JP6439500B2 - Radio communication system, radio communication system control method, and radio communication apparatus - Google Patents

Description

  The present invention relates to a radio communication system, a radio communication system control method, and a radio communication apparatus, and is applied to, for example, a communication system in which a communication system including a radio base station and a mobile station and a communication system communicating between mobile stations are mixed. Can do.

  Conventionally, as a wireless communication system (hereinafter also referred to as “road-to-vehicle communication system”) including a base station on a road and a vehicle as a mobile station that wirelessly communicates with the base station, for example, an automobile toll collection system or a narrow area There are communication systems. As a conventional automobile toll collection system, for example, a system called ETC (Electronic Toll Collection system) is widely used. In the conventional ETC, in order for one base station to communicate with one or a plurality of mobile stations (terminals mounted on a vehicle), a TDMA scheme in which the base station controls the transmission timing of the mobile station is adopted.

  Conventionally, as a communication system existing on a road, there is a communication system that performs wireless communication between a plurality of vehicles (mobile stations) (hereinafter referred to as “vehicle-to-vehicle communication system”). A conventional inter-vehicle communication system performs direct wireless communication with surrounding vehicles without using an infrastructure device such as a base station. In a conventional inter-vehicle communication system, for example, when driving information is shared between vehicles (between mobile stations) and there is a possibility of danger for the host vehicle, the driver's safety is ensured by alerting the driver. There is something that realizes driving assistance. In a conventional inter-vehicle system, for example, a plurality of mobile stations use the same transmission / reception channel and start communication after confirming the channel usage state, thereby avoiding communication packet collision.

  Since both the road-to-vehicle communication system and the vehicle-to-vehicle communication system are areas for wireless communication on the road (hereinafter also referred to as “communication areas”), the two communication systems can use the same frequency band or adjacent frequency bands. When using, since mutual interference occurs, a means for avoiding the interference is necessary. For example, such a situation is assumed when a vehicle (mobile station) of the inter-vehicle system enters the communication area of the base station of the road-vehicle communication system.

  Conventionally, for example, there are technologies described in Patent Documents 1 and 2 as conventional technologies applicable to radio wave interference suppression of communication in a road-to-vehicle communication system and communication in a vehicle-to-vehicle communication system.

  Patent Document 1 describes an in-vehicle wireless device that has an automatic toll collection service means, a narrow area communication means, and an inter-vehicle communication means that are used in the microwave band, and that corresponds to a function that can be switched. In the in-vehicle wireless device described in Patent Document 1, when an automatic toll collection communication signal is detected, communication is performed by a narrow area communication means or a vehicle-to-vehicle communication means. Switch to communication means.

  Conventionally, there is a technique described in Patent Document 2 as a technique for reducing interference waves with a receiver of the own station and receiving a desired wave signal normally. Patent Document 2 describes an interference wave removing device that extracts and suppresses interference waves. The interference wave elimination device described in Patent Document 2 measures the distance from the receiver to the interference source, and includes a delay circuit corresponding to the delay time difference of the interference wave obtained thereby in the interference wave extraction unit. Even if the delay time of the interference signal changes, the interference wave can be reduced satisfactorily.

JP 2004-246687 A Japanese Patent Laid-Open No. 7-321681

  However, in the technology described in Patent Document 1, the vehicle (mobile station) of the inter-vehicle communication system avoids interference in the communication area of the road-to-vehicle communication system (in the communication area of the base station on the road) and in the vicinity thereof. The operation must be stopped (for example, the radio wave output is stopped). That is, in the vehicle-to-vehicle communication system, the communication service area for road-to-vehicle communication is detected and transmitted at a point where the necessary separation distance is sufficiently secured so as not to interfere with the base station or mobile station of the road-vehicle communication system. Need to stop.

  In addition, when the technology described in Patent Document 2 is applied to a communication system in which a road-to-vehicle communication system and a vehicle-to-vehicle communication system are mixed, a vehicle (mobile station) of the vehicle-to-vehicle communication system is used at a base station of the road-to-vehicle communication system. The interference wave emitted from the mobile phone can be reduced, and the desired wave signal with the mobile station of the road-vehicle communication system can be received normally. However, when the technology described in Patent Document 2 is applied to a communication system in which a conventional road-to-vehicle communication system and a vehicle-to-vehicle communication system are mixed, the desired wave power versus interference with respect to the interference wave attenuation of the interference wave reducing device. Wave power ratio (Signal to Interference Ratio; hereinafter referred to simply as “SIR”) and SIR required for the base station to communicate with the mobile station (hereinafter referred to as “required SIR”) Must satisfy the relationship of “required SIR> SIR−interference wave attenuation”. And when an interference wave reducing device cannot exhibit the performance which satisfies the above-mentioned relation, it will be said that communication quality of a road-vehicle communication system cannot be secured.

  In view of the above problems, when communication is performed in a first wireless communication system including a mobile station and a wireless communication device (for example, a base station), interference caused by radio waves transmitted from the second wireless communication system. A wireless communication system, a wireless communication system control method, and a wireless communication apparatus that can suppress the above are desired.

