JP7535550B2 - Communication Systems - Google Patents

Description

The present invention relates to a communication system.

Non-Patent Document 1 and Non-Patent Document 2 describe the effectiveness of antenna spatial diversity in the vertical direction in vehicle-to-vehicle direct communication in which direct communication is performed between vehicle-mounted wireless terminal devices. Non-Patent Document 3 describes that, with regard to antenna spacing for which spatial diversity is effective in cellular mobile communication in which a wireless base station device and a wireless terminal device communicate with each other, it is sufficient to set the antenna spacing horizontally to half a wavelength or more on the mobile station side and 10 wavelengths or more on the base station side, assuming non-line-of-sight communication.
[Prior Art Literature]
[Non-Patent Literature]
[Non-Patent Document 1] Akihito Kato, Katsuyoshi Sato, Masayuki Fujise, and Shigeru Kawakami, "Propagation Characteristics of 60-GHz Millimeter Wave for ITS Inter-Vehicle Communications," IEICE Trans. Commun., vol.E84-B, no.9, pp.2530-2539, Sept. 2001.
[Non-Patent Document 2] Yoshio Karasawa, "Basic Study on Road Reflection Fading and Space Diversity in ITS Millimeter Wave Vehicle-to-Vehicle Communications," IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J83-B, No. 4, pp. 518-524, Apr. 2000.
[Non-Patent Document 3] Yoshio Karasawa, "Radio Wave Propagation Fundamentals for Digital Mobile Communications," Corona Publishing, Revised Edition, 1st Printing, Mar. 2016.

According to one embodiment of the present invention, a communication system is provided. The communication system includes a first communication device mounted on a first mobile body and a second communication device mounted on a second mobile body. The second communication device may have an antenna array including a plurality of second orthogonally polarized antennas arranged at a spatial distance in at least one of a vertical direction and a horizontal direction. The first communication device may have a first orthogonally polarized antenna. The first communication device may have a control unit that controls the implementation of polarized MIMO multiplexing transmission by the first orthogonally polarized antenna based on the propagation path conditions between the first communication device and the second communication device.

In any of the above communication systems, the control unit may control the first orthogonally polarized antenna to perform the polarized MIMO multiplexing transmission when the propagation path conditions satisfy a propagation condition that provides a space diversity effect due to the arrangement of the multiple second orthogonally polarized antennas.

In any of the above communication systems, the second communication device may further include an estimation unit that estimates a propagation path condition between the second communication device and the first communication device, and an FB information transmission unit that transmits feedback information based on the propagation path condition estimated by the estimation unit to the first communication device, the first communication device may further include a receiver that receives the feedback information, and the control unit may implement either polarization diversity or the polarization MIMO multiplexing transmission according to the feedback information.

In any of the communication systems, the second orthogonally polarized antennas may be spatially spaced apart by an odd multiple of a half period of the period of the level fluctuation due to the antenna position at a first distance that is predetermined as the distance between the first communication device and the second communication device. The first distance may be a distance that is predetermined as the distance between the first moving body and the second moving body. The first distance may be a distance that is predetermined as the maximum distance between the first moving body and the second moving body. In any of the communication systems, the first moving body and the second moving body may be vehicles, and the first distance may be a distance that is predetermined as the distance between two vehicles traveling in front and behind each other. In any of the communication systems, the second orthogonally polarized antennas may be spatially spaced apart in the lateral direction by an odd multiple of a half period of the period of the level fluctuation due to the antenna lateral position at the first distance. In any of the above communication systems, the second orthogonally polarized antennas may be arranged spatially separated in the height direction at a distance that is an odd multiple of a half period of the period of level fluctuation due to antenna height at the first distance.

In any of the communication systems, the second orthogonally polarized antennas may be arranged at a spatial separation by an antenna interval determined based on the distance between the first orthogonally polarized antenna and the reflector along a direction from the first orthogonally polarized antenna to a reflector that reflects radio waves emitted by the first orthogonally polarized antenna. In any of the communication systems, the reflector may be the ground, and the second orthogonally polarized antennas may be arranged at a spatial separation by the antenna interval determined based on the antenna height of the first orthogonally polarized antenna along a direction perpendicular to the reflector. In any of the communication systems, the second orthogonally polarized antennas may be arranged at a spatial separation by the antenna interval determined by the distance between the first orthogonally polarized antenna and the reflector and distance interval data indicating the antenna interval for each distance between the first orthogonally polarized antenna and the reflector. In any of the communication systems, the distance interval data may be data generated based on a result of simulating a level of radio waves received by the multiple second orthogonal polarized antennas from the first orthogonal polarized antenna when a distance between one of the second orthogonal polarized antennas and the reflector and a transmitting/receiving antenna distance between the first orthogonal polarized antenna and the one second orthogonal polarized antenna are changed for each distance between the first orthogonal polarized antenna and the reflector for each interval between the multiple second orthogonal polarized antennas. In any of the communication systems, the distance interval data may be data generated based on a result of actually measuring a level of radio waves received by the multiple second orthogonal polarized antennas from the first orthogonal polarized antenna when a distance between one of the second orthogonal polarized antennas and the reflector and a transmitting/receiving antenna distance between the first orthogonal polarized antenna and the one second orthogonal polarized antenna are changed for each distance between the first orthogonal polarized antenna and the reflector for each interval between the multiple second orthogonal polarized antennas. In any of the communication systems, the distance interval data may be data generated based on an approximate maximum value of the minimum value of the higher level of the radio wave received from the first orthogonal polarized antenna among the plurality of second orthogonal polarized antennas for each interval between the plurality of second orthogonal polarized antennas. In any of the communication systems, the distance interval data may be data generated based on an approximate minimum value of the correlation coefficient of the phase difference between the direct wave and the reflected wave from the first orthogonal polarized antenna among the plurality of second orthogonal polarized antennas for each interval between the plurality of second orthogonal polarized antennas.

Note that the above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions.

An example of a vehicle 10 equipped with a communication device 100 is shown in schematic form. An example of a vehicle 10 equipped with a communication device 100 is shown in schematic form. 10 is an explanatory diagram for explaining a reflection interference component due to road surface reflection; FIG. 10 is an explanatory diagram for explaining a reflected interference component due to a lateral reflection; FIG. 2 illustrates an example of a functional configuration of a communication device 100 and a communication device 200. 2 shows a schematic diagram of an example of the configuration of the orthogonally polarized antenna 112 and the transmitter baseband section 150 of the communication device 100. 2 shows a schematic diagram of an example of the configuration of the orthogonally polarized antenna 222 and the receiver baseband section 250 of the communication device 200. 2 shows another example of the configuration of the orthogonally polarized antenna 112 and the transmitter baseband section 150 of the communication device 100. 2 shows another example of the configuration of the orthogonally polarized antenna 222 and the receiver baseband section 250 of the communication device 200. 1 is an explanatory diagram for explaining fluctuations in reception level in the antenna height direction and horizontal position direction of the antenna array 120. FIG. 10 shows an example of level fluctuations due to the horizontal position of a receiving antenna when the receiving antenna height is fixed. 10 shows an example of level fluctuations due to the height of a receiving antenna when the receiving antenna is fixed in a horizontal position. 10 shows an example of a period _Lw of level fluctuations due to the horizontal position of the receiving antenna when the receiving antenna height is fixed. 10 shows an example of a period _Lh of level fluctuations due to the height of the receiving antenna when the receiving antenna is fixed in a horizontal position. 2 shows a schematic diagram of an example of the configuration of the antenna array 120. 2 shows a schematic diagram of an example of the configuration of the antenna array 120. 1 is an explanatory diagram for explaining radio waves transmitted by an antenna 60 and received by an antenna array 70 of a communication partner. 5 shows an example of graph data 500 showing minimum levels when the vehicle distance changes for each receiving antenna height. 5 shows an example of graph data 520 showing minimum levels when the height of the receiving antennas changes for each receiving antenna interval. An example of distance interval data 530 is shown diagrammatically. 1 is an explanatory diagram for explaining radio waves transmitted by an antenna 60 and received by an antenna array 70 of a communication partner. The formulas expressing the received power P _r1 at the antenna 72 and the received power P _r2 at the antenna 74 are shown below. 5A and 5B are schematic diagrams illustrating an example of graph data 540 showing the relationship between the receiving antenna interval and the correlation coefficient of the phase difference. An example of the functional configuration of a data processing device 800 and a manufacturing device 900 is shown in schematic form. An example of the flow of a manufacturing process of the antenna array 70 by the manufacturing apparatus 900 is shown generally below. An example of a hardware configuration of a computer 1200 functioning as the communication device 100, the communication device 200, the data processing device 800, or the manufacturing device 900 is shown in schematic form.

In direct vehicle-to-vehicle communication, although the main propagation scenario is short-distance line-of-sight communication between the transmitting and receiving antennas, the radio wave strength varies drastically depending on the distance between the transmitting and receiving antennas due to the influence of road surface reflection interference and lateral reflection interference from soundproof side walls. In use cases requiring high reliability and low latency, such as applications to automatic driving technology including BRT (Bus Rapid Transit) and electronically coupled trucks, antenna space diversity using multiple transmitting or receiving antennas is positioned as a very effective technology from the perspective of realizing stable communication. However, the optimal antenna distance in antenna space diversity depends on the antenna height, the distance of the reflector relative to the line-of-sight path, and the distance between the antennas. In conventional antenna space diversity configurations designed (quasi-optimized) under the assumption that the distance between the transmitting and receiving antennas is sufficiently long relative to the antenna height and the distance of the reflector relative to the line-of-sight path, the effect of applying antenna space diversity in conditions where this assumption does not hold is not necessarily obtained. The communication system according to this embodiment includes multiple communication devices 100, and for example, uses orthogonal polarized antennas for transmission and reception, and in addition to space diversity using multiple orthogonal polarized antennas for transmission or reception, it also uses orthogonal polarized transmission and reception (polarized MIMO diversity transmission and reception) for transmission and reception, and closed-loop precoding control based on feedback from the receiver side.

The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

FIGS. 1 and 2 show an example of a vehicle 10 equipped with a communication device 100 according to this embodiment. The vehicle 10 may be an example of a moving body. The vehicle 10 may be an automobile.

Figure 1 shows a schematic view of the front of the vehicle 10, and Figure 2 shows a schematic view of the rear of the vehicle 10. An orthogonally polarized antenna 112 is disposed on the front of the vehicle 10. An antenna array 120 consisting of multiple orthogonally polarized antennas is disposed on the rear of the vehicle 10.

The communication device 100 includes an orthogonally polarized antenna 112. The communication device 100 may use the orthogonally polarized antenna 112 for transmission. Although FIG. 1 illustrates a case in which the communication device 100 includes one orthogonally polarized antenna 112, this is not limiting, and the communication device 100 may include multiple orthogonally polarized antennas 112. Furthermore, each orthogonally polarized antenna 122 may be configured using multiple single-polarized antennas that are orthogonal to each other.

The communication device 100 includes an antenna array 120. The communication device 100 may use the antenna array 120 for reception. In FIG. 2, the antenna array 120 is illustrated as being composed of two orthogonally polarized antennas 122, but this is not limiting, and the antenna array 120 may be composed of three or more orthogonally polarized antennas 122. Furthermore, each orthogonally polarized antenna 122 may be composed of multiple single-polarized antennas that are orthogonal to each other.

The communication device 100 uses the orthogonally polarized antenna 112 and the antenna array 120 to communicate with a communication device 100 (sometimes referred to as a communication partner) mounted on another vehicle 10 different from the vehicle 10 (sometimes referred to as the own vehicle) on which the communication device 100 is mounted. For example, the communication device 100 uses the orthogonally polarized antenna 112 and the antenna array 120 to communicate with the communication device 100 of the other vehicle 10 traveling in front of the own vehicle and the communication device 100 of the other vehicle 10 traveling behind the own vehicle.

The multiple orthogonally polarized antennas 122 are arranged at a spatial distance in at least one of the vertical and horizontal directions. Figure 2 illustrates an example in which the antenna array 120 has two orthogonally polarized antennas 122, and the two orthogonally polarized antennas 122 are arranged at a spatial distance in the vertical and horizontal directions.

By arranging multiple orthogonally polarized antennas 122 at spatial intervals in the vertical direction, it is possible to suppress interference caused by reflectors present in the vertical direction. For example, when a communication device 100 communicates with a communication device 100 (sometimes referred to as a communication partner) mounted on another vehicle 10 traveling behind the vehicle, it is possible to suppress road surface reflection interference by arranging multiple orthogonally polarized antennas 122 at spatial intervals in the vertical direction. This is achieved by utilizing the property that the direct waves from the communication partner and the locations where radio waves are weakened due to road surface reflection interference differ depending on the antenna height. Such an antenna diversity wireless communication technology that arranges multiple antennas at spatial intervals in the vertical direction is sometimes referred to as vertical antenna space diversity.

By arranging multiple orthogonally polarized antennas 122 at spatial intervals in the horizontal direction, interference from reflectors existing in the horizontal direction can be suppressed. For example, when a communication device 100 communicates with a communication device 100 mounted on another vehicle 10 traveling behind the vehicle, by arranging multiple orthogonally polarized antennas 122 at spatial intervals in the vertical direction, reflection interference from side reflectors such as soundproof walls can be suppressed. This is achieved by utilizing the property that the direct wave from the communication partner and the location where the radio wave is weakened due to side reflection interference differ depending on the distance from the side reflector. Such an antenna diversity wireless communication technology that arranges multiple antennas at spatial intervals in the horizontal direction is sometimes referred to as horizontal antenna space diversity.

As mentioned above, vertical antenna space diversity is likely to be effective in countering road surface reflection interference, while horizontal antenna space diversity is likely to be effective in countering side reflection interference. By changing not only the horizontal position but also the vertical position, i.e. by arranging the antennas at a spatial distance in an oblique direction, it is expected that the vertical antenna space diversity effect and the horizontal antenna space diversity effect can be obtained simultaneously. This makes it easier to efficiently obtain the antenna diversity effect with a smaller number of antennas in an environment where antenna road surface reflection and side reflection interference exist simultaneously.

Furthermore, according to Non-Patent Document 2, it is theoretically known that the optimal antenna spacing in antenna space diversity for vehicle-to-vehicle direct communication under road surface reflected wave interference depends on the vehicle-to-vehicle distance and antenna height. Also, based on the same theory, it is considered that the optimal antenna spacing in antenna space diversity for vehicle-to-vehicle direct communication in an environment where side reflector interference exists also depends on the antenna height and the distance from the side reflector. However, the optimal antenna spacing converges as the vehicle distance increases. Therefore, by utilizing this property, it is possible to optimize the antenna arrangement by assuming that the antenna height and the distance from the side reflector for the line-of-sight path between the transmitting and receiving antennas are sufficiently wide compared to the vehicle distance. However, when antennas are arranged in this way using a single polarization, it is easy to obtain a sufficient space diversity effect when the vehicle distance is wide, but it may be difficult to obtain the space diversity effect when the vehicle distance is short.

Therefore, in the communication device 100 according to this embodiment, antenna polarization diversity, which simultaneously uses two orthogonal polarized waves, vertical and horizontal, is used in combination with antenna space diversity.

Figure 3 is an explanatory diagram for explaining the reflected interference components due to road surface reflection. Graph 300 shows an example of the relationship between the angle of incidence to the road surface 30 between the antenna 42 of the rear vehicle 40 on the transmitting side and the antenna 52 of the front vehicle 50 on the receiving side, and the reflection coefficient, for both horizontally polarized waves 302 and vertically polarized waves 304.

Graph 300 was calculated based on electromagnetic field theory at a frequency of 29 GHz. Regarding the medium constant that affects the reflection coefficient of radio waves on the road surface, the relative permeability is fixed at 1. However, taking into consideration that the conductivity changes depending on the condition of the road surface, calculations were performed by changing the conductivity of the road surface to 0.001, 0.01, and 0.1, but there was no significant difference between these values.

As can be seen from Figure 3, there is an incidence angle range where the reflection coefficient of vertical polarization is smaller than that of horizontal polarization, so the signal strength of the reflection interference component due to road surface reflection in vehicle-to-vehicle direct communication is smaller for vertical polarization than for horizontal polarization. According to the inter-vehicle distance between the rear vehicle 40 and the front vehicle 50 in a typical driving environment, the incidence angle is expected to be in the range of approximately 60 degrees to 90 degrees, and the difference in road surface reflection interference between vertically polarized waves and horizontally polarized waves is particularly large in this incidence angle range.

From the above, it can be said that the use of vertical polarization is advantageous in vehicle-to-vehicle direct communication from the viewpoint of suppressing road surface reflection interference as the polarization plane of the radio waves used in vehicle-to-vehicle direct communication.

Figure 4 is an explanatory diagram for explaining the reflected interference components due to side reflection. Graph 310 shows an example of the relationship between the angle of incidence on the side reflector 32 and the reflection coefficient between the antenna 42 of the rear vehicle 40 on the transmitting side and the antenna 52 of the front vehicle 50 on the receiving side, for horizontally polarized waves 312 and vertically polarized waves 314. Graph 310, like graph 300, is calculated based on electromagnetic field theory. Note that, regarding the medium constants that affect the reflection coefficient of radio waves at the roadside reflector, the relative permeability is fixed at 1 assuming a non-magnetic material, but assuming that the conductivity changes depending on the material, etc., the conductivity was changed to 0.001, 0.01, and 0.1 for calculation, but there was no significant difference between these values.

As shown in Figure 4, there is an incidence angle range where the reflection coefficient of horizontal polarization is smaller than that of vertical polarization, so the intensity of the reflected interference component due to lateral reflection in vehicle-to-vehicle direct communication is smaller for horizontal polarization than for vertical polarization. According to the inter-vehicle distance between the rear vehicle 40 and the front vehicle 50 in a typical driving environment, the incidence angle is expected to be in the range of approximately 60 degrees to 90 degrees, and the difference in road surface reflection interference between vertically polarized waves and horizontally polarized waves is particularly large in this incidence angle range.

From the above, it can be said that using horizontal polarization is advantageous in terms of suppressing side reflection interference as the polarization plane of radio waves used in vehicle-to-vehicle direct communication.

As described above, the radio wave propagation characteristics of vehicle-to-vehicle direct communication where the transmitting and receiving antennas are within line of sight are such that the influence of road surface reflection interference is smaller for vertically polarized waves than for horizontally polarized waves, and the influence of side reflection interference tends to be smaller for horizontally polarized waves than for vertically polarized waves. The communication device 100 according to this embodiment takes advantage of this property and uses antenna polarization diversity, which simultaneously uses vertically and horizontally orthogonal polarized waves, in combination with antenna space diversity. This can contribute to improving communication quality in vehicle-to-vehicle direct communication.

In addition, for example, the propagation path conditions grasped by the receiving communication device 100 may be fed back to the transmitting communication device 100, and the transmitting communication device 100 may perform multi-layer transmission using orthogonal polarization and closed-loop controlled precoding based on the propagation path conditions for that purpose. For example, under propagation conditions in which the effect of space diversity is difficult to obtain, a diversity effect is obtained by polarization diversity, and under propagation conditions in which the effect of space diversity is obtainable, a throughput increase effect per bandwidth is obtained by spatial multiplexing through polarization MIMO multiplexing transmission. This can contribute to further improvement of communication quality in vehicle-to-vehicle direct communication.

Figure 5 shows an example of a schematic diagram of a functional configuration related to transmission in the transmitting communication device 100 and a functional configuration related to reception in the receiving communication device 200. For ease of explanation, the transmitting function of the communication device 100 and the receiving function of the communication device 200 are shown, but each of the communication device 100 and the communication device 200 may have both the transmitting function and the receiving function shown in Figure 5. The notation of part F is omitted.

The communication device 100 is mounted on the vehicle 10. The communication device 100 includes a transmitter baseband unit 150 that controls communication using an orthogonally polarized antenna 112. The communication device 100 may include at least an FB receiver 152 for receiving FB (Feedback) information from the communication device 200. Note that a typical configuration is to provide a transmission RF (Radio Frequency) unit between the transmitter baseband unit 150 and the orthogonally polarized antenna 112, but this is omitted from FIG. 5.

The communication device 200 is mounted on the vehicle 20. The communication device 200 includes a receiver baseband unit 250 that controls communication using multiple orthogonally polarized antennas 222. In the example shown in FIG. 5, the communication device 200 includes two orthogonally polarized antennas 222. The two orthogonally polarized antennas 222 may be arranged spatially separated in at least one of the vertical and horizontal directions. In this example, the two orthogonally polarized antennas 222 are arranged spatially separated in the vertical and horizontal directions. The communication device 200 may include a propagation path estimation unit 252 and an FB information transmission unit 254. Note that a receiving RF unit is generally provided between the receiver baseband unit 250 and the orthogonally polarized antennas 222, but is not shown in FIG. 5.

In this example, the vehicle 10 may be an example of a first moving body. The communication device 100 may be an example of a first communication device. The orthogonally polarized antenna 112 may be an example of a first orthogonally polarized antenna. The vehicle 20 may be an example of a second moving body. The communication device 200 may be an example of a second communication device. The orthogonally polarized antenna 222 may be an example of a second orthogonally polarized antenna.

The transmitter baseband unit 150 is configured to implement polarization diversity without implementing polarization MIMO multiplexing transmission under propagation conditions in which the effect of space diversity achieved by the arrangement of the two orthogonally polarized antennas 222 is difficult to obtain, and to implement polarization diversity under propagation conditions in which the effect can be obtained.

The transmitter baseband unit 150 performs polarized MIMO transmission and controls it using the orthogonally polarized antenna 112 based on the propagation path conditions between the communication device 100 and the communication device 200. When the propagation path conditions between the communication device 100 and the communication device 200 satisfy the propagation conditions that can obtain the effect of space diversity by arranging the two orthogonally polarized antennas 222, the transmitter baseband unit 150 may control the orthogonally polarized antenna 112 to perform polarized MIMO multiplex transmission. In other words, the transmitter baseband unit 150 may control the orthogonally polarized antenna 112 to transmit different data using each of the vertically polarized antenna and the horizontally polarized antenna included in the orthogonally polarized antenna 112.

When the propagation path conditions between the communication device 100 and the communication device 200 do not satisfy the propagation conditions that can obtain the effect of space diversity by arranging the two orthogonally polarized antennas 222, the transmitter baseband unit 150 may control the orthogonally polarized antenna 112 to implement polarization diversity. In other words, the transmitter baseband unit 150 may control the orthogonally polarized antenna 112 to transmit the same data using each of the vertically polarized antenna and the horizontally polarized antenna included in the orthogonally polarized antenna 112.

As a result, when antenna space diversity alone is insufficient, it can be complemented with polarization diversity, and when antenna space diversity alone is sufficient, spatial multiplexing can be used to increase throughput per bandwidth, making a significant contribution to improving communication quality.

When the communication device 100 and the communication device 200 use TDD (Time Division Duplex), the transmitter baseband unit 150 may estimate the propagation path conditions from the communication device 100 to the communication device 200 by the FB receiver 152 receiver by utilizing the reciprocity of the propagation path. Then, the transmitter baseband unit 150 may perform closed-loop control type precoding based on the estimated propagation path conditions, thereby appropriately switching between polarization diversity and polarization MIMO multiplexing transmission.

When the communication device 100 and the communication device 200 use FDD (Frequency Division Duplex), the transmitter baseband unit 150 may receive feedback information based on the propagation path conditions estimated by the communication device 200 from the communication device 200. For example, the propagation path estimation unit 252 estimates the propagation path conditions between the communication device 100 and the communication device 200, the FB information transmission unit 254 transmits feedback information based on the propagation path conditions estimated by the propagation path estimation unit 252 to the communication device 100, and the FB receiver 152 receives the feedback information. The transmitter baseband unit 150 performs either polarization diversity or polarization MIMO multiplexing transmission depending on the FB information received by the FB receiver 152.

Figure 6 shows an example of the configuration of the orthogonal polarized antenna 112 and the transmitter baseband unit 150 of the communication device 100. Figure 7 shows an example of the configuration of the orthogonal polarized antenna 222 and the receiver baseband unit 250 of the communication device 200. Figures 6 and 7 show an example of the configuration assuming that a frequency band of quasi-millimeter wave band or higher is used as the carrier frequency band. However, in Figures 6 and 7, some of the components provided in a general wireless transmitter and receiver, such as filters provided for the purpose of suppressing out-of-band unwanted wave emission and suppressing out-of-band interference, are omitted. Here, the communication device 100 is mainly described as having one orthogonal polarized antenna 112, but as shown by the dashed line in Figure 6, the communication device 100 may have multiple orthogonal polarized antennas 112. Here, the communication device 100 and the communication device 200 are described as using FDD as an example.

The transmitter baseband unit 150 may include a channel coding unit 1501, an interleaver unit 1502, a rate matching unit 1503, a scrambling unit 1504, a symbol modulation unit 1505, a layer mapper unit 1506, a precoder unit 1507, a secondary modulation unit 1508, a pilot signal multiplexing unit 1509, a DAC (Digital Analog Converter) unit 1510, an UpConverter unit 1511, a desired signal reception level estimator 1512, a pilot signal sequence selector 1513, a pilot signal generator 1514, and a precoding control unit 1515.

The channel coding unit 1501 performs forward error correction coding on the information bit sequence after error detection bits are added using CRC (Cyclic Redundancy Check) coding or the like, using error correction coding such as convolutional coding, turbo coding, LDPC (Low Density Parity Check Code) coding, polar coding, etc., to reduce transmission errors caused by factors that deteriorate the desired signal on the channel, such as radio interference and receiver thermal noise, through decoding processing on the receiving side. The interleaver unit 1502 randomizes burst errors by interleaving the order of the error correction coded transmission data sequence, thereby improving the error correction capability of the channel coding.

The rate matching unit 1503 appropriately adjusts the coding rate of the coded transmission bit sequence according to the selected primary modulation method by bit repetition or bit puncturing according to the state information CSI (Channel State Information) of the wireless propagation path in order to perform wireless transmission with high frequency utilization efficiency. The scrambling unit 1504 performs exclusive OR processing with a pseudo noise sequence on the transmission bit sequence after rate matching in order to randomize the same channel interference from surrounding base stations and terminals on the receiver side. The symbol modulation unit 1505 performs appropriate symbol modulation from among predefined symbol modulation method candidates such as QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM so that efficient wireless transmission can be performed by CSI.

The layer mapper unit 1506 and the precoder unit 1507 perform the necessary processing to transmit the symbol-modulated transmission data sequence using different polarizations and multiple antennas based on instructions from the precoding control unit 1515. The number of signal outputs in the precoder unit 1507 is the same as the number of antennas used for simultaneous transmission.

The secondary modulation unit 1508 is used when performing processing for multi-carrier transmission such as OFDM (Orthogonal Frequency Division Multiplex) on each transmission symbol sequence after precoding. The pilot signal multiplexing unit 1509 multiplexes a signal for propagation path estimation required for demodulation on the receiving side onto the transmission signal. In FIG. 6, the pilot signal is multiplexed onto the transmission symbol after secondary modulation, but it may also be multiplexed onto the transmission symbol before secondary modulation.

The DAC unit 1510 converts the baseband digital transmission signal into an analog signal, and the UpConverter unit 1511 converts the baseband analog transmission signal into an intermediate frequency band or radio frequency band, or converts the intermediate frequency band analog transmission signal into a radio frequency band signal.

When using multiple high frequency antenna modules and spatial diversity based on a selection diversity method, the transmitter baseband section 150 may include a high frequency antenna module selection controller 1516 and a selector 1517, as illustrated in FIG. 6.

The radio frequency antenna module selection controller 1516 selects the antenna module that is determined to have the best radio propagation path based on the CSI information fed back from the FB receiver 152, and instructs the selector 1517 on the radio frequency antenna module to be used. Based on the instruction from the radio frequency antenna module selection controller 1516, the selector 1517 sends a transmission signal to the radio frequency antenna module to be used for transmission. Each radio frequency antenna module has an upconverter section and an antenna corresponding to a plurality of mutually orthogonal polarizations, for example, vertical polarization and horizontal polarization, and the transmission signal in the baseband band or intermediate frequency band corresponding to each polarization is upconverted to a radio frequency signal in the carrier frequency band, and the transmission signal is output from each antenna. In the example shown in FIG. 6, the transmission RF section & antenna section includes a vertical polarization antenna 113, a horizontal polarization antenna 114, a transmission RF section 115, and an upconverter section 116.

The receiver baseband unit 250 includes a downconverter unit 2501, an ADC (Analog Digital Converter) unit 2502, a selector or combiner or separator unit 2503, a postcoder and layer demapper unit 2504, a log-likelihood ratio generator unit 2505 for each transmitted bit, a descrambler unit 2506, a derate matcher unit 2507, a deinterleaver unit 2508, a communication path decoder unit 2509, a propagation path estimator unit 252, and an FB information transmitter unit 254.

In the example shown in FIG. 7, the receiving RF section and antenna section includes a vertically polarized antenna 223, a horizontally polarized antenna 224, an LNA (Low Noise Amplifier) 225, a Down Converter section 226, and an IF AMP section (Intermediate Frequency Amplifier) 227. The LNA 225 is used as a low noise amplifier that amplifies the signals input from the vertically polarized antenna 223 and the horizontally polarized antenna 224. The signal amplified by the LNA 225 is down-converted to an intermediate frequency band signal by the Down Converter section 226, and amplified by the IF AMP section 227.

The downconverter unit 2501 downconverts the signal from the receiving RF unit and antenna unit to the baseband. The ADC unit 2502 converts the analog signal input from the downconverter unit 2501 into a digital signal.

The propagation path estimation unit 252 estimates the amplitude and phase of the propagation path and the interference noise level required for demodulation processing from the reception results of the pilot signal. The selector, combiner, or separator 2503 performs antenna selection processing when diversity is performed based on a selective diversity reception method, reception diversity processing based on EGC (Equal Gain Combining) or MRC (Maximum Ratio Combining), and multiple signal separation processing in MIMO spatial multiplexing.

The postcoder and layer demapper unit 2504 performs the inverse process of the process performed by the precoder unit 1507 and layer mapper unit 1506 on the transmitter baseband unit 150 side, and performs symbol demodulation based on the amplitude and phase information of the propagation path obtained by the propagation path estimation unit 252. The log likelihood ratio generation unit 2505 for each transmitted bit calculates a log likelihood ratio equivalent to a soft decision value (soft bit value) for each transmitted bit based on the received signal after symbol demodulation and information on the estimated interference noise level.

The descrambler unit 2506 performs the reverse process of the process performed by the scrambling unit 1504 on the transmitter baseband unit 150 side, thereby descrambling the received signal bit sequence and randomizing co-channel interference from surrounding base stations and terminals. The derate matcher unit 2507 inserts 0 as a dummy value of the log-likelihood ratio for each bit punctured by the rate matching unit 1503 on the transmitter baseband unit 150 side, i.e., it assumes that the probability of each punctured bit being 0 is equal to the probability of each bit being 1, and performs a process equivalent to maximum ratio combining for the repeatedly transmitted bits by adding (combining) the log-likelihood ratios.

By these processes, the coding rate of the received sequence is returned to the coding rate in the channel coding unit 1501 in the transmitter baseband unit 150, i.e., the sequence with the original coding rate. The deinterleaver unit 2508 performs the reverse process of the interleaver unit 1502 in the transmitter baseband unit 150, thereby returning the bit order to the original order of the coded sequence and randomizing burst errors. The channel decoding unit 2509 processes the soft bit sequence (log-likelihood ratio information) output from the deinterleaver unit 2508, thereby performing error correction decoding processing and estimating the transmitted information bit sequence. If no bit errors are detected by processing such as CRC decoding, it is determined that the transmitted bits can be correctly estimated. If a bit error is detected, a retransmission may be requested from the transmitting side.

During polarization diversity transmission, the layer mapper unit 1506 and the precoder unit 1507 may perform controls such as transmit antenna selection, beamforming, and inter-polarized transmission power control. During polarization MIMO multiplexing transmission, the layer mapper unit 1506 and the precoder unit 1507 may perform controls such as parallel transmission, multi-orthogonal beam transmission, and per-layer transmission power control.

The propagation path estimation unit 252 may, for example, use an RS (Reference Signal) transmitted by the vertically polarized antenna 113 and the horizontally polarized antenna 114 of the orthogonal polarized antenna 112 to predict and evaluate the transmission capacity for each candidate transmission and reception method from the MIMO Channel Matrix that can be grasped, and estimate a PMI (Precoding Matrix Indicator) and RI (Rank Indicator) that correspond to a candidate for index information corresponding to an optimal precoding matrix (transmitting antenna weight matrix) and the number of spatial multiplexing layers that maximizes the predicted throughput after precoding. The FB information transmission unit 254 may transmit FB information including the estimation results of the appropriate PMI and RI to the communication device 100.

As long as polarization MIMO multiplexing and polarization diversity are included, the allocation of RI and PMI may be set arbitrarily. For example, RI=1 may be polarization diversity transmission, and RI=2 may be polarization MIMO multiplexing.

For example, as the PMI when RI = 1, PMI = 0 is a precoding matrix corresponding to [1; 0] and uses vertical polarization, PMI = 1 is a precoding matrix corresponding to [0; 1] and uses horizontal polarization, PMI = 2 is a precoding matrix corresponding to [1; 1] and uses vertical polarization and horizontal polarization in phase to assign the same data, and PMI = 3 is a precoding matrix corresponding to [1; -1] and uses vertical polarization and horizontal polarization with the horizontal polarization in opposite phase to assign the same data. For example, as the PMI when RI = 2, PMI = 0 is a precoding matrix corresponding to [1 1; 1 -1] and PMI = 1 is a precoding matrix corresponding to [1 j; 1 -j]. These are just examples, and various combinations can be set.

Note that when communication device 100 and communication device 200 use TDD and use the reversibility of the propagation paths in the transmission and reception directions to directly obtain CSI on the transmitter side without using FB from the receiver side, the parameters (amplitude, phase) corresponding to the precoding matrix PMI can be continuously specified, making it possible to achieve more fine-grained adjustments.

Figure 8 shows a schematic diagram of another example of the configuration of the orthogonally polarized antenna 112 and the transmitter baseband section 150 of the communication device 100. Figure 9 shows a schematic diagram of another example of the configuration of the orthogonally polarized antenna 222 and the receiver baseband section 250 of the communication device 200. Figures 8 and 9 show example configurations assuming the use of a low SHF (Super High Frequency) band as the carrier frequency band. Here, differences from Figures 6 and 7 will be mainly described.

The transmitter baseband unit 150 may include a channel coding unit 1501, an interleaver unit 1502, a rate matching unit 1503, a scrambling unit 1504, a symbol modulation unit 1505, a layer mapper unit 1506, a precoder unit 1507, a secondary modulation unit 1508, a pilot signal multiplexing unit 1509, a DAC unit 1510, an upconverter unit 1511, a desired signal reception level estimator 1512, a pilot signal sequence selector 1513, a pilot signal generator 1514, and a precoding control unit 1515. In the example shown in FIG. 8, the upconverter unit 1511 changes the analog transmission signal in the baseband to a signal in the RF band.

When using multiple high frequency antenna modules and spatial diversity based on a selection diversity method, the transmitter baseband section 150 may include a transmit RF section selection controller 1520, as illustrated in FIG. 8.

The transmission RF section selection controller 1520 is provided for at least the number of antenna ports used for simultaneous transmission, selects an antenna module whose wireless propagation path is determined to be good based on CSI information fed back from the FB receiver 152, and instructs the selector 1521 on the high frequency antenna module to be used. Based on the instruction from the transmission RF section selection controller 1520, the selector 1521 sends the transmission signal received from the upconverter section 1511 via the transmission RF section 115 to the high frequency antenna module to be used for transmission. Then, the transmission signal is output from each antenna. When using a frequency band below the low SHF band, the effect of cable loss between the transmission RF section and the antenna is relatively small, so RF band transmission may be used as shown in FIG. 8.

The receiver baseband unit 250 includes an LNA 2510, a downconverter unit 2501, an ADC unit 2502, a selector or combiner or separator 2503, a postcoder and layer demapper unit 2504, a log-likelihood ratio generator for each transmitted bit 2505, a descrambler unit 2506, a derate matcher unit 2507, a deinterleaver unit 2508, a channel decoder unit 2509, a propagation channel estimation unit 252, and an FB information transmitter unit 254. In the example shown in FIG. 9, the downconverter unit 2501 downconverts a signal from the orthogonal polarization antenna 222 to the RF band.

When using a frequency band below the low SHF band, the effect of cable loss between the antenna and the receiver baseband unit 250 is relatively small, so RF band transmission may be used, as illustrated in FIG. 9. As shown by the dashed line in FIG. 9, the LNA 225 may be placed directly below the orthogonally polarized antenna 222 to improve the receiving SNR. When the LNA 225 is placed directly below the orthogonally polarized antenna 222, the LNA 2510 does not need to be used.

Figure 10 is an explanatory diagram for explaining the fluctuation of the reception level in the antenna height direction and horizontal position direction of the antenna array 120 (sometimes referred to as the receiving antenna). Figure 11 shows a schematic example of the level fluctuation due to the horizontal position of the receiving antenna when the receiving antenna height is fixed. Figure 12 shows a schematic example of the level fluctuation due to the receiving antenna height when the receiving antenna horizontal position is fixed.

The receiving antenna receives radio waves transmitted by an orthogonally polarized antenna 112 (sometimes referred to as a transmitting antenna) of another vehicle 10 traveling behind the vehicle. The radio waves received by the receiving antenna may be subject to interference from road surface reflected waves and side reflected waves. The antenna height is the distance between the receiving antenna and the ground. The antenna horizontal position is the distance between the receiving antenna and a side reflector. The antenna horizontal position may be an example of the antenna lateral position.

Figure 11 shows the level fluctuations depending on the horizontal position of the receiving antenna when the receiving antenna height is fixed for each inter-vehicle distance between the vehicle itself and another communication partner vehicle 10. Level fluctuation 412 shows the case where the inter-vehicle distance is 10 m, level fluctuation 414 shows the case where the inter-vehicle distance is 35 m, level fluctuation 416 shows the case where the inter-vehicle distance is 70 m, and level fluctuation 418 shows the case where the inter-vehicle distance is 100 m. As shown in Figure 11, the longer the inter-vehicle distance, the larger the period of the fluctuations.

Figure 12 shows the level fluctuations depending on the receiving antenna height when the receiving antenna is fixed in the horizontal position for each inter-vehicle distance between the vehicle itself and another communication partner vehicle 10. Level fluctuation 422 shows the case where the inter-vehicle distance is 10 m, level fluctuation 424 shows the case where the inter-vehicle distance is 35 m, level fluctuation 426 shows the case where the inter-vehicle distance is 70 m, and level fluctuation 428 shows the case where the inter-vehicle distance is 100 m. As shown in Figure 12, the longer the inter-vehicle distance, the larger the period of the fluctuations.

Fig. 13 shows an example of the period _Lw of the level fluctuation depending on the horizontal position of the receiving antenna when the receiving antenna height is fixed. As shown in Fig. 13, the longer the inter-vehicle distance, the longer the period _Lw . Also, the closer to the side reflector, the longer the period _Lw .

Fig. 14 shows an example of the period _Lh of the level fluctuation due to the receiving antenna height when the receiving antenna is fixed in the horizontal position. As shown in Fig. 14, the longer the inter-vehicle distance, the longer the period _Lh . Also, the lower the transmitting antenna height, the longer the period _Lh .

The period of the level fluctuation depends on the transmitting antenna height, the horizontal position of the transmitting antenna, and the vehicle distance. The characteristics shown in Fig. 13 and Fig. 14 can be determined by actual measurements in an experiment. For example, the respective characteristics can be determined by performing actual measurements for each frequency used, each vehicle distance, each antenna height, and each horizontal position. The characteristics shown in Fig. 13 and Fig. 14 can also be determined by a formula. For example, the period _Lw can be determined by the following formula 1, and the period _Lh can be determined by the following formula 2.

w _TX indicates the distance between the transmitting antenna and the side reflector, and h _TX indicates the transmitting antenna height. Since the level has periodicity with respect to the antenna position, the diversity effect cannot be obtained by simply increasing the antenna spacing. In this embodiment, by arranging multiple antennas at an odd multiple of a half cycle of the fluctuation cycle L, that is, at intervals of (2n+1)L/2, it is possible to prevent multiple antennas from becoming null points at the same time. And, by arranging multiple antennas at intervals of (2n+1)L/2, a diversity effect can be obtained.

FIG. 14 is a schematic diagram showing an example of the configuration of the antenna array 120. In the example shown in FIG. 15, the antenna array 120 includes two orthogonally polarized antennas 122. The two orthogonally polarized antennas 122 are arranged to be shifted in the horizontal direction by a distance that is an odd multiple of a half period of the period L _w1 of the level fluctuation due to the horizontal position of the antenna at the vehicle distance d _1. The horizontal direction may be an example of the lateral direction. As a result, even if the level of one of the two orthogonally polarized antennas 122 becomes a null point, the level of the other orthogonally polarized antenna 122 is arranged to be high, so that the possibility of them becoming null points at the same time can be reduced.

15 illustrates an example in which antenna array 120 includes two orthogonally polarized antennas 122, but antenna array 120 may include three or more orthogonally polarized antennas 122. Three or more orthogonally polarized antennas 122 may be arranged shifted in the horizontal direction by a distance that is an odd multiple of a half period of the period _Lw1 of the level fluctuation due to the horizontal position of the antenna at inter-vehicle distance _d1 .

The distance between the multiple orthogonally polarized antennas 122 may be adjustable by physical tuning, etc. The distance between the multiple orthogonally polarized antennas 122 may be adjustable by electronic tuning, etc.

The inter-vehicle distance d ₁ may be a distance that is determined in advance as a distance between the vehicle and the communication partner vehicle 10. For example, the inter-vehicle distance d ₁ may be an average inter-vehicle distance among a large number of vehicles. Also, for example, the inter-vehicle distance d ₁ may be a distance that is set by the manufacturer of the communication device 100 or the manufacturer of the vehicle 10 in which the communication device 100 is mounted. The inter-vehicle distance d ₁ may be a distance that is determined in advance as a maximum distance between the vehicle and the communication partner vehicle 10. For example, when the guaranteed communication distance of wireless communication using the orthogonally polarized antenna 112 and the antenna array 120 by the communication device 100 is 100 m, the inter-vehicle distance d ₁ may be 100 m.

The multiple orthogonally polarized antennas 122 may be arranged to be shifted in the horizontal direction and in the height direction. The height direction may be, for example, the vertical direction. For example, the multiple orthogonally polarized antennas 122 may be arranged to be shifted in the horizontal direction by a distance that is an odd multiple of a half period of the period _Lw1 of the level fluctuation due to the horizontal position of the _antenna at the vehicle distance d1, and to be shifted in the height direction by a distance that is an odd multiple of a half period of the period _Lh1 of the level fluctuation due to the antenna height at the vehicle distance _d1 .

The antenna array 120 may include multiple antenna sets. For example, the antenna array 120 includes a first antenna set and a second antenna set.

In the first antenna set, the multiple orthogonally polarized antennas 122 may be arranged with a horizontal offset by a distance that is an odd multiple of half the period _Lw1 of the level fluctuation due to the horizontal position of the antenna at a vehicle distance _d1 , and in the second antenna set, the multiple orthogonally polarized antennas 122 may be arranged with _a horizontal offset by a distance that is an odd multiple of half the period _Lw2 of the level fluctuation due to the horizontal position of the antenna at a vehicle distance d2.

The period of the level fluctuation depends on the vehicle distance, so there are vehicle distances that cannot be handled by only one antenna set. In contrast, by having the antenna array 120 have multiple antenna sets, the range of vehicle distances that can be handled can be increased.

The multiple orthogonal polarized antennas 122 of the first antenna set and the multiple orthogonal polarized antennas 122 of the second antenna set may be arranged to be shifted in the horizontal direction and in the vertical direction. For example, the multiple orthogonal polarized antennas 122 of the first antenna set may be arranged to be shifted in the horizontal direction by a distance that is an odd multiple of a half period of the period _Lw1 of the level fluctuation due to the horizontal position of the antenna at the vehicle distance _d1 , and to be shifted in the vertical direction by a distance that is an odd multiple of a half period of the period _Lh1 of the level fluctuation due to the antenna height at the vehicle distance _d1 . Also, the multiple orthogonal polarized antennas 122 of the second antenna set may be arranged to be shifted in the horizontal direction by a distance that is an odd multiple of a half period of the period _Lw2 of the level fluctuation due to the horizontal position of the antenna at the vehicle distance d2, and to be shifted in the horizontal direction by a distance that is an odd multiple of a half period of the period _Lh2 of the level fluctuation due to the antenna height at _the vehicle distance _d2 .

Fig. 16 shows a schematic diagram of an example of the configuration of the antenna array 120. In the example shown in Fig. 16, the antenna array 120 includes two orthogonally polarized antennas 122. The two orthogonally polarized antennas 122 are arranged to be shifted in the height direction by a distance that is an odd multiple of a half period of the period L _h1 of the level fluctuation due to the antenna height at the inter-vehicle distance d _1. As a result, even if the level of one of the two orthogonally polarized antennas 122 becomes a null point, the other orthogonally polarized antenna 122 is arranged to have a high level, so that the possibility of them becoming null points at the same time can be reduced.

16 illustrates an example in which antenna array 120 includes two orthogonally polarized antennas 122, but antenna array 120 may include three or more orthogonally polarized antennas 122. Three or more orthogonally polarized antennas 122 may be arranged shifted in the height direction by a distance that is an odd multiple of a half period of the period L _h1 of the level fluctuation due to the antenna height at inter-vehicle distance d ₁ .

The distance between the multiple orthogonally polarized antennas 122 may be adjustable by physical tuning, etc. The distance between the multiple orthogonally polarized antennas 122 may be adjustable by electronic tuning, etc.

The antenna array 120 may include a plurality of antenna sets. The antenna array 120 may include, for example, a first antenna set and a second antenna set. The plurality of orthogonally polarized antennas 122 of the first antenna set may be arranged to be shifted in the height direction by a distance that is an odd multiple of a half period of a period L _h1 of level fluctuations due to antenna height at a vehicle distance d ₁ , and the plurality of orthogonally polarized antennas 122 of the second antenna set are arranged to be shifted in the height direction by a distance that is an odd multiple of a half period of a period L _h2 of level fluctuations due to antenna height at a vehicle distance d ₂ .

The period of the level fluctuation depends on the vehicle distance, so there are vehicle distances that cannot be handled by only one antenna set. In contrast, by having the antenna array 120 have multiple antenna sets, the range of vehicle distances that can be handled can be increased.

Figure 17 is an explanatory diagram for explaining radio waves transmitted by antenna 60 and received by antenna array 70 of the communication partner. In the example shown in Figure 17, antenna array 70 includes antenna 72 and antenna 74. Antenna 60 may be an orthogonally polarized antenna 112. Antenna array 70 may be antenna array 120. Each of antenna 72 and antenna 74 may be an orthogonally polarized antenna 122.

The transmitting antenna height ht indicates the antenna height, which is the distance between the antenna 60 and the road surface 30. The receiving antenna height hra indicates the receiving antenna height, which is the distance between the antenna 72 and the road surface 30. The receiving antenna spacing Δhr indicates the spacing between the antenna 72 and the antenna 74. The vehicle distance corresponds to the distance between the antenna 60 and the antennas 72 and 74.

Figure 18 shows an example of graph data 500 that shows the minimum level value when the vehicle distance changes for each receiving antenna height. Figure 18 shows an example of graph data 500 when the transmitting antenna height ht of antenna 60 is 1.5 m.

The horizontal axis of graph data 500 is the receiving antenna height hra of antenna 72, and the vertical axis is the minimum value of the higher of the levels of radio waves received by antenna 72 and antenna 74 from antenna 60 when the vehicle distance is changed. Level minimum value 501 indicates the case where the distance between antenna 72 and antenna 74 (sometimes referred to as receiving antenna distance) is 0.015 m, level minimum value 502 indicates the case where it is 0.030 m, level minimum value 503 indicates the case where it is 0.045 m, level minimum value 504 indicates the case where it is 0.060 m, level minimum value 505 indicates the case where it is 0.075 m, level minimum value 506 indicates the case where it is 0.090 m, level minimum value 507 indicates the case where it is 0.105 m, level minimum value 508 indicates the case where it is 0.119 m, level minimum value 509 indicates the case where it is 0.134 m, level minimum value 510 indicates the case where it is 0.149 m, and level minimum value 511 indicates the case where it is 0.164 m.

Graph data 500 can be generated by simulation. Graph data 500 can be generated, for example, by using a simulator that can output the level of radio waves that antenna 72 and antenna 74 receive from antenna 60 by specifying the arrangement of antenna 60, antenna 72, and antenna 74, radio wave settings, etc.

Graph data 500 can also be generated by actual measurements. For example, graph data 500 can be generated by measuring the level of radio waves received by antennas 72 and 74 from antenna 60 while changing the arrangement and radio wave settings of antennas 60, 72, and 74.

Figure 19 shows an example of graph data 520 that shows the minimum level value when the receiving antenna height changes for each receiving antenna interval. The graph data 520 can be generated based on the graph data 500.

For example, by referring to graph data 500, the minimum value of the level minimum value when the receiving antenna height hra changes for each receiving antenna spacing Δhr is identified. For example, for level minimum value 501 in FIG. 18, approximately -116.5 dB is identified. Since level minimum value 501 indicates a case where receiving antenna spacing Δhr is 0.015 m, in graph data 520, a level minimum value of approximately -116.5 dB is plotted for receiving antenna spacing Δhr = 0.015. Graph data 520 is generated by plotting in the same manner for each receiving antenna spacing Δhr.

The maximum value 522 indicates the maximum value of the level minimum value in the graph data 520. By identifying the maximum value 522, it is possible to identify the receiving antenna spacing Δhr at which the level minimum value is highest when the vehicle distance and the receiving antenna height hra are variously changed.

Figure 20 shows an example of distance interval data 530. Distance interval data 530 indicates the optimal receiving antenna spacing for each transmitting antenna height ht.

Distance interval data 530 can be generated based on graph data 520 generated for multiple transmitting antenna heights ht. In Figures 18 and 19, the case where graph data 520 is generated when the transmitting antenna height ht is 1.5 m is described, but graph data 520 can be generated for multiple transmitting antenna heights ht in a similar manner. Distance interval data 530 can be generated by plotting the receiving antenna interval Δhr corresponding to the approximate maximum value of each of the minimum level values of graph data 520 for multiple transmitting antenna heights ht.

The near-maximum value includes the maximum value and also includes a range of error from the maximum value. It is desirable to use the receiving antenna spacing Δhr that corresponds to the maximum value, but due to manufacturing errors, etc., it may be necessary to use a receiving antenna spacing Δhr that corresponds to a value that is slightly shifted from the maximum value. The spacing between antennas 72 and 74 in this embodiment allows for such errors.

Although Figs. 17 to 20 have described the case where distance interval data 530 is generated based on simulation or actual measurement, this is not limiting. Distance interval data 530 can also be generated theoretically using a formula. Another example of a method for generating distance interval data will be described using Figs. 21 to 23.

Figure 21 is an explanatory diagram for explaining radio waves transmitted by antenna 60 and received by antenna array 70 of the communication partner. In the example shown in Figure 21, antenna array 70 includes antenna 72 and antenna 74. Antenna 60 may be an orthogonally polarized antenna 112. Antenna array 70 may be antenna array 120. Each of antenna 72 and antenna 74 may be an orthogonally polarized antenna 122.

は、直接波指向性利得を示す。

は、反射波指向性利得を示す。 D indicates the distance between the road surface 30 and the antenna 60. The direct wave ground angle φ _D indicates the ground angle of the direct wave from the antenna 60 to the antennas 72 and 74. The reflected wave ground angle φ _R indicates the ground angle of the reflected wave from the antenna 60 to the antennas 72 and 74. Δr indicates the path difference between the direct wave and the reflected wave from the antenna 60 to the antennas 72 and 74.

denotes the direct wave directional gain.

denotes the reflected wave directional gain.

22 shows mathematical expressions expressing the received power P _r1 at antenna 72 and the received power P _r2 at antenna 74. _r1 indicates the path length of the direct wave from antenna 60 to antenna 72, _r1 ' indicates the path length of the reflected wave from antenna 60 to antenna 72, and _Δr1 indicates the path difference between them. _r2 indicates the path length of the direct wave from antenna 60 to antenna 74, _r2 ' indicates the path length of the reflected wave from antenna 60 to antenna 74, and _Δr2 indicates the path difference between them.

When the inter-vehicle distance is sufficiently long, _r1 and _r2 also become large, so that they can be approximated as in the following formula 3, and the distance between antenna 72 and antenna 74 can also be approximated as being equal.

Furthermore, the reflection coefficient can be approximated as shown in Equation 4 below.

From the formula shown in Figure 22, it can be said that the diversity effect is maximized when the correlation coefficient of the phase difference is -1 (a relationship in which the phase difference is inverted).

Figure 23 shows an example of graph data 540 that shows the relationship between the receiving antenna spacing and the correlation coefficient of the phase difference. Figure 23 shows an example in which the transmitting antenna height ht is 3.5 m. The graph data 540 can be generated by using the formula in Figure 22.

The minimum value 542 indicates the minimum value of the correlation coefficient in the graph data 540. By identifying the minimum value 542, it is possible to identify the receiving antenna spacing Δhr at which the diversity effect is maximized.

In FIG. 23, the case where graph data 540 is generated when the transmitting antenna height ht is 3.5 m is described, but graph data 540 can be generated for multiple transmitting antenna heights ht in a similar manner. Then, distance interval data 530 can be generated by plotting the receiving antenna interval Δhr corresponding to the minimum value of the correlation coefficient of each of the graph data 540 for multiple transmitting antenna heights ht.

The near minimum value includes the minimum value and also includes a range of error from the minimum value. It is desirable to use the receiving antenna spacing Δhr that corresponds to the minimum value, but due to manufacturing errors, etc., it may be necessary to use a receiving antenna spacing Δhr that corresponds to a value that is slightly deviated from the minimum value. The receiving antenna spacing Δhr in this embodiment allows for such errors.

Figure 24 shows an example of the functional configuration of a data processing device 800 and a manufacturing device 900. The data processing device 800 generates distance interval data 530. The data processing device 800 includes a result acquisition unit 802, a distance interval data generation unit 804, and a distance interval data output unit 806. Note that it is not essential that the data processing device 800 includes all of these.

The result acquisition unit 802 acquires the results of simulations for antenna 60, antenna 72, and antenna 74. For example, the result acquisition unit 802 acquires the results of simulating the level of radio waves received by antenna 72 and antenna 74 from antenna 60 when the distance between antenna 72 and a reflector that reflects radio waves emitted by antenna 60 and the distance between receiving antenna 72 and receiving antenna 74 and the transmitting/receiving antenna distance between antenna 60 and antenna 72 are changed for each distance between antenna 60 and a reflector that reflects radio waves emitted by antenna 60. The result acquisition unit 802 may acquire the results from a simulator. The result acquisition unit 802 may acquire the results via manual input.

The result acquisition unit 802 acquires the results of actual measurements of antenna 60, antenna 72, and antenna 74. For example, the result acquisition unit 802 acquires the results of actual measurements of the levels of radio waves received by antenna 72 and antenna 74 from antenna 60 when the distance between antenna 72 and a reflector that reflects radio waves emitted by antenna 60 and the distance between receiving antenna 72 and receiving antenna 74 are changed, and the transmitting/receiving antenna distance between antenna 60 and antenna 72 is changed for each distance between antenna 60 and a reflector that reflects radio waves emitted by antenna 60. The result acquisition unit 802 may acquire the results through manual input.

The distance interval data generating unit 804 generates the distance interval data 530 using the results acquired by the result acquiring unit 802. For example, the distance interval data generating unit 804 generates data such as graph data 500, in which the horizontal axis is the distance between the antenna 72 and the reflector, and the vertical axis is the minimum value of the higher of the levels of the radio waves received from the antenna 60 by the antennas 72 and 74 when the transmitting and receiving antenna distance is changed, for each distance between the antenna 60 and the reflector that reflects the radio waves emitted by the antenna 60. Note that the distance interval data generating unit 804 does not need to generate graph data if it is possible to grasp the relationship between the distance between the antenna 72 and the reflector and the minimum value of the higher of the levels of the radio waves received from the antenna 60 by the antennas 72 and 74 when the transmitting and receiving antenna distance is changed. The distance interval data generating unit 804 may generate distance interval data 530 indicating the receiving antenna interval between antennas 72 and 74 for each distance between the antenna 60 and the reflector based on the approximate maximum value of the minimum values for each distance between antennas 72 and 74. For example, the distance interval data generating unit 804 generates data such as graph data 520 indicating the minimum value for each distance between antennas 72 and 74 by specifying a level minimum value corresponding to the distance between antenna 72 and the reflector having the smallest minimum value for each distance between antennas 72 and 74. The distance interval data generating unit 804 may generate distance interval data 530 indicating the receiving antenna interval between antennas 72 and 74 for each distance between antenna 60 and the reflector by specifying a receiving antenna interval corresponding to an approximate maximum value of the level minimum value from each of data such as graph data 520 generated for each distance between antenna 60 and the reflector. Note that the distance interval data generating unit 804 does not need to generate graph data if it is possible to grasp the relationship between the distance between the antennas 72 and 74 and the minimum value. The distance interval data generating unit 804 may generate the distance interval data 530 using the method described with reference to Figures 17 to 20.

The distance interval data generating unit 804 may generate the distance interval data 530 based on the approximate minimum value of the correlation coefficient of the phase difference between the direct wave and the reflected wave from the antenna 60 for the antennas 72 and 74 for each distance between the antennas 72 and 74. The distance interval data generating unit 804 may generate the distance interval data 530 by the method described using Figures 21 to 23.

The distance interval data output unit 806 outputs the distance interval data 530 generated by the distance interval data generation unit 804. The distance interval data output unit 806 may display and output the distance interval data 530. The distance interval data output unit 806 may transmit and output the distance interval data 530.

The manufacturing apparatus 900 manufactures the antenna array 70. The manufacturing apparatus 900 includes a distance interval data acquisition unit 902, a distance interval data storage unit 904, a condition acquisition unit 906, and a manufacturing unit 908. The data processing device 800 and the manufacturing apparatus 900 may be integrated. That is, the data processing device 800 may further include the functions of the manufacturing apparatus 900. Note that it is not essential that the manufacturing apparatus 900 includes all of these.

The distance interval data acquisition unit 902 acquires the distance interval data 530. The distance interval data acquisition unit 902 may acquire the distance interval data 530 that has been manually input. The distance interval data acquisition unit 902 may receive the distance interval data 530 from the distance interval data output unit 806. The distance interval data storage unit 904 stores the distance interval data 530 acquired by the distance interval data acquisition unit 902.

The condition acquisition unit 906 acquires the manufacturing conditions. The condition acquisition unit 906 may acquire the manufacturing conditions through manual input. The condition acquisition unit 906 acquires, for example, the transmitting antenna height of the antenna 60. The condition acquisition unit 906 acquires, for example, the receiving antenna height of the antenna 72.

The manufacturing unit 908 manufactures the antenna array 70 using the manufacturing conditions acquired by the condition acquisition unit 906 and the distance interval data 530 stored in the distance interval data storage unit 904. The manufacturing unit 908 refers to the distance interval data 530 to identify the optimal antenna interval corresponding to the transmitting antenna height included in the manufacturing conditions. The manufacturing unit 908 determines the arrangement of the antennas 72 and 74 from the receiving antenna height of the antenna 72 included in the manufacturing conditions and the identified antenna interval. The manufacturing unit 908 manufactures the antenna array 70 in which the antennas 72 and 74 are arranged according to the determined arrangement.

Figure 25 shows an example of the flow of the manufacturing process of the antenna array 70 by the manufacturing device 900. In step (sometimes abbreviated to S) 102, the condition acquisition unit 906 acquires the transmitting antenna height. In S104, the condition acquisition unit 906 acquires the receiving antenna height.

In S106, the manufacturing unit 908 reads out the distance interval data 530 from the distance interval data storage unit 904. In S108, the manufacturing unit 908 refers to the distance interval data 530 read out in S106 to identify the receiving antenna interval corresponding to the transmitting antenna height obtained in S102. In S110, the manufacturing unit 908 determines the arrangement of the antennas 72 and 74 based on the receiving antenna height obtained in S104 and the receiving antenna interval determined in S108. The manufacturing unit 908 manufactures the antenna array 70 in which the antennas 72 and 74 are arranged according to the determined arrangement.

26 shows an example of a hardware configuration of a computer 1200 functioning as a communication device 100, a communication device 200, a data processing device 800, or a manufacturing device 900. A program installed on the computer 1200 can cause the computer 1200 to function as one or more "parts" of the device according to the present embodiment, or to execute operations or one or more "parts" associated with the device according to the present embodiment, and/or to execute a process or a step of the process according to the present embodiment. Such a program may be executed by the CPU 1212 to cause the computer 1200 to execute specific operations associated with some or all of the blocks of the flowcharts and block diagrams described herein.

The computer 1200 according to this embodiment includes a CPU 1212, a RAM 1214, and a graphics controller 1216, which are connected to each other by a host controller 1210. The computer 1200 also includes input/output units such as a communication interface 1222, a storage device 1224, a DVD drive 1226, and an IC card drive, which are connected to the host controller 1210 via an input/output controller 1220. The DVD drive 1226 may be a DVD-ROM drive, a DVD-RAM drive, or the like. The storage device 1224 may be a hard disk drive, a solid state drive, or the like. The computer 1200 also includes a ROM 1230 and a legacy input/output unit such as a keyboard, which are connected to the input/output controller 1220 via an input/output chip 1240.

The CPU 1212 operates according to the programs stored in the ROM 1230 and the RAM 1214, thereby controlling each unit. The graphics controller 1216 acquires image data generated by the CPU 1212 into a frame buffer or the like provided in the RAM 1214 or into itself, and causes the image data to be displayed on the display device 1218.

The communication interface 1222 communicates with other electronic devices via a network. The storage device 1224 stores programs and data used by the CPU 1212 in the computer 1200. The DVD drive 1226 reads programs or data from a DVD-ROM 1227 or the like and provides them to the storage device 1224. The IC card drive reads programs and data from an IC card and/or writes programs and data to an IC card.

ROM 1230 stores therein a boot program, etc., executed by computer 1200 upon activation, and/or a program that depends on the hardware of computer 1200. I/O chip 1240 may also connect various I/O units to I/O controller 1220 via USB ports, parallel ports, serial ports, keyboard ports, mouse ports, etc.

The programs are provided by a computer-readable storage medium such as a DVD-ROM 1227 or an IC card. The programs are read from the computer-readable storage medium, installed in the storage device 1224, RAM 1214, or ROM 1230, which are also examples of computer-readable storage media, and executed by the CPU 1212. The information processing described in these programs is read by the computer 1200, and brings about cooperation between the programs and the various types of hardware resources described above. An apparatus or method may be constructed by realizing the operation or processing of information according to the use of the computer 1200.

For example, when communication is performed between computer 1200 and an external device, CPU 1212 may execute a communication program loaded into RAM 1214 and instruct communication interface 1222 to perform communication processing based on the processing described in the communication program. Under the control of CPU 1212, communication interface 1222 reads transmission data stored in a transmission buffer area provided in RAM 1214, storage device 1224, DVD-ROM 1227, or a recording medium such as an IC card, and transmits the read transmission data to the network, or writes received data received from the network to a reception buffer area or the like provided on the recording medium.

The CPU 1212 may also cause all or a necessary portion of a file or database stored in an external recording medium such as the storage device 1224, DVD drive 1226 (DVD-ROM 1227), IC card, etc. to be read into the RAM 1214, and perform various types of processing on the data on the RAM 1214. The CPU 1212 may then write back the processed data to the external recording medium.

Various types of information, such as various types of programs, data, tables, and databases, may be stored in the recording medium and may undergo information processing. The CPU 1212 may perform various types of processing on the data read from the RAM 1214, including various types of operations, information processing, conditional judgment, conditional branching, unconditional branching, information search/replacement, etc., as described throughout this disclosure and specified by the instruction sequence of the program, and writes back the results to the RAM 1214. The CPU 1212 may also search for information in a file, database, etc. in the recording medium. For example, when multiple entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored in the recording medium, the CPU 1212 may search for an entry whose attribute value of the first attribute matches a specified condition from among the multiple entries, read the attribute value of the second attribute stored in the entry, and thereby obtain the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition.

The above-described programs or software modules may be stored in a computer-readable storage medium on the computer 1200 or in the vicinity of the computer 1200. In addition, a recording medium such as a hard disk or RAM provided in a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, thereby providing the programs to the computer 1200 via the network.

The blocks in the flowcharts and block diagrams in this embodiment may represent stages of a process in which an operation is performed or "parts" of a device responsible for performing the operation. Particular stages and "parts" may be implemented by dedicated circuitry, programmable circuitry provided with computer-readable instructions stored on a computer-readable storage medium, and/or a processor provided with computer-readable instructions stored on a computer-readable storage medium. The dedicated circuitry may include digital and/or analog hardware circuits and may include integrated circuits (ICs) and/or discrete circuits. The programmable circuitry may include reconfigurable hardware circuits including AND, OR, XOR, NAND, NOR, and other logical operations, flip-flops, registers, and memory elements, such as, for example, field programmable gate arrays (FPGAs) and programmable logic arrays (PLAs).

A computer-readable storage medium may include any tangible device capable of storing instructions that are executed by a suitable device, such that a computer-readable storage medium having instructions stored thereon comprises an article of manufacture that includes instructions that can be executed to create means for performing the operations specified in the flowchart or block diagram. Examples of computer-readable storage media may include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, and the like. More specific examples of computer-readable storage media may include floppy disks, diskettes, hard disks, random access memories (RAMs), read-only memories (ROMs), erasable programmable read-only memories (EPROMs or flash memories), electrically erasable programmable read-only memories (EEPROMs), static random access memories (SRAMs), compact disk read-only memories (CD-ROMs), digital versatile disks (DVDs), Blu-ray disks, memory sticks, integrated circuit cards, and the like.

The computer readable instructions may include either assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including object-oriented programming languages such as Smalltalk (registered trademark), JAVA (registered trademark), C++, etc., and conventional procedural programming languages such as the "C" programming language or similar programming languages.

The computer-readable instructions may be provided to a processor of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus, or a programmable circuit, either locally or over a local area network (LAN), a wide area network (WAN), such as the Internet, etc., so that the processor of the general-purpose computer, special-purpose computer, or other programmable data processing apparatus, or the programmable circuit, executes the computer-readable instructions to generate means for performing the operations specified in the flowcharts or block diagrams. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc.

In the above embodiment, a vehicle 10 is shown as an example of a moving body, but this is not limited to this. Other examples of moving bodies include railroad cars and unmanned aerial vehicles.

The present invention has been described above using an embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms incorporating such modifications or improvements can also be included in the technical scope of the present invention.

The order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before" or "prior to," and it should be noted that the processes may be performed in any order, unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the processes in that order.

10 vehicle, 20 vehicle, 30 road surface, 32 side reflector, 40 vehicle, 42 antenna, 50 vehicle, 52 antenna, 60 antenna, 70 antenna array, 72 antenna, 74 antenna, 100 communication device, 112 orthogonal polarization antenna, 113 vertical polarization antenna, 114 horizontal polarization antenna, 115 transmission RF section, 116 UpConverter section, 120 antenna array, 122 orthogonal polarization antenna, 150 transmitter baseband section, 152 receiver, 20 vehicle, 200 communication device, 222 orthogonal polarization antenna, 223 vertical polarization antenna, 224 horizontal polarization antenna, 225 LNA, 226 DownConverter section, 227 IF AMP section, 250 receiver baseband section, 252 Propagation path estimation unit, 254 FB information transmission unit, 302 Horizontal polarization, 304 Vertical polarization, 312 Horizontal polarization, 314 Vertical polarization, 412, 414, 416, 418, 422, 424, 426, 428 Level fluctuation, 500 Graph data, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511 Level minimum value, 520 Graph data, 522 Maximum value, 530 Distance interval data, 540 Graph data, 542 Minimum value, 800 Data processing device, 802 Result acquisition unit, 804 Distance interval data generation unit, 806 Distance interval data output unit, 900 Manufacturing device, 902 Distance interval data acquisition unit, 904 Distance interval data storage unit, 906 Condition acquisition unit, 908 manufacturing unit, 1200 computer, 1210 host controller, 1212 CPU, 1214 RAM, 1216 graphic controller, 1218 display device, 1220 input/output controller, 1222 communication interface, 1224 storage device, 1230 ROM, 1240 input/output chip, 1501 communication path coding unit, 1502 interleaver unit, 1503 rate matching unit, 1504 scrambling unit, 1505 symbol modulation unit, 1506 layer mapper unit, 1507 precoder unit, 1508 secondary modulation unit, 1509 pilot signal multiplexing unit, 1510 DAC unit, 1511 UpConverter unit, 1512 desired signal reception level estimator, 1513 pilot signal sequence selector, 1514 pilot signal generator, 1515 Precoding control unit, 1516, RF antenna module selection controller, 1517, selector, 1520, RF transmission unit selection controller, 1521, selector, 2501, DownConverter unit, 2502, ADC unit, 2503, selector, combiner unit, or separator unit, 2504, postcoder & layer demapper unit, 2505, log likelihood ratio generator unit for each transmission bit, 2506, descrambler unit, 2507, derate matcher unit, 2508, deinterleaver unit, 2509, channel decoder unit, 2510, LNA

Claims (15)

A first communication device mounted on a first moving object;
A second communication device mounted on the second moving object,
The second communication device is
an antenna array including a plurality of second orthogonally polarized antennas arranged at a distance from each other in at least one of a vertical direction and a horizontal direction;
The first communication device is
a first orthogonally polarized antenna;
a control unit that controls execution of polarized MIMO multiplexing transmission by the first orthogonally polarized antenna based on a propagation path state between the first communication device and the second communication device,
the plurality of second orthogonally polarized antennas include vertically polarized antennas and horizontally polarized antennas;
The second communication device is
an estimation unit that uses RSs transmitted by the vertically polarized antenna and the horizontally polarized antenna to predict and evaluate a transmission capacity for each candidate transmission/reception method from a MIMO Channel Matrix that can be grasped, and estimates a PMI and an RI that correspond to candidates for index information corresponding to a precoding matrix and the number of spatial multiplexing layers that maximize a predicted throughput after precoding;
and an FB information transmission unit configured to transmit feedback information including an estimation result by the estimation unit to the first communication device,
The first communication device is
a receiver for receiving the feedback information,
The control unit implements either polarization diversity or the polarization MIMO multiplexing transmission depending on the value of the RI included in the feedback information, and determines the precoding matrix to be used and the polarization to be used between vertical polarization and horizontal polarization depending on a combination of the value of the RI and the value of the PMI included in the feedback information . The communication system according to claim 1, wherein the control unit controls the first orthogonally polarized antenna to perform the polarized MIMO multiplexing transmission when the propagation path conditions satisfy a propagation condition that provides a space diversity effect due to the arrangement of the multiple second orthogonally polarized antennas. The communication system according to claim 1, wherein the plurality of second orthogonally polarized antennas are spatially spaced apart at a distance that is an odd multiple of a half period of the period of the level fluctuation due to the antenna position at a first distance that is predetermined as the distance between the first communication device and the second communication device. The communication system according to claim 3, wherein the first distance is a predetermined distance between the first moving body and the second moving body. The communication system according to claim 4, wherein the first distance is a distance that is predetermined as a maximum distance between the first mobile unit and the second mobile unit. the first moving body and the second moving body are vehicles,
The communication system according to claim 3 , wherein the first distance is a predetermined distance between two vehicles traveling one behind the other. The communication system according to claim 3, wherein the second orthogonally polarized antennas are spaced apart in the horizontal direction by a distance equal to an odd multiple of a half period of the period of the level fluctuation due to the lateral position of the antenna at the first distance. The communication system according to claim 3, wherein the second orthogonally polarized antennas are arranged at a distance equal to an odd multiple of a half period of the period of the level fluctuation due to the antenna height at the first distance, and are spatially separated in the height direction. The communication system according to claim 1, wherein the second orthogonally polarized antennas are arranged spatially separated from each other by an antenna spacing determined based on the distance between the first orthogonally polarized antenna and the reflector along a direction from the first orthogonally polarized antenna to a reflector that reflects radio waves emitted by the first orthogonally polarized antenna. The reflector is the ground,
10. The communication system of claim 9, wherein the second orthogonally polarized antennas are spatially spaced apart from each other along a direction perpendicular to the reflector by an antenna spacing determined based on an antenna height of the first orthogonally polarized antenna. The communication system according to claim 10, wherein the second orthogonally polarized antennas are spatially spaced apart by an antenna spacing determined by the distance between the first orthogonally polarized antenna and the reflector and distance spacing data indicating the antenna spacing for each distance between the first orthogonally polarized antenna and the reflector. The communication system according to claim 11, wherein the distance interval data is data generated based on the results of simulating the level of radio waves received by the multiple second orthogonal polarized antennas from the first orthogonal polarized antenna when the distance between one of the second orthogonal polarized antennas and the reflector and the transmitting/receiving antenna distance between the first orthogonal polarized antenna and the one second orthogonal polarized antenna are changed for each distance between the first orthogonal polarized antenna and the reflector and for each interval between the multiple second orthogonal polarized antennas. The communication system according to claim 11, wherein the distance interval data is data generated based on the results of actual measurements of the levels of radio waves received by the multiple second orthogonal polarized antennas from the first orthogonal polarized antenna when the distance between one of the second orthogonal polarized antennas and the reflector and the transmitting/receiving antenna distance between the first orthogonal polarized antenna and the one second orthogonal polarized antenna are changed for each distance between the first orthogonal polarized antenna and the reflector and for each interval between the multiple second orthogonal polarized antennas. The communication system according to claim 12, wherein the distance interval data is data generated based on a maximum value among the minimum values of the levels of the higher level of the radio waves received from the first orthogonally polarized antenna among the plurality of second orthogonally polarized antennas for each interval between the plurality of second orthogonally polarized antennas, and a near maximum value including an error range from the maximum value. The communication system according to claim 11, wherein the distance interval data includes a minimum value of a correlation coefficient of a phase difference between a direct wave and a reflected wave from the first orthogonally polarized antenna of the second orthogonally polarized antennas for each interval between the second orthogonally polarized antennas, and is data generated based on an approximately minimum value that includes an error range from the minimum value.

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