RIS and mobile body communication system

Abstract

The present invention realizes a multi-functional RIS. An RIS (20) comprises a first backscatter communication element (21) that performs backscatter communication with a self-driving vehicle (50) that is at a first position (P1) on a road surface positioned in the vicinity of an installation position. The first backscatter communication element performs on-off keying with respect to incident radio waves (41) from a base station (10), thereby notifying the self-driving vehicle at the first position of first self-driving assistance information.

Description

RIS and Mobile Communication System

[0001] The present invention relates to a RIS and a mobile communication system including the RIS.

[0002] In the mobile communication network to which the present invention is applied, optimization and automation of radio resources of a RAN (Radio Access Network) are realized by a so-called RIC (RAN Intelligent Controller). In such a mobile communication network, for the purpose of improving the coverage of a high-frequency band and the quality of wireless communication, the deployment of a device called a RIS (Reconfigurable Intelligent Surface) is being considered.

[0003] Regarding the RIS, in addition to improving the coverage of the high-frequency band and the quality of wireless communication, giving it another function is also being considered. For example, Patent Document 1 discloses using a RIS as an example of a power transmission device that wirelessly powers a terminal device.

[0004] WO2024 / 142334

[0005] One aspect of the present invention aims to realize a multifunctional RIS or the like.

[0006] In order to solve the above problems, a RIS according to one aspect of the present invention is a RIS (Reconfigurable Intelligent Surface) that extends the coverage of a cell in a mobile communication network, and includes a downlink communication element that reflects radio waves of downlink communication from a base station to a terminal in the cell, and a first backscatter communication element that performs backscatter communication with an autonomous vehicle located at a first position on a road surface near the installation position of the RIS. The first backscatter communication element notifies first autonomous driving support information to the autonomous vehicle located at the first position by performing on-off keying on the radio waves incident from the base station.

[0007] According to one aspect of the present invention, a multifunctional RIS or the like can be realized.

[0008] This figure illustrates a schematic of a mobile communication system including RIS according to Embodiment 1. This figure illustrates a schematic of a mobile communication system including RIS according to Embodiment 2.

[0009] [Embodiment 1] Figure 1 is a diagram illustrating the schematic of a mobile communication system 100 according to Embodiment 1. The mobile communication system 100 provides a mobile communication network to a terminal 30 capable of wireless communication. The terminal 30 is, for example, a portable information terminal such as a smartphone or tablet. As shown in Figure 1, the mobile communication system 100 includes a base station 10 and a RIS (Reconfigurable Intelligent Surface) 20.

[0010] For simplicity, Figure 1 shows only one base station 10, one RIS 20, and one terminal 30. However, the mobile communication system 100 may have multiple base stations 10 and multiple RIS 20s. Furthermore, the mobile communication system 100 may provide a mobile communication network to multiple terminals 30.

[0011] Base station 10 constitutes a cell in the mobile communication network. Specifically, base station 10 emits radio waves 41. Radio waves 41 are radio waves for downlink communication from base station 10 to terminal 30. The range in which terminal 30 can receive radio waves 41 is the coverage of the cell formed by base station 10.

[0012] RIS20 extends cell coverage in mobile communication networks. RIS20 comprises multiple downlink communication elements 25 that reflect radio waves 41. Each downlink communication element 25 is a reflective element whose direction of reflection of the radio waves 41 can be arbitrarily controlled. Multiple downlink communication elements 25 can scatter the radio waves 41 in various directions, for example. Furthermore, multiple downlink communication elements 25 can concentrate the radio waves 41 at a specific location as needed.

[0013] The downlink communication element 25 reflects the radio waves 41 emitted from the base station 10 to areas where the radio waves 41 cannot directly reach, such as areas located in the shadow of a building relative to the base station 10. As a result, the terminal 30 can receive the radio waves 41 reflected by the downlink communication element 25, as shown in Figure 1, even in areas where the radio waves 41 emitted from the base station 10 cannot directly reach. In other words, the coverage of the cell formed by the base station 10 is extended by the RIS 20 to areas where the radio waves 41 emitted from the base station 10 cannot directly reach.

[0014] Furthermore, the RIS 20 may perform spatial division multiplexing transmission using multiple downlink communication elements 25. This can improve the speed of downlink communication from the base station 10 to the terminal 30.

[0015] The RIS 20 further comprises a first backscatter communication element 21. The first backscatter communication element 21 performs backscatter communication with the autonomous vehicle 50. The autonomous vehicle 50 is a vehicle equipped with an autonomous driving function, located at a first position P1 on the road surface near the installation location of the RIS 20.

