Communication system, mobile body, base station, and program

Abstract

To provide a communication system comprising a mobile body and a first base station, the mobile body, a base station, and a program.SOLUTION: In a system 10 comprising a mobile body 100 and a base station, the mobile body and the base station perform mobile body communication in such a way that the product of the antenna gain of a communication antenna on the transmission side and the antenna gain of a communication antenna on the reception side of the mobile body communication between a mobile body using a radio wave in a terahertz band frequency and a base station 200 is proportionate to the square of cosecant of the elevation and depression angle in a propagation direction of the radio wave. The mobile body includes a communication unit that performs mobile body communication with the base station using a communication antenna 150 that the mobile body has in such a way that the product of the antenna gain of a communication antenna used in mobile body communication between the mobile body and a base station 300 and the communication antenna on the transmission side of the mobile body communication between the mobile body using the radio wave of the terahertz band frequency and the base station 200 and the antenna gain of a communication antenna on the reception side of mobile body communication is proportionate to the square of cosecant of the elevation and depression angle in the propagation direction of the radio wave.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a communication system, a mobile body, a base station, and a program.

Background Art

[0002] Patent Document 1 describes a P-MPFWA system including a base station antenna capable of expanding a communication area significantly improved as compared with the conventional one in the elevation angle direction while suppressing a decrease in the maximum gain in the horizontal direction as much as possible. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent No. 3761821

Summary of the Invention

Means for Solving the Problems

[0003] According to an embodiment of the present invention, a communication system is provided. The communication system may include a mobile body. The communication system may include a first base station. The mobile body and the first base station may perform mobile body communication such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile body communication using radio waves having a frequency in the terahertz band is proportional to the square of the cosecant of the elevation and depression angles in the propagation direction of the radio waves.

[0004] In the communication system, the received power (P RE ) may satisfy the following formula.

[0005]

Equation

[0006] Here, P TR is the transmission power of the radio wave, G TR is the antenna gain of the communication antenna on the transmission side, G REis the antenna gain of the communication antenna on the receiving side, λ is the wavelength of the radio wave, h is the altitude difference between the altitude of the communication antenna on the transmitting side and the altitude of the communication antenna on the receiving side, and θ is the elevation angle.

[0007] In any of the communication systems, the mobile body may have a first communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation angle, and the first base station may have a second communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation angle.

[0008] In any of the communication systems, the mobile body may have a first communication antenna whose antenna gain is omnidirectional with respect to the elevation angle, and the first base station may have a second communication antenna whose antenna gain is proportional to the second power of the cosecant of the elevation angle.

[0009] In any of the communication systems, the mobile body uses radio waves with a frequency lower than the terahertz band to perform mobile body communication with a second base station having a coverage area including the coverage area of the first base station, and receives from the second base station first presence information indicating that the first base station exists within the coverage area of the second base station, and may perform mobile body communication with the first base station based on the first presence information.

[0010] Any of the communication systems may further include a notification device. The notification device is arranged outside the coverage area of the first base station and may transmit second presence information indicating that the first base station exists within a predetermined range from the notification device to the mobile body using radio waves with a frequency in the terahertz band. The mobile body may perform mobile body communication with the first base station based on the second presence information.

[0011] According to one embodiment of the present invention, a mobile body is provided. The mobile body may include a communication antenna used for mobile body communication between the mobile body and a base station. The mobile body may include a communication unit that performs mobile body communication with the base station using the communication antenna included in the mobile body, such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile body communication between the mobile body and the base station using radio waves having a frequency in the terahertz band is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves.

[0012] In the mobile body, the antenna gain of the communication antenna included in the mobile body may be proportional to the first power of the cosecant of the elevation angle.

[0013] According to one embodiment of the present invention, a program is provided that, when executed by a computer, causes the computer to function as any of the mobile bodies.

[0014] According to one embodiment of the present invention, a base station is provided. The base station may include a communication antenna used for mobile body communication between the mobile body and the base station. The base station may include a communication unit that performs mobile body communication with the mobile body using the communication antenna included in the base station, such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile body communication between the mobile body and the base station using radio waves having a frequency in the terahertz band is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves.

[0015] In the base station, the antenna gain of the communication antenna included in the base station may be proportional to the first power of the cosecant of the elevation angle.

[0016] According to one embodiment of the present invention, a program is provided that, when executed by a computer, causes the computer to function as any of the base stations.

[0017] Furthermore, the above summary of the invention does not list all the necessary features of the present invention. Also, sub - combinations of these groups of features can also be inventions.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0019] In the future, due to the popularization of connected cars and the smartening of trains, etc., it is predicted that the amount of wireless communication traffic generated on roads and railways will increase. With the current network capacity, it is not possible to accommodate these traffic demands, so it is necessary to build coverage areas for roads and railways. To build such coverage areas, it is conceivable to utilize broadband communication using high-frequency radio waves in the millimeter-wave band or terahertz band, which makes it easier to secure communication capacity. However, radio waves in the millimeter-wave band or terahertz band, which have large propagation attenuation, make it difficult to extend the communication distance. According to the system according to this embodiment, for example, the mobile body and the base station adopt a mechanism for performing mobile communication such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side is proportional to the square of the cosecant of the elevation and depression angles in the propagation direction of radio waves with a frequency in the terahertz band.

[0020] Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention.

[0021] FIG. 1 schematically shows an example of the system 10. The system 10 may include a mobile body 100 and a base station 200. The system 10 may further include a base station 300. The system 10 may be an example of a communication system.

[0022] The mobile body 100 may be any mobile body having a mobile communication function. The mobile body 100 is, for example, a vehicle. The vehicle is, for example, an automobile. The vehicle is, for example, a two-wheeled vehicle. The vehicle may be a railway vehicle. The railway vehicle is, for example, a train. The train is, for example, a bullet train. FIG. 1 shows an example of the case where the mobile body 100 is an automobile.

