodiments of the present invention will be described below with reference to the respective figures.

First, the configuration and usage environment of the vehicle wireless communication system will be described.
FIG. 1 shows an example of the arrangement state of each wireless terminal 10 of the vehicle wireless communication system mounted on the own vehicle 50 as viewed from above.

In the configuration shown in FIG. 1, a plurality of wireless terminals 10-0 to 10-6 are installed in various locations on the own vehicle 50 in a dispersed state. Of course, the number of wireless terminals 10 actually mounted on the own vehicle 50 is increased or decreased as necessary. Further, on the outside of the own vehicle 50, there is a possibility that various types of interference wireless terminals 100 exist at various positions depending on the situation at that time.

Each of the wireless terminals 10-1 to 10-6 is connected to, for example, input devices such as various sensors and switches mounted on various parts of the vehicle, auxiliary equipment (electrical components) having various loads, and the like. Further, the wireless terminal 10-0 shown in FIG. 1 receives a signal from each input device or receives a signal from each input device by wirelessly communicating with each of the wireless terminals 10-1 to 10-6. The load status can be controlled. Of course, the present invention is not limited to such a form, and a plurality of wireless terminals 10-0 to 10-6 may be configured to perform autonomous control.

Therefore, in the example of FIG. 1, the wireless terminals 10-0 have a function of transmitting data and a function of receiving data by wireless communication, and each of the wireless terminals 10-1 to 10-6 transmits data by wireless communication. It has at least one of the functions of transmitting and receiving data.

As shown in FIG. 1, by configuring the wireless communication system for vehicles using a plurality of wireless terminals 10-0 to 10-6, it is not necessary to connect them with electric wires, and the wireless terminals are mounted on the vehicle. The configuration of the wire harness can be simplified. Alternatively, the communication path required for redundancy can be secured to improve the reliability of the entire system.

In the configuration shown in FIG. 1, assuming the case of wireless communication between the wireless terminal 10-0 and the wireless terminal 10-2, for example, the wireless signal (radio wave) transmitted by the wireless terminal 10-2 and the interference in the vicinity. It is assumed that the wireless terminal 100 or the wireless signal transmitted by any of the wireless terminals 10-1, 10-3 to 10-6 interferes with each other. Alternatively, it is assumed that the wireless signal transmitted by the wireless terminal 10-0 interferes with the wireless signal transmitted by the interfering wireless terminal 100 or any of the wireless terminals 10-1, 10-3 to 10-6. .. Due to such interference, the signal power to interference power ratio SIR of the signal to be received by the wireless terminals 10-0 and 10-2 may decrease, and data communication may fail.

Therefore, when a general wireless communication technique is adopted, as shown in Patent Document 1 and Patent Document 2, the wireless channel (frequency) to be used is automatically switched in order to avoid the influence of interference. Is done. As will be described later, the vehicle wireless communication system of the present embodiment has a special function for reducing the influence of interference of wireless signals from the interfering wireless terminal 100 without requiring switching of the wireless channel to be used. I have.

Further, although not shown in FIG. 1, there is a case where another one or a plurality of other wireless communication systems coexist on the own vehicle 50. In that case, there is a possibility that radio signals (radio waves) transmitted by another wireless communication system on the own vehicle 50 may interfere with each other. Even with respect to such interference, the vehicle wireless communication system of the present embodiment can reduce the influence of the interference without requiring switching of the wireless channel to be used.

Next, a configuration example of each wireless terminal 10 will be described.
FIG. 2 shows a configuration example of one wireless terminal 10 included in the vehicle wireless communication system of the embodiment of the present invention. In the case of the vehicle wireless communication system shown in FIG. 1, all the components of the wireless terminal 10 of FIG. 2 are mounted on the wireless terminal 10-0. Further, all the components or a part of the components of the wireless terminal 10 of FIG. 2 are mounted on each of the wireless terminals 10-1 to 10-6.

The wireless terminal 10 shown in FIG. 2 includes a wireless signal receiving unit (Rx) 11, a receiving buffer 12, a calculating unit 13, a non-volatile memory 14, a transmission power control unit 15, a wireless signal transmitting unit (Tx) 16, and a transmitting buffer 17. , Interfaces (I / F) 18a, 18b, antennas 19a, and 19b.

The radio signal receiving unit 11 has a radio signal receiving function, and the radio signal transmitting unit 16 has a radio signal transmitting function. Further, the wireless signal receiving unit 11 and the wireless signal transmitting unit 16 of the present embodiment are wireless communication devices capable of interconnecting the devices.

Further, although not shown in FIG. 2, a plurality of antennas 19a and 19b may be provided respectively. Further, the radio signal receiving unit 11 and the radio signal transmitting unit 16 of the present embodiment are devices capable of acquiring CSI (Channel Status Information), which is a new radio frequency (RF) channel property.

The radio signal receiving unit 11 processes the radio signal (radio wave) received by the antenna 19a to acquire the CSI, or acquires the contents of data such as the received packet. In addition, a function to scan various wireless channels within a predetermined frequency band, a function to identify whether or not each wireless channel is in use, a function to measure the power of a wireless signal received by each wireless channel, and a function to measure the power of a wireless signal received by each wireless channel. The radio signal receiving unit 11 is also provided with a function of estimating the signal power to interference power ratio SIR.

The radio signal transmission unit 16 generates a high-frequency signal in which the data to be transmitted is matched with a format such as a predetermined packet, and transmits this as a radio wave from the antenna 19b. The wireless signal transmission unit 16 of the present embodiment has a function for making the transmission output power variable.

The reception buffer 12 is a semiconductor memory having a function of temporarily storing and holding the data received by the radio signal receiving unit 11. Each piece of data held in the receive buffer 12 is sequentially read out and output from the interface 18a. The data output by the interface 18a is used, for example, to control the on / off of loads of various auxiliary machines mounted on the own vehicle 50.

The calculation unit 13 is composed of a microcomputer, and performs various calculation processes necessary for realizing the characteristic functions in the present invention. For example, it has a function for calculating the distance between the own terminal and another terminal based on the CSI information acquired by the radio signal receiving unit 11.

The non-volatile memory 14 is a semiconductor memory capable of writing and reading data, and can hold data even when the power supply is cut off. The non-volatile memory 14 of the present embodiment is located at a position where each of the wireless terminals 10-0 to 10-6 belonging to one vehicle wireless communication system mounted on the own vehicle 50 is installed. Constant data representing the linear distance between them is stored in advance.

For example, in the case of the non-volatile memory 14 in the wireless terminal 10-0 shown in FIG. 1, each of the following six types of distance constant data D1 to D6 is written in advance.
D1: Distance between wireless terminals 10-0 and 10-1 [m]
D2: Distance between wireless terminals 10-0 and 10-2 [m]
D3: Distance between wireless terminals 10-0 and 10-3 [m]
D4: Distance between wireless terminals 10-0 and 10-4 [m]
D5: Distance between wireless terminals 10-0 and 10-5 [m]
D6: Distance between wireless terminals 10-0 and 10-6 [m]
The resolution of the distance data held by the non-volatile memory 14 is assumed to be set to about 0.1 [m].

The transmission power control unit 15 is composed of, for example, the same microcomputer as the calculation unit 13, and controls the transmission power, which is a characteristic function of the present invention. The details will be described later, but for example, when there is interference of the received radio wave from the interfering wireless terminal 100 or the like, the constant data of the distance held by the non-volatile memory 14 and the value of the distance calculated by the calculation unit 13 , And control such as enhancement of the transmission power of the radio signal transmission unit 16 is performed according to the result. Further, when the instruction information from another terminal belonging to the same system is received, the control for reducing the transmission power of, for example, the wireless signal transmission unit 16 is performed according to the instruction information.

The transmission buffer 17 is a memory having a function of receiving data before transmission by the wireless signal transmission unit 16 from the interface 18b and temporarily storing and holding the data. Each piece of data held in the transmission buffer 17 is sequentially read out and transmitted by the radio signal transmission unit 16 as a radio signal in the form of a packet or the like. The data input to the interface 18b corresponds to signals output by input devices such as various sensors and switches mounted on the own vehicle 50, for example. Of course, it is also possible to connect various other in-vehicle devices to the interface 18b.

<Operation example-1>
FIG. 3 shows an operation example-1 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. For example, when the wireless terminal 10-0 shown in FIG. 1 performs wireless communication with each wireless terminal 10-1 to 10-6 on the same own vehicle 50, the wireless terminal having the configuration shown in FIG. 2 10-1 executes the process shown in FIG. This process is actually executed by a microcomputer including the functions of the calculation unit 13 and the transmission power control unit 15 shown in FIG. The operation example-1 of FIG. 3 will be described below.

When the power supply of the wireless terminal 10-0 is turned on, the microcomputer of the wireless terminal 10-0 selects the reception mode and starts the channel scan (S11 to S13). That is, the wireless signal transmitting unit 16 stops transmission, and the wireless signal receiving unit 11 sequentially switches frequencies and the like within a predetermined frequency band to vacate a wireless channel (a channel not used by other terminals for transmission). To search for. When the wireless channel used by the wireless terminal 10-0 is fixed in advance, the detection process of whether or not the wireless channel is free is performed only for the corresponding wireless channel.

If all the radio channels are in use and are not available, or if a predetermined specific radio channel is in use and is not available, the process proceeds from steps S14 to S15. In step S15, the microcomputer selects one radio channel and uses the radio signal receiving unit 11 to measure the received power in this radio channel.

In the next step S16, the microcomputer estimates the signal power to interference power ratio SIR in the currently selected radio channel based on the received power information obtained from the measurement in S15. That is, the radio wave transmitted by the own terminal is transmitted based on the current magnitude of the transmission output power of the radio signal transmission unit 16 itself and the reception power of the radio signal from the interference source (corresponding to the interference radio terminal 100 or the like). The signal power to interference power ratio SIR at the receiving point (target terminal) is calculated. In this calculation, the signal power to interference power ratio SIR can be calculated more accurately by using the constant data of the distance held by the non-volatile memory 14.

In step S17, the microcomputer identifies whether or not the target PER can be achieved based on the signal power to interference power ratio SIR obtained in S16 and the predetermined target PER (packet error rate). If it can be achieved, the process proceeds to step S21, and if it cannot be achieved, the process proceeds to step S18. That is, when the influence of the interference is too large, it is necessary to take measures to improve the signal power to interference power ratio SIR, so the process proceeds to S18.