[0016] The first backscatter communication element 21 is a reflective element that can switch between a state in which it reflects radio waves 41 toward the first position P1 and a state in which it does not reflect them. By switching between the state in which it reflects radio waves 41 and the state in which it does not reflect them, the first backscatter communication element 21 generates radio waves 55 that include a signal indicating the first automated driving support information and transmits it to the automated driving vehicle 50. That is, the first backscatter communication element 21 notifies the automated driving support information to the automated driving vehicle 50 by performing on / off keying to the radio waves 41 incident from the base station 10. The first automated driving support information is information related to the automated driving of the automated driving vehicle 50 in the first position P1 and its vicinity, and is, for example, information on traffic signals and / or traffic signs.

[0017] The autonomous vehicle 50 can appropriately perform autonomous driving at the first position P1 and its vicinity by receiving first autonomous driving support information from the first backscatter communication element 21. Therefore, with the RIS 20, autonomous driving of the autonomous vehicle 50 can be supported without installing dedicated equipment for notifying the autonomous vehicle 50 of the first autonomous driving support information. In other words, a multi-functional RIS 20 can be realized that has the function of supporting autonomous driving in addition to expanding cell coverage in the mobile communication network.

[0018] The first backscatter communication element 21 may add a header to the signal of the first automated driving support information to distinguish it from the downlink communication signal, and then broadcast the first automated driving support information to the automated driving vehicle 50. This allows the RIS 20 to broadcast the signal of the first automated driving support information to the automated driving vehicle 50 in a state that can be distinguished from the downlink communication signal included in the radio wave 41.

[0019] The first backscatter communication element 21 does not necessarily have to add the above header to the signal of the first automated driving support information. For example, if the direction in which the radio waves 41 are reflected for downlink communication is assumed to be different from the direction of the first position P1, the automated driving vehicle 50 can identify the signal of the first automated driving support information according to its own position. A specific example is the case in which it is assumed that the terminal 30 will not approach the first position P1.

[0020] Furthermore, as described above, the radio wave 55 is generated by on / off keying. For this reason, the radio wave 55 has a different waveform from the radio wave 41. Specifically, the radio wave 55 takes only one value, either 0 or 1, while the radio wave 41 includes other values. For this reason, the autonomous vehicle 50 can distinguish the radio wave 55 from the radio wave 41 by its waveform, thereby distinguishing the signal of the first autonomous driving support information from the signal of downlink communication.

[0021] The RIS 20 may be equipped with multiple first backscatter communication elements 21. In this case, the multiple first backscatter communication elements 21 may perform the same on / off keying on each other. That is, the multiple first backscatter communication elements 21 may generate radio waves 55 indicating the same first automatic driving support information. This makes it possible to perform beamforming of the radio waves 55 using spatial multiplexing when the element is ON.

[0022] Furthermore, if the RIS 20 is equipped with multiple first backscatter communication elements 21, the multiple first backscatter communication elements 21 may be arranged so as not to be adjacent to each other. This suppresses interference of the beamformed radio waves 55 outside its range and increases the SINR (Signal to Interference-plus-Noise Ratio) of the radio waves 55. An example of interference of the radio waves 55 outside its range is interference with radio waves 41.

[0023] In RIS20, the structure of the first backscatter communication element 21 may be the same as the structure of the downlink communication element 25. In other words, in RIS20, multiple reflective elements having the same structure, which can arbitrarily control the direction in which they reflect radio waves 41, may be divided into downlink communication elements 25 and first backscatter communication elements 21 depending on the application.

[0024] By dividing the reflective elements of the RIS20 into a downlink communication element 25 and a first backscatter communication element 21 depending on the application, downlink communication and backscatter communication can be performed simultaneously as needed. Furthermore, self-interference between downlink communication and backscatter communication can be prevented. In addition, since the structure of the first backscatter communication element 21 and the structure of the downlink communication element 25 are the same, the manufacturing cost of the RIS20 is reduced compared to when they are different.

[0025] In the RIS 20, the number of first backscatter communication elements 21 may be less than or equal to the number of downlink communication elements 25. Specifically, the number of first backscatter communication elements 21 may be the minimum number required for backscatter communication. In this case, the number of downlink communication elements 25 will be the total number of reflecting elements in the RIS 20 minus the number of first backscatter communication elements 21.