A first aspect of the present invention is a wireless communication system comprising one or a plurality of mobile stations and a wireless communication device that wirelessly communicates with the mobile station. (1) The wireless communication device is (1-1) the mobile station. A demodulator that determines a radio wave that cannot be normally received as an interference wave from among the radio waves received from (1), (1-2) a separation distance between a radio wave transmission source received by the wireless communication device and the wireless communication device a distance obtaining means for obtaining a, and interference wave power acquisition unit that acquires an interference wave power (1-3) the interference wave transmitted from a predetermined or more distance transmission source, (1-4) the fixed Communication condition determining means for determining a communication condition between the radio communication apparatus and the mobile station according to the interference wave power acquired by the interference wave power acquisition means for the interference wave transmitted from the transmission source of the above separation distance It is characterized by having .

According to a second aspect of the present invention, there is provided a communication control method for a communication system including one or a plurality of mobile stations and a wireless communication device that wirelessly communicates with the mobile station. (1) The wireless communication device includes a demodulator, a separation distance, (2) the demodulator determines that a radio wave that cannot be normally received among radio waves received from the mobile station is an interference wave, and (3) The separation distance acquisition means acquires a separation distance between a radio wave transmission source received by the wireless communication apparatus and the wireless communication apparatus. ( 4 ) The interference wave power acquisition means has a certain distance or more. ( 5 ) The communication condition determining means obtains the interference wave power for the interference wave transmitted from the transmission source having a certain distance or more. Interference wave power acquired by the means A communication condition between the wireless communication apparatus and the mobile station is determined according to the power.

According to a third aspect of the present invention, in a wireless communication apparatus that wirelessly communicates with one or a plurality of mobile stations, (1) a demodulator that determines a radio wave that cannot be normally received among radio waves received from the mobile station as an interference wave; (2) a radio wave source received, the the distance obtaining means for obtaining a distance between the wireless communication device, (3) above a certain interference of the interference wave transmitted from the transmission source separation ( 4 ) the movement according to the interference wave power acquired by the interference wave power acquisition unit with respect to the interference wave transmitted from the transmission source having a certain distance or more. It has a communication condition determining means for determining a communication condition with a station.

  ADVANTAGE OF THE INVENTION According to this invention, when performing communication of a 1st radio | wireless communications system provided with a mobile station and a radio | wireless communication apparatus, the interference by the electromagnetic wave sent out from a 2nd radio | wireless communications system can be suppressed.

It is the block diagram shown about the functional structure of the base station (wireless communication apparatus) which concerns on embodiment. It is explanatory drawing shown about the example of the whole structure of the communication system containing the road-vehicle communication system which concerns on embodiment. It is explanatory drawing shown about the example of the separation distance calculation in the arrival direction estimation part which concerns on embodiment. It is the graph shown about the angle and the distance at the time of the arrival direction estimation part which concerns on embodiment perform separation distance calculation. It is explanatory drawing shown about the structural example of the mobile station management information which concerns on embodiment. It is explanatory drawing shown about the structural example of the interference wave power information which concerns on embodiment. It is the flowchart shown about operation | movement of the base station (control part) which concerns on embodiment. 5 is a timing chart illustrating the operation of the communication system according to the embodiment. It is explanatory drawing shown about the structural example of the transmission frame on the road-vehicle communication system which concerns on embodiment.

(A) Main Embodiment Hereinafter, an embodiment of a radio communication system, a control method of a radio communication system, and a radio communication apparatus according to the present invention will be described in detail with reference to the drawings. Below, the example which applied the radio | wireless communications system and radio | wireless communication apparatus of this invention to the road-to-vehicle communication system and base station is demonstrated.

(A-1) Configuration of Embodiment FIG. 2 is an explanatory diagram showing the overall configuration of the communication system 1.

  In the communication system 1, two radio communication systems, a road-vehicle communication system 2 </ b> A and a vehicle-vehicle communication system 2 </ b> B, are arranged on the road R.

  The road-to-vehicle communication system 2A includes a base station 10 that is fixedly arranged on the road R and one or a plurality of mobile stations A that are mounted on a vehicle that moves (runs) on the road R. In FIG. 2, one base station 10 and three mobile stations A1 to A3 are illustrated, but the number of base stations 10 and mobile stations A arranged in the road-to-vehicle communication system 2A is not limited.

  Although the specific configuration of the mobile station A is not limited, for example, a conventional ETC terminal (on-vehicle device) or the like can be applied. In addition, the specific configuration of the mobile station B is not limited, but for example, a wireless communication device including various wireless LAN interfaces can be applied.

  The inter-vehicle communication system 2B has a plurality of mobile stations B mounted on a vehicle that moves (runs) on the road R. In FIG. 2, three mobile stations B1 to B3 are shown, but the number of mobile stations B arranged in the inter-vehicle communication system 2B is not limited.

  In the road-to-vehicle communication system 2A and the vehicle-to-vehicle communication system 2B, communication is performed using communication channels in the same or nearby frequency band, so that radio communication between the two systems may interfere with each other when radio waves are transmitted simultaneously. It shall be. In this embodiment, as an example, the road-to-vehicle communication system 2A and the vehicle-to-vehicle communication system 2B will be described as performing wireless communication using a communication channel of 5.8 GHz band (5.725 to 5.875 GHz). . As shown in FIG. 2, since the mobile station A of the road-to-vehicle communication system 2A and the mobile station B of the vehicle-to-vehicle communication system 2B move on the road R, the communication areas (radio transmission and reception of the two communication systems). It is assumed that interference may occur when radio waves are transmitted simultaneously.