[0023] The mobile body 100 communicates with, for example, the base station 200. The mobile body 100 performs mobile communication with the base station 200 using, for example, radio waves having a frequency in the terahertz band. The frequency in the terahertz band may be a frequency in a band ranging from about 100 GHz to about 10 THz. The mobile body 100 may access the network 20 via the base station 200.

[0024] The network 20 includes, for example, a core network provided by a communications carrier. The core network complies with, for example, a 5G (5th Generation) communication system. The core network may comply with a communication system after the 6G (6th Generation) communication system. The core network may also comply with a 3G (3rd Generation) communication system or an LTE (Long Term Evolution) communication system. The network 20 may include the Internet.

[0025] The mobile body 100 and the base station 200 perform mobile communication such that, for example, the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile communication between the mobile body 100 and the base station 200 using radio waves having a frequency in the terahertz band is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio wave. For example, when the mobile body 100 has a communication antenna 150 whose antenna gain is proportional to the first power of the cosecant of the elevation angle, and the base station 200 has a communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation angle, the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile communication is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio wave. Also, for example, when the mobile body 100 has a communication antenna 150 whose antenna gain is omnidirectional with respect to the elevation angle, and the base station 200 has a communication antenna whose antenna gain is proportional to the square of the cosecant of the elevation angle, the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile communication is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio wave. The base station 200 may be an example of a first base station.

[0026] The base station 200 forms a coverage area 220, for example, using a communication antenna. The base station 200 forms a coverage area 220 along a road, for example. The road includes, for example, a national highway. The national highway includes, for example, an expressway. The national highway may include a general national highway. The road includes, for example, a prefectural road. The road may include a municipal road. The base station 200 forms a coverage area 220 along a railway line, for example. The railway line is, for example, a railway line for railway vehicles. The railway line is, for example, a railway line for trains. The railway line is, for example, a railway line for the Shinkansen. The base station 200 may form a linear coverage area 220.

[0027] The base station 200 is installed on a sign, for example. The base station 200 is installed on a traffic signal, for example. When the base station 200 is installed on a sign or a traffic signal, the base station 200 is installed at a height of about 5 m or more. The base station 200 is installed on a billboard, for example. The base station 200 is installed on a utility pole, for example. The base station 200 may be installed at any other location. FIG. 1 illustrates an example in which the base station 200 is installed on a sign 50.

[0028] The base station 200 is installed along a road, for example. The base station 200 may be installed along a railway line.

[0029] For example, two adjacent base stations 200 are installed such that at least a part of their coverage areas overlaps. Two adjacent base stations 200 may be installed such that their coverage areas do not overlap.

[0030] The mobile unit 100 performs mobile communication with a base station 300, for example. The mobile unit 100 performs mobile communication with the base station 300 using radio waves having a frequency lower than the terahertz band, for example. The mobile unit 100 performs mobile communication with the base station 300 using radio waves having a frequency in the anchor band, for example. The mobile unit 100 performs mobile communication with the base station 300 using radio waves having a frequency in the 2.1 GHz band, for example. The mobile unit 100 may access the network 20 via the base station 300.

[0031] The mobile body 100 performs mobile communication with the base station 300, for example, before performing mobile communication with the base station 200. The mobile body 100 establishes mobile communication with the base station 300 at a timing when the mobile body 100 is located, for example, outside the coverage area 220 of the base station 200 and inside the coverage area 320 of the base station 300.

[0032] The mobile body 100 may perform mobile communication with the base station 300 using a communication antenna different from the communication antenna 150. Therefore, the mobile body 100 may have two communication antennas, namely, the communication antenna 150 for performing mobile communication with the base station 200 and the communication antenna for performing mobile communication with the base station 300.

[0033] The base station 300 forms the coverage area 320 using, for example, a communication antenna. The base station 300 forms a coverage area 320 that is, for example, wider than the coverage area 220 of the base station 200. The base station 300 forms a coverage area 320 that includes, for example, the coverage area 220 of the base station 200. The base station 300 may be an example of a second base station.

[0034] The base station 300 executes a setting process for the mobile body 100 to start data communication at a timing when the mobile body 100 establishes mobile communication with the base station 300, for example. The base station 300 executes a subscriber authentication process for authenticating the subscriber information of the mobile body 100, for example. The base station 300 executes an assignment process for assigning an IP (Internet Protocol) address to the mobile body 100, for example. The base station 300 may execute any other process.

[0035] The base station 300 transmits presence information indicating that the base station 200 exists within the coverage area 320 of the base station 300, for example, after establishing mobile communication with the mobile body 100. The presence information includes, for example, communication antenna information indicating the communication antenna of the base station 200.

[0036] The mobile body 100 may receive presence information from the base station 300 and perform mobile communication with the base station 200 based on the received presence information. For example, the mobile body 100 sets the state of the communication antenna 150 to a state capable of receiving radio waves in order to establish mobile communication with the base station 200.

[0037] For example, when the mobile body 100 is located at a position within the coverage area 220 of the base station 200 and within the coverage area 320 of the base station 300, the mobile body 100 performs data communication using both the mobile communication between the mobile body 100 and the base station 200 and the mobile communication between the mobile body 100 and the base station 300. For example, the mobile body 100 performs the data communication using the protocol of carrier aggregation. The mobile body 100 may perform data communication using only the mobile communication between the mobile body 100 and the base station 200 when the mobile body 100 is located at a position within the coverage area 220 of the base station 200 and within the coverage area 320 of the base station 300.

[0038] In the future, in order to construct a coverage area for roads and railway lines whose traffic volume is predicted to increase, it is conceivable to utilize broadband communication using high-frequency radio waves in the terahertz band. However, radio waves in the terahertz band, which have high propagation attenuation, are difficult to extend the communication range. Also, in order to extend the communication range of mobile communication using radio waves in the terahertz band, the introduction of beamforming is conceivable. However, beamforming is not a technology for expanding the coverage area itself, but a technology for extending the communication range by following a beam that forms a communicable spot for a mobile body equipped with a mobile communication function. Therefore, in order to make the mobile body accurately follow the beam, the base station has to execute a huge amount of calculations including matrix operations in accordance with the movement of the mobile body. In particular, when the mobile body is moving at high speed, such as when a car is running on a highway, the base station has to execute the calculation at a higher speed. Therefore, when extending the communication range of mobile communication using radio waves in the terahertz band by using beamforming, the base station has to be equipped with hardware that satisfies high calculation processing requirements, and as a result, the base station becomes large and expensive.

[0039] In contrast, according to the system 10 according to the present embodiment, the mobile body 100 and the base station 200 perform mobile body communication between the mobile body 100 and the base station 200 using radio waves in the terahertz band such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio wave. The system 10 according to the present embodiment mounts a cosecant directive antenna on the base station 200 and forms a coverage area 220 along a road or a line using the cosecant directive antenna, thereby extending the communication range of mobile body communication using radio waves in the terahertz band without introducing beamforming, compared to the communication range of conventional mobile body communication using radio waves in the terahertz band. For example, the system 10 according to the present embodiment can extend the communication range of mobile body communication using radio waves in the terahertz band to about 200 m. Further, the system 10 according to the present embodiment performs mobile body communication such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio wave, so that when the mobile body moves with the height of the communication antenna of the mobile body being constant, the received power of the communication antenna on the reception side can be made constant. Thereby, the system 10 according to the present embodiment can make the communication quality of mobile body communication using radio waves in the terahertz band more stable. In addition, the system 10 according to the present embodiment forms a coverage area along a road or a line, and can suppress the occurrence of radio wave interference between the radio waves in one coverage area and the radio waves in the other coverage area when coverage areas are formed in each of the adjacent lanes and lines. From the above, the system 10 according to the present embodiment can realize extending the communication range of mobile body communication using radio waves in the terahertz band and making the communication quality of the mobile body communication more stable by using a low-cost and small-sized base station.

[0040] Furthermore, according to the system 10 according to the present embodiment, the mobile body 100 performs mobile communication with a base station 300 having a coverage area 320 that includes the coverage area 220 of the base station 200. And before the mobile body 100 starts mobile communication with the base station 200, the base station 300 executes a setting process for the mobile body 100 to start data communication. Thereby, at the timing when the mobile body 100 starts mobile communication with the base station 200, since the setting process for the mobile body 100 to start data communication has already been executed by the base station 300, the system 10 according to the present embodiment enables the mobile body to start data communication using radio waves of frequencies in the terahertz band in a short time. Also, when the mobile body 100 is located at a position within the coverage area 220 of the base station 200 and within the coverage area 320 of the base station 300, the mobile body 100 can perform data communication using both the mobile communication between the mobile body 100 and the base station 200 and the mobile communication between the mobile body 100 and the base station 300. Therefore, the system 10 according to the present embodiment can realize high-speed mobile body data communication as a whole system. In addition, when the mobile body 100 moves from within the coverage area 220 of the base station 200 to outside the coverage area 220 of the base station 200, the mobile body 100 can continue data communication using the mobile communication between the mobile body 100 and the base station 300. Therefore, the system 10 according to the present embodiment can realize seamless mobile body data communication as a whole system.

[0041] FIG. 2 is an explanatory diagram for explaining the propagation characteristics of radio waves. In the xy coordinate system illustrated in FIG. 2, the x-axis is the horizontal direction and the y-axis is the vertical direction.

[0042] The communication antenna 150 is located at (x v , y v ). The communication antenna 250 of the base station 200 is located at (x b , y b ).

[0043] When communication antenna 150 transmits radio waves and communication antenna 250 receives radio waves, communication antenna 150 is the transmitting-side communication antenna and communication antenna 150 is the receiving-side communication antenna. On the other hand, when communication antenna 250 transmits radio waves and communication antenna 150 receives radio waves, communication antenna 250 is the transmitting-side communication antenna and communication antenna 150 is the receiving-side communication antenna. It is assumed that the propagation direction of the radio waves is parallel to the straight line passing through communication antenna 150 and communication antenna 250.

[0044] r is the distance between the transmitting-side communication antenna and the receiving-side communication antenna. r satisfies the following formula.

[0045]

Number

[0046] d is the distance in the x-axis direction between the transmitting-side communication antenna and the receiving-side communication antenna. d satisfies the following formula.

[0047]

Number

[0048] h is the altitude difference between the altitude of the transmitting-side communication antenna and the altitude of the receiving-side communication antenna. h satisfies the following formula.

[0049]

Number

[0050] θ is the elevation angle of the propagation direction of the radio waves. When communication antenna 150 is the transmitting-side communication antenna and communication antenna 250 is the receiving-side communication antenna, θ is the elevation angle. On the other hand, when communication antenna 250 is the transmitting-side communication antenna and communication antenna 150 is the receiving-side communication antenna, θ is the depression angle.

[0051] The received power of the radio wave (PRE ) can be derived from the transmitted power (P TR ) of the radio wave using the Friis transmission formula shown below. In the Friis transmission formula shown below, G TR is the antenna gain of the communication antenna on the transmitting side, G RE is the antenna gain of the communication antenna on the receiving side, and λ is the wavelength of the radio wave.

[0052]

Equation

[0053] Here, substitute r = h × cosecθ into the Friis transmission formula shown above. In this case, P RE satisfies the following equation.

[0054]

Equation

[0055] As shown in the above equation, since P RE includes (1 / cosecθ) 2 , when G TR × G RE is proportional to (cosecθ) 2 , P RE becomes constant regardless of d. Therefore, when G TR × G RE is proportional to (cosecθ) 2 , the communication quality of mobile communication using radio waves in the terahertz band can be made more stable.

[0056] Figure 3 is an explanatory diagram for explaining the antenna gain of the communication antenna. In Figure 3, an example of a region where the antenna gain of the communication antenna is greater than the gain threshold (G th ) is illustrated.

[0057] The upper part of FIG. 3 illustrates an example where the antenna gain of communication antenna 150 is omnidirectional with respect to the elevation and depression angles, and the antenna gain of communication antenna 250 is proportional to the square of the cosecant of the elevation and depression angles. The lower part of FIG. 3 illustrates an example where the antenna gain of communication antenna 150 is proportional to the first power of the cosecant of the elevation and depression angles, and the antenna gain of communication antenna 250 is proportional to the first power of the cosecant of the elevation and depression angles. As shown in FIG. 3, the antenna gain of the communication antenna is G th The larger region is, in order, the communication antenna whose antenna gain is proportional to the square of the cosecant of the elevation and depression angles, the communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation and depression angles, and the communication antenna whose antenna gain is omnidirectional with respect to the elevation and depression angles.

[0058] Here, the sizes of the communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation and depression angles and the communication antenna whose antenna gain is proportional to the square of the cosecant of the elevation and depression angles will be described. The size of the communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation and depression angles is smaller than the size of the communication antenna whose antenna gain is proportional to the square of the cosecant of the elevation and depression angles. The size of the communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation and depression angles is, for example, about 1 / 2 to 1 / 3 of the size of the communication antenna whose antenna gain is proportional to the square of the cosecant of the elevation and depression angles. The size of the communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation and depression angles is, for example, about 1 cm 3 ~4 cm 3 in the 300 GHz band.

[0059] As described above, the size of the communication antenna in which the antenna gain is proportional to the first power of the cosecant of the elevation angle is small. Therefore, when the communication antenna in which the antenna gain is proportional to the first power of the cosecant of the elevation angle is adopted as the communication antenna 150, the communication antenna 150 can be easily installed at a position where the wiring connected to the communication antenna 150 can be hidden or at a position with a good view with respect to the communication antenna 250. Further, when the communication antenna in which the antenna gain is proportional to the first power of the cosecant of the elevation angle is adopted as the communication antenna 250, the communication antenna 250 can be easily installed at a position that does not obstruct the confirmation of signs, traffic lights, etc. where the base station 200 is installed. Thereby, when the communication antenna in which the antenna gain is proportional to the first power of the cosecant of the elevation angle is adopted as the communication antenna 150 and the communication antenna 250, the degree of freedom in the installation position of the communication antenna can be further increased for the entire system.

[0060] FIG. 4 is an explanatory diagram for explaining an example of the communication state of the mobile body 100. Here, the state in which the mobile body 100 has not established mobile communication is set as the start state. Note that the base station 202 installed on the sign 52 and the base station 204 installed on the sign 54 have the same functions as the base station 200, and the traveling direction of the mobile body 100 is assumed to be from right to left.

[0061] The upper part of FIG. 4 illustrates an example in the case where the mobile body 100 moves from outside the coverage area 320 of the base station 300 into the coverage area 320 of the base station 300. The mobile body 100 establishes mobile communication with the base station 300 using radio waves having a frequency lower than the terahertz band, for example, in response to moving from outside the coverage area 320 of the base station 300 into the coverage area 320 of the base station 300.

[0062] The base station 300 may execute a setting process for the mobile body 100 to start data communication at the timing of establishing mobile communication with the mobile body 100. The mobile body 100 may start data communication using the mobile communication between the mobile body 100 and the base station 300 in response to the completion of the setting process by the base station 300.

[0063] The lower part of FIG. 4 illustrates an example when the mobile object 100 moves from outside the coverage area 222 of the base station 202 into the coverage area 222 of the base station 202. When the mobile object 100 moves from outside the coverage area 222 of the base station 202 into the coverage area 222 of the base station 202, for example, the mobile object 100 establishes mobile communication with the base station 202 using radio waves with a frequency in the terahertz band. In response to establishing mobile communication with the base station 202, the mobile object 100 may start data communication using both the mobile communication between the mobile object 100 and the base station 202 and the mobile communication between the mobile object 100 and the base station 300.

[0064] FIG. 5 is an explanatory diagram for explaining another example of the communication state of the mobile object 100. Here, mainly the points different from the explanation of FIG. 4 will be explained.

[0065] The upper part of FIG. 5 illustrates an example when the mobile object 100 is moving within the coverage area 222 of the base station 202. When the mobile object 100 is located within the coverage area 222 of the base station 202, the mobile object 100 may perform data communication using both the mobile communication between the mobile object 100 and the base station 202 and the mobile communication between the mobile object 100 and the base station 300.

[0066] For example, while the mobile object 100 is located within the coverage area 222 of the base station 202, the mobile object 100 transmits position information indicating the position of the mobile object 100 to the base station 300. Based on the position of the mobile object 100 indicated by the position information received from the mobile object 100, the base station 300 determines whether to perform a handover (HO) of the base station for the mobile object 100 to perform mobile communication using radio waves with a frequency in the terahertz band from the base station 202 to the base station 204.

[0067] For example, when the mobile unit 100 is located within the coverage area 222 of the base station 202, if the distance from the mobile unit 100 to the base station 204 is shorter than a predetermined distance threshold, the base station 300 determines to perform a handover from the base station 202 to the base station 204. On the other hand, when the mobile unit 100 is located within the coverage area 222 of the base station 202, if the distance from the mobile unit 100 to the base station 204 is longer than the distance threshold, the base station 300 determines not to perform a handover from the base station 202 to the base station 204. Here, continuing the explanation assuming that the base station 300 has determined to perform a handover from the base station 202 to the base station 204.

[0068] In response to determining to perform a handover from the base station 202 to the base station 204, the base station 300 transmits a handover instruction to the mobile unit 100 instructing the mobile unit 100 to perform a handover of the base station for mobile communication using radio waves of a frequency in the terahertz band from the base station 202 to the base station 204. The handover instruction includes, for example, handover source information indicating the handover source base station. The handover instruction includes, for example, handover destination information indicating the handover destination base station.

[0069] In response to receiving the handover instruction from the base station 300, the mobile unit 100 may perform a handover of the base station for mobile communication using radio waves of a frequency in the terahertz band from the base station 202 to the base station 204. Here, continuing the explanation assuming that the mobile unit 100 has performed a handover of the base station for mobile communication using radio waves of a frequency in the terahertz band from the base station 202 to the base station 204.

[0070] The lower part of FIG. 5 illustrates an example when the mobile body 100 moves from outside the coverage area 224 of the base station 204 into the coverage area 224 of the base station 204. In response to the mobile body 100 moving from outside the coverage area 224 of the base station 204, which is the handover destination, into the coverage area 224 of the base station 204, the mobile body 100 may start data communication using both the mobile communication between the mobile body 100 and the base station 204 and the mobile communication between the mobile body 100 and the base station 300.

[0071] FIG. 6 is an explanatory diagram for explaining another example of the communication state of the mobile body 100. Here, mainly the points different from the explanations for FIG. 4 and FIG. 5 will be explained.

[0072] The upper part of FIG. 6 illustrates an example when the mobile body 100 is moving within the coverage area 224 of the base station 204. While the mobile body 100 is located within the coverage area 224 of the base station 204, the mobile body 100 may perform data communication using both the mobile communication between the mobile body 100 and the base station 204 and the mobile communication between the mobile body 100 and the base station 300.

[0073] For example, while the mobile body 100 is located within the coverage area 224 of the base station 204, the mobile body 100 transmits location information to the base station 300. Based on the location of the mobile body 100 indicated by the location information received from the mobile body 100, the base station 300 determines whether to hand over the base station from which the mobile body 100 performs mobile communication using radio waves of a frequency in the terahertz band from the base station 204 to another base station.

[0074] For example, when the mobile body 100 is located within the coverage area 224 of the base station 204, if there is another base station whose distance from the mobile body 100 is shorter than a predetermined distance threshold, the base station 300 determines that a handover is to be made from the base station 204 to the other base station. On the other hand, when the mobile body 100 is located within the coverage area 224 of the base station 204 and there is no other base station whose distance from the mobile body 100 is shorter than the distance threshold, the base station 300 determines that a handover is not to be made from the base station 204 to the other base station. Here, the description will continue assuming that the base station 300 has determined that a handover is not to be made from the base station 204 to the other base station.

[0075] The lower part of FIG. 6 illustrates an example in which the mobile body 100 moves from within the coverage area 224 of the base station 204 to outside the coverage area 224 of the base station 204. In response to the mobile body 100 moving from within the coverage area 224 of the base station 204 to outside the coverage area 224 of the base station 204, the mobile body 100 may start data communication using mobile body communication between the mobile body 100 and the base station 300.

[0076] According to the system 10 according to FIGS. 4 to 6, when the mobile body 100 is located within the coverage area 320 of the base station 300 and the mobile body 100 is located in at least one of the coverage areas 222 of the base station 202 and the coverage area 224 of the base station 204, the mobile body 100 performs data communication using both the mobile body communication between the mobile body 100 and the base station 202 or the base station 204 and the mobile body communication between the mobile body 100 and the base station 300. On the other hand, when the mobile body 100 is located within the coverage area 320 of the base station 300 and the mobile body 100 is not located in either the coverage area 222 of the base station 202 or the coverage area 224 of the base station 204, the mobile body 100 performs data communication using the mobile body communication between the mobile body 100 and the base station 300. Thereby, the system 10 according to FIGS. 4 to 6 can realize high-speed and seamless mobile body data communication as a whole system.

[0077] FIG. 7 schematically shows another example of the system 10. Here, the differences from the system 10 illustrated in FIG. 1 will be mainly described.

[0078] The system 10 may further include a notification device 400. The notification device 400 notifies the mobile body 100 that the base station 200 is present in the vicinity.

[0079] The notification device 400 forms a coverage area 420, for example, using a communication antenna. The notification device 400 forms a coverage area 420 along a road, for example. The notification device 400 forms a coverage area 420 along a line, for example. The notification device 400 may form a linear coverage area 420.

[0080] The notification device 400 notifies the mobile body 100 that the base station 200 is present in the vicinity, for example, by transmitting presence information indicating that the base station 200 is present within a predetermined range from the notification device 400 to the mobile body 100. The presence information includes, for example, communication antenna information of the base station 200.

[0081] The notification device 400 transmits the presence information to the mobile body 100 using radio waves having a frequency in the terahertz band, for example. The notification device 400 may transmit the presence information to the mobile body 100 using radio waves having a frequency lower than the terahertz band.

[0082] The mobile body 100 receives the presence information from the notification device 400, for example, and performs mobile body communication with the base station 200 based on the received presence information. The mobile body 100 sets the state of the communication antenna 150 to a state capable of receiving radio waves, for example, to establish mobile body communication with the base station 200.

[0083] The notification device 400 may be connected to the network 20. The notification device 400 may not be connected to the network 20.

[0084] The notification device 400 is disposed, for example, outside the coverage area 220 of the base station 200. The notification device 400 is disposed, for example, outside the coverage area 320 of the base station 300.

[0085] According to the system 10 shown in FIG. 7, in response to receiving the presence information from the notification device 400, the mobile body 100 changes the state of the communication antenna 150 to a state in which radio waves can be received. As a result, before the mobile body 100 moves from outside the coverage area 220 of the base station 200 to inside the coverage area 220 of the base station 200, the state of the communication antenna 150 can be changed to a state in which radio waves can be received. Therefore, the system 10 shown in FIG. 7 can more quickly establish mobile body communication between the mobile body and the base station using radio waves in the terahertz band. Further, when the notification device 400 forms a coverage area 420 along a road or a railway, the system 10 shown in FIG. 7 can prevent notification to communication terminals and mobile bodies located around the road or the railway. As a result, unnecessary power consumption of communication terminals and mobile bodies located around the road or the railway can be prevented.

[0086] FIG. 8 is an explanatory diagram for explaining an example of the installation position of the communication antenna 150. FIG. 8 shows an example of the installation position of the communication antenna 150 when the mobile body 100 is an automobile.

[0087] The communication antenna 150 is installed, for example, at a position where the wiring connected to the communication antenna 150 can be hidden. The communication antenna 150 is installed, for example, at a position with a good view of the communication antenna 250. The communication antenna 150 is installed, for example, at a position where the wiring connected to the communication antenna 150 can be hidden and where there is a good view of the communication antenna 250.

[0088] In an example of the installation position of the communication antenna 150 shown in FIG. 8, the communication antenna 150 is installed on the back side of the rearview mirror or on the shark fin antenna. The communication antenna 150 may be installed at any other position of the mobile body 100.

[0089] FIG. 9 schematically shows an example of the functional configuration of the mobile body 100. The mobile body 100 includes a storage unit 102, a communication unit 104, a position information acquisition unit 106, a communication antenna 150, and a communication antenna 160. Note that it is not always essential for the mobile body 100 to have all of these configurations.

[0090] The storage unit 102 stores various types of information. The storage unit 102 stores, for example, communication antenna information indicating the communication antennas possessed by the mobile body 100.

[0091] The communication unit 104 performs mobile body communication with a base station. The communication unit 104 performs mobile body communication with the base station 200 using, for example, the communication antenna 150. The communication unit 104 performs mobile body communication between the mobile body 100 and the base station 200 using, for example, radio waves having a frequency in the terahertz band, such that the product of the antenna gain of the transmitting-side communication antenna and the antenna gain of the receiving-side communication antenna in the mobile body communication is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves, using the communication antenna 150.

[0092] When establishing mobile body communication with the base station 200, for example, the communication unit 104 transmits an establishment request to the base station 200. The establishment request includes, for example, the communication antenna information stored in the storage unit 102.

[0093] The communication unit 104 performs mobile body communication with the base station 300 using, for example, the communication antenna 160. The communication unit 104 performs mobile body communication with the base station 300 using, for example, radio waves having a frequency lower than the terahertz band. The communication unit 104 receives presence information from the base station 300, for example.

[0094] The communication unit 104 may perform wireless communication with the notification device 400. The communication unit 104 performs wireless communication with the notification device 400 using, for example, the communication antenna 150. The communication unit 104 may perform wireless communication with the notification device 400 using the communication antenna 160. The communication unit 104 receives presence information from the notification device 400, for example.

[0095] The communication unit 104 performs mobile communication with the base station 200 based on, for example, the presence information received from the base station 300 or the notification device 400. The mobile body 100, for example, sets the state of the communication antenna 150 to a state capable of receiving radio waves in order to establish mobile communication with the base station 200.

[0096] The communication unit 104 performs mobile communication with the base station 200 based on, for example, the communication antenna information of the base station 200 included in the presence information received from the base station 300 or the notification device 400. For example, when the antenna gain of the communication antenna 150 is proportional to the first power of the cosecant of the elevation angle of the radio wave propagation direction, if the base station 200 has a communication antenna 250 whose antenna gain is proportional to the first power of the cosecant of the elevation angle of the radio wave propagation direction, the communication unit 104 sets the state of the communication antenna 150 to a state capable of receiving radio waves. On the other hand, when the antenna gain of the communication antenna 150 is proportional to the first power of the cosecant of the elevation angle of the radio wave propagation direction and the base station 200 does not have a communication antenna 250 whose antenna gain is proportional to the first power of the cosecant of the elevation angle of the radio wave propagation direction, the communication unit 104 does not set the state of the communication antenna 150 to a state capable of receiving radio waves.

[0097] For example, when the antenna gain of the communication antenna 150 is omnidirectional with respect to the elevation angle of the radio wave propagation direction, if the base station 200 has a communication antenna 250 whose antenna gain is proportional to the second power of the cosecant of the elevation angle of the radio wave propagation direction, the mobile body 100 sets the state of the communication antenna 150 to a state capable of receiving radio waves. On the other hand, when the antenna gain of the communication antenna 150 is omnidirectional with respect to the elevation angle of the radio wave propagation direction and the base station 200 does not have a communication antenna 250 whose antenna gain is proportional to the second power of the cosecant of the elevation angle of the radio wave propagation direction, the mobile body 100 does not set the state of the communication antenna 150 to a state capable of receiving radio waves.

[0098] The position information acquisition unit 106 acquires the position information of the mobile body 100. The position information acquisition unit 106 acquires the position information by using, for example, a GNSS (Global Navigation Satellite System) function. The position information acquisition unit 106 acquires the position information by using, for example, a GPS (Global Positioning System) function. The position information acquisition unit 106 may acquire the position information by using an RTK (Real Time Kinematic) function.

[0099] The position information acquisition unit 106 acquires the position information, for example, while the mobile body 100 is located within the coverage area 220 of the base station 200. The communication unit 104 may transmit the position information acquired while the mobile body 100 is located within the coverage area 220 of the base station 200 to the base station 300.

[0100] The communication unit 104 receives, for example, a handover instruction from the base station 300. In response to receiving the handover instruction from the base station 300, the communication unit 104 may hand over the base station where the mobile body 100 performs mobile body communication using radio waves of a frequency in the terahertz band from the source base station to the target base station.

[0101] FIG. 10 schematically shows an example of the functional configuration of the base station 200. The base station 200 includes a communication antenna 252, a communication antenna 254, and a communication unit 256. Note that it is not always essential for the base station 200 to have all of these configurations.

[0102] The communication antenna 252 may have an antenna gain proportional to the first power of the cosecant of the elevation angle in the propagation direction of radio waves of a frequency in the terahertz band. The communication antenna 254 may have an antenna gain proportional to the second power of the cosecant of the elevation angle in the propagation direction of radio waves of a frequency in the terahertz band.

[0103] The communication unit 256 performs mobile communication with the mobile body 100. For example, the communication unit 256 uses the communication antenna 252 to perform mobile communication with the mobile body 100. For example, the communication unit 256 uses the communication antenna 254 to perform mobile communication with the mobile body 100. The communication unit 256 performs mobile communication with the mobile body 100 using the communication antenna 252 or the communication antenna 254 such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile communication between the mobile body 100 and the base station 200 using radio waves with a frequency in the terahertz band is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves.

[0104] The communication unit 256 performs mobile communication with the mobile body 100 based on the communication antenna information of the mobile body 100 included in the establishment request received from the mobile body 100. For example, when the mobile body 100 has a communication antenna 150 whose antenna gain is proportional to the first power of the cosecant of the elevation angle in the propagation direction of the radio waves, the communication unit 256 uses the communication antenna 252 to perform mobile communication with the mobile body 100. For example, when the mobile body 100 has a communication antenna 150 whose antenna gain is omnidirectional with respect to the elevation angle in the propagation direction of the radio waves, the communication unit 256 uses the communication antenna 254 to perform mobile communication with the mobile body 100.

[0105] FIG. 11 is an explanatory diagram for explaining an example of the processing flow of the system 10. Here, the state where the mobile body 100 has not established mobile communication is set as the start state.

[0106] In step (the step may be abbreviated as S) 102, in response to the mobile body 100 moving from outside the coverage area 320 of the base station 300 to inside the coverage area 320 of the base station 300, the communication unit 104 uses the communication antenna 160 to establish mobile communication with the base station 300. In S104, the base station 300 transmits presence information to the mobile body 100 in response to establishing mobile communication with the mobile body 100 in S102.

[0107] In S106, based on the presence information received from the base station 300 in S104, the communication unit 104 establishes mobile communication with the base station 200 using the communication antenna 150. The mobile unit 100 establishes mobile communication with the base station 200 using the communication antenna 150 in response to the mobile unit 100 moving from outside the coverage area 220 of the base station 200 to inside the coverage area 220 of the base station 200. The mobile unit 100 and the base station 200 start mobile communication such that the product of the antenna gain of the transmitting-side communication antenna and the antenna gain of the receiving-side communication antenna in the mobile communication between the mobile unit 100 and the base station 200 using radio waves of a frequency in the terahertz band is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves.

[0108] In S108, in response to establishing mobile communication with the base station 200, the communication unit 104 transmits the position information of the mobile unit 100 acquired by the position information acquisition unit 106 to the base station 300. In S110, based on the position information received from the mobile unit 100 in S108, the base station 300 determines whether to hand over the base station where the mobile unit 100 performs mobile communication using radio waves of a frequency in the terahertz band from the base station 200 to another base station. Here, it is assumed that the base station 300 has determined to hand over from the base station 200 to another base station, and the description will continue.

[0109] In S112, the base station 300 transmits a handover instruction to the mobile unit 100. In S114, based on the handover instruction received from the base station 300 in S112, the communication unit 104 hands over the base station where mobile communication using radio waves of a frequency in the terahertz band is performed from the base station 200 to another base station. Thereafter, the mobile communication between the mobile unit 100 and the base station 200 ends.

[0110] FIG. 12 schematically shows an example of the hardware configuration of a computer 1200 that functions as the mobile body 100 or the base station 200. Programs installed in the computer 1200 cause the computer 1200 to function as one or more “units” of the apparatus according to the above-described embodiment, or cause the computer 1200 to execute an operation or the one or more “units” associated with the apparatus according to the above-described embodiment, and / or cause the computer 1200 to execute the process or a stage of the process according to the above-described embodiment. Such a program may be executed by the CPU 1212 so as 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.

[0111] The computer 1200 according to the present embodiment includes a CPU 1212, a RAM 1214, and a graphic controller 1216, which are interconnected 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 legacy input / output units such as a ROM 1230 and a keyboard 1242, which are connected to the input / output controller 1220 via an input / output chip 1240.

[0112] The CPU 1212 operates according to programs stored in the ROM 1230 and the RAM 1214, thereby controlling each unit. The graphic controller 1216 acquires image data generated by the CPU 1212 in a frame buffer or the like provided in the RAM 1214 or in itself, and causes the image data to be displayed on the display device 1218.

[0113] 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.

[0114] The ROM 1230 stores therein a boot program or the like executed by the computer 1200 at activation and / or a program that depends on the hardware of the computer 1200. The input / output chip 1240 may also connect various input / output units to the input / output controller 1220 via a USB port, a parallel port, a serial port, a keyboard port, a mouse port, or the like.

[0115] The program is provided by a computer-readable storage medium such as a DVD-ROM 1227 or an IC card. The program is read from the computer-readable storage medium, installed in the storage device 1224, the RAM 1214, or the ROM 1230, which is also an example of a computer-readable storage medium, and executed by the CPU 1212. The information processing described in these programs is read by the computer 1200, resulting in cooperation between the programs and the various types of hardware resources described above. The device or method may be configured by realizing the operation or processing of information according to the use of the computer 1200.

[0116] For example, when communication is executed between the computer 1200 and an external device, the CPU 1212 may execute a communication program loaded in the RAM 1214 and instruct the communication interface 1222 to perform communication processing based on the processing described in the communication program. Under the control of the CPU 1212, the communication interface 1222 reads transmission data stored in a transmission buffer area provided in a recording medium such as the RAM 1214, the storage device 1224, the DVD-ROM 1227, or an IC card, transmits the read transmission data to a network, or writes received data received from the network to a reception buffer area or the like provided on the recording medium.

[0117] Also, the CPU 1212 may cause all or a necessary part of a file or database stored in an external recording medium such as the storage device 1224, the DVD drive 1226 (DVD-ROM 1227), or an IC card to be read into the RAM 1214 and execute 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.

[0118] Various types of information such as various types of programs, data, tables, and databases may be stored in a 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 judgments, conditional branches, unconditional branches, search / replacement of information, etc., described throughout this disclosure and specified by the instruction sequence of the program, and write back the results to the RAM 1214. Also, the CPU 1212 may search for information in files, databases, etc. within the recording medium. For example, when a plurality of 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 searches for an entry that matches the condition where the attribute value of the first attribute is specified among the plurality of entries, reads the attribute value of the second attribute stored in the entry, and thereby may obtain the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition.

[0119] The programs or software modules described above may be stored in a computer-readable storage medium on or near the computer 1200. Also, a recording medium such as a hard disk or RAM provided within a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, thereby providing the program to the computer 1200 via the network.