[0026] When performing backscatter communication using a relatively low modulation called on-off keying, increasing the number of first backscatter communication elements 21 beyond the minimum number required for backscatter communication does not provide any benefits such as an increase in the number of transmittable bits. Therefore, by setting the number of first backscatter communication elements 21 as described above, backscatter communication can be enabled, and the reduction in downlink communication speed can be minimized compared to the case where the first backscatter communication elements 21 are absent.

[0027] [Embodiment 2] Figure 2 is a diagram illustrating the schematic of a mobile communication system 200 according to Embodiment 2. As shown in Figure 2, the mobile communication system 200 differs from the mobile communication system 100 in that it includes a RIS20A instead of a RIS20. In addition to the configuration of the RIS20, the RIS20A further includes a second backscatter communication element 22.

[0028] The second backscatter communication element 22 performs backscatter communication with the autonomous vehicle 60. The autonomous vehicle 60 is a vehicle equipped with an autonomous driving function, located at a second position P2, which is different from the first position P1, on the road surface near the installation position of the RIS 20A.

[0029] The second backscatter communication element 22 is a reflective element that can switch between a state in which it reflects the radio waves 41 toward the second position P2 and a state in which it does not reflect them. By switching between the state in which it reflects the radio waves 41 and the state in which it does not reflect them, the second backscatter communication element 22 generates radio waves 65 containing a signal indicating the second automated driving support information and transmits it to the automated driving vehicle 60. In other words, the second backscatter communication element 22 notifies the automated driving vehicle 60 of the second automated driving support information by performing on / off keying to the radio waves 41 incident from the base station 10.

[0030] The second automated driving support information is information related to the automated driving of the automated driving vehicle 60 at the second position P2 and its vicinity, such as information on traffic signals and / or traffic signs. By receiving the second automated driving support information from the second backscatter communication element 22, the automated driving vehicle 60 can appropriately perform automated driving at the second position P2 and its vicinity. Therefore, according to RIS 20A, in addition to notifying the automated driving vehicle 50 of the first automated driving support information, it is also possible to notify the automated driving vehicle 60 of the second automated driving support information.

[0031] The second backscatter communication element 22 may add a header to the signal of the second automated driving support information to distinguish it from the downlink communication signal and the signal of the first automated driving support information, and then broadcast the second automated driving support information to the automated driving vehicle 60. As a result, the RIS 20A can broadcast the signal of the second automated driving support information to the automated driving vehicle 50 in a state in which it can be distinguished from the downlink communication signal included in the radio wave 41 and the signal of the first automated driving support information included in the radio wave 55.

[0032] The second backscatter communication element 22 does not necessarily have to add the above header to the signal of the second automated driving support information. For example, if it is assumed that the direction in which the radio waves 41 are reflected for downlink communication, the direction of the first position P1, and the direction of the second position P2 are different from each other, the automated driving vehicle 50 can identify the signals of the first automated driving support information and the second automated driving support information according to its own position.

[0033] The RIS 20A may be equipped with multiple second backscatter communication elements 22. In this case, the multiple second backscatter communication elements 22 may perform the same on / off keying to each other. That is, the multiple second backscatter communication elements 22 may generate radio waves 65 that include signals indicating the same second automated driving support information. As a result, even if a malfunction occurs in one of the multiple second backscatter communication elements 22, the other second backscatter communication elements 22 can notify the automated driving support information to the automated driving vehicle 60.

[0034] Furthermore, if the RIS 20A is equipped with multiple second backscatter communication elements 22, the multiple second backscatter communication elements 22 may be arranged so as not to be adjacent to each other. Moreover, the multiple second backscatter communication elements 22 may be arranged so as not to be adjacent to each of the multiple first backscatter communication elements 21. This reduces the impact on spatial division multiplexing transmission between the base station 10 and the terminal 30 caused by the RIS 20A being equipped with multiple first backscatter communication elements 21 and second backscatter communication elements 22.

[0035] In RIS20A, the structure of the second backscatter communication element 22 may be the same as that of the downlink communication element 25 and the first backscatter communication element 21. In other words, in RIS20A, multiple reflective elements having the same structure may be divided into the downlink communication element 25, the first backscatter communication element 21, and the second backscatter communication element 22.

[0036] In Figure 2, the number of first backscatter communication elements 21 and the number of second backscatter communication elements 22 in the RIS20A are equal. However, the number of first backscatter communication elements 21 and the number of second backscatter communication elements 22 in the RIS20A may be different.

[0037] In RIS20A, the sum of the number of first backscatter communication elements 21 and the number of second backscatter communication elements 22 may be less than or equal to the number of downlink communication elements 25. Specifically, the number of first backscