JP2022118990A - Wireless base station, vehicle communication device, mobile communication method - Google Patents

Abstract

To provide a mobile communication system capable of performing reliable communication.SOLUTION: A leading vehicle transmits a CSI estimation value associated with positional coordinates of an observation spot to a following vehicle using vehicle-to-vehicle communication. An own vehicle, as the following vehicle, compares CSI at a certain spot provided from the leading vehicle with CSI at the same spot calculated by the own vehicle to calculate a difference between an antenna characteristic of the leading vehicle and that of the own vehicle. In a state in which the antenna characteristic difference can be calculated, beam control is performed using the antenna characteristic difference and CSI of respective spots that is provided from the leading vehicle at any time.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a technology for performing wireless communication considering the influence of multipath.

As disclosed in Non-Patent Document 1, in recent years, techniques have been developed for expanding the communication area and communication capacity by beam forming using Massive MIMO. For example, in 4G, by transmitting and receiving a predetermined pilot signal between communication devices, the propagation path state between the communication devices is estimated, and based on the propagation path estimation result, at least one of the transmitting side and the receiving side is beam controlled. is done. As a result, the effect of suppressing deterioration in communication quality due to the influence of multipath propagation paths can be expected. The channel state is also called CSI (Channel State Information).

Further, in Patent Document 1, focusing on the point that the influence of multipath varies depending on the location and frequency, a radio wave propagation map showing the propagation path characteristics for each point is created, and the terminal position is determined using the radio wave propagation map. A configuration is disclosed for performing beam control in response to .

JP 2017-139727 A

3GPP TR 21.915 V15.0.0 (2019-09) 3rd Generation Partnership Project, “Technical Specification Group Services and System Aspects; Release 15 Description;Summary of Rel-15 Work Items (Release 15)”

In order to increase the reliability of communication, it is preferable to apply highly accurate channel estimation values by beam control. However, since a vehicle or the like moves faster than a pedestrian, the difference between the point at which the propagation path characteristics are estimated and the actual position at the time of data communication can be greatly different. As a result, the propagation path estimation error may increase.

In Patent Literature 1, use of a radio wave propagation map that associates propagation path characteristics for each point is considered, but differences in antenna characteristics between vehicles are not taken into consideration. If the vehicle model, vehicle type, etc. are different, it is assumed that the antenna characteristics are also different. In the method disclosed in Patent Literature 1, there remains a possibility that the estimation error may increase due to the difference in antenna characteristics between the vehicle used for map creation and the vehicle that actually performs data communication.

The present disclosure has been made based on this situation, and an object thereof is to provide a mobile communication system capable of performing highly reliable communication.

A vehicle communication device for achieving the object is a vehicle communication device configured to be capable of inter-vehicle communication, and includes a plurality of antennas for wireless communication with a radio base station (2). Section (13) and the first propagation path information indicating the estimated value of the state of the propagation path with the radio base station observed when the preceding vehicle (u1) is present at an arbitrary comparison point is transmitted between the preceding vehicle and the vehicle. Based on the preceding vehicle estimated value acquisition unit (F4) acquired by communication and the reception result of the predetermined reference signal emitted from the radio base station, the estimated value of the propagation path state when the own vehicle is present at the comparison point is obtained. By comparing the first propagation path information and the second propagation path information with the propagation path estimation unit (F2) that acquires the second propagation path information shown, the characteristic difference, which is the difference between the antenna characteristics of the preceding vehicle and the own vehicle and a beam control unit (F6) for controlling beams of a plurality of antennas included in the radio communication unit, and the preceding vehicle estimated value acquisition unit is configured to determine the direction of travel from the comparison point. Third propagation path information indicating the estimated value of the propagation path state observed by the preceding vehicle at the application point, which is an arbitrary point on the side, is also obtained, and the beam control unit determines the characteristic difference specified by the characteristic difference specifying unit and the applied It is configured to perform beam control for communication with the radio base station at the application point based on the third propagation path information observed at the point.

According to the above configuration, based on the difference between the propagation path state observed by the preceding vehicle and the propagation path state observed by the own vehicle at the same point (comparison point), the characteristic difference indicating the difference in antenna characteristics from the preceding vehicle identify. Then, when the own vehicle passes through the application point, which is a point after the comparison point, that is, when the characteristic difference between the preceding vehicle and the own vehicle has already been specified, the propagation provided by the preceding vehicle through inter-vehicle communication Beam control is performed using road conditions and characteristic differences.

In this way, according to the configuration that performs beam control in consideration of the real-time propagation path state for each point provided by vehicle-to-vehicle communication from the preceding vehicle and the antenna characteristic difference between the preceding vehicle and the preceding vehicle, it is possible to obtain a propagation path state with less error. Beam control based on the estimated value can be performed. Therefore, it is possible to improve the reliability of communication.

A radio base station for achieving the above object communicates with a radio communication module (22) having a plurality of antennas for radio communication with a vehicle and a first vehicle (u1) existing at an arbitrary comparison point. Observation by communicating with the second vehicle (u2), which is the second vehicle following the first vehicle, when the first propagation path information, which is an estimated value of the observed propagation path state, and the second vehicle (u2) are present at the comparison point A propagation path information acquisition unit (J2) that acquires second propagation path information indicating an estimated value of the propagation path state obtained by comparing the first propagation path information and the second propagation path information to obtain the first vehicle and An individual difference identification unit (J3) that identifies a characteristic difference that is a difference in antenna characteristics of the second vehicle, and a beam control unit (J4) that controls beams of a plurality of antennas included in the wireless communication module, and a propagation path The information acquisition unit also acquires third propagation path information indicating an estimated value of the propagation path state observed by communicating with the first vehicle at the application point, which is an arbitrary point on the traveling direction side of the comparison point, and obtains the beam The control unit performs beamforming for communication with the second vehicle existing at the application point based on the characteristic difference identified by the individual difference identification unit and the third propagation path information observed at the application point. is configured as

According to the radio base station, the characteristic difference indicating the difference in antenna characteristics between the preceding vehicle and the following vehicle is specified based on the difference in the propagation path state for each vehicle at the same point (comparison point). After the comparison point, in other words, when the difference in antenna characteristics between the preceding vehicle and the following vehicle has already been specified, the following vehicle is perform beam control for communication with According to this configuration, it is possible to perform beam control based on the estimated value of the propagation path state with less error, and it is possible to improve the reliability of communication.

It should be noted that the symbols in parentheses described in the claims indicate the corresponding relationship with specific means described in the embodiments described later as one aspect, and limit the technical scope of the present disclosure. is not.

1 is a diagram schematically showing the configuration of a vehicle communication system Sys; FIG. 2 is a block diagram for explaining the configuration of the vehicle-mounted device 1; FIG. 3 is a block diagram for explaining the configuration of a wireless communication unit; FIG. 2 is a block diagram for explaining functions of the vehicle-mounted device 1; FIG. FIG. 4 is a diagram showing the configuration of CSI-related information; 2 is a block diagram for explaining the configuration of a radio base station 2; FIG. 1 is a diagram showing a configuration example of a vehicle-mounted device 1 and a wireless base station 2 when CSI-related information is shared within a vehicle group; FIG. FIG. 2 is a diagram for explaining a configuration in which a radio base station 2 performs beam control for a following vehicle using CSI observed by a preceding vehicle;

Embodiments of the present disclosure will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a vehicle communication system Sys to which the mobile communication system of the present disclosure is applied.

<Overall composition>
As shown in FIG. 1 , the vehicle communication system Sys includes a plurality of vehicle-mounted devices 1 and radio base stations 2 . In FIG. 1, only two onboard vehicles U, which are vehicles equipped with the onboard device 1, are shown, but in reality, there may be three or more onboard vehicles U as a whole system. A plurality of wireless base stations 2 may also exist.

In this embodiment, as an example, the mounted vehicle U is assumed to be a four-wheeled vehicle. Hereinafter, for the vehicle-mounted device 1, the vehicle in which the vehicle-mounted device 1 is mounted is also referred to as the subject vehicle, and vehicles other than the subject vehicle are referred to as other vehicles. Vehicles u1 and u2 are both loaded vehicles U, and vehicle u1 corresponds to a preceding vehicle for vehicle u2. Also, the vehicle u2 corresponds to the following vehicle for the vehicle u1. Vehicle u1 corresponds to the first vehicle, and vehicle u2 corresponds to the second vehicle.

Hereinafter, a case where the own vehicle corresponds to the following vehicle u2 will be described as an example. As the preceding vehicle u1, among vehicles capable of inter-vehicle communication, for example, another vehicle located in front of the own vehicle and closest to the own vehicle can be adopted. The preceding vehicle u1 is preferably a vehicle traveling in front of the own vehicle in the same lane as the own vehicle.

The loaded vehicle U is a vehicle that travels on the road. The mounted vehicle U may be a four-wheeled vehicle, a two-wheeled vehicle, a three-wheeled vehicle, or the like. Two-wheeled vehicles also include motorized bicycles.

The vehicle-mounted device 1 is a communication device having a function of performing wireless communication with other vehicles and a wireless base station 2 . The vehicle-mounted device 1 corresponds to a vehicle communication device. The vehicle-mounted device 1 is configured to be capable of performing wireless communication with a wireless base station 2 in compliance with standards such as LTE (Long Term Evolution). The vehicle-mounted device 1 corresponds to a user equipment (UE: User Equipment) for the radio base station 2 . In addition, the vehicle-mounted device 1 is configured to be directly wirelessly communicable with other vehicles. That is, each vehicle is configured to be able to directly perform wireless communication (so-called inter-vehicle communication) with each other via the vehicle-mounted device 1 .

The radio base station 2 is radio equipment that provides a mobile communication system conforming to, for example, LTE (Long Term Evolution) and 4G standards. The radio base station 2 is also called an eNB (evolved NodeB). Note that the radio base station 2 may perform communication conforming to the 5G standard. For example, the radio base station 2 may be a gNB (next generation NodeB). Further, the wireless base station 2 is a facility that performs wireless communication with a vehicle in compliance with the WAVE (Wireless Access in Vehicular Environment) standard and the DSRC (Dedicated Short Range Communications) standard disclosed in IEEE 1509. good too. In other words, the radio base station 2 may be a so-called roadside unit arranged along the road. The radio base station 2 can also be called an RSU (Road Side Unit).

Hereinafter, LTE, 3G, 4G, 5G, etc. are collectively referred to as LTE. The wireless base station 2 transmits/receives wireless signals conforming to LTE or the like to/from the vehicle-mounted device 1 . The following embodiments can be implemented with appropriate modifications so as to comply with communication architectures such as 3G, 4G, and 5G defined by 3GPP (Third Generation Partnership Project).

The radio base station 2 transmits or receives various reference signals (RS: Reference Signal) at any time. Reference signals include CRS (Cell-specific RS), SRS (Sounding RS), CSI-RS (CSI-Reference Signal), DMRS (DeModulation RS), and the like. A reference signal can also be called a pilot signal. Note that the CRS is a reference signal used for cell switching by the UE, for example. SRS, CSI-RS, and DMRS are reference signals for estimating the state of an uplink or downlink transmission path. The information indicating the channel state is also called CSI (Channel State Information).

Transmission of the reference signal by the radio base station 2 may be performed periodically, or may be performed in response to the occurrence of a predetermined event. The transmission of the reference signal by the radio base station 2 may be triggered by, for example, receiving an inquiry from a user equipment (UE: User Equipment) or exceeding a predetermined threshold for the frequency of occurrence of communication errors. good. Transmission conditions may differ depending on the type of reference signal. For example, some reference signals such as SRS can be transmitted from the vehicle-mounted device 1 toward the radio base station 2 .

The radio base station 2 is connected to a core network via an access line such as an IP (Internet Protocol) network. The wireless base station 2 relays traffic between the vehicle-mounted device 1 and the core network. Note that the core network is, for example, an EPC (Evolved Packet Core). The core network provides functions such as user authentication, contract analysis, data packet transfer route setting, and QoS (Quality of Service) control. Core networks may include public telecommunications networks provided by telecommunications operators, such as IP networks and cellular networks.

<Example of in-vehicle device communicating with on-vehicle device 1>
As shown in FIG. 2, the vehicle-mounted device 1 is used by being connected to a locator 3, a driving support ECU 4, and a multimedia ECU 5 via an in-vehicle network IvN, which is a communication network built in the vehicle. The ECU in the member name is an abbreviation for Electronic Control Unit, and refers to an electronic control unit. The vehicle-mounted device 1 can also be understood as a kind of ECU. Here, the configuration including the vehicle-mounted device 1 and the device connected to the vehicle-mounted device 1 is also referred to as the vehicle-mounted system IvS.

The locator 3 is a device that sequentially identifies the position of the vehicle using the locator 3 (that is, the own vehicle). For example, the locator 3 includes a GNSS receiver that receives positioning signals transmitted by positioning satellites forming a GNSS (Global Navigation Satellite System), and calculates a position using the positioning signals received by the GNSS receiver. Note that the locator 3 may determine the position by combining the positioning result of the GNSS receiver and the measurement result of a gyro sensor, vehicle speed sensor, or the like. Furthermore, the locator 3 may correct the position by performing a so-called map matching process in which the locus of the determined position is superimposed on the road shape indicated by the map data. Position information indicating the current position sequentially specified by the locator 3 is provided to the vehicle-mounted device 1 .

Also, the locator 3 may be configured to be able to perform localization processing. In the localization process, the detailed position of the vehicle is obtained by matching the coordinates of the landmarks identified based on the images captured by the surrounding surveillance cameras such as the front camera with the coordinates of the landmarks registered in the map data. refers to the process of identifying Landmarks are, for example, guide signs such as direction signs, and three-dimensional structures installed along roads such as traffic lights and poles.

The driving assistance ECU 4 has at least one of a driving assistance function that assists the driving operation of a driver (so-called driver) and a substitute driving function that can perform the driving operation on behalf of the driver. The driving support ECU 4 implements the driving support functions and the like by the processor executing a predetermined vehicle control program stored in the internal memory. The driving support ECU 4 acquires, for example, a dynamic map from an external server (not shown) via the vehicle-mounted device 1, and uses the dynamic map to create a vehicle control plan. The dynamic map here refers to the position and movement state of other moving objects existing around the current position, the position and type of obstacles, the road surface condition at each point, the weather, and the position and lighting state of traffic lights. It refers to data about at least one. The dynamic map may be data in which road data indicating a detailed road structure and the above data are associated with each other.

The multimedia ECU 5 is an ECU that provides functions such as navigation, audio and video playback, and web browsing. For example, the multimedia ECU 5 acquires, for example, music data, video data, etc. from an external server and performs streaming reproduction. The multimedia ECU 5 can also be called a navigation ECU in one aspect. A part or all of the functions provided by the vehicle-mounted device 1 may be provided by the multimedia ECU 5 .

<Regarding the configuration of the vehicle-mounted device 1>
The vehicle-mounted device 1 includes a control unit 11 , an in-vehicle communication unit 12 , a wireless communication unit 13 , and an inter-vehicle communication unit 14 .

The control unit 11 is mainly composed of a computer. The control unit 11 includes a processor 111 , RAM 112 and storage 113 . Processor 111 is hardware for arithmetic processing coupled with RAM 112 . The processor 111 is configured to include at least one arithmetic core such as a CPU. The processor 111 executes various processes by accessing the RAM 112 . The storage 113 is configured to include a non-volatile storage medium such as flash memory. A vehicle communication control program is stored in the storage 113 as a program executed by the processor 111 . Execution of the program by the processor 111 corresponds to execution of a vehicle communication control method, which is a method corresponding to the vehicle communication control program.

For example, the control unit 11 multiplies a digital signal of data transmitted/received to/from the radio base station 2 by a dynamically changeable weighting factor (digital weight), which is so-called digital beamforming (hereinafter referred to as digital BF). process. Digital BF can be implemented using algorithms such as MR (Maximum Ratio), ZF (Zero Forcing), SVD (Singular Value Decomposition), MMSE (Minimum Mean Square Error), and MLD (Maximum Likelihood Detection). MMSE is sometimes called regularized zero forcing (RZF). A part or all of the digital signal processing performed by the control unit 11 on data transmitted and received with the wireless base station 2 may be configured to be performed by the wireless communication unit 13 .