In step S18, the microcomputer performs the process of measuring the position of the interference source. Specifically, the distance Dt between the own terminal and the interference source is calculated based on the radio waves received by the radio terminal 10-0, which is the own terminal, from the interference source (corresponding to the interference radio terminal 100 or the like). This distance Dt can be calculated by, for example, the following equation.

Dt = "speed of light" x "radio wave propagation delay time between transmission and reception points"
= 2.9 × 10 ⁸ × (−φ / 2πf mod 1 / f) ・ ・ ・ (1)
φ: Radio channel phase f: Frequency

Information on the phase φ of the radio channel is included in, for example, CSI (Channel Status Information) obtained as a radio frequency (RF) channel property. CSI consists of amplitude and phase for each subcarrier.

A technique for measuring the propagation delay time between transmission / reception points with high accuracy is shown in, for example, Non-Patent Document 1. According to Non-Patent Document 1, it is said that the distance can be measured with an accuracy of about 0.1 [m]. It can be said that a distance measurement accuracy of about 0.1 [m] is sufficient to specify the position of each terminal on the vehicle.

In the next step S19, the microcomputer compares the distance Dt with the interference source calculated in S18 with the distances D1 to D6 with each other terminal on the own vehicle 50 held on the non-volatile memory 14, respectively. do. When the distance Dt does not match any of the distances D1 to D6, the interference source is outside the vehicle wireless communication system to which the wireless terminal 10-0, which is the own terminal, belongs (terminal outside the own vehicle 50, Alternatively, it is regarded as another system on the own vehicle 50), and the process proceeds to step S20. If the distance Dt substantially matches any one of the distances D1 to D6, it is considered that there is an interference source in the vehicle wireless communication system to which the own terminal belongs, and the process proceeds to step S23.

In step S20, the microcomputer on the wireless terminal 10-0, which is the own terminal, executes the function of the transmission power control unit 15. Specifically, the wireless signal transmission unit 16 is controlled so as to increase the wireless transmission power of the own terminal by, for example, a predetermined amount. Further, the microcomputer on the wireless terminal 10-0, which is the own terminal, switches the own terminal to the transmission mode in the next step S21, and further starts the data transmission in the next step S22.

Here, as a result of the control in step S20, the signal power of the radio wave from the transmission destination terminal, for example, the wireless terminal 10-0 reaching the wireless terminal 10-2 increases, so that the wireless terminal 10-2 transmits this wireless signal. The signal power to interference power ratio SIR at the time of reception is improved. Therefore, the packet error rate PER is also improved, and the data communication between the wireless terminal 10-0 and the wireless terminal 10-2 becomes successful. Moreover, it is not necessary to switch the channel used for communication, and it is not necessary to wait until a free channel is generated.

On the other hand, when the interference source is in the vehicle wireless communication system to which the own terminal belongs, the microcomputer on the wireless terminal 10-0 which is the own terminal has the function of the transmission power control unit 15 after step S23. Executes the processing of.

In step S23, the microcomputer creates instruction information for suppressing the transmission power by, for example, a certain amount. Then, after switching the own terminal to the transmission mode in step S24, the instruction information created in S23 is applied to all other wireless terminals 10-1 to 10- belonging to the same system as the own terminal in the next step S25. Send to 6.

After the process of step S23, each of the wireless terminals 10-1 to 10-6 that received the instruction information reduces the transmission power by, for example, a predetermined amount according to the instruction information. As a result, when the wireless terminal 10-0, which is the own terminal, transmits data with the wireless terminal 10-2 as the transmission destination, the interference power of the radio wave received by the wireless terminal 10-2 of the transmission destination is reduced, and the signal power is reduced. The power ratio to interference SIR is improved. Therefore, the packet error rate PER is also improved, and the data communication between the wireless terminal 10-0 and the wireless terminal 10-2 becomes successful. Moreover, it is not necessary to switch the channel used for communication, and it is not necessary to wait until a free channel is generated.

Actually, after the own terminal transmits the instruction information in step S25, the signal power to interference power ratio SIR calculated in step S16 is improved, so that the own terminal proceeds to data from steps S17 to S21 and S22. Start sending. At this time, since the influence of interference is suppressed, the data communication is in a successful state.

<Operation example-2>
FIG. 4 shows an operation example-2 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. The operation example-2 shown in FIG. 4 is a modification of the operation example-1 shown in FIG. 3, and only the steps S18A, S18B, S20A, and S23A in FIG. 4 are different from the contents of FIG. Each of these different steps will be described below. The configuration of each wireless terminal 10-0 to 10-6 is the same as in FIG.

In step S18A, the microcomputer on the wireless terminal 10-0, which is the own terminal, calculates the transmission power increase / decrease width ΔP based on the signal power to interference power ratio SIR estimated in S16 and the target packet error rate PER. In other words, transmission indicating how much the transmission power of the own terminal should be increased or the transmission power of other terminals belonging to the own system, which may be an interference source, should be suppressed to achieve the target packet error rate PER. The power increase / decrease width ΔP is calculated in S18A.

In step S18B, similarly to step S18 of FIG. 3, the microcomputer on the wireless terminal 10-0, which is the own terminal, measures the position of the interference source.

