JP2012070452A - Radio communication device and transmission power control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication device which adjusts a communication-capable range autonomously and controls the number of communication devices within a communication zone averagely when a direct communication is performed between mobile communication devices via no base station.SOLUTION: A radio communication device 1-1 has a radio part 13 and a transmission power control part 11. The radio part 13 receives a first radio signal including a first transmission power setting value as a setting value of power for transmission from a destination radio communication device 1-2 and measures a first reception power as power for receiving the first radio signal. The transmission power control part 11 determines a second transmission power setting value as a setting value of power for transmission of a second radio signal to be transmitted to the destination radio communication device 1-2 on the basis of the first transmission power setting value and the measured first reception power. The radio part 13 transmits the second radio signal including the second transmission power setting value to the destination radio communication device 1-2 with the transmission power indicated as the second transmission power setting value.

Description

  The present invention relates to a wireless communication device and a transmission power control method, and more particularly to a wireless communication device and a transmission power control method with improved transmission power control.

  A wireless communication system that performs direct communication between mobile communication devices without using a base station, such as an inter-vehicle communication system, is known. In this wireless communication system, the communication state changes from moment to moment as the communication device moves. For example, with the movement of a communication device, there may be a situation where there are no communication partners in the communication range or there are few communication partners, and conversely, a situation where there are a large number of communication partners in a certain area that can communicate closely. The

  In particular, when communication devices are congested, communication in a wireless section is congested, which causes problems such as congestion and reduced throughput. In such a case, when communication is performed via the base station, the base station can control the transmission power to adjust the communicable range and equivalently suppress the number of communication devices in the communication area. it can. Thereby, it is possible to secure a wireless link with surrounding communication devices, and to reduce the occurrence of congestion and a decrease in throughput. However, in a wireless communication system that performs direct communication between mobile communication devices without using a base station, such as an inter-vehicle communication system, each mobile communication device communicates directly. Therefore, it is difficult to appropriately set the transmission power of these mobile communication devices. It is expected that each mobile communication device itself sets an appropriate transmission power autonomously according to the distribution of surrounding communication devices.

  Japanese Unexamined Patent Application Publication No. 2003-143048 discloses a mobile communication device and a mobile communication method. This inter-mobile communication apparatus exchanges information by wireless communication between a plurality of mobile bodies. The inter-mobile communication device searches for a peripheral mobile body that can relay the transmission of the transmission information to the target mobile body according to the communication state with the target mobile body that is the other party to which information is to be transmitted. And when the relay mobile body in which relay operation | movement is possible is searched, it has a means to wirelessly transmit the said transmission information to the said target mobile body via this relay mobile body. That is, this inter-mobile communication device is capable of transmitting and receiving without increasing the transmission power by changing the transmission path of the transmission data based on the reception quality of the reception data.

  Japanese Patent Application Laid-Open No. 2003-258715 describes a wireless communication device, a transmitter, a control method thereof, a control program, and a recording medium. This wireless communication device is mounted on a vehicle and used for wireless communication between vehicles. The wireless communication device detects the number of vehicles around the host vehicle, determines a transmission interval at random according to the number of vehicles, and transmits a frame including vehicle information at the transmission interval. In addition, the wireless communication device may randomly determine a transmission interval according to the traveling speed corresponding to the traveling speed information of the host vehicle input from the outside, and may transmit a frame including the vehicle information at the transmission interval. .

JP 2003-143048 A JP 2003-258715 A

  It is an object of the present invention to autonomously adjust a communicable range in a wireless communication system that directly communicates between mobile communication devices without using a base station, such as an inter-vehicle communication system. An object of the present invention is to provide a wireless communication device and a transmission power control method capable of adjusting the number of communication devices.

  Another object of the present invention is to autonomously adjust transmission power to an optimal value in a wireless communication system that directly communicates between mobile communication devices without using a base station, such as an inter-vehicle communication system. An object of the present invention is to provide a wireless communication device and a transmission power control method that are possible.

  Still another object of the present invention is to enable stable and highly reliable communication in a wireless communication system that performs direct communication between mobile communication devices without using a base station, such as a vehicle-to-vehicle communication system. To provide a wireless communication device and a transmission power control method.

  These objects and other objects and benefits of the present invention can be easily confirmed by the following description and the accompanying drawings.

  Hereinafter, means for solving the problem will be described using the numbers and symbols used in the embodiments for carrying out the invention. These numbers and symbols are added with parentheses in order to clarify the correspondence between the description of the claims and the mode for carrying out the invention. However, these numbers and symbols should not be used for interpreting the technical scope of the invention described in the claims.

  In order to solve the above problems, the wireless communication device of the present invention directly communicates with the counterpart wireless communication device (1-2). The wireless communication device (1-1) includes a wireless unit (13) and a transmission power control unit (11). The wireless unit (13) receives a first wireless signal including a first transmission power setting value as a power setting value during transmission from the counterpart wireless communication device (1-2), and receives the first wireless signal. The first received power is measured as the hourly power. The transmission power control unit (11) is configured to transmit a second radio signal to be transmitted to the counterpart wireless communication device (1-2) based on the first transmission power setting value and the measured first received power. A second transmission power setting value as a power setting value is determined. The wireless unit (13) transmits the second wireless signal including the second transmission power setting value to the counterpart wireless communication device (1-2) with the transmission power indicated by the second transmission power setting value.

  In the above wireless communication device, the transmission power control unit (11) associates the first transmission power setting value and the first received power with ID information for specifying the counterpart wireless communication device (1-2), and the surrounding vehicle. Store as a table (22). Based on the ID information, the second transmission power setting value is determined with reference to the surrounding vehicle table (22).

  In the above wireless communication device, the transmission power control unit (11) includes a transmission power setting value of the transmission-side wireless communication device, a reception power of the reception-side wireless communication device, and a transmission power setting value of the reception-side wireless communication device. And a transmission power setting table (21) associated with. Based on the ID information, the first transmission power set value and the first received power are acquired by referring to the surrounding vehicle table (22). Based on the first received power and the first transmission power setting value, the second transmission power setting value is determined with reference to the transmission power setting table (21).

  In the above wireless communication device, there are a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). The wireless unit (13) receives a first wireless signal including a first transmission power setting value for each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...) First received power as power at the time of receiving the first radio signal is measured. The transmission power control unit (11) is based on the first transmission power setting value and the first received power for each of the plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). Then, the second transmission power setting value is determined. One of the plurality of determined second transmission power setting values that satisfies a predetermined condition is determined as the final second transmission power setting value. The radio unit (13) transmits the second radio signal including the final second transmission power setting value with the transmission power indicated by the final second transmission power setting value to a plurality of radio communication devices (1- 2, 1-3, 1-4, ...).

  In the above wireless communication device, the transmission power control unit (11) sets the first transmission power setting value for each of the plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). The first received power is stored as a surrounding vehicle table (22) in association with ID information for specifying each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). A transmission power setting table (21) is provided that associates the transmission power setting value of the transmission-side wireless communication device, the reception power of the reception-side wireless communication device, and the transmission power setting value of the reception-side wireless communication device. For each of the plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...), The first transmission power setting value is referred to the surrounding vehicle table (22) based on the ID information. And the first received power. Transmission power setting table (21) for each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...) Based on the first received power and the first transmission power setting value. Referring to FIG. 4, the second transmission power setting value is determined.

  In the above wireless communication device, the transmission power control unit (11) includes the number of counterpart wireless communication devices (1-2, 1-3, 1-4,...) Having the final second transmission power setting value. However, the final second transmission power setting value is lowered so as to be smaller than the predetermined number.

  In the wireless communication device, the transmission power control unit (11) refers to the transmission power setting table (21), and the transmission power setting value of the reception-side wireless communication device is the final second transmission power setting value. A set of the transmission power setting value of the transmission-side wireless communication device and the reception power of the reception-side wireless communication device is extracted as follows. With reference to the surrounding vehicle table (22), ID information that is the same as the set from which the first received power and the first transmission power set value are extracted is extracted. The final second transmission power setting value is lowered so that the number of ID information is smaller than a predetermined number.

  In the above wireless communication device, the counterpart wireless communication device is a wireless communication device arranged on the roadside.

  In order to solve the above problems, the transmission power control method of the present invention is a transmission power control method for the wireless communication device (1-1) that performs direct communication with the counterpart wireless communication device (1-2). (A) The first wireless signal including the first transmission power setting value as the power setting value at the time of transmission is received from the counterpart wireless communication device (1-2), and the power at the time of reception of the first wireless signal is received. Measuring the first received power, and (b) a second radio that is transmitted to the counterpart wireless communication device (1-2) based on the first transmission power set value and the measured first received power. Determining a second transmission power setting value as a power setting value at the time of signal transmission; and (c) a second radio including the second transmission power setting value at the transmission power indicated by the second transmission power setting value. Transmitting a signal to the counterpart wireless communication device (1-2).

  In the above transmission power control method, the step (b) includes (b1) associating the first transmission power setting value and the first received power with the ID information for identifying the counterpart wireless communication device (1-2) Storing as a vehicle table (22), (b2) obtaining a first transmission power set value and a first received power with reference to the surrounding vehicle table (22) based on the ID information; b3) Refer to the transmission power setting table (21) in which the transmission power setting value of the transmission-side wireless communication device, the reception power of the reception-side wireless communication device, and the transmission power setting value of the reception-side wireless communication device are associated with each other. And determining a second transmission power setting value based on the first received power and the first transmission power setting value.