[0120] In the flowchart and block diagram in this embodiment, a block may represent a stage of a process in which an operation is performed or a "part" of a device having a role of performing an operation. A specific stage and "part" may be implemented by a dedicated circuit, a programmable circuit supplied with computer-readable instructions stored on a computer-readable storage medium, and / or a processor supplied with computer-readable instructions stored on a computer-readable storage medium. The dedicated circuit may include digital and / or analog hardware circuits, and may include an integrated circuit (IC) and / or discrete circuits. The programmable circuit may include, for example, a reconfigurable hardware circuit including logical products, logical sums, exclusive logical sums, negative logical products, negative logical sums, and other logical operations, flip-flops, registers, and memory elements, such as a field programmable gate array (FPGA) and a programmable logic array (PLA).

[0121] The computer-readable storage medium may include any tangible device capable of storing instructions executable by an appropriate device. As a result, a computer-readable storage medium having instructions stored therein will comprise a product including instructions executable to create means for performing the operations specified in the flowchart or block diagram. Examples of the computer-readable storage medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, a semiconductor storage medium, and the like. More specific examples of the computer-readable storage medium may include a floppy (registered trademark) disk, a diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a Blu-ray (registered trademark) disk, a memory stick, an integrated circuit card, and the like.

[0122] Computer-readable instructions may include any combination of one or more programming languages, including assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or object-oriented programming languages such as Smalltalk®, JAVA®, C++, and conventional procedural programming languages such as the "C" programming language or similar programming languages, either in source code or object code.

[0123] The computer-readable instructions may be provided locally or via a wide area network (WAN) such as a local area network (LAN), the Internet, etc., to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, or a programmable circuit, for the processor of the general-purpose computer, special-purpose computer, or other programmable data processing device, or the programmable circuit to execute the operations specified in the flowchart or block diagram by generating means for executing the computer-readable instructions. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc.

[0124] As described above, the present invention has been described using embodiments. However, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that forms with such changes or improvements may also be included in the technical scope of the present invention.

[0125] In the claims, the specification, and the drawings, the execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown is not explicitly indicated as "earlier" or "preceding" etc. in particular. It should be noted that, unless the output of the previous process is used in the subsequent process, it can be realized in any order. Regarding the operation flows in the claims, the specification, and the drawings, even if explanations are made using "first," "next," etc. for convenience, it does not mean that it is essential to implement in this order.

Explanation of Reference Signs

[0126] 10 System, 20 Network, 50 Sign, 52 Sign, 54 Sign, 100 Mobile Body, 102 Storage Unit, 104 Communication Unit, 106 Position Information Acquisition Unit, 150 Communication Antenna, 200 Base Station, 202 Base Station, 204 Base Station, 220 Coverage Area, 222 Coverage Area, 224 Coverage Area, 250 Communication Antenna, 252 Communication Antenna, 254 Communication Antenna, 256 Communication Unit, 300 Base Station, 320 Coverage Area, 400 Notification Device, 420 Coverage Area, 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, 1226 DVD Drive, 1227 DVD-ROM, 1230 ROM, 1240 Input / Output Chip, 1242 Keyboard

Claims

1. A mobile body, a first base station, and are provided with, in the mobile body communication between the mobile body and the first base station using radio waves in the terahertz band, the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves, and mobile body communication is performed. A communication system.

2. The received power (P ＲＥ ) of the radio wave satisfies the following formula, 【Number 1】 Here, P ＴＲ is the transmission power of the radio wave, G ＴＲ is the antenna gain of the communication antenna on the transmission side, G ＲＥ is the antenna gain of the communication antenna on the reception side, λ is the wavelength of the radio wave, h is the altitude difference between the altitude of the communication antenna on the transmission side and the altitude of the communication antenna on the reception side, and θ is the elevation angle. The communication system according to claim 1.

3. The mobile body has a first communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation angle, The first base station has a second communication antenna whose antenna gain is proportional to the first power of the cosecant of the elevation angle, The communication system according to claim 1 or 2.

4. The mobile body has a first communication antenna whose antenna gain is omnidirectional with respect to the elevation angle, The first base station has a second communication antenna whose antenna gain is proportional to the square of the cosecant of the elevation angle, The communication system according to claim 1 or 2.

5. The mobile body performs mobile body communication with a second base station that has a coverage area including the coverage area of the first base station using radio waves having a frequency lower than the terahertz band, and receives, from the second base station, first presence information indicating that the first base station exists within the coverage area of the second base station, and performs mobile body communication with the first base station based on the first presence information. The communication system according to claim 1 or 2.

6. An informing device is further provided, The informing device is disposed outside the coverage area of the first base station, and transmits, using radio waves in the terahertz band, second presence information indicating that the first base station exists within a predetermined range from the informing device to the mobile body, The mobile body performs mobile body communication with the first base station based on the second presence information. The communication system according to claim 1 or 2.

7. A mobile body, a communication antenna used for mobile body communication between the mobile body and a base station, and a communication unit that performs mobile body communication with the base station using the communication antenna provided in the mobile body such that the product of the antenna gain of the communication antenna on the transmission side and the antenna gain of the communication antenna on the reception side in the mobile body communication between the mobile body and the base station using radio waves in the terahertz band is proportional to the square of the cosecant of the elevation angle in the propagation direction of the radio waves. A mobile body provided with.

8. The mobile body according to claim 7, wherein the antenna gain of the communication antenna included in the mobile body is proportional to the first power of the cosecant of the elevation angle.

9. A program which, when executed by a computer, causes the computer to function as the mobile body according to claim 7 or 8.

10. A base station, comprising: a communication antenna used for mobile body communication between the mobile body and the base station; a communication unit that performs mobile body communication between the mobile body and the base station using radio waves having a frequency in the terahertz band, wherein the product of the antenna gain of the transmission-side communication antenna and the antenna gain of the reception-side communication antenna in the mobile body communication is proportional to the second power of the cosecant of the elevation angle in the propagation direction of the radio waves, and the communication unit uses the communication antenna included in the base station; A base station comprising the above.

11. The base station according to claim 10, wherein the antenna gain of the communication antenna included in the base station is proportional to the first power of the cosecant of the elevation angle.

12. A program which, when executed by a computer, causes the computer to function as the base station according to claim 10 or 11.

Images