The in-vehicle communication unit 12 is a circuit module for communicating with other devices via the in-vehicle network IvN. The in-vehicle communication unit 12 is implemented using an analog circuit element, an IC, a PHY chip conforming to the communication standard of the in-vehicle network IvN, and the like. Various data such as vehicle position information detected by the locator 3 are input to the in-vehicle communication unit 12 .

The in-vehicle communication unit 12 is a storage area that temporarily holds data for external transmission input from other in-vehicle devices such as the driving support ECU 4 and the multimedia ECU 5 until it is wirelessly transmitted to the wireless base station 2. Contains buffers. Data for external transmission is data destined for a device outside the vehicle, such as an external server or another vehicle. The buffer may be implemented using a rewritable storage medium such as RAM. The in-vehicle communication unit 12 also has a function of monitoring the amount of data retained in the buffer and the information stored in the headers of those data. The data in the buffer is sequentially transmitted to the destination server through a communication path according to the data input source. Components of the communication path here can include frequencies, modulation schemes, and the like.

The wireless communication unit 13 is a communication module that wirelessly connects to the wireless base station 2 and allows the vehicle-mounted device 1 to communicate with an external device, which is another communication device, via the core network. The wireless communication unit 13 includes multiple antennas 131 , a receiving unit 132 and a transmitting unit 133 .

The plurality of antennas 131 are arranged in a row or in a matrix at predetermined intervals so as to operate as an array antenna A131, for example. Note that the antennas 131 do not necessarily have to be arranged regularly in one or more rows, and the intervals between them and the shape of the elements may be random. Each antenna 131 is configured to resonate in a predetermined frequency band used for wireless communication with the wireless base station 2 . The receiving unit 132 demodulates the signal received by the array antenna A131 and provides the control unit 11 with the demodulated signal. The transmitter 133 modulates the data input from the controller 11, outputs the data to the array antenna A131, and wirelessly transmits the data.

In addition, the wireless communication section 13 includes, for example, an analog-to-digital conversion section E1, an analog signal processing section E2, a distribution coupling circuit E3, and a phase shifter E4 as a more detailed configuration as shown in FIG. The analog-to-digital converter E1 is configured to convert between a digital signal and an analog signal. That is, the analog-to-digital converter E1 functions as a D/A (Digital to Analog) converter and an A/D (Analog to Digital) converter.

The analog signal processing unit E2 is a circuit group that performs various predetermined signal processing on analog signals, such as frequency conversion between analog signals in the baseband band and analog signals in the RF band, rectification, and amplification. be. The distribution/coupling circuit E3 includes a circuit for distributing an analog signal as a transmission signal to each of the plurality of antennas 131, and a circuit for connecting the analog signals input from each antenna 131 and inputting them to the analog signal processing section E2.

The phase shifter E4 is configured to multiply or add a weighting coefficient (analog weight) designated by the control unit 11 to the analog signal and output the result. Phase shifter E4 changes the amplitude and phase shift of the analog signal according to the weighting factor. A set of phase shifters E4 connected to each antenna 131 controls the directivity of the array antenna A131 by multiplying each analog signal by a weighting factor. In other words, the set of phase shifters E4 realizes beamforming based on the weighting factors set in each phase shifter E4. A weighting factor set in each phase shifter E4 is controlled by a beam controller F6 of the controller 11, which will be described later.

The vehicle-to-vehicle communication unit 14 is a communication module for performing direct wireless communication (that is, vehicle-to-vehicle communication) with the vehicle-mounted device 1 provided in another vehicle using radio waves in a predetermined frequency band. The vehicle-to-vehicle communication unit 14 includes an antenna and a transmission/reception unit for vehicle-to-vehicle communication. The vehicle-to-vehicle communication antenna is configured to be capable of transmitting and receiving radio waves in the frequency band used for vehicle-to-vehicle communication. The transmission/reception unit for inter-vehicle communication modulates the data input from the control unit 11, outputs the data to the inter-vehicle communication antenna, and wirelessly transmits the data. Further, the transmitting/receiving unit demodulates the signal received by the vehicle-to-vehicle communication antenna and provides the signal to the control unit 11 .

In this embodiment, as an example, vehicle-to-vehicle communication is performed by a communication method different from the communication method with the radio base station 2, but the present invention is not limited to this. Vehicle-to-vehicle communication may also be implemented according to standards such as LTE. Accordingly, the vehicle-to-vehicle communication unit 14 may be integrated with the wireless communication unit 13 . The wireless communication unit 13 may be configured to be able to implement cellular V2X.

<Functions of onboard device 1>
Here, the functions and operations of the vehicle-mounted device 1 will be described with reference to FIG. The vehicle-mounted device 1 includes, as functional units, a position acquisition unit F1, a CSI estimation unit F2, a CSI transmission unit F3, another vehicle data acquisition unit F4, an antenna characteristic difference identification unit F5, and a beam control unit F6. Each functional unit may be implemented by the processor 111 executing a predetermined vehicle communication control program, or may be implemented using an IC or the like. The vehicle-mounted device 1 also includes a reception CSI holding unit M1 and an antenna characteristic difference holding unit M2. The reception CSI holding unit M1 and the antenna characteristic difference holding unit M2 can be realized using part of the storage area provided in the RAM 112 .

The position acquisition unit F1 sequentially acquires position information of the own vehicle calculated by the locator 3 . The position information of the own vehicle (so-called own vehicle position information) acquired by the position acquisition unit F1 is used by the CSI transmission unit F3, the antenna characteristic difference identification unit F5, and the beam control unit F6.

The CSI estimation unit F2 is configured to calculate uplink or downlink CSI using reference signals. The CSI estimator F2 corresponds to the channel estimator. Various methods can be adopted as the CSI calculation method. For example, the CSI at a point p is the reference signal actually received at that point r, and the reference signal before being affected by the propagation path (that is, the original) is s. It is obtained by multiplying from . That is, the matrix H corresponding to CSI can be calculated by Equation 1 below. CSI is represented by a matrix H having the number of rows and columns corresponding to the number of antennas. r corresponds to the reception result of the reference signal.

行列Ｈは、検出行列あるいはプリコーディング行列とも称される。行列Ｈの上に付与しているチルダ「～」は、真値ではなく、推定値であることを示す。ＣＳＩは、概略的には伝搬過程における信号の減衰量としての振幅の差と、位相差を示す。

Matrix H is also called a detection matrix or a precoding matrix. A tilde "~" added above the matrix H indicates that it is an estimated value, not a true value. CSI generally indicates an amplitude difference and a phase difference as signal attenuation in the propagation process.

Note that p in parentheses attached to the right side of parameters such as H and r indicates an observation point, and u indicates a communication partner with the radio base station 2 . For example, H(p,u) denotes the CSI observed when vehicle U is at point p. The subject of observation may be the vehicle U or the radio base station 2 . A line "-" added above the characters indicates complex conjugate. Furthermore, the asterisk "*" attached to the upper right of the characters indicates that the matrix is transposed.

The CSI estimator F2 stores the calculated CSI in the RAM in association with the vehicle position information at that time. For example, the CSI estimating unit F2 calculates the downlink CSI at that time each time it receives a reference signal such as DMRS emitted from the radio base station 2 . The CSI associated with the position information is referred to by the CSI transmitter F3 and the beam controller F6, which will be described later.

The CSI transmission unit F3 cooperates with the vehicle-to-vehicle communication unit 14 to transmit the CSI estimated by the CSI estimation unit F2 to the other vehicle in association with the position information of the observation point. For the sake of convenience, information including CSI for each observation point is also referred to as CSI-related information.

The CSI-related information includes, for example, source information, destination information, position coordinates of observation points, observation time information, and CSI, as shown in FIG. The transmission source information is identification information (so-called vehicle ID) assigned in advance to the transmission source vehicle for distinguishing it from other mounted vehicles. The source information may be identification information (that is, device ID) assigned in advance to the vehicle-mounted device 1 as a source for distinguishing the vehicle-mounted device 1 from other vehicle-mounted devices 1 . Since the vehicle-mounted device 1 corresponds to the vehicle on a one-to-one basis, the vehicle-mounted device 1 can be used instead of the vehicle as the source/destination of the radio signal/data.

The destination information indicates the destination of the data. Note that the data field in which the destination information is stored is an arbitrary element and may be omitted. Also, in the destination field, a usage vehicle condition, which is a condition of a vehicle that can use/recommend use of the estimated value of the CSI, may be inserted. As the vehicle conditions, for example, the running lane, running speed, model of the vehicle-mounted device 1, etc. can be adopted. More specifically, the used vehicle condition can be set for a vehicle traveling in the same lane as the observation vehicle.

Moreover, the CSI-related information may include at least one of device information and observation environment information as a more preferable aspect. The device information indicates the model name and version information of the vehicle-mounted device 1, for example. The device information may include the manufacturer name, the model number of the wireless chip used, the configuration of the array antenna A131, and the like. Device information can also be called terminal information. The model name and version information of the vehicle-mounted device 1 can be used by the later-described antenna characteristic difference specifying unit F5 to learn the antenna characteristic difference for each model or version of the vehicle-mounted device 1 .

The observation environment information indicates the surrounding environment at the time of observation. The observation environment information indicates, for example, whether or not there was a large vehicle in the vicinity of the host vehicle (for example, front, rear, left, or right) at the time of observation. A large vehicle here refers to a vehicle such as a tank truck, a truck, or a large bus that is 1.5 times or more larger than the body of the own vehicle. A large vehicle is defined using at least one of a vehicle type, a longitudinal length, and a vehicle height. CSI can change greatly depending on whether or not there is a large vehicle in the vicinity of the host vehicle. In particular, the CSI may differ depending on whether or not a large vehicle is located on the side where the radio base station 2 is present when viewed from the host vehicle. That is, even if the CSI is for the same point, the CSI may differ depending on whether or not there is a large vehicle near the point.

By including the presence or absence of a large vehicle in the CSI-related information, it becomes possible to determine whether or not other vehicles can use the CSI indicated in the CSI-related information. Specifically, the CSI observed by the preceding vehicle u1 can be used as information for determining whether or not the own vehicle as the following vehicle u2 can be diverted. If there is no large vehicle in the vicinity of the preceding vehicle u1 and there is a large vehicle in the vicinity of the own vehicle, a difference in communication environment and thus CSI is expected. If there is no large vehicle in the vicinity of the preceding vehicle u1 but there is a large vehicle in the vicinity of the own vehicle, the beam control unit F6 may stop beam control based on the CSI observed by the preceding vehicle u1. . Whether or not there is a large vehicle may be represented by a flag of about 1-2 bits. In addition, the observed environment information may include information on dynamic environmental factors such as the number of vehicles existing around the vehicle and whether or not the vehicle is in a traffic jam.

The CSI-related information may be transmitted by broadcast, or may be transmitted by multicast or unicast after specifying the destination. The other vehicle, which is the destination of the CSI-related information, may be a vehicle within a predetermined sharing target distance from the own vehicle. The sharing target distance can be, for example, 100m, 200m, or 300m. The shared target distance may be defined by the concept of inter-vehicle time. For example, the sharing target distance may be set to a value that makes the inter-vehicle time within 5 seconds or 10 seconds. The inter-vehicle time corresponds to the time from when the preceding vehicle u1 passes a landmark, which is a predetermined structure on the road such as a sign post, to when the following vehicle u2 passes the landmark. . The inter-vehicle time roughly corresponds to a value obtained by dividing the inter-vehicle distance by the traveling speed of the own vehicle or the following vehicle u2.

Furthermore, the CSI transmission unit F3 may limit the transmission destination of the CSI-related information to vehicles traveling in the same lane as the own vehicle. Also, the transmission destination of the CSI-related information may be limited to vehicles in the same vehicle group, which are set by the vehicle group organizing section, which will be described later. Furthermore, the destination of the CSI-related information may be limited to vehicles located behind the own vehicle. According to the structure to which the said limitation is applied, the communication load and communication congestion of each onboard equipment 1 can be reduced. The CSI transmission unit F3 may be configured to transmit CSI-related information to the radio base station 2. FIG. According to this configuration, the wireless base station 2 can collect CSI with the wireless base station 2 viewed from the vehicle-mounted device 1 .

The other vehicle data acquisition part F4 is a structure which acquires the data transmitted by the vehicle-to-vehicle communication from the other vehicle by cooperation with the vehicle-to-vehicle communication part 14. FIG. For example, the other vehicle data acquisition unit F4 acquires the CSI-related information transmitted from the preceding vehicle u1. The other vehicle data obtaining section F4 corresponds to the preceding vehicle estimated value obtaining section.

The other vehicle data acquisition unit F4 stores the CSI observed by the other vehicle, which is received through inter-vehicle communication, in the received CSI holding unit M1 in association with observation points and the like. Hereinafter, CSI observed by other vehicles is also referred to as other vehicle CSI. In addition, among other vehicle CSI, CSI provided particularly from the preceding vehicle u1 is referred to as preceding vehicle CSI. Furthermore, the CSI estimated by the CSI estimator F2 of the own vehicle with respect to the other vehicle's CSI is referred to as the own vehicle's CSI. It should be noted that the other vehicle's CSI can also be called received CSI, and the own vehicle's CSI can be called internally generated CSI.

In addition, each vehicle-mounted device 1 periodically collects a data set indicating the driving state such as the position of the own vehicle, the driving speed, the traveling direction, the driving lane ID, the operation state of the direction indicator, the operation response of the wiper, etc. as vehicle information. may be configured to transmit to Information such as the traveling speed and the operating state of the wiper is input from various on-vehicle sensors or a body ECU via the in-vehicle network IvN. In that case, the other vehicle data acquisition unit F4 receives the vehicle information transmitted by the other vehicle and stores it in the RAM 112 or the like. Information on other vehicles can be used to identify the preceding vehicle u1, create a control plan, and the like.

An antenna characteristic difference specifying unit F5 compares the CSI observed by the preceding vehicle u1 at a certain point p with the CSI estimated by the own vehicle at the same point p, thereby determining the antenna characteristics of the preceding vehicle u1 and the own vehicle. An antenna characteristic difference, which is the difference, is calculated. For example, the antenna characteristic difference is represented by the difference between the CSI of the preceding vehicle u1 at a certain point p and the CSI of the own vehicle. That is, the estimated value of the antenna characteristic difference between the preceding vehicle u1 at the point p and the vehicle u2 as the own vehicle can be calculated by the following equation 2. D in Equation 2 is a parameter indicating the antenna characteristic difference and is expressed by a matrix.

なお、式２中のＨ（ｐ，ｕ２）は、地点ｐにおける自車両でのＣＳＩの推定値を示す。また、Ｈ（ｐ，ｕ１）は、地点ｐにおける先行車ｕ１でのＣＳＩの推定値を示す。Ｈ^＊（ｐ，ｕ１）は、先行車ｕ１でのＣＳＩ推定値の転置行列を示す。つまり、先行車ｕ１と自車両とのアンテナ特性差は、自車両でのＣＳＩ推定結果に対して、先行車ｕ１でのＣＳＩ推定結果の転置行列を右側から乗じることによって算出される。当該アンテナ特性差は、振幅と位相の差を示す。

Note that H(p, u2) in Equation 2 indicates the estimated value of CSI in the host vehicle at point p. Also, H(p, u1) indicates the estimated value of the CSI at the preceding vehicle u1 at the point p. H ^* (p, u1) denotes the transposed matrix of the CSI estimation value for the preceding vehicle u1. That is, the antenna characteristic difference between the preceding vehicle u1 and the own vehicle is calculated by multiplying the CSI estimation result of the own vehicle by the transposed matrix of the CSI estimation result of the preceding vehicle u1 from the right side. The antenna characteristic difference indicates a difference in amplitude and phase.

The beam control unit F6 is configured to control the beam of the array antenna A131. Beam control can be realized by adjusting the weighting factor of the phase shifter E4 connected to each antenna 131 based on the CSI observed by the preceding vehicle u1 and the antenna characteristic difference between the preceding vehicle u1 and the host vehicle. . Beam control may be performed on at least one of the transmitting side and the receiving side.

For example, beam control during transmission is performed according to Equation 3A below. Beam control during reception is also performed according to Equation 3B. That is, the weighting coefficients for various signals are determined by the transposed matrix obtained by multiplying the CSI estimated value of the preceding vehicle u1 by the antenna characteristic difference.

なお、式中のｘは、補正前の送信信号を表し、上部にチルド「～」を付与したｘは、実際の（補正後の）送信信号を表す。また、ｙは実際の受信信号を表すものであって、例えば式４で表現されうる。式４中のｎは、ノイズ成分を表す。また、前述の通り、上部にチルド「～」が付与されていないＨは、伝搬路特性の真値を指す。上部にチルド「～」を付与したｙは、伝搬路の影響を補正後の受信信号を示す。

Note that x in the formula represents the transmission signal before correction, and x with a tilde “~” attached to the top represents the actual transmission signal (after correction). Also, y represents an actual received signal and can be expressed by Equation 4, for example. n in Equation 4 represents a noise component. Also, as described above, H without a tilde ".about." at the top indicates the true value of the propagation path characteristic. A y with a tilde “~” at the top indicates the received signal after correction for the influence of the propagation path.

In the formula, q is a point on the traveling direction side of the point p and indicates a point where the own vehicle actually performs data communication. The point q is different from the point p used to calculate the antenna characteristic difference. Any point on the traveling direction side of the point p can be applied as q. If the current position of the own vehicle is located between the two points where the preceding vehicle u1 observed the CSI, the values obtained by linearly interpolating the estimated values at those points are adopted as the CSI at the current position. may

Of the two arbitrary points p and q existing along the traveling direction, the point q located relatively on the traveling direction side corresponds to the application point, and the point p used for calculating the antenna characteristic difference is Corresponds to the comparison point. The CSI-related information about the CSI estimated value observed by the preceding vehicle u1 at the point p corresponds to the first channel information, and the CSI-related information about the CSI estimated value observed by the preceding vehicle u1 at the point q is the third channel information. corresponds to Further, the data indicating the CSI estimated value observed by the own vehicle at the point p corresponds to the second propagation path information.

By the way, the matrix H as the CSI observed by the preceding vehicle u1 is multiplied from the right side by the matrix D as the antenna characteristic difference with the preceding vehicle u1. This corresponds to the corrected CSI corrected by the antenna characteristic difference with u1. Note that the corrected CSI conceptually corresponds to the CSI obtained by adding the antenna characteristic difference from the preceding vehicle u1 to the CSI observed by the preceding vehicle u1. Corrected CSI corresponds to the corrected estimate.

<Configuration of wireless base station 2>
Next, here, the configuration of the radio base station 2 will be described using FIG. 6 and the like. The radio base station 2 includes a base station controller 21, a base station radio section 22, and a network connection device 23, as shown in FIG.

The base station controller 21 is mainly composed of a computer including a processor 211 , a RAM 212 and a storage 213 . The storage 213 stores a base station program as a program executed by the processor 211 . Execution of the program by the processor 211 corresponds to execution of the base station communication control method, which is a method corresponding to the base station program.

The base station control unit 21 is connected to each of the base station radio unit 22 and the network connection device 23 so as to be mutually communicable. The base station controller 21 controls these operations. The base station control unit 21 is configured to cooperate with the base station radio unit 22 to execute processing related to digital BF.

The base station radio unit 22 is a communication module for radio communication with the vehicle-mounted device 1 . The base station radio section 22 corresponds to a radio communication module. The base station radio section 22 has an array antenna 221 including a plurality of antenna elements 221e. The base station radio section 22 includes an AD converter, a DA converter, an analog signal processing section, and the like, like the radio communication section 13 included in the vehicle-mounted device 1 . The array antenna 221 has, for example, a plurality of antenna elements 221e arranged in a matrix or grid. The base station control unit 21 realizes digital BF by adjusting weighting coefficients of analog signals input to and output from each antenna element 221e that constitutes the array antenna 221. FIG. The base station radio unit 22 transmits radio signals directed to the vehicle-mounted device 1 under the control of the base station control unit 21 . Also, the base station radio section 22 receives a radio signal from the vehicle-mounted device 1 and outputs a digital signal corresponding to the received signal to the base station control section 21 .

The network connection device 23 is a configuration for communicating with equipment that constitutes the core network. Equipment that configures the core network is, for example, MME (Mobility Management Entity) and AMF (Access and Mobility Management Function). The network connection device 23 is configured to be able to communicate with the core network using, for example, an optical fiber. The network connection device 23 outputs data input from the core network to the base station controller 21 . Also, the network connection device 23 outputs data input from the base station control unit 21 to the core network. The data output to the core network is transferred through a path according to the destination and arrives at a server or the like as the destination.

<Effects of the above configuration>
According to the above configuration, the CSI estimated value is shared in inter-vehicle communication, and the difference in antenna characteristics between vehicles ( individual differences). When the antenna characteristic difference between the preceding vehicle u1 and the host vehicle has already been specified, the signal transmitted and received by each antenna is obtained using the CSI at each point provided by the preceding vehicle u1 and the antenna characteristic difference between the preceding vehicle u1. adjustment of the intensity (power) and phase of the beam, that is, beam control. In this way, according to the configuration for controlling the transmission/reception level in consideration of the CSI for each point provided in real time from another vehicle and the difference in antenna characteristics with the other vehicle, the effect of improving the antenna gain and the reliability of communication can be achieved. can be expected to have the effect of increasing

Further, according to the above configuration, communication using the estimated value becomes possible at the position where the propagation path estimation is performed. Therefore, it is possible to reduce the possibility of deviation between the position at the time of CSI estimation and the data communication execution point. As a result, it is possible to suppress the estimation error of the propagation path used for adjusting the weighting factor. In addition, it is possible to improve beam accuracy by forming beams in consideration of antenna characteristic differences in the CSI of the preceding vehicle u1.

Also, since the CSI used for beam control is obtained from the preceding vehicle u1, it can be expected to be an estimated value at a time relatively close to the current time, such as within several seconds. If the momentary presence of an obstructing object such as a large vehicle can be ignored, the CSI does not fluctuate significantly within one second to several seconds. Therefore, compared with the case of using the radio wave propagation map, the effect of suppressing the CSI estimation error can be expected relatively.

As the preceding vehicle u1 used for beam control, among the vehicles running in front of the own vehicle in the same lane as the own vehicle, a vehicle having the same model and version as the onboard unit 1 of the own vehicle is preferentially adopted. good too. According to this configuration, it is possible to reduce the antenna characteristic difference reflected in the beam control, and also reduce the error included in the estimated value of the antenna characteristic difference. As a result, it can be expected that more appropriate beam control can be performed.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications described below are also included in the technical scope of the present disclosure. Various modifications can be made without departing from the scope of the present invention. For example, the various modified examples below can be implemented in combination as appropriate within a range that does not cause technical contradiction. It should be noted that members having the same functions as those of the members described in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted. Also, when only part of the configuration is mentioned, the configuration of the previously described embodiments can be applied to the other portions.

<Application of vehicle groups>
When each vehicle moves in units of a vehicle group set according to a predetermined rule, the vehicle group may be configured to share CSI-related information. An example of a configuration corresponding to the technical concept will be described below.

As shown in FIG. 7, the vehicle-mounted device 1 includes, as functional units, a communication quality acquisition unit G1, a report processing unit G2, and a vehicle group setting acquisition unit G3 in addition to a position acquisition unit F1 and the like. 7, illustration of some of the functional units shown in FIG. 2, such as the position acquisition unit F1, is omitted.

When the vehicle-to-vehicle communication unit 14 receives a radio signal from another vehicle, the communication quality acquisition unit G1 stores information indicating the communication quality with the vehicle in association with the vehicle ID indicating the transmission source. . When the subject vehicle is in a state in which inter-vehicle communication is possible with a plurality of other vehicles, the communication quality acquisition unit G1 distinguishes and manages and stores the communication quality information for each vehicle. The communication quality information for each vehicle is temporarily stored in the RAM 112, for example.

The information indicating the quality of wireless communication between vehicles includes at least some of various indices such as received signal strength, signal-to-noise ratio of received signals, bit error rate (BER), and packet loss rate. The received signal strength can also be expressed as RSSI (Received Signal Strength Indication). The signal-to-noise ratio is a parameter indicating the ratio or difference between signal and noise. The signal-to-noise ratio can also be expressed as SNR (Signal-to-Noise Ratio), SN ratio, S/N, and the like. The higher the signal-to-noise ratio, the better the quality. The packet loss rate corresponds to the data reception failure rate per fixed time. Measurement of RSSI and the like are performed by an intensity detection circuit or the like provided in the vehicle-to-vehicle communication section 14 . The vehicle-to-vehicle communication unit 14 is configured to calculate part or all of the quality index. Note that the control unit 11 may have a function of calculating some or all of the various quality indexes described above.

The report processing unit G2 generates a running state report, which is a data set (for example, a communication packet) indicating the running state of the own vehicle, at a predetermined cycle, and transmits it to the wireless base station 2 in cooperation with the wireless communication unit 13. . The driving state report includes, for example, data on the state of communication between the own vehicle and other vehicles. The communication status here includes communication quality for each communication partner. In addition, the driving state report includes the current position of the own vehicle, the driving speed, and the like.

Additionally, the driving condition report may include a long-term or medium-term control plan. A long-term control plan corresponds to, for example, information roughly showing a travel route from the current position to the destination. The medium-term plan is a more detailed/specific control plan than the long-term plan, and includes, for example, driving lanes, driving speeds, etc. in the range that the vehicle is expected to pass within 5 to 10 minutes. A long-term/medium-term control plan can include travel points, travel speeds, and the like for each time.

The vehicle group setting acquisition unit G3 is configured to acquire vehicle group setting data transmitted from the radio base station 2 . The vehicle group setting acquisition section G3 corresponds to the vehicle group information acquisition section. The vehicle group here is a group of a plurality of vehicles. The vehicle group setting data includes, for example, identification information of each vehicle belonging to the same vehicle group, and data indicating settings of communication paths within the vehicle group. As the vehicle identification information, a unique number assigned in advance to each vehicle (so-called vehicle ID) can be used. Further, the vehicle identification information may be address information for each vehicle used in communication. A communication route in a vehicle group can be formed in a tree shape, for example, with the leading vehicle as the starting point (root). The communication path within the vehicle group may be set by the wireless base station 2, or may be dynamically set by each vehicle in consideration of the actual communication status.

Vehicles belonging to one vehicle group share, for example, content data distributed in a divided state from the radio base station 2 through vehicle-to-vehicle communication and complement each other. The content data here refers to, for example, high-precision map data, dynamic map data, software update data, and the like. High-precision map data is data that indicates the detailed road structure with high precision, such as position coordinates of lane marks, road signs, road edges, and the like. The dynamic map data includes at least one of the following: average vehicle speed, traffic volume, lighting status of traffic lights, section where traffic is restricted, end of traffic jam, position of fallen object on the road. This is data indicating one.

Based on the vehicle group setting data acquired by the vehicle group setting acquisition unit G3, the CSI transmission unit F3 transmits CSI-related information to other vehicles belonging to the same vehicle group as the own vehicle, in other words, other constituent members. Transmit by inter-vehicle communication. Deployment of the CSI-related information to other vehicles in the vehicle group by the CSI transmission unit F3 may be performed in a unicast manner or in a multicast manner. If confirmation of arrival of CSI-related information is unnecessary due to system design, transmission by multicast is preferable in order to improve communication efficiency.

The radio base station 2 includes, as functional units, an individual information acquisition unit H1, a vehicle group formation unit H2, and a vehicle group setting notification unit H3, as shown in FIG. Each functional unit may be realized by the processor 211 executing the base station program, or may be realized using hardware such as an IC.

The individual information acquisition unit H1 acquires a driving state report transmitted from each vehicle, and temporarily stores it in the RAM 212 or the like. As described above, some or all of the information included in the driving condition report corresponds to context data for configuring the vehicle fleet.

The vehicle group formation unit H2 is configured to organize a vehicle group based on the context data for each vehicle acquired by the individual information acquisition unit H1. For example, the vehicle group formation unit H2 sets vehicles whose RSSI is greater than or equal to a predetermined grouping strength into the same group (in other words, vehicle group). The grouping strength may be set to a value that enables stable inter-vehicle communication, and may be changed according to the standard value of transmission power defined by the inter-vehicle communication standard. The grouping strength may be set to a value such that, for example, the expected value of the packet arrival rate is 95% or higher. A state in which communication is stable can be, for example, a state in which the packet loss rate is less than 5%. The required communication quality can be determined according to communication usage and the like. The grouping strength may be -60 dBm, -50 dBm, -40 dBm, -30 dBm, etc., depending on the value of the transmission power defined by the vehicle-to-vehicle communication standard. The grouping strength can be set based on, for example, RSSI simulation results in an environment where communication is stable (hereinafter referred to as a good environment). As a good environment, it is assumed that the vehicle-to-vehicle distance is 25 m and there are no obstacles between the vehicles.

The RSSI used to organize the vehicle group may be the latest observed value, or may be the average, median, maximum, or minimum value of the observed values within the most recent predetermined time period. Here, as an example, RSSI is used to select vehicles to be included in the same vehicle group, but the present invention is not limited to this. The condition for grouping may be that the SNR is equal to or greater than a predetermined value, or that the packet loss rate within the most recent predetermined time period is less than a predetermined value. A threshold for each item that defines grouping conditions is also referred to as a grouping threshold. The aforementioned grouping strength also corresponds to an example of the grouping threshold.

Since the vehicle group formation unit H2 forms a vehicle group based on the quality information of inter-vehicle communication, it is possible to reduce the possibility of including vehicles that are difficult to communicate with in the same vehicle group. In other words, it becomes easier to ensure communication quality within the vehicle group. Of course, the vehicle group formation unit H2 may be configured to set the vehicle group by using the inter-vehicle distance in addition to at least one parameter indicating the inter-vehicle communication quality. For example, the conditions for belonging to the same vehicle group may be that the RSSI is greater than or equal to the grouping strength and the inter-vehicle distance is less than a predetermined grouping distance. The grouping distance can be, for example, 50 mm, 100 m, 150 m, or the like.

Based on the control plan for each vehicle, the vehicle group organization unit H2 organizes each vehicle group so that vehicles whose relative positional relationship can be expected to remain unchanged for a certain period of time or longer belong to the same vehicle group. is preferred. Vehicles whose relative positional relationship can be expected to remain unchanged for a certain period of time are, for example, vehicles that have similar destinations, traveling directions, average running speeds, and target values for automatic speed adjustment. is.

The vehicle group setting notification unit H3 transmits vehicle group setting data from the vehicle group formation unit H2 to each corresponding vehicle-mounted device 1 . The destination of the vehicle group setting data and the like may be all the vehicles forming the vehicle group, or may be only the vehicle corresponding to the leading vehicle. If the destination of the vehicle group setting data, etc., is only one of the vehicles that make up the target vehicle group, the vehicle that receives the vehicle group setting data will enter the same vehicle group indicated by the vehicle group setting data. Vehicle group setting data may be transferred to other vehicles belonging to the vehicle through vehicle-to-vehicle communication.

According to the above premise configuration, each vehicle-mounted device 1 identifies the vehicle group to which the own vehicle belongs and its constituent members based on the vehicle group setting data provided from the radio base station 2 . That is, each vehicle-mounted device 1 recognizes the vehicle group to which its own vehicle belongs, in other words, the other vehicle with which the CSI-related information should be shared. Each vehicle-mounted device 1 transmits CSI-related information to other vehicles belonging to the same vehicle group by inter-vehicle communication.

According to the above configuration, the CSI for each point is shared within the vehicle group. Along with this, the difference in antenna characteristics is specified between the vehicles that constitute the vehicle group. Therefore, the above beam control can be performed for each vehicle group. In addition, as one mode, the vehicle group formation unit H2 sets vehicles that can be expected to remain in the same relative positional relationship for a certain period of time or more in the same vehicle group. According to this aspect, since the mutual relationship between the preceding vehicle u1 and the following vehicle u2 is also maintained for a relatively long period of time, it is possible to extend the period during which the identified antenna characteristic difference can be utilized. In other words, it becomes possible to suppress the frequency of calculating the antenna characteristic difference.

A vehicle that transmits CSI-related information may be limited to only the leading vehicle of a vehicle group. In the vehicle group, non-lead vehicles, which are vehicles other than the lead vehicle, correspond to vehicles following the lead vehicle. According to the above configuration, the non-leading vehicle in the vehicle group can perform beam control based on the CSI-related information transmitted by the leading vehicle in the vehicle group and the antenna characteristic difference between the leading vehicle and the own vehicle. Thereby, the reliability of communication between the non-leading vehicle and the radio base station 2 can be improved. In addition, since the CSI needs to be calculated only by the leading vehicle, it is possible to reduce the processing load of the vehicle-mounted device 1 in the non-leading vehicle.