  Next, the internal configuration of the base station 10 will be described.

  The base station 10 includes a transmission antenna unit 11, a reception antenna unit 12, a transmission unit 13, a local transmission unit 14, a reception unit 15, a received electric field strength (RSSI) signal detection unit 16, a data demodulation unit 17, an arrival direction estimation unit 18, And a communication control unit 19.

  The transmission antenna unit 11 and the reception antenna unit 12 are antennas for the base station 10 to wirelessly communicate with surrounding mobile stations.

  The transmission antenna unit 11 has an antenna 111 dedicated to transmission. The reception antenna unit 12 includes a plurality of reception-specific antennas 121 and has a function capable of controlling antenna directivity. In this embodiment, the receiving antenna unit 12 will be described as having four antennas 121 (121-1 to 121-4). In this embodiment, the base station 10 is described as having a dedicated antenna for transmission and reception, but for example, a transmission / reception switching or duplexer may be used to share the antenna for transmission and reception. Good. The transmission antenna unit 11 may also be configured to be able to control the antenna directivity. The specific method of forming the antenna directivity in the receiving antenna unit 12 is not limited.

  The local transmitter 14 generates and outputs a channel carrier wave (5.8 GHz band carrier wave) according to a control signal (hereinafter referred to as a “frequency setting signal”) supplied from the communication controller 19. is there.

  The transmission unit 13 is a signal indicating data of a transmission packet (frame) supplied from the communication control unit 19 at a timing according to a control signal (hereinafter referred to as “transmission enable signal”) supplied from the communication control unit 19. A transmission signal corresponding to the signal is generated and a wireless signal is transmitted using the transmission antenna unit 11. The transmitter 13 generates a 5.8 GHz band transmission signal based on the 5.8 GHz band frequency carrier supplied from the local transmitter 14 when generating the radio signal.

  The receiving unit 15 demodulates a received signal (wireless signal) from radio waves received using the receiving antenna unit 12. The reception unit 15 includes reception processing units 151 (151-1 to 151-4) corresponding to the antennas 121 (121-1 to 121-4). Then, the reception processing units 151 (151-1 to 151-4) perform processing for demodulating the reception signal from the radio waves received using the corresponding antennas 121 (121-1 to 121-4). The reception unit 15 supplies the demodulated reception signal to the reception data demodulation unit 17, the RSSI signal detection unit 6, and the arrival direction estimation unit 18.

  The RSSI signal detector 16 measures the received power of the received signal received from each mobile station A belonging to the road-to-vehicle communication system 2A. Assume that the RSSI signal detection unit 16 can detect the reception power for each mobile station An (n = 1, 2,...) In association with the reception packet data demodulated by the data demodulation unit 17. The RSSI signal detection unit 16 can also measure the received power of the received signal received from the mobile station B belonging to the inter-vehicle communication system 2B. However, since the data demodulating unit 17 cannot demodulate the packet received from the mobile station B of the inter-vehicle communication system 2B, the mobile station B is not identified and is interpreted as having an interference wave within a certain period, and the maximum interference wave power It shall be held as a value.

  The arrival direction estimation unit 18 detects (estimates) the angle (direction) of the arrival direction of the signal received from the mobile station A or the mobile station B by the reception unit 15, and based on the detected angle (direction), the base station 10 (reception antenna unit 12) and a distance (hereinafter also referred to as “separation distance”) between the signal transmission source mobile station. Since the reception antenna unit 12 includes the antenna 121, the arrival direction estimation unit 18 can obtain the angle (direction) of the arrival direction of this signal from signals received by the plurality of antennas 121, for example. . In addition, since various processes can be applied to the specific method for obtaining the angle (direction) of the arrival direction of the signal received by the arrival direction estimation unit 18, detailed description thereof is omitted.

  Next, a method in which the arrival direction estimation unit 18 obtains the separation distance from the transmission source (mobile station) based on the angle (direction) of the transmission source (mobile station) of the received signal (received radio wave) will be described with reference to FIG. I will explain.

  In FIG. 3, the distance from the base station 10 (receiving antenna unit 12) to the mobile station A that is the target for calculating the separation distance is illustrated as the separation distance X1. In FIG. 3, the dimension from the ground to the position where the mobile station A is arranged (for example, the height from the ground to the ceiling of the vehicle in which the mobile station is installed) is shown as Y1. Further, in FIG. 3, the dimension from the ground to the position where the base station 10 (receiving antenna unit 12) is arranged is illustrated as Y0. In the following, “Y0-Y1” is represented as a height h at which the base station 10 (receiving antenna unit 12) is arranged. In FIG. 3, an angle formed by a line connecting the base station 10 (receiving antenna unit 12) and the mobile station A at a height h and a plane parallel to the ground is represented by θ. In the following, it is assumed that the arrival direction estimation unit 18 performs the process of estimating θ shown in FIG. 3 as the arrival direction of the received signal (the direction in which the mobile station is located).