In step S20A, the microcomputer on the wireless terminal 10-0, which is the own terminal, executes the function of the transmission power control unit 15. Specifically, the wireless signal transmission unit 16 is controlled so as to increase the wireless transmission power of the own terminal by the transmission power increase / decrease width ΔP calculated in S18A. Further, also in step S23A, the microcomputer executes the function of the transmission power control unit 15 and creates instruction information for suppressing the transmission power by the transmission power increase / decrease width ΔP calculated in S18A.

Therefore, in the case of the operation shown in FIG. 4, the signal power to interference power ratio SIR achieves the target packet error rate PER only by executing the process of step S20A or S23A once, and FIG. 3 shows. Compared with the operation shown, the waiting time until the start of data transmission is shortened.

<Operation example-3>
A part (first half) of the operation example-3 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention is shown in FIG. 5, and the remaining part (second half) is shown in FIG. For example, when the wireless terminal 10-0 shown in FIG. 1 performs wireless communication with each wireless terminal 10-1 to 10-6 on the same own vehicle 50, the wireless terminal having the configuration shown in FIG. 2 10-0 performs the processes shown in FIGS. 5 and 6. This process is actually executed by a microcomputer including the functions of the calculation unit 13 and the transmission power control unit 15 shown in FIG. The operation example-3 of FIGS. 5 and 6 will be described below.

In the initial state, the microcomputer of the wireless terminal 10-0 stores the numerical value “0” in the memory for temporarily holding the value of the measurement distance D0 of the interference source in step S31. Then, when the power supply of the wireless terminal 10-0 is turned on, the reception mode is selected and the operation of the internal timer is started (S32 to S34).

In step S35, the microcomputer of the wireless terminal 10-0 identifies whether or not it is necessary to start data transmission. For example, it identifies whether or not a packet representing a data transmission request is input from the interface 18b to the wireless terminal 10-0. If it is necessary to start data transmission, the process proceeds from S35 to S48, and if it is not necessary, the process proceeds to S36.

Until it is necessary to start data transmission, the microcomputer of the wireless terminal 10-1 repeats the processes of steps S35, S36, and S37 in the standby state. Further, every time a certain time elapses in this standby state, that is, when the value of the internal timer that started the operation in S34 exceeds the threshold value, the process proceeds to the process of step S38 and subsequent steps.

Then, the microcomputer of the wireless terminal 10-0 resets the internal timer, switches the own terminal to the reception mode, and performs the same channel scan as in step S13 (S38 to S40). As a result of step S40, if the currently selected wireless channel is in use, the process proceeds from S41 to S44, and if it is free, the process returns from S41 to S36.

In step S44, the microcomputer of the wireless terminal 10-0 performs the reception power measurement of the wireless signal on the currently selected wireless channel as in S15. Further, in the next step S45, the signal power to interference power ratio SIR is estimated in the same manner as in S16, and whether or not this signal power to interference power ratio SIR achieves the target packet error rate PER is identified in step S46. .. If it has been achieved, it returns from S46 to S36, and if it has not been achieved, it proceeds from S46 to S47.

In step S47, the microcomputer of the wireless terminal 10-0 measures the position of the interference source in the same manner as in S18, and based on the result, updates the contents of the memory for temporarily holding the value of the measurement distance D0 of the interference source. do. Therefore, the latest value representing the measurement distance D0 of the interference source is stored in the memory.

When it becomes necessary to start data transmission, the microcomputer of the wireless terminal 10-0 resets the internal timer and performs a channel scan to identify whether or not the selected wireless channel is in use (S48 to S48 to). S50). If the wireless channel is in use, it proceeds to S51, and if it is not in use, it proceeds to S42.

In step S42, the microcomputer of the wireless terminal 10-1 switches its own terminal to the transmission mode, and starts data transmission in the next step S43.

In step S51, the microcomputer of the wireless terminal 10-0 performs the interference source position measurement process and calculates the distance Dt between the own terminal and the interference source in the same manner as in S18.

In the next step S52, the microcomputer of the wireless terminal 10-0 compares the distance Dt obtained in S51 with the predetermined in-vehicle distance threshold value Dr1, so that the position where the interference source exists is on the own vehicle 50. Identifies whether it is outside the system. Here, by setting the in-vehicle distance threshold value Dr1 to a value of, for example, several meters (a predetermined constant), the interference source on the own vehicle 50 and the interference source on the outside of the own vehicle 50 can be correctly distinguished. There is a high possibility that it can be done. Therefore, if the condition of "Dt> Dr1" is satisfied (the interference source is outside the vehicle), the process proceeds from S52 to S60, and if this condition is not satisfied, the process proceeds from S52 to S53.

In step S53, the microcomputer of the wireless terminal 10-1 compares the measurement distance D0 of the interference source with the numerical value “0” to identify whether or not the distance measurement of the interference source has been performed. Then, if the condition of "D0> 0" is satisfied, the process proceeds to S54, and if the condition is not satisfied, the process proceeds to S55.

In step S54, the microcomputer of the wireless terminal 10-0 performs a comparison of the following conditional expressions.
｜ Dt-D0 ｜ ＞ Dr2 ・ ・ ・ (2)
Dr2: Distance fluctuation threshold (predetermined constant)

If the condition of the above conditional expression is satisfied, the process proceeds to S60, and if the condition is not satisfied, the process proceeds to S55. That is, in a state where the detected distance variation "| Dt-D0 |" is large, there is a high possibility that the own terminal and the interference source are relatively moving, and there is a possibility that the interference source exists outside the own vehicle 50. Is high. Further, in a state where the detected distance variation "| Dt-D0 |" is relatively small, it is highly possible that the own terminal and the interference source are present on the same own vehicle 50.