As described above, the configuration in which the leading vehicle of the vehicle group calculates the CSI and deploys it in the vehicle group has one aspect in which the leading vehicle generates a dynamic radio map showing the CSI for each point and calculates the CSI within the vehicle group. It corresponds to the configuration shared and used by In addition, in the configuration in which the leading vehicle of the vehicle group calculates the CSI and deploys it within the vehicle group, the processing load on the leading vehicle increases. When forming the vehicle group, the vehicle group formation unit H2 may form the vehicle group so that the vehicle-mounted device 1 having a relatively high-performance processor/IC becomes the leading vehicle. The performance of each vehicle-mounted device 1 may be specified from device information.

<Supplement to how to use antenna characteristic differences>
Even in a situation where the antenna characteristic difference with the preceding vehicle u1 has already been identified, the antenna characteristic difference identifying unit F5 re-identifies the antenna characteristic difference with the preceding vehicle u1 periodically or in response to the occurrence of a predetermined event. It may be configured to calculate, verify and update the antenna characteristic difference. In addition, the beam control unit F6 determines that the degree of variation (dispersion or deviation) of the antenna characteristic difference calculated within the most recent predetermined time period by the antenna characteristic difference identifying unit F5 is equal to or greater than a predetermined value, the CSI of the preceding vehicle and the antenna Beam control using characteristic differences may be discontinued. For example, the beam control unit F6, when the state in which the variation in the antenna characteristic difference calculated within the most recent predetermined time period is equal to or greater than a predetermined threshold continues for a predetermined time period (for example, 5 seconds), uses the corrected CSI beam. You can stop controlling.

The antenna characteristic difference used for beam control can be an average value (so-called moving average value) of antenna characteristics calculated within the most recent predetermined time period. Also, the median value can be used instead of the average value. According to these aspects, it is possible to reduce the possibility that momentary noise may increase the error between the corrected CSI and the true value.

Further, when the difference in antenna characteristics from the preceding vehicle u1 has been specified, the vehicle-mounted device 1 compares the CSI calculated by the own vehicle with the corrected CSI, and the corrected CSI and the own vehicle CSI match. It may be determined whether Match here is not limited to perfect match, and can include, for example, a difference of about ±10%. That is, the concept of match also includes approximate match.

In the above configuration, the beam control unit F6 may be configured to stop beam control using the corrected CSI based on the fact that the difference between the corrected CSI and the vehicle's CSI is greater than or equal to a predetermined threshold. . More specifically, the beam control unit F6 uses the corrected CSI when the difference between the corrected CSI and the own vehicle CSI is equal to or greater than a predetermined threshold value and continues for a certain period of time (for example, 5 seconds). Beam control may be stopped.

In addition, the degree of change in CSI over time may increase in situations where the relative position with surrounding vehicles fluctuates significantly, such as when the relative speed with respect to a vehicle traveling in an adjacent lane is greater than or equal to a predetermined value. Therefore, in a situation where the positional relationship with the surrounding vehicles is unstable, the beam control using the CSI of the preceding vehicle and the antenna characteristic difference with the preceding vehicle u1 may be stopped. Whether or not the positional relationship with surrounding vehicles is stable may be determined based on the position information and speed of other vehicles acquired through inter-vehicle communication, and the relative speed between the surrounding vehicles and the own vehicle. For example, when there is no other vehicle whose relative speed to the own vehicle is equal to or higher than a predetermined threshold, it can be determined that the positional relationship with the surrounding vehicles is stable. Whether or not the positional relationship with surrounding vehicles is stable may be determined based on sensing information from a surrounding monitoring sensor such as a camera.

Various supplements related to the method of utilizing the difference in antenna characteristics described above can also be applied to the case where the radio base station 2 performs beam control, as described below.

<Regarding the configuration for performing beam control in the radio base station 2>
In the above-described embodiment, the vehicle-mounted device 1 discloses a mode in which beam control is performed using the corrected CSI at the time of signal transmission or reception, but the present invention is not limited to this. The radio base station 2 may estimate the difference in antenna characteristics between vehicles and notify each vehicle. Also, the radio base station 2 may perform beam control for the following vehicle u2 based on the CSI observed in communication with the preceding vehicle u1 and the antenna characteristic difference between the preceding vehicle u1 and the following vehicle u2. An example of a configuration corresponding to such a technical idea will be described below.

As shown in FIG. 8, the radio base station 2 includes, as functional units, a vehicle position acquisition unit J1, a CSI estimation unit J2, an individual difference identification unit J3, and a beam control unit J4. The base station control unit 21 also includes a CSI storage unit M3 and an individual difference storage unit M4. The CSI storage unit M3 may be implemented using part of the storage area of the RAM 212 or may be implemented using a storage device separate from the RAM 212 . The same applies to the individual difference holding unit M4.

The vehicle position acquisition unit J1 is configured to acquire the position of each vehicle-mounted device 1 existing within the communication area (in other words, cell) of the wireless base station 2 . The location information of each vehicle-mounted device 1 is reported from each vehicle-mounted device 1 . For example, the vehicle position acquisition unit J1 acquires the current position of each vehicle based on the running state report transmitted from each vehicle-mounted device 1 . The position information for each vehicle acquired by the vehicle position acquisition unit J1 is output to, for example, the CSI estimation unit J2.

Information transmitted from the vehicle to the radio base station 2, such as a driving state report, preferably includes information about the preceding vehicle u1 and the following vehicle, that is, information indicating the anteroposterior relationship. According to the configuration in which each vehicle transmits information about vehicles positioned in front of or behind its own vehicle to the wireless base station 2, it becomes easier for the wireless base station 2 to identify the front-back relationship of a plurality of vehicles.

The CSI estimator J2 estimates at least one of uplink and downlink CSI for each point and for each vehicle by transmitting and receiving a predetermined reference signal to and from the vehicle (vehicle-mounted device 1). Note that since the radio signal propagation path is reversible, the CSI for either one of the uplink and the downlink can be used as the CSI for the other. The CSI estimation unit J2 stores the CSI for each vehicle and for each point in the CSI storage unit M3 in association with the identification information and location information of the vehicle. The CSI estimator J2 corresponds to the channel information acquisition unit.

The individual difference specifying unit J3 determines the difference in antenna characteristics, in other words, the difference in antenna characteristics between the vehicles in the relationship between the preceding vehicle u1 and the following vehicle u2, based on the CSI for each vehicle and for each point stored in the CSI storage unit M3. Calculate the difference. Antenna characteristic differences (individual differences) can be calculated using Equations 1 and 2 described above. The anteroposterior relationship between vehicles may be specified based on position information for each time, or may be specified based on a report from the vehicle. The vehicle-to-vehicle antenna characteristic difference identified by the individual difference identification unit J3 is stored in the individual difference storage unit M4 together with data indicating the combination of vehicles. The individual difference identification unit J3 may calculate the antenna characteristic difference between the preceding vehicle u1 and the following vehicle u2 periodically or each time a predetermined reference signal is transmitted and received.

The beam control unit J4 performs beam control in communication with each vehicle based on the CSI for each point and for each vehicle stored in the CSI storage unit M3 and the antenna characteristic difference stored in the individual difference storage unit M4. conduct. A specific method of beam control is the same as the case where the vehicle-mounted device 1 performs beam control. That is, the beam control unit J4 calculates the corrected CSI for the following vehicle u2 by combining the CSI specified by communication with the preceding vehicle u1 and the antenna characteristic difference between the preceding vehicle u1 and the following vehicle u2. Beam control is performed using corrected CSI.

According to the above configuration, since the wireless base station 2 estimates the CSI, the processing load on the vehicle-mounted device 1 can be reduced. In addition, there is no need for vehicles to transmit and receive CSI-related information through vehicle-to-vehicle communication. Therefore, the processing load on the vehicle-mounted device 1 can be further reduced. Of course, as in the above embodiment, it is possible to perform communication using the estimated value at the position where the propagation path estimation is performed. Therefore, it is possible to reduce the possibility of deviation between the position at the time of CSI estimation and the data communication execution point. As a result, communication reliability can be improved.

As described above, the control of performing/stopping beam control using antenna characteristic differences based on the degree of variation in antenna characteristic differences can also be applied when the radio base station 2 performs beam control. For example, when the variation in the antenna characteristic difference calculated within the most recent predetermined time period is greater than or equal to a predetermined threshold value, the beam control unit J4 uses the CSI estimated in communication with the preceding vehicle u1 to communicate with the following vehicle u2. It may be configured not to perform beam control for communication.

Further, the beam control unit J4 maintains a state in which the difference between the corrected CSI for the following vehicle u2 for the same point and the estimated value of the CSI calculated by communication with the following vehicle u2 is equal to or greater than a predetermined value for a predetermined period of time. Beam control using corrected CSI may be discontinued based on what has been done.

In addition, the driving state report transmitted from each vehicle may include information indicating whether or not there is a large vehicle in the vicinity, that is, observation environment information. When a large vehicle exists around at least one of the preceding vehicle u1 and the following vehicle u2, the radio base station 2 stops the process of calculating the antenna characteristic difference and the corrected CSI related to those vehicles. may In other words, the radio base station 2 and the vehicle-mounted device 1 may perform part or all of the various processes described above in situations where differences in antenna characteristics tend to include errors, or situations where CSI at the same location tends to change dynamically. may be discontinued.

<Additional notes>
The apparatus, systems, and techniques described in this disclosure may be implemented by a special purpose computer comprising a processor programmed to perform one or more functions embodied by a computer program. . The apparatus and techniques described in this disclosure may also be implemented using dedicated hardware logic. Additionally, the apparatus and techniques described in this disclosure may be implemented by one or more special purpose computers configured in combination with a processor executing a computer program and one or more hardware logic circuits. The computer program may also be stored as computer-executable instructions on a computer-readable non-transitional tangible recording medium. That is, the means and/or functions provided by the vehicle-mounted device 1 and the like can be provided by software recorded in a physical memory device, a computer that executes the software, only software, only hardware, or a combination thereof. For example, some or all of the functions provided by the vehicle-mounted device 1 may be implemented as hardware. A mode of implementing a certain function as hardware includes a mode of implementing it using one or a plurality of ICs. The vehicle-mounted device 1 may be implemented using an MPU, a GPU, or a DFP (Data Flow Processor) instead of the CPU. The vehicle-mounted device 1 may be implemented by combining multiple types of arithmetic processing units such as a CPU, an MPU, and a GPU. The vehicle-mounted device 1 may be realized as a system-on-chip (SoC: System-on-Chip). Furthermore, the various processing units may be implemented using FPGAs (Field-Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits). Various programs may be stored in a non-transitory tangible storage medium. Various storage media such as HDD (Hard-disk Drive), SSD (Solid State Drive), flash memory, and SD (Secure Digital) card can be used as the program storage medium. The non-transitional physical recording medium also includes ROM such as EPROM (Erasable Programmable Read Only Memory).

In addition to the vehicle-mounted device 1 described above, various forms such as a system including the vehicle-mounted device 1 as a component are also included in the scope of the present disclosure. For example, a program for causing a computer to function as the vehicle-mounted device 1, a form of a non-transitional substantive recording medium such as a semiconductor memory in which the program is recorded, and the like are also included in the scope of the present disclosure. The same applies to the radio base station 2 as well.

1 on-vehicle device, 2 wireless base station, 13 wireless communication unit, 22 wireless communication module, F2 CSI estimation unit (propagation path estimation unit), F4 other vehicle data acquisition unit (preceding vehicle estimated value acquisition unit), F5 antenna characteristic difference identification Unit, F6 beam control unit, G2 report processing unit, G3 vehicle group setting acquisition unit (vehicle group information acquisition unit), J2 CSI estimation unit (propagation path information acquisition unit), J3 individual difference identification unit, J4 beam control unit, u1 Preceding vehicle (first vehicle), u2 Own vehicle (second vehicle).

Claims (7)

A vehicle communication device configured to enable inter-vehicle communication,
a radio communication unit (13) having a plurality of antennas for radio communication with a radio base station (2);
By performing vehicle-to-vehicle communication with the preceding vehicle, the first propagation path information indicating an estimated value of the propagation path state with the radio base station observed when the preceding vehicle (u1) is present at an arbitrary comparison point a preceding vehicle estimated value acquisition unit (F4) to acquire;
A propagation path estimation unit ( F2) and
a characteristic difference identifying unit (F5) that identifies a characteristic difference, which is a difference in antenna characteristics between the preceding vehicle and the host vehicle, by comparing the first channel information and the second channel information;
a beam control unit (F6) that controls the beams of the plurality of antennas provided in the wireless communication unit;
The preceding vehicle estimated value acquisition unit also acquires third propagation path information indicating the estimated value of the propagation path state observed by the preceding vehicle at an application point that is an arbitrary point on the traveling direction side of the comparison point. ,
The beam control unit controls communication with the radio base station at the application point based on the characteristic difference identified by the characteristic difference identification unit and the third propagation path information observed at the application point. A vehicle communication device configured to perform beam control for a vehicle. The vehicle communication device according to claim 1,
a report processing unit (G2) for transmitting the communication status with other vehicles to the radio base station;
Vehicle group setting data, which is data about the vehicle group to which the own vehicle belongs, which is set by the radio base station based on the communication status with the other vehicles transmitted from a plurality of vehicles including the own vehicle, is transmitted by the radio. A vehicle group information acquisition unit (G3) that acquires from a base station,
When the own vehicle corresponds to the leading vehicle of the vehicle group, the propagation path state is sequentially estimated, and the propagation path state estimated value for each point is used for inter-vehicle communication to configure the vehicle group as the following vehicle. vehicle communication device for transmitting to the other vehicle. The vehicle communication device according to claim 1 or 2,
The characteristic difference identifying unit sequentially calculates the characteristic difference from the preceding vehicle,
The vehicle communication device, wherein the beam control unit is configured to perform the beam control using an average value or a median value of the characteristic differences calculated within the most recent predetermined time. The vehicle communication device according to any one of claims 1 to 3,
The characteristic difference identifying unit sequentially calculates the characteristic difference from the preceding vehicle,
The beam control unit calculates the degree of variation of the characteristic difference calculated within the most recent predetermined time, and stops the beam control using the characteristic difference when the degree of variation is equal to or greater than a predetermined threshold. A vehicle communication device configured as follows. The vehicle communication device according to any one of claims 1 to 4,
The propagation path estimation unit estimates the propagation path state also at the application point,
The beam control unit
calculating a corrected estimated value obtained by combining the third channel information and the characteristic difference;
The characteristic difference is calculated based on a state in which a difference between the estimated value of the propagation path state at the application point estimated by the propagation path estimation unit and the corrected estimated value is equal to or greater than a predetermined value and continues for a predetermined time. A vehicular communication device configured to discontinue the beam control used. The vehicle communication device according to any one of claims 1 to 5,
The vehicle communication device, wherein the propagation path information distributed from the preceding vehicle includes observation environment information including whether or not a large vehicle was present around the preceding vehicle at the time of propagation path estimation. a wireless communication module (22) comprising a plurality of antennas for wireless communication with a vehicle;
First propagation path information, which is an estimated value of the propagation path state observed by communicating with a first vehicle (u1) existing at an arbitrary comparison point, and a second vehicle (u2 ) is present at the comparison point, a propagation path information acquisition unit (J2) for acquiring second propagation path information indicating the estimated value of the propagation path state observed by communicating with the second vehicle;
an individual difference identification unit (J3) that identifies a characteristic difference, which is a difference in antenna characteristics between the first vehicle and the second vehicle, by comparing the first propagation path information and the second propagation path information;
a beam control unit (J4) that controls the beams of the plurality of antennas included in the wireless communication module;
The propagation path information acquisition unit is configured to obtain a third propagation path that indicates an estimated value of the propagation path state observed by communicating with the first vehicle at an application point that is an arbitrary point on the traveling direction side of the comparison point. also get information
Based on the characteristic difference specified by the individual difference specifying unit and the third propagation path information observed at the application point, the beam control unit is configured to determine the relationship between the second vehicle and the second vehicle existing at the application point. A radio base station configured to beamform for communications.

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