Then, the arrival direction estimation unit 18 can obtain the separation distance X1 based on the height h (= Y0−Y1) of the base station 10 (receiving antenna unit 12) and the angle θ. The arrival direction estimation unit 18 can obtain the separation distance X1 using, for example, the following equation (1).
X1 = (Y0−Y1) / tan θ (1)

  Depending on the height h (= Y0−Y1) of the base station, the detected angle θ and the characteristic (relationship) of the separation distance X1 are different. For example, when h = 6 [m], the relationship between the angle θ and the separation distance X1 is as shown in FIG. Further, in this embodiment, it is assumed that the error in detecting the angle θ by the arrival direction estimation unit 18 is ± 2 ° at the maximum. In FIG. 4, L1 represents the separation distance X1 calculated when there is no error in the angle θ detected by the arrival direction estimation unit 18. 4, L2 and L3 represent the separation distance X1 calculated when an error (maximum error) of + 2 ° and −2 ° occurs in the angle θ detected by the arrival direction estimation unit 18, respectively. . Furthermore, in this embodiment, it is assumed that the maximum error allowed for the separation distance X1 calculated by the arrival direction estimation unit 18 is ± 5 [m]. Then, the distance Xs that can be detected by the arrival direction estimation unit 18 within the range of the above-described maximum error ± 5 [m] is about 20 m. Note that the maximum error of 5 [m] described above is, for example, an error within 5 m in consideration of the vehicle head interval at the time of traffic congestion, so that the arrival direction estimation unit 18 does not erroneously detect the position of the mobile station (vehicle). This is the value set in the premise (example). That is, the accuracy required for the arrival direction estimation unit 18, the reception antenna unit 12, the reception unit 15, and the like is changed according to the error of the separation distance X 1 allowed by the arrival direction estimation unit 18.

  Next, a detailed configuration of the communication control unit 19 will be described.

  The communication control unit 19 uses the information supplied from the arrival direction estimation unit 18 and the RSSI signal detection unit 16 to determine communication conditions for each mobile station A, and communicates with each mobile station A according to the determined communication conditions. Perform communication control. Specifically, the communication control unit 19 determines communication conditions for each mobile station A so as to suppress interference with radio waves emitted by the mobile station B of the inter-vehicle communication system 2B.

  The communication control unit 19 of this embodiment manages (updates) predetermined management information based on information supplied from the arrival direction estimation unit 18 and the RSSI signal detection unit 16, and each mobile station based on the management information. A description will be given assuming that the communication condition for A is determined. The communication control unit 19 of this embodiment manages information of mobile station management information 19a, first interference wave power information 19b, and second interference wave power information 19c as management information.

  Next, the mobile station management information 19a will be described. The mobile station management information 19a is information for managing the information of each mobile station A.

  FIG. 5 is an explanatory diagram showing a configuration example of the mobile station management information 19a.

  In the mobile station management information 19a shown in FIG. 5, items of terminal identification information, separation distance, desired wave power, and SIR for each mobile station A are managed.

  In FIG. 5, the terminal identification information (addresses) of the mobile stations A1 to A3 are illustrated as M1 to M3, respectively. Further, in FIG. 5, the separation distances of the mobile stations A1 to A3 are illustrated as Xa1, Xa3, and Xa2, respectively (separation distances corresponding to the above-described state of FIG. 2 are illustrated). In FIG. 5, the desired wave powers of the mobile stations A1 to A3 are illustrated as Pa1 to Pa3, respectively. Further, in FIG. 5, the SIRs of the mobile stations A1 to A3 are illustrated as Ra1 to Ra3, respectively.

  In the following description, the separation distance of the end portion of the communication area of the road-to-vehicle communication system 2A set by the base station 10 (hereinafter referred to as “area end point”) is represented as Xat.

  Next, the first interference wave power information 19b and the second interference wave power information 19c will be described.

  The first interference wave power information 19b is information of received power related to a radio wave (interference wave) emitted from a position where the separation distance is closer (shorter) than Xs.

  The second interference wave power information 19c is information on received power related to a radio wave (interference wave) emitted from a position having a separation distance of Xs or more.

  FIG. 6 is an explanatory diagram showing a configuration example of the first interference wave power information 19b and the second interference wave power information 19c. FIG. 6A shows a configuration example of the first interference wave power information 19b, and FIG. 6B shows a configuration example of the second interference wave power information 19c.

  In the first interference wave power information 19b and the second interference wave power information 19c, the separation distance and the interference wave power (reception intensity) received at the position (direction) of each separation distance are registered.

(A-2) Operation of Embodiment Next, the operation of the communication system 1 of this embodiment having the above-described configuration (the communication system control method of the embodiment) will be described.

  First, the basic operation of the base station 10 will be described using the flowchart of FIG.

  When the reception unit 15 receives the radio wave (S100), the RSSI signal detection unit 16 and the arrival direction estimation unit 18 calculate the separation distance based on the arrival direction estimation without distinguishing between the road-to-vehicle communication system 2A and the vehicle-to-vehicle communication system 2B. Received power measurement is performed (S101). It is assumed that the RSSI signal detection unit 16 and the arrival direction estimation unit 18 always perform the calculation of the separation distance and the reception power measurement based on the arrival direction estimation. Further, as a means for acquiring the separation distance by the arrival direction estimation unit 18, a position detection system such as GPS may be used.

  Next, in the base station 10, the data demodulator 17 extracts a frame from the signal based on the received radio wave (extracts a frame received from any mobile station A) (S102). At this time, the base station 10 operates from step S106 to be described later when the frame can be demodulated (when the frame of the mobile station A is extracted), and operates from step S103 to be described later when it cannot be demodulated. To do.