  In the above transmission power control method, there are a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). (A) The step receives (a1) a first wireless signal including a first transmission power setting value for each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). And measuring the first received power as the power when receiving the first radio signal. (B) The step is based on the first transmission power setting value and the first received power for each of (b4) a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). Determining a second transmission power setting value; and (b5) determining one of the determined second transmission power setting values satisfying a predetermined condition as a final second transmission power setting value. The step of carrying out is provided. (C) The step includes (c1) transmitting a second wireless signal including the final second transmission power setting value with the transmission power indicated by the final second transmission power setting value to a plurality of radio communication devices ( 1-2, 1-3, 1-4,...)).

  In the above transmission power control method, (b4) step includes (b41) a first transmission power setting value for each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). And the first received power are stored as a surrounding vehicle table (22) in association with ID information for specifying each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...). (B42) For each of a plurality of counterpart wireless communication devices (1-2, 1-3, 1-4,...), Referring to the surrounding vehicle table (22) based on the ID information, A step of obtaining one transmission power setting value and a first reception power; (b43) a transmission power setting value of a transmission side wireless communication device; a reception power of a reception side wireless communication device; and a reception side wireless communication device. With reference to the transmission power setting table (21) in which the transmission power setting value is associated, Based on the first received power and the first transmission power setting value, the second transmission power setting value is set for each of a number of wireless communication devices (1-2, 1-3, 1-4,...). Determining.

  In the above transmission power control method, the (b5) step refers to (b51) the transmission power setting table (21), and the transmission power setting value of the receiving-side radio communication device is the final second transmission power setting value. And a step of extracting a set of the transmission power setting value of the wireless communication device on the transmission side and the reception power of the wireless communication device on the reception side, and (b52) referring to the surrounding vehicle table (22), A step of extracting ID information in which the first received power and the first transmission power set value are the same as the extracted set; and (b53) final so that the number of ID information is smaller than a predetermined number. Lowering the second transmission power set value.

  In order to solve the above problems, the present invention is a program for executing the transmission power control method according to any one of the above items.

  According to the present invention, in a wireless communication system that directly communicates between mobile communication devices without using a base station such as an inter-vehicle communication system, it is possible to autonomously control transmission power and adjust a communicable range. Thus, the number of communication devices within the communication range can be reduced equivalently. Thereby, it is possible to secure a wireless link with surrounding communication devices and reduce congestion and a decrease in throughput.

FIG. 1 is a block diagram showing a configuration of an embodiment of an in-vehicle communication device as a wireless communication device of the present invention. FIG. 2 is a block diagram showing a configuration of an embodiment of an in-vehicle communication device as a wireless communication device of the present invention. FIG. 3 is a schematic diagram illustrating an example of a situation assumed in the embodiment of the transmission power control method of the present invention. FIG. 4 is a table showing the surrounding vehicle table. FIG. 5 is a table showing a transmission power setting table. FIG. 6 is a flowchart showing an embodiment of the transmission power control method of the present invention. FIG. 7 is a flowchart showing details of S04. FIG. 8 is a flowchart showing the additional processing of S15.

  Hereinafter, embodiments of a wireless communication device and a transmission power control method of the present invention will be described with reference to the accompanying drawings. Here, an example will be described in which the transmission power control method of the present invention is applied to an inter-vehicle communication system, and the wireless communication device of the present invention is an in-vehicle communication device that is a communication device mounted on an automobile. In the inter-vehicle communication system, wireless communication is performed between a plurality of in-vehicle communication devices 1 (1-1, 1-2,...).

  In this case, each in-vehicle communication device first transmits vehicle position information, set value of transmission power, and the like to surrounding vehicles. Also, information such as vehicle position information, transmission power setting values, and received power at that time received from surrounding vehicles is retained as information on surrounding vehicles, and the information is updated each time a new signal is received from surrounding vehicles. To do. Based on the information of the surrounding vehicles, the propagation loss is estimated from the transmission power set value of the surrounding vehicles and the actual received power. In addition, when transmitting from the own vehicle, after estimating the number of vehicles that can be received according to the transmission power setting value, set the transmission power so that signals do not reach more vehicles than necessary and output the signal To do. Hereinafter, embodiments of the present invention will be described in detail.

  1 and 2 are block diagrams showing the configuration of an embodiment of an in-vehicle communication device as a wireless communication device of the present invention. The in-vehicle communication device 1 includes a transmission power control unit 11, an in-vehicle wireless unit 12, and an in-vehicle control unit 13. Here, although the in-vehicle communication device 1-1 will be described, the in-vehicle communication devices 1-2,... Of surrounding vehicles also have the same configuration as the in-vehicle communication device 1-1.