In step S55, the microcomputer of the wireless terminal 10-0 considers that the interference source exists on the same own vehicle 50. Therefore, in the following step S56, instruction information for suppressing the transmission power is created, in step S57, the own terminal is switched to the transmission mode, and in step S58, the instruction information of S56 is used for all other wireless terminals 10-1 to 10-10. Send to -6. Then, in step S59, the own terminal is switched to the reception mode and the process returns to step S49.

On the other hand, when the measured distance Dt of the interference source is larger than the in-vehicle distance threshold value Dr1, or when the detected distance variation "| Dt-D0 |" is larger than the threshold value Dr2, the microcomputer of the wireless terminal 10-0 is set to step S60. It is considered that the interference source exists outside the same own vehicle 50. Then, similarly to S20, the transmission power of the own terminal is increased in step S61. After that, the process proceeds to S43 through step S42 to start data transmission.

For example, in the example shown in FIG. 1, the distance D3 from the wireless terminal 10-0 to the wireless terminal 10-3 and the distance Dx from the wireless terminal 10-0 to the interfering wireless terminal 100 are about the same. Further, since the distance Dx is about the same as the distance inside the own vehicle 50, it is difficult to distinguish that the interference radio terminal 100 exists outside the own vehicle 50 by the in-vehicle distance threshold value Dr1.

However, in the situation shown in FIG. 1, for example, the interfering radio terminal 100 is likely to exist and move on another vehicle traveling in the lane adjacent to the own vehicle 50. Further, even when the interfering radio terminal 100 is not moving, if the own vehicle 50 is traveling, the position of the interfering radio terminal 100 as seen from each terminal on the own vehicle 50 moves relatively. Will be there. That is, since the interfering wireless terminal 100 moves relatively, the distance Dx detected by the own terminal fluctuates. Therefore, by comparing the distance variation “| Dt−D0 |” with the threshold value Dr2 in step S54 of FIG. 6, it is possible to correctly recognize that the interfering radio terminal 100 exists outside the own vehicle 50.

<Operation example-4>
FIG. 7 shows a main part of an operation example-4 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. The operation example-4 shown in FIG. 7 is a modification of the operation example-3 shown in FIG. 6, and the remaining operations in FIG. 7 are almost the same as those in the “operation example-3”.

In the operation example-4 shown in FIG. 7, processing for considering the fluctuation of the received power is added as steps S71, S72, and S73. Further, in the operation example-4, it is assumed that the information of the received power measured in step S44 shown in FIG. 5 is stored in a predetermined memory. Other than that, it is the same as in FIG. Each added step will be described below.

In step S71, the microcomputer of the wireless terminal 10-0 measures the received power of the wireless signal in the currently selected wireless channel as in S15 and S44.

In step S72, the absolute value of the difference between the received power of the radio signal measured in step S44 of FIG. 5 and the received power of the radio signal measured in step S71 is set as the received power fluctuation amount ΔP2, and the wireless terminal 10-0 is used. Calculated by the microcomputer.

In step S73, the microcomputer of the wireless terminal 10-0 compares the received power fluctuation amount ΔP2 calculated in S72 with the predetermined fluctuation amount threshold value Pr1. Then, if the condition of "ΔP2> Pr1" is satisfied, the process proceeds from S73 to S60, and if the condition is not satisfied, the process proceeds to S54.

That is, when the interfering wireless terminal 100 is moving relative to the position of the own terminal, not only the distance Dx but also the received power of the interfering radio waves fluctuates. Therefore, by comparing the received power fluctuation amount ΔP2 with the fluctuation amount threshold value Pr1 in step S73, it is possible to correctly identify whether or not the interference source is located outside the own vehicle 50. The process of step S54 shown in FIG. 7 may be omitted.

<Operation example-5>
FIG. 8 shows an arrangement state of each wireless terminal of the vehicle wireless communication system mounted on the vehicle and an example of a region within the directional range by the directional antenna as viewed from above. Further, FIG. 9 shows an operation example-5 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention.

In the operation example-5 shown in FIG. 9, it is assumed that one or more wireless terminals of the vehicle wireless communication system mounted on the own vehicle 50 use directional antennas (19a, 19b). doing.

For example, in the example shown in FIG. 8, since the wireless terminal 10-4 uses a directional antenna, the range in which the radio waves transmitted by the wireless terminal 10-4 reach without being significantly attenuated is the directional range. It is limited to the area AR1 in. Outside this region AR1, the incoming radio waves are greatly attenuated. Further, the radio waves transmitted from the terminals outside the area AR1 are greatly attenuated as compared with the radio waves transmitted from the terminals inside the area AR1, and reach the wireless terminals 10-4.

Further, in the example shown in FIG. 8, when the wireless terminal 10-4 transmits, the wireless terminals 10-0 and 10-1 and the interfering wireless terminal 100-2 exist in the region AR1 where the radio waves reach without attenuation. , The radio terminals 10-2, 10-3, 10-5, 10-6, and the interfering radio terminal 100 exist outside the radio terminal 100.

When the wireless terminal 10-4 shown in FIG. 8 transmits, for example, if the directivity of the antenna of the wireless terminal 10-4 is variable, the received power of the interference wave fluctuates while rotating the direction of the directivity. By monitoring, it is possible to identify the direction in which the interference source exists. It is also possible to identify whether the position of the interference source is inside or outside with respect to the region AR1 within the directivity range of the direction used when performing data transmission.

In consideration of the situation shown in FIG. 8, the operation example-5 shown in FIG. 9 includes the control content for reducing the influence of the interference of the interfering radio terminals 100 and 100-2. The contents of the steps S11 to S17, S21, S22, S24, and S25 shown in FIG. 9 are the same as those of the steps having the same numbers shown in FIG. In the operation example-5 shown in FIG. 9, a step different from the content shown in FIG. 3 will be described below. Further, the operation example-5 shown in FIG. 9 will be described on the assumption that the wireless terminal 10-4 shown in FIG. 8 is executed.

In step S91, in a situation where the wireless terminal 10-0 receives the radio wave transmitted by the wireless terminal 10-4 shown in FIG. 8, assuming a case where the interference power is constant, the data reception of the wireless terminal 10-0 is successful. The microcomputer of the wireless terminal 10-4 calculates the amount of increase in signal power ΔS required for the operation. Specifically, the target packet error rate PER is achieved by considering the reception power of the interference wave measured in S15, the transmission power before the change of the wireless terminal 10-4, the gain of the directional antenna on the transmission side, and the like. The signal power increase amount ΔS is calculated as a value required to obtain the signal power to interference power ratio SIR.

In step S92, in a situation where the wireless terminal 10-0 receives the radio wave transmitted by the wireless terminal 10-4 shown in FIG. 8, assuming that the signal power is constant, the data reception of the wireless terminal 10-0 is successful. The interference power attenuation amount ΔI required for this is calculated by the microcomputer of the wireless terminal 10-4. Specifically, a signal for achieving the target packet error rate PER in consideration of the reception power of the interference wave measured in S15, the transmission power of the wireless terminal 10-4, the gain of the directional antenna on the transmission side, and the like. The interference power attenuation ΔI is calculated as a value required to obtain the power-to-interference power ratio SIR.

In step S18C, the microcomputer of the wireless terminal 10-4 measures the distance Dt with respect to the position of the interference source in the same manner as in S18.

In step S19B, the microcomputer of the wireless terminal 10-4 compares the measured distance Dt of the interference source measured in S18C with the in-vehicle distance threshold value Dr1. Assuming that the interference source is on the own vehicle 50, only the wireless terminal 10-1 included in the region AR1 is a candidate for the interference source. Therefore, as a result of measuring the position of the interference source, if the measurement distance Dt of the interference source is different from the distance D2 from the wireless terminal 10-4 to the wireless terminal 10-1, it is easy to say that the interference source is outside the own vehicle. I can judge. Therefore, the measurement distance Dt of the interference source may be compared with the distance from the wireless terminal on the transmitting side to the wireless terminal included in the directional region AR1. Further, the wireless terminal 10-4 may measure the direction in which the interference source exists by monitoring the fluctuation of the received power of the interference wave while rotating the direction of the directivity of the receiving antenna. Then, if either "Dt> Dr1" or "the direction of the interference source is outside the area AR1" is satisfied, or if "Dt is different from the distance to the wireless terminal in the area AR1", the process proceeds to S20B. In other cases, the process proceeds to S23B.

In step S20B, the microcomputer of the wireless terminal 10-4 is controlled to increase (add) the transmission output power of the wireless signal transmission unit 16 by the amount of the signal power increase amount ΔS calculated in S91.

In step S23B, the microcomputer of the wireless terminal 10-4 creates instruction information for suppressing the transmission output power of the wireless signal by the amount of the interference power attenuation ΔI calculated in S92. This instruction information is transmitted in S25 to all terminals belonging to the same system as the wireless terminals 10-4.

Therefore, for example, in the situation shown in FIG. 8, when the interfering radio terminal 100 is the interference source, the position of the interfering radio terminal 100 is outside the region AR1 within the directivity range, so from step S19B in FIG. Proceeding to S20B, the transmission output power when the wireless terminal 10-4 transmits data by the wireless signal is increased by the signal power increase amount ΔS. Therefore, the signal power received by the wireless terminal 10-0 is increased, the signal power to interference power ratio SIR is improved, and the influence of the interference wave is suppressed.

Further, for example, in the situation shown in FIG. 8, when the interfering radio terminal 100-2 is the interference source, the position of the interfering radio terminal 100-2 is inside the region AR1 within the directivity range. However, since the distance Dt of the interfering radio terminal 100-2 is larger than the in-vehicle distance threshold value Dr1, the process proceeds from steps S19B to S20B in FIG. 9 in this case as well, and is the same as the above case.

On the other hand, when another wireless terminal belonging to the same system as the wireless terminal 10-4 is the interference source, the process proceeds from steps S19B to S23B in FIG. Therefore, the instruction information for suppressing the transmission output power of the wireless signal is transmitted to the wireless terminal of the interference source by the amount of the interference power attenuation ΔI. As a result, the interference power received by the wireless terminal 10-0 is reduced, so that the signal power to interference power ratio SIR is improved and the influence of the interference wave is suppressed.

<Operation example-6>
FIG. 10 shows a main part of an operation example-6 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. The operation example-6 shown in FIG. 10 is an operation in which the features of both the above-mentioned "operation example-3" and "operation example-5" are combined, and the remaining operations not shown in FIG. 10 are the operations shown in FIG. Is the same as.

Therefore, in the operation example-6 shown in FIG. 10, in step S52B, in consideration of the distance, the variation of the distance, and the antenna directivity range, “Dt> Dr1” and “whether the direction of the interference source is outside the region AR1”. If any of the conditions of "whether or not" is satisfied, the process proceeds to S60.

Further, in step S54 of FIG. 10, in consideration of the fluctuation range of the distance of the interference source, even if the condition of "| Dt-D0 |> Dr2" is satisfied, the process proceeds to S60.

<Operation example-7>
FIG. 11 shows an operation example-7 of one wireless terminal included in the vehicle wireless communication system of the embodiment of the present invention. In the operation example-7 shown in FIG. 11, for example, when a device such as an in-vehicle electronic control unit (ECU) requests data transmission from the wireless terminal 10-1 shown in FIG. 1 via the interface 18b. It is assumed that the request signal and the wireless signal transmitted by each wireless terminal 10-1 to 10-6 include information indicating the priority of transmission.

That is, various types of devices are mounted on the vehicle. For example, in consideration of safety and reliability while the vehicle is running, the signals of some devices are preferentially handled or used for backup. It is also important to prepare a communication path. Therefore, even in a system that performs wireless communication on a vehicle, it is necessary to assign priorities to the signals to be handled so that priority control can be performed.

Among the processes shown in FIG. 11, steps S11 to S14 and S20 to S22 are the same as the processes having the same numbers shown in FIG.

In step S81 of FIG. 11, when the transmission request is generated, the microcomputer of the wireless terminal 10-0 acquires the information indicating the priority of the transmission data, sets this as the priority Dp1 of the transmission request, and proceeds to step S12.

If the channel is in use in step S14, the process proceeds to step S82 to acquire priority information of the signal received from the interference source. This priority is set as the priority Dp2 of the received signal.

In the next step S83, the microcomputer of the wireless terminal 10-0 compares the priority Dp1 of the transmission request with the priority Dp2 of the received signal. Then, if the condition of "Dp1> Dp2" is satisfied, the process proceeds to step S20, and if this condition is not satisfied, the process proceeds to step S84.

That is, when the transmission request has a higher priority than the data currently transmitted by another wireless terminal that is an interference source, the transmission output power of the wireless terminal 10-0, which is the own terminal, is set in step S20. Strengthen. As a result, it is possible to prevent the communication of high-priority data from failing. In addition, the signal power to interference power ratio SIR is improved.

On the other hand, when the priority of the received signal is higher, in step S84, the process waits until the transmission of the signal by the other wireless terminal is completed.

As described above, for example, in the case of a vehicle wireless communication system having the function of operation example-1 shown in FIG. 3, another wireless terminal belonging to the same system is a radio wave interference source. Since the transmission power of the interference source can be suppressed in steps S23 to S25, the interference of other wireless terminals can be reduced without switching the wireless channel.

Further, the position of the interference source is measured in step S18, and the distance to each wireless terminal on the same system held in the non-volatile memory 14 is compared with the distance obtained by the measurement, so that the interference source is the same. It can automatically identify whether it is another wireless terminal belonging to the system. Then, when another wireless terminal that does not belong to the same system is the interference source, the transmission output power of the own terminal is increased in step S20, so that the signal power received by the target wireless terminal of the transmission destination increases. However, the signal power to interference power ratio SIR can be improved.

Further, in the case of the vehicle wireless communication system having the function of the operation example-3 shown in FIGS. 5 and 6, interference is caused by comparing the measured distance Dt of the interference source with the in-vehicle distance threshold Dr1 in step S52. Since it is possible to automatically identify whether or not the position of the source is inside the own vehicle 50, a more appropriate response becomes possible. Further, by monitoring the fluctuation range of the distance of the interference source in step S54, even if the interference source exists in the vicinity of the own vehicle 50, it is possible to prevent an erroneous determination regarding the position thereof.

Further, in the case of the vehicle wireless communication system having the function of the operation example-5 shown in FIG. 9, since the directional antenna is used and the control is performed in consideration of the directional region, other than the control target. The number of terminals can be reduced and the possibility of erroneous judgment can be reduced.

Here, the features of the above-described embodiments of the vehicle wireless communication system according to the present invention are briefly summarized and listed below in [1] to [6], respectively.
[1] A local terminal (wireless terminal 10-0) installed in a vehicle and capable of transmitting and receiving wireless signals, and
With other terminals (wireless terminals 10-1 to 10-6) installed in the vehicle and capable of transmitting at least wireless signals,
With
The own terminal includes a own terminal control unit (transmission power control unit 15) that controls transmission / reception of wireless signals.
The other terminal includes at least another terminal control unit (transmission power control unit 15) that controls transmission of wireless signals.
When the own terminal control unit acquires a wireless signal transmission request, it detects the transmission of the wireless signal by the other terminal, and when it is determined that the other terminal is interfering with the other terminal, the other terminal control unit is notified. The transmission power of the other terminal is reduced (S19, S23 to S25: see FIG. 3).
A wireless communication system for vehicles characterized by this.

[2] A distance storage unit (nonvolatile memory 14) that stores the distance between the own terminal and the other terminal, and the like.
A distance calculation unit (S18) for calculating the distance from the transmission source of the signal received by the own terminal is further provided.
When the distance of the transmission source of the radio signal received by the own terminal and the distance stored in the distance storage unit are different from each other, the own terminal control unit increases the transmission power of the own terminal (S19, S20: see FIG. 3),
The vehicle wireless communication system according to the above [1].

[3] The own terminal control unit determines when the fluctuation of the distance of the transmission source calculated by the distance calculation unit is equal to or greater than a predetermined value (S54), or the fluctuation of the received power of the signal received from the transmission source is predetermined. When it is equal to or more than the value (S72, S73), it is determined that the transmission source is outside the vehicle (S60), and it is reflected in the transmission power control of at least one of the own terminal and the other terminal (FIG. 6, FIG. (See Fig. 7),
The vehicle wireless communication system according to the above [2].

[4] The distance calculation unit calculates the position where the transmission source exists, and then
The own terminal control unit compares the position of the transmission source calculated by the distance calculation unit with the distance of the other terminal included in the predetermined directivity range of the directional antenna existing on the vehicle. Depending on the result, it is determined whether or not the transmission source is outside the vehicle (S18C, S19B: see FIG. 9).
The vehicle wireless communication system according to the above [2] or [3].

[5] The radio signal includes a priority signal indicating the priority of transmission.
When the transmission source of the received signal is the other terminal and the priority represented by the received signal is lower than the priority represented by the radio signal for which the transmission request has been made, the own terminal control unit has a lower priority. Increases the transmission power of the own terminal (S84, S20: see FIG. 11).
The vehicle wireless communication system according to the above [2].

[6] The own terminal control unit automatically adjusts the amount of increase / decrease in the transmission power of at least one of the own terminal and the other terminal according to the power strength of the radio signal received by the own terminal (S18A, S20A, S23A: see FIG. 4),
The vehicle wireless communication system according to any one of the above [2] to [5].

10, 10-0, 10-1, 10-2, 10-3, 10-4, 10-5 Wireless terminal 11 Radio signal receiver 12 Receive buffer 13 Calculation unit 14 Non-volatile memory 15 Transmission power control unit 16 Radio signal Transmitter 17 Transmission buffer 18a, 18b Interface 19a, 19b Antenna 50 Own vehicle 100 Interference radio terminal AR1 Area within directional range D1, D2, D3, D4, D5, D6 Distance D0, Dt Measurement distance of interference source Dr1 In-vehicle distance Threshold Dr2 Distance fluctuation width Threshold PER Packet error rate SIR Signal power to interference power ratio ΔP Transmission power increase / decrease width ΔP2 Received power fluctuation amount Pr1 Received power fluctuation amount Threshold ΔS Required signal power increase amount ΔI Required interference power attenuation amount Dp1 Received signal Priority of Dp2 transmission request priority

Claims (6)

A terminal installed in the vehicle that can send and receive wireless signals,
With other terminals installed in the vehicle and capable of transmitting at least wireless signals,
With
The own terminal includes a own terminal control unit that controls transmission / reception of wireless signals.
The other terminal includes at least another terminal control unit that controls transmission of a wireless signal.
When the own terminal control unit acquires a wireless signal transmission request, it detects the transmission of the wireless signal by the other terminal, and when it is determined that the other terminal is interfering with the other terminal, the other terminal control unit is notified. To reduce the transmission power of the other terminal,
A wireless communication system for vehicles characterized by this. A distance storage unit that stores the distance between the own terminal and the other terminal,
A distance calculation unit for calculating the distance from the transmission source of the signal received by the own terminal is further provided.
When the distance of the transmission source of the radio signal received by the own terminal and the distance stored in the distance storage unit are different from each other, the own terminal control unit increases the transmission power of the own terminal.
The vehicle wireless communication system according to claim 1. When the fluctuation of the distance of the transmission source calculated by the distance calculation unit is equal to or more than a predetermined value, or when the fluctuation of the received power of the signal received from the transmission source is equal to or more than a predetermined value, the own terminal control unit has a predetermined value or more. , Determines that the transmission source is outside the vehicle, and increases the transmission power of the own terminal .
The vehicle wireless communication system according to claim 2. The distance calculation unit calculates the position where the transmission source exists, and
The own terminal control unit compares the position of the transmission source calculated by the distance calculation unit with the distance of the other terminal included in the predetermined directivity range of the directional antenna existing on the vehicle. Depending on the result, it is determined whether or not the transmission source is outside the vehicle.
The vehicle wireless communication system according to claim 2 or 3. The radio signal includes a priority signal indicating the priority of transmission.
When the transmission source of the received signal is the other terminal and the priority represented by the received signal is lower than the priority represented by the radio signal for which the transmission request has been made, the own terminal control unit has a lower priority. Increases the transmission power of the own terminal,
The vehicle wireless communication system according to claim 2. The own terminal control unit automatically adjusts the amount of increase / decrease in the transmission power of at least one of the own terminal and the other terminal according to the power strength of the wireless signal received by the own terminal.
The vehicle wireless communication system according to any one of claims 2 to 5.

Images