  If the frame cannot be demodulated in step S102 described above, the communication control unit 19 checks whether the separation distance of the received radio wave is equal to or greater than Xs (S103). The base station 10 operates from step S104 described later when the separation distance is equal to or greater than Xs, and operates from step S109 described below otherwise.

  If the separation distance is equal to or greater than Xs in step S103 described above, the communication control unit 19 determines whether or not the reception intensity of the radio wave received this time is greater than the interference wave power held in the second interference wave power information 19c. (S104). The base station 10 starts from step S105, which will be described later, when the reception intensity is higher than the interference wave power held in the second interference wave power information 19c, and otherwise, the base station 10 does not update the current signal. The process related to radio wave reception ends.

  If it is determined in step S104 described above that the received intensity is greater than the interference wave power held in the second interference wave power information 19c, the communication control unit 19 sets the second interference wave power information 19c. The interference wave power and the separation distance are updated to those of the currently received radio wave (S105), and the process proceeds to step S110 described later.

  If the separation distance is shorter than Xs in step S103 described above, the communication control unit 19 updates the first interference wave power information 19b (separation distance and interference wave power) to that of the currently received radio wave (S109), The process related to the current radio wave reception is terminated.

  On the other hand, when the signal based on the received radio wave can be demodulated in the above-described step S102 (when the signal is successfully received as a frame from the mobile station A), the communication control unit 19 determines that the separation distance of the received radio wave is within Xs. It is determined whether or not (S106). The base station 10 operates from step S107 described later when the separation distance is within Xs, and operates from step S101 described above otherwise.

  If it is determined in step S106 described above that the separation distance of the received radio wave is within Xs, the communication control unit 19 determines that the radio wave received this time (the radio wave received from the mobile station A) is the desired wave (S107). ), The RSSI signal related to the radio wave received this time is held as information on the desired wave reception power (S108).

  Next, the communication control unit 19 updates the content of the mobile station management information 19a based on the latest acquired or updated information (S110), and ends the processing related to the current radio wave reception.

  For example, when the second interference wave power information 19c is updated in step S105 described above, the communication control unit 19 updates the SIR corresponding to each mobile station A (terminal identification information) in the mobile station management information 19a ( The recalculation process is performed based on the updated second interference wave power information 19c. When the RSSI signal related to the currently received radio wave is held as information on the desired wave received power in step S108 described above, the communication control unit 19 specifies the terminal identification information related to the currently received radio wave (for example, The address as the terminal identification information is acquired from the demodulation result of the data demodulator 17), and the information related to the radio wave received this time (terminal identification information, desired wave power, separation distance, and SIR) is updated. If information about the same terminal identification information (address) has already been registered in the mobile station management information 19a, the communication control unit 19 adds new values (separation distance, desired wave power) to the already registered information. , And SIR). On the other hand, when the terminal identification information (address) to be updated this time is not registered in the mobile station management information 19a, the communication control unit 19 performs a process of adding information about the new terminal identification information.

  As described above, the communication control unit 19 updates and manages each information (the mobile station management information 19a, the first interference wave power information 19b, and the second interference wave power information 19c), and uses the updated management information. Thus, the communication condition for each mobile station A is determined.

  Next, a specific operation of the process in which the communication control unit 19 updates the management information will be described with reference to FIG.

  FIG. 8A is a timing chart showing the frame transmission timing by the mobile stations B1 to B3 in which the base station 10 belongs to the inter-vehicle communication system 2B. FIG. 8B shows a change in received power of radio waves received by the base station 10 from the mobile stations A1 to A3, a change in interference wave power of the second interference wave power information 19c held in the base station 10, and 6 is a timing chart showing changes in required received power (minimum received power to satisfy required SIR) for each sequence.

  In the following, it is assumed that the separation distance Xa0 of the position of the base station 10 (receiving antenna unit 12) is the starting point (that is, the separation distance is 0 m) as shown in FIG. And the separation distance Xat of the area end point of the road-vehicle communication system 2A shall be shorter than the separation distance Xs. In the state shown in FIG. 2, the mobile stations A1 to A3 and the mobile station B3 are all located at a position where the separation distance is closer than Xat. In the state of FIG. 2, the separation distance of the mobile station A1 is Xa1, the separation distance of the mobile station B3 and the mobile station A3 is Xa2, and the separation distance of the mobile station A2 is Xa3. It is assumed that the relationship is Xa1 <Xa2 <Xa3. Furthermore, in the state shown in FIG. 2, the mobile stations B1 and B2 are arranged at positions farther than the separation distance Xs. In the state of FIG. 2, the separation distance of the mobile station B1 is Xb1, and the separation distance of the mobile station B2 is Xb2. It is assumed that Xb1 <Xb2.

  In the process of the flowchart of FIG. 7 described above, the separation distance Xs may be replaced with an arbitrary distance as long as the distance measurement with the required accuracy can be performed by the arrival direction estimation unit 18. For example, in the process of the flowchart of FIG. 7 described above, the separation distance Xs is set to an arbitrary distance equal to or greater than Xat (however, the distance at which the arrival direction estimation unit 18 can perform distance measurement with the required accuracy is set as the upper limit). You may make it do.

  In FIG. 8, it is assumed that the positional relationships among the mobile stations A1 to A3 and the mobile stations B1 to B3 are initially in the state shown in FIG.

  At timing T100, it is assumed that frame transmission is performed by the mobile station B2 having a separation distance of Xs or more, and the radio wave is received by the base station 10. Thereby, the communication control unit 19 updates the second interference wave power information 19c as the second interference wave power information 19c based on the interference wave power received from the mobile station B2 (see FIG. 6B described above). Will do. In the second interference wave power information 19c shown in FIG. 6B, the separation distance is illustrated as Xb2, which is the separation distance of the mobile station B2, and the interference wave power is represented as Pb2 received from the mobile station B2.

  After that, at timing T101, it is assumed that frame transmission is performed by the mobile station B3 whose separation distance is closer than Xs, and the radio wave is received by the base station 10. Thereby, the communication control unit 19 updates the first interference wave power information 19b as the first interference wave power information 19b based on the interference wave power received from the mobile station B3 (see FIG. 6A described above). Will do. In the first interference wave power information 19b shown in FIG. 6A, the separation distance is illustrated as Xa2 which is the separation distance of the mobile station B3, and the interference wave power is represented as Pb3 received from the mobile station B32.

  Thereafter, at timing T102, radio transmission (frame transmission) is performed by the mobile stations A1 to A3, and the communication control unit 19 updates the contents of the mobile station management information 19a based on the reception result. .

  Thereafter, at timing T103, it is assumed that frame transmission is performed by the mobile station B1 having a separation distance of Xs or more and the radio wave is received by the base station 10. As a result, the communication control unit 19 updates the second interference wave power information 19c to information based on the interference wave power received from the mobile station B1 (separation distance: Xb1, interference wave power: Pb1). At this time, the communication control unit 19 updates the SIR corresponding to each mobile station A in the mobile station management information 19a based on the latest updated interference wave power (Pb1).

  Note that the communication control unit 19 cannot identify the detailed separation distance (high-precision separation distance) of the mobile stations B1 and B2 that are separated by Xs or more, but can recognize that the separation distance is at least Xs or more. Suppose that

  Next, a basic policy when the communication control unit 19 determines communication conditions for each mobile station A based on the updated and managed information will be described. Note that the communication control unit 19 may apply all of the first to fourth policies described below, or only a part thereof. Further, the communication control unit 19 may apply other policies in addition to the first to fourth policies described below.

[First policy]
When a mobile station B with a separation distance shorter than the separation distance Xs (a transmission source of radio waves other than the mobile station A) is detected, the communication control unit 19 detects the interference wave power of the radio waves emitted from the mobile station B (mobile station A It can be predicted that the influence of the interference wave power on the radio wave emitted from (2) is very large. Therefore, the communication control unit 19 does not perform data transmission / reception with the mobile station A at a timing at which radio wave transmission from the mobile station is expected while the mobile station B with a separation distance shorter than the separation distance Xs is detected. It is assumed that communication control (communication control to make an empty slot for this timing) is performed. The method for the communication control unit 19 to grasp the timing of radio wave transmission (frame transmission) by the mobile station B is not limited. For example, the timing of radio wave transmission (frame transmission) from the mobile station B is periodic. If it is an object, the communication control unit 19 predicts the next radio wave transmission (frame transmission) timing from the mobile station B based on the cycle and the radio wave timing received from the mobile station B in the past, As for the timing, communication control without performing data transmission / reception with each mobile station A may be performed.

[Second policy]
If there is a mobile station A managed by the mobile station management information 19a that has a SIR smaller than the required SIR (SIR <required SIR), the communication control unit 19 performs SIR <required SIR. During this state, the mobile station A does not transmit / receive data.

[Third policy]
The communication control unit 19 preferentially communicates with the mobile station A1 having the smallest separation distance and SIR> required SIR.

[Fourth policy]
The communication control unit 19 may communicate with the mobile station A satisfying “SIR <required SIR” by controlling the antenna directivity to attenuate the interference wave signal. Since the receiving antenna unit 12 includes a plurality of antennas 121 (121-1 to 121-4), the receiving antenna unit 12 has directivity (radio wave reception) of these antennas 121 (121-1 to 121-4). Is directed toward a predetermined mobile station A (an angle θ related to the mobile station A according to the control of the communication control unit 19), and radio waves (interference wave signals, etc.) arriving from other directions are attenuated. The extracted radio wave can be extracted.

  Therefore, for example, even if there is a mobile station A having a relationship of SIR <required SIR, the communication control unit 19 controls the antenna directivity to change the interference wave signal to a predetermined attenuation amount N [dbm] (antenna If the requirement “SIR-N> required SIR” can be satisfied by attenuation by the amount of attenuation of the interference wave signal obtained by controlling the directivity, the mobile station A has the second It is assumed that communication is performed with priority according to the separation distance, ignoring the policy. That is, the fourth policy has priority over the above-described second policy.

  In this embodiment, the base station 10 controls the antenna directivity to attenuate the interference wave signal and raise the SIR. However, the specific means for raising the SIR is not limited. For example, the base station 10 may use other means (for example, various frequency filters) to attenuate the interference wave signal, enhance the desired wave (target wave), etc., and raise the SIR. At this time, it is desirable that the communication control unit 19 controls the antenna directivity only during the period in which the mobile station A that has decided to control the antenna directivity transmits radio waves.

  Next, a specific example in which the base station 10 performs communication control based on the above policy will be described. Here, it is assumed that the mobile stations A1 to A3 and the mobile stations B1 to B3 are in the state shown in FIG.

  At this time, the communication control unit 19 detects an interference wave emitted from the mobile station B3 having a separation distance Xa3 shorter than the separation distance Xs (see the first interference wave power information 19b in FIG. 6A). . Therefore, the communication control unit 19 performs communication control that does not perform data transmission / reception with all the mobile stations A at a timing at which radio wave transmission from the mobile station B is expected according to the first policy described above (for the timing, (Communication control to make an empty slot).

  At this time, it is assumed that the mobile stations A1 and A2 satisfy the requirement “SIR> required SIR”, and the mobile station A3 does not satisfy the requirement and is in a state of “SIR <required SIR”.

  Therefore, in this case, the communication control unit 19 preferentially communicates with A1 based on the above third policy. In addition, the communication control unit 19 performs communication preferentially for the mobile station A2 after the mobile station A1.

  Then, since the communication control unit 19 has “SIR <required SIR” for the mobile station A3, communication cannot be started based on the above third policy. However, when the attenuation amount N [dB] due to the antenna directivity is considered and it can be estimated that “SIR−N> required SIR” is satisfied, the communication control unit 19 establishes communication with the mobile station A3 according to the above fourth policy. It is determined that communication is performed, and a priority order corresponding to the separation distance is given. Accordingly, when it can be estimated that “SIR−N> required SIR” is satisfied for the mobile station A3, the communication control unit 19 performs communication by giving priority to the mobile station A3 having a shorter separation distance than the mobile station A2, and then the mobile station It is determined that communication is performed with A2. However, here, it is assumed that the communication control unit 19 determines that the mobile station A3 does not satisfy “SIR-N> required SIR” and cannot communicate with the mobile station A3 at this time. Note that the communication control unit 19 starts communication with the A3 at the timing when the mobile station A3 is in a state satisfying “SIR-N> required SIR” or “SIR <required SIR” at a later timing. Become.

  Here, it is assumed that the communication control unit 19 selects the order of the mobile stations A1 and A2 as the priority order for final communication. Further, it is assumed that the communication control unit 19 determines that A3 cannot be communicated at the present time as described above.

  Further, at this time, it is assumed that the communication control unit 19 knows the timing of frame transmission (radio wave transmission) from the mobile station B3 that exists in an area where the separation distance is shorter than Xs. In this case, the communication control unit 19 performs communication control that does not execute data transmission / reception with the mobile stations A1 to A3 at a timing at which radio wave transmission from the mobile station B3 is expected based on the first policy described above. Is determined to perform communication control to make an empty slot.

  As described above, when the communication control unit 19 determines the communication control of the mobile stations A1 to A3 based on the above-described policy, the configuration of the frames transmitted and received on the road-to-vehicle communication system 2A (the base station 10 The frame configuration for transmission / reception is, for example, as shown in FIG.

  In FIG. 9, two frames F1 and F2 transmitted and received on the road-to-vehicle communication system 2A are arranged in chronological order. Therefore, in FIG. 9, it is assumed that the frames F1 and F2 are generated in this order. In the DSRC communication, each frame F includes an FCMS (Frame Control Message Slot) channel for controlling communication using each channel (slot) in the frame, a mobile station A, and a message (data). It is composed of MDS (Message Data Slot) channels for transmission and reception.

  Each frame F shown in FIG. 9 includes a leading FCMS and four slots (channels) following the FCMS. The slot following the FCMS may be inserted with an MDS or may be empty (a state in which no MDS is inserted).

  Each frame F shown in FIG. 9 is illustrated as a mixed frame configuration for uplink communication (communication from mobile station A to base station 10) and downlink communication (communication from base station 10 to mobile station A). However, communication that is actually adopted in the DSRC system, that is, communication using both TDMA and FDD (Frequency Division Duplex) is performed. FIG. 9 merely shows an example of a frame configuration when communicating with the mobile station A1 and the mobile station A2 in the priority order determined by the base station 10 (communication in the order of the mobile stations A1 and A2). The frame configuration is not limited.

  In the first frame F1 shown in FIG. 9, the first two slots are empty slots. This is because in the base station 10, it is predicted that frame transmission from the mobile station B3 will occur at the timing of these two empty slots. 9, the base station 10 transmits and receives data (transmission and reception of MDS) to and from the mobile station A1 in a total of three slots, the last two slots of the frame F1 and the first one slot of the frame F1 (the next slot after FCMS). )It is carried out. Further, in the last three slots of the frame F2 shown in FIG. 9, the base station 10 performs data transmission / reception (MDS transmission / reception) with the mobile station A2.

  As described above, the base station 10 moves each movement under the communication conditions determined by the communication control unit 19 based on the above-described policy (for example, communication priority, communication method (for example, antenna directivity control), etc.). Communication with the stations A1 to A3 is performed.

(A-3) Effects of Embodiment According to this embodiment, the following effects can be achieved.

  In this embodiment, the base station 10 eliminates a wasteful time in which the communication quality of the road-to-vehicle communication system 2A cannot be ensured by collision between the packets of the road-to-vehicle communication system 2A and the vehicle-to-vehicle communication system 2B, and avoids a decrease in throughput. It is possible. Therefore, when the mobile station B of the inter-vehicle communication system 2B approaches and enters, communication within the road-to-vehicle communication system 2A can be continued without stopping the service of the inter-vehicle communication system 2B.

  In particular, when the transmission power related to the radio wave of the vehicle-to-vehicle communication system 2B is larger than that of the road-to-vehicle communication system 2A, the road-to-vehicle communication system 2A and the vehicle-to-vehicle communication system 2B are the same or interfere with each other. If there is, the mobile station B of the vehicle-to-vehicle communication system 2B has a road-to-vehicle communication system at a point where a necessary separation distance is sufficiently secured so as not to interfere with the base station 10 and the mobile station A of the road-to-vehicle communication system 2A. It was necessary to detect the 2A communication service area and stop transmission. Therefore, in the conventional technology, it is necessary to lengthen the service stop section of the inter-vehicle communication system 2B. However, in the communication system 1 of this embodiment, it is necessary to perform the above-described control on the inter-vehicle communication system 2B side. There will be no.

(B) Other Embodiments The present invention is not limited to the above-described embodiments, and may include modified embodiments as exemplified below.

  (B-1) In the above embodiment, the example in which the road-to-vehicle communication system 2A is applied as the wireless communication system of the present invention has been described. However, the wireless communication system of the present invention is used as a mobile station and a wireless communication device (for example, a base station). You may make it apply to the other radio | wireless communications system which has. That is, in the wireless communication system of the present invention, the communication method between the wireless communication device (base station) and the mobile station is not limited.

  (B-2) In the above embodiment, the inter-vehicle communication system 2B is exemplified as a radio communication system that interferes with the road-to-vehicle communication system 2A, but other radio wave transmission sources may be applied (assumed). .

  DESCRIPTION OF SYMBOLS 1 ... Communication system, 2A ... Road-to-vehicle communication system, 2B ... Inter-vehicle communication system, 10 ... Base station, 11 ... Transmission antenna part, 12 ... Reception antenna part, 121, 1211-1 to 121-4 ... Antenna, 13 ... Transmission unit, 14 ... Local transmission unit, 15 ... Reception unit, 151, 151-1 to 151-4 ... Reception processing unit, 16 ... RSSI signal detection unit, 17 ... Data demodulation unit, 18 ... Arrival direction estimation unit, 19 ... Communication control unit, 19a ... mobile station management information, 19b ... first interference wave power information, 19c ... second interference wave power information, A, A1-A3, B, B1-B3 ... mobile station.

Claims (7)

In a wireless communication system comprising one or more mobile stations and a wireless communication device that wirelessly communicates with the mobile station,
The wireless communication device is
Of the radio waves received from the mobile station, a demodulator that determines radio waves that cannot be normally received as interference waves,
A radio wave source receives a distance obtaining means for obtaining a distance between the wireless communication device,
And the interference wave power acquisition unit that acquires an interference wave power of the interference wave transmitted from a predetermined or more distance transmission source,
Communication conditions for determining communication conditions between the radio communication apparatus and the mobile station according to the interference wave power acquired by the interference wave power acquisition means for the interference wave transmitted from a transmission source of a certain distance or more A wireless communication system comprising: determining means;   2. The communication condition determining means determines communication conditions for each mobile station in consideration of desired wave power based on radio waves received by the wireless communication apparatus from the mobile stations. The wireless communication system according to 1.   The wireless communication system according to claim 2, wherein the communication condition determining means determines communication priority or communication timing as a communication condition for each of the mobile stations.   The wireless communication system according to claim 2 or 3, wherein the wireless communication device further includes an antenna directivity control means for controlling antenna directivity when communicating with the mobile station.   The communication condition determining means determines the communication condition for each mobile station in consideration of the attenuation amount of the interference wave power when the antenna directivity is directed to the mobile station. The wireless communication system according to claim 4. In a communication control method of a communication system comprising one or a plurality of mobile stations and a wireless communication device that wirelessly communicates with the mobile station,
The wireless communication apparatus includes a demodulation unit, a separation distance acquisition unit, an interference wave power acquisition unit, and a communication condition determination unit.
The demodulator determines that radio waves that cannot be normally received from radio waves received from the mobile station are interference waves,
The separation distance obtaining means obtains a separation distance between the transmission source of the radio wave received by the wireless communication device and the wireless communication device,
The interference wave power acquisition unit acquires an interference wave power of the interference wave transmitted from a predetermined or more distance transmission source,
The communication condition determining means determines whether the wireless communication apparatus and the mobile station are in accordance with the interference wave power acquired by the interference wave power acquisition means for the interference wave transmitted from the transmission source having a certain distance or more . A communication control method for a wireless communication system, characterized by determining communication conditions. In a wireless communication device that wirelessly communicates with one or more mobile stations,
Of the radio waves received from the mobile station, a demodulator that determines radio waves that cannot be normally received as interference waves,
A separation distance obtaining means for obtaining a separation distance between a transmission source of the received radio wave and the wireless communication device;
And the interference wave power acquisition unit that acquires an interference wave power of the interference wave transmitted from a predetermined or more distance transmission source,
Communication condition determining means for determining a communication condition with the mobile station according to the interference wave power acquired by the interference wave power acquisition means for the interference wave transmitted from a transmission source having a certain distance or more. A wireless communication apparatus.

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