  The in-vehicle radio unit 12 transmits and receives radio signals to and from the in-vehicle communication devices 1-2 of the surrounding vehicles. That is, at the time of reception, the in-vehicle wireless unit 12 receives a wireless reception signal from the other in-vehicle communication device 1. Then, the wireless reception signal is converted into reception data, and the reception data and reception power data are output to the in-vehicle control unit 13. Here, the received power data indicates the magnitude of received power (received power measurement value) when the radio received signal is received.

  On the other hand, at the time of transmission, the in-vehicle wireless unit 12 receives transmission data from the in-vehicle control unit 13 and vehicle data from the transmission power control unit 11. Here, the vehicle data includes transmission power data indicating the magnitude of transmission power (transmission power setting value) when transmitting a radio transmission signal, and ID information for identifying the in-vehicle communication device 1-1. . The position information of this vehicle-mounted communication device 1-1 may be included. The in-vehicle wireless unit 12 converts the transmission data to which the vehicle data is added into a wireless transmission signal, and converts the wireless transmission signal into the in-vehicle communication device 1- 1 of the surrounding vehicle by the transmission power specified by the transmission power setting value. 2. Send to ...

  The in-vehicle control unit 13 controls the flow of signals (data) in the in-vehicle communication device 1-1. Further, data (vehicle communication device input / output data) is input / output to / from an external device of the vehicle communication device 1-1, for example, the vehicle application system 15. Examples of the in-vehicle application system 15 include a GPS system and an in-vehicle sensor. Further, the vehicle data received from the in-vehicle communication devices 1-2 of the surrounding vehicles is output to the transmission power control unit 11.

  For example, at the time of reception, the in-vehicle control unit 13 receives the received data and the received power data from the in-vehicle wireless unit 12, transmits the received data to the in-vehicle application system 15, and controls the transmission power of the vehicle data and the received power data in the received data. Output to the unit 11. In this case, the vehicle data is transmission power data indicating the magnitude of transmission power (transmission power setting value) when another in-vehicle communication device 1-2 transmits a radio reception signal received by the in-vehicle communication device 1-1. , And ID information for specifying other in-vehicle communication device 1-2. The vehicle data may include position information of the in-vehicle communication devices 1-2 of the surrounding vehicles.

  On the other hand, at the time of transmission, the in-vehicle control unit 13 receives transmission data from the in-vehicle application system 15 and outputs it to the in-vehicle wireless unit 12. Further, the ID information of the in-vehicle communication device 1 that is the transmission destination of the transmission data is output to the transmission power control unit 11. The transmission data may include position information (by GPS) of the in-vehicle communication device 1-1 included in the vehicle data by the in-vehicle wireless unit 12.

  The transmission power control unit 11 receives vehicle data and reception power data in the reception data from the in-vehicle control unit 13. As described above, the vehicle data in the received data includes transmission power data (transmission power setting value) and position information at the time of transmission in the in-vehicle communication device 1-2 of the surrounding vehicle, and the ID of the in-vehicle communication device 1-2. Contains information. The transmission power control unit 11 stores the vehicle data ID information, the transmission power setting value, the reception power measurement value of the reception power data, and the data reception time in association with each other as the surrounding vehicle table 22. The peripheral vehicle table 22 is stored in, for example, a semiconductor memory or a HDD (Hard Disk Drive).

  FIG. 4 is a table showing the surrounding vehicle table. ID information, transmission power setting value, reception power measurement value, and reception time are associated with each other. When data related to the same ID information is received, the reception time, transmission power setting value, and reception power measurement value are updated in the surrounding vehicle table 22. Location information may be included. Each data may be deleted if there is no update for a predetermined time.

  The transmission power control unit 11 further stores a transmission power setting table 21 in which the received power measurement value and the transmission power setting value are associated with each other. This is based on the received power measurement value (a) of the wireless signal measured by the in-vehicle communication device 1-1 and the transmission power setting value (b) in the in-vehicle communication device 1-2 that transmits the wireless signal. Next, it is a table | surface which calculates | requires the transmission power setting value (c) in the vehicle-mounted communication apparatus 1-1 in the case of performing wireless transmission from the vehicle-mounted communication apparatus 1-1 to the vehicle-mounted communication apparatus 1-2. The transmission power setting table 21 is stored in, for example, a semiconductor memory or an HDD (Hard Disk Drive).

  FIG. 5 is a table showing a transmission power setting table. However, in this table, in order to simplify the explanation, specific numerical values are not shown as an example, and the intensity category is set to “strong”, “medium”, and “weak”, that is, the received power measurement The value (a) and the transmission power setting value (b) are assumed to belong to one of these categories. For example, when the received power measurement value (a) is “medium” and the transmission power setting value (b) is “strong”, the transmission power setting value (c) in the in-vehicle communication device 1-1 is “strong”. Become. Note that “strong”, “medium”, and “weak” specifically indicate predetermined power ranges (1 to 5 W / 5 to 10 W / 10 to 15 W) and energy ranges, respectively. A method for generating the transmission power setting table 21 will be described later.

  When transmitting data to the vehicle of the ID information received from the in-vehicle control unit 13, the transmission power control unit 11 refers to the surrounding vehicle table 22 and acquires a received power measurement value and a transmission power setting value corresponding to the ID information. . And the transmission power setting value (c) corresponding to the received power measurement value (a) and the transmission power setting value (b) is extracted. Thereafter, vehicle data including transmission power data indicating the transmission power setting value and ID information for specifying its own in-vehicle communication device 1-1 is generated and output to the in-vehicle wireless unit 12.

  Here, the transmission power control unit 11, the in-vehicle wireless unit 12 (excluding transmission / reception) and the in-vehicle control unit 13 may be configured by hardware such as a circuit, or by software such as a program on a computer. Or a combination of them may be used.

  Next, an embodiment of the transmission power control method (operation of the in-vehicle communication device) of the present invention will be described. FIG. 3 is a schematic diagram illustrating an example of a situation assumed in the embodiment of the transmission power control method of the present invention. In the inter-vehicle communication system, the in-vehicle communication device 1-1 is assumed to receive radio signals from a plurality of in-vehicle communication devices 1 such as other in-vehicle communication devices 1-2, 1-3, and 1-4. . At this time, the received power in the in-vehicle communication device 1-1 depends on the set value of the transmission power of each of the in-vehicle communication devices 1-2, ..., the distance between the in-vehicle communication devices and the state of the propagation path. Here, when a radio signal is received from another in-vehicle communication device 1-2,..., If the time interval until the radio signal is transmitted in the opposite direction is short, the situation of the propagation path at the time of reception and the time of transmission It can be assumed that the situation of the propagation path is almost the same.

  For example, when a signal is received from the in-vehicle communication device 1-2 in the area A1, if the time interval until the signal is transmitted to the in-vehicle communication device 1-2 is short, the in-vehicle communication device 1-2 is substantially the same area A1. It can be assumed that the conditions of the propagation paths are almost the same. Similarly, when signals are received from the in-vehicle communication devices 1-3 and 1-4 in the areas A2 and A3, if the time interval until the signals are transmitted to the in-vehicle communication devices 1-3 and 1-4 is short, It can be assumed that the in-vehicle communication devices 1-3 and 1-4 are substantially in the same area A <b> 2 and A <b> 3, and the propagation path conditions are substantially the same.

  Here, communication between the in-vehicle communication device 1-1 and the in-vehicle communication device 1-2 is considered. When the transmission power setting value of the in-vehicle communication device 1-2 of the communication partner is “strong” and the reception power of the in-vehicle communication device 1-1 at that time is “weak”, the in-vehicle communication device 1-1 is in the in-vehicle communication device 1. In the case of transmitting back to -2, even if the transmission power setting is “strong”, it can be expected that the reception power at the counterpart vehicle-mounted communication device 1-2 will be “weak”. On the other hand, when the transmission power setting of the in-vehicle communication device 1-2 of the communication partner is “strong” and the reception power of the in-vehicle communication device 1-1 at that time is also “strong”, the in-vehicle communication device 1-1 is the in-vehicle communication device. Even if the transmission power setting for transmitting back to 1-2 is set to “medium”, it can be expected that the reception power at the partner side will be “medium”. Therefore, if the reception power is “medium” and stable reception is possible, in the latter case, the transmission power setting at the time of return can be lowered to “medium”. Based on such a concept, the transmission power setting value for return transmission can be set from the combination of the transmission power setting value at the other party's in-vehicle communication device and the received power measurement value at the other side. The transmission power setting table 21 in FIG. 5 is generated based on such a concept.

  The transmission power setting table 21 in FIG. 5 can be applied as it is when only two in-vehicle communication devices 1 exist in the communication area and communicate one-to-one.

  Referring to FIG. 3, on the other hand, in the case of communication in which a large number of in-vehicle communication devices 1 exist in the communication range and exchange information with each other, with some in-vehicle communication devices 1 (example: 1-4) “High” is required as the transmission power setting value for communication, and “medium” is the transmission power setting value for communication with some other in-vehicle communication devices 1 (example: 1-3). It is necessary, and “weak” is sufficient as the transmission power setting value for communication with some other in-vehicle communication devices 1 (example: 1-2). In this case, when the transmission power set value is set to “medium”, the communicable range can be limited to the area A2 including the area A1, and the number of in-vehicle communication devices 1 that can communicate can be limited. Furthermore, when the transmission power set value is set to “weak”, the communicable range can be limited within the area A1, and the number of in-vehicle communication devices 1 that can communicate can be further limited. In this way, by changing the transmission power setting value to limit the communicable range, it becomes possible to reduce congestion and a decrease in throughput.

  In this case, in addition to the combination of the transmission power setting value and the reception power measurement value, transmission power control can be performed in consideration of the number of in-vehicle communication devices that can communicate. In the example of FIG. 3, if it is “strong”, the communicable range is the area A <b> 3, and three in-vehicle communication devices 1-2 to 1-4 can communicate. If it is “medium”, the communicable range is the area A2, and the two in-vehicle communication devices 1-2 to 1-3 can communicate. If it is “weak”, the communicable range is the area A1, and one of the in-vehicle communication devices 1-2 can communicate.

Next, a specific flow in the embodiment of the transmission power control method (operation of the in-vehicle communication device) of the present invention will be described. FIG. 6 is a flowchart showing an embodiment of the transmission power control method of the present invention. Here, an example in which the in-vehicle communication device 1-1 communicates with the in-vehicle communication device 1-2 of a surrounding vehicle will be described.

The in-vehicle wireless unit 12 receives a wireless reception signal from the in-vehicle communication device 1-2 (S01).
Next, the in-vehicle wireless unit 12 measures the power of the wireless reception signal and obtains the received power measurement value (S02). Subsequently, reception power data indicating the reception power measurement value is generated. Then, the wireless reception signal is converted into reception data, and the reception data and reception power data are output to the in-vehicle control unit 13.
The in-vehicle control unit 13 receives the received data and the received power data from the in-vehicle wireless unit 12. Next, vehicle data is extracted from the received data, and the received data is output to the in-vehicle application system 15. Then, the in-vehicle control unit 13 outputs the extracted vehicle data (including the transmission power setting value and ID information) and the reception power data to the transmission power control unit 11.
The transmission power control unit 11 receives vehicle data and reception power data from the in-vehicle control unit 13. Next, the transmission power control unit 11 extracts ID information and a transmission power set value from the vehicle data (S03). Then, the ID information, the transmission power setting value, the reception power measurement value of the reception power data, and the data reception time are associated and stored as the surrounding vehicle table 22.

The in-vehicle control unit 13 receives transmission data from the in-vehicle application system 15 to the in-vehicle communication device 1-2 and outputs the data to the in-vehicle wireless unit 12. At the same time, ID information (vehicle communication device 1-2) of the transmission destination of the transmission data is output to the transmission power control unit 11.
The transmission power control unit 11 acquires ID information (in-vehicle communication device 1-2) of the transmission destination of transmission data from the in-vehicle control unit 13. Next, referring to the surrounding vehicle table 22, the transmission power setting value (in-vehicle communication device 1-2) and the received power measurement value (in-vehicle communication device 1-1) corresponding to the ID information (in-vehicle communication device 1-2). ) To get. Then, referring to the transmission power setting table 21, the transmission at the time of the next transmission data transmission corresponding to the transmission power setting value (in-vehicle communication device 1-2) and the received power measurement value (in-vehicle communication device 1-1). A power setting value (vehicle communication device 1-1) is determined (S04). Thereafter, the transmission power control unit 11 generates vehicle data including transmission power data indicating the transmission power set value (on-vehicle communication device 1-1) and ID information identifying the on-vehicle communication device 1-1, and the on-vehicle wireless unit 12 is output.
The in-vehicle wireless unit 12 receives transmission data from the in-vehicle control unit 13 and vehicle data from the transmission power control unit 11. And the vehicle-mounted radio | wireless part 12 converts the transmission data which added the vehicle data into a radio | wireless transmission signal, and transmits the radio | wireless transmission signal to the vehicle-mounted communication apparatus 1-2 with the transmission power designated by the transmission power setting value. (S05).

  Here, in S04, in the case of communication in which a large number of in-vehicle communication devices 1 exist in the communication area and exchange information with each other, a method for determining the transmission power setting value will be described. FIG. 7 is a flowchart showing details of S04. Here, an example in which the in-vehicle communication device 1-1 communicates with the in-vehicle communication devices 1-2 and 1-3 of the surrounding vehicles will be described.

The in-vehicle control unit 13 receives transmission data from the in-vehicle application system 15 to the plurality of in-vehicle communication devices 1-2 and 1-3 and outputs the data to the in-vehicle wireless unit 12. At the same time, a plurality of ID information (in-vehicle communication devices 1-2, 1-3) of transmission destinations of transmission data is output to the transmission power control unit 11.
The transmission power control unit 11 acquires a plurality of pieces of ID information (vehicle communication devices 1-2, 1-3) as transmission destinations of transmission data from the vehicle-mounted control unit 13 (S11). Next, one piece of ID information (in-vehicle communication device 1-2) is selected from a plurality of ID information (in-vehicle communication devices 1-2, 1-3) (S12). Then, referring to the surrounding vehicle table 22, the transmission power setting value (in-vehicle communication device 1-2) and the received power measurement value (in-vehicle communication device 1-1) corresponding to the ID information (in-vehicle communication device 1-2). To get. Then, referring to the transmission power setting table 21, the transmission at the time of the next transmission data transmission corresponding to the transmission power setting value (in-vehicle communication device 1-2) and the received power measurement value (in-vehicle communication device 1-1). A power setting value (vehicle communication device 1-1) is determined (S13). The above S12 and S13 are executed for all ID information (S14). As a result, a plurality of transmission power setting values are obtained corresponding to the plurality of ID information. Thereafter, the transmission power control unit 11 determines the largest transmission power setting value from the plurality of transmission power setting values as the final transmission power setting value (S15).

  In S15, the largest transmission power setting value is selected from a plurality of transmission power setting values, but may be determined by other rules. For example, the largest number of transmission power setting values.

  By the transmission power control method of the present invention (operation of the in-vehicle communication device) as described above, the in-vehicle communication device 1 itself of each vehicle autonomously responds to the situation of the transmission path with the counterpart in-vehicle communication device 1. Thus, it is possible to control the transmission power. As a result, excess or deficiency of transmission power can be resolved, and communication stability and reliability can be improved. At the same time, it is possible to adjust the communicable range by autonomously controlling the transmission power according to the distribution of the in-vehicle communication devices 1 in the vicinity, and equivalently suppress the number of communication devices in the communication area. As a result, it is possible to secure a wireless link with surrounding communication devices and reduce congestion and a decrease in throughput.

  Furthermore, by adding the following processing to S15, it is also possible to determine the transmission power setting value in consideration of information on the number of in-vehicle communication devices 1 of vehicles (mobile bodies) capable of communication. FIG. 8 is a flowchart showing the additional processing of S15. That is, first, for the transmission power setting value (c) determined in S11 to S15, the transmission power setting value (b) having the same or lower transmission power setting value (c) and the received power measurement value (a) Are extracted from the transmission power setting table 21 (FIG. 5) (S21). Next, ID information of the in-vehicle communication device 1 having the combination (transmission power setting value (b) and reception power measurement value (a)) is extracted from the surrounding vehicle table 22 (S22). Then, the number of ID information (= number of vehicles) is calculated. As a result, when the number of vehicles is equal to or greater than the desired number (S23: Yes), the transmission power set value determined in S11 to S15 is decreased by one step (S24). And it returns to S21 and performs a process. If the number of vehicles is less than the desired number (S23: No), the transmission power setting value at that time is determined as the final transmission power setting value (S25).

  In the above embodiment, the example in which the present invention is applied to the inter-vehicle communication system has been shown. However, even when the road-to-vehicle communication and the inter-vehicle communication are shared, a part of the plurality of in-vehicle communication devices is used as the road-side communication device. By translating, it is possible to apply the transmission power control method and the wireless communication device of the present invention in the same manner.

  According to the present invention, in a wireless communication system that performs direct communication between mobile communication devices without using a base station, each mobile communication device itself is distributed in the surrounding communication devices, particularly when the communication devices are crowded. In response, the transmission power is controlled autonomously to adjust the communicable range and equivalently suppress the number of communication devices in the communication area, thereby securing radio links with surrounding communication devices, and reducing congestion and throughput. It is possible to reduce the decrease.

  The present invention is not limited to the embodiments described above, and it is obvious that the embodiments can be appropriately modified or changed within the scope of the technical idea of the present invention.

1, 1-1, 1-2,..., 1-n In-vehicle communication device 11 Transmission power control unit 12 In-vehicle wireless unit 13 In-vehicle control unit 15 In-vehicle application system 21 Transmission power setting table 22 Peripheral vehicle table

Claims (7)

A wireless communication device that directly communicates with a plurality of counterpart wireless communication devices,
For each of the plurality of partner wireless communication devices, a first wireless signal including a first transmission power setting value as a power setting value at the time of transmission is received from the partner wireless communication device, and the first wireless signal is transmitted. A wireless unit that measures first received power as power at the time of reception of a signal;
For each of the plurality of counterpart wireless communication devices, with reference to the first transmission power setting value and the measured first reception power, a second wireless signal to be transmitted to the counterpart wireless communication device A transmission power control unit for determining a second transmission power setting value as a power setting value at the time of transmission,
The transmission power control unit
For each of the plurality of counterpart wireless communication devices, the first transmission power setting value and the first reception power are stored as a surrounding vehicle table,
A transmission power setting table associating a transmission power setting value of a transmission-side wireless communication device, a reception power of a reception-side wireless communication device, and a transmission power setting value of the reception-side wireless communication device;
For each of the plurality of counterpart wireless communication devices, one of the plurality of second transmission power setting values determined with reference to the transmission power setting table is finally determined as the second Determine the transmission power setting value,
With reference to the transmission power setting table, a transmission power setting value of the transmission-side radio communication device, wherein a transmission power setting value of the reception-side wireless communication device is equal to or lower than the final second transmission power setting value; , Extract a pair with the reception power of the wireless communication device on the receiving side,
Referring to the surrounding vehicle table, the first received power and the first transmission power set value are the same as the extracted set, so that the number of counterpart wireless communication devices is smaller than a predetermined number. And lowering the final second transmission power setting value,
The radio unit transmits the second radio signal including the final second transmission power setting value with the transmission power indicated by the lowered final second transmission power setting value to the counterpart radio communication device. Transmit to a wireless communication device. The wireless communication device according to claim 1,
The transmission power control unit
For each of the plurality of counterpart wireless communication devices, the first transmission power setting value and the first reception power are associated with ID information identifying each of the plurality of counterpart wireless communication devices, and the surrounding vehicle Stored as a table,
For each of the plurality of counterpart wireless communication devices, referring to the surrounding vehicle table based on the ID information, obtaining the first transmission power setting value and the first reception power,
For each of the plurality of counterpart wireless communication devices, the second transmission power setting value is determined by referring to the transmission power setting table based on the first reception power and the first transmission power setting value. Yes Wireless communication device. The wireless communication device according to claim 1 or 2,
The counterpart wireless communication device includes a wireless communication device arranged on a roadside. The wireless communication device according to any one of claims 1 to 3,
The counterpart wireless communication device and the wireless communication device include a wireless communication device mounted on a vehicle. A transmission power control method for a wireless communication device that performs direct communication with a plurality of counterpart wireless communication devices,
(A) For each of the plurality of partner wireless communication devices, receiving a first wireless signal including a first transmission power setting value as a power setting value during transmission from the partner wireless communication device; Measuring the first received power as the power at the time of receiving the first radio signal;
(B) For each of the plurality of counterpart wireless communication devices, the second transmission power is transmitted to the counterpart wireless communication device with reference to the first transmission power setting value and the measured first reception power. Determining a second transmission power setting value as a power setting value during transmission of the radio signal;
(C) transmitting the second radio signal including the second transmission power setting value to the counterpart wireless communication device at the transmission power indicated by the second transmission power setting value;
The step (b)
For each of the plurality of counterpart wireless communication devices, storing the first transmission power setting value and the first reception power as a surrounding vehicle table;
For each of the plurality of counterpart wireless communication devices, referring to the surrounding vehicle table, obtaining the first transmission power setting value and the first reception power;
For each of the plurality of counterpart wireless communication devices, the transmission power setting value of the transmitting wireless communication device, the reception power of the receiving wireless communication device, and the transmission power setting value of the receiving wireless communication device Determining one of the plurality of second transmission power setting values determined with reference to the associated transmission power setting table as a final second transmission power setting value, satisfying a predetermined condition;
With reference to the transmission power setting table, a transmission power setting value of the transmission-side radio communication device, wherein a transmission power setting value of the reception-side wireless communication device is equal to or lower than the final second transmission power setting value; Extracting a set with the reception power of the reception-side wireless communication device;
Referring to the surrounding vehicle table, the first received power and the first transmission power set value are the same as the extracted set, so that the number of counterpart wireless communication devices is smaller than a predetermined number. And lowering the final second transmission power setting value,
The step (c) includes:
(C1) The second radio signal including the final second transmission power setting value at the transmission power indicated by the lowered final second transmission power setting value is transmitted to the plurality of counterpart wireless communication devices. A transmission power control method comprising the steps of: The transmission power control method according to claim 5,
The step (b)
For each of the plurality of counterpart wireless communication devices, the first transmission power setting value and the first reception power are associated with ID information identifying each of the plurality of counterpart wireless communication devices, and the surrounding vehicle Storing as a table;
For each of the plurality of counterpart wireless communication devices, referring to the surrounding vehicle table based on the ID information, obtaining the first transmission power setting value and the first reception power;
With reference to the transmission power setting table, the second transmission power setting value is determined based on the first reception power and the first transmission power setting value for each of the plurality of counterpart wireless communication devices. And a transmission power control method.   A program for executing the transmission power control method according to claim 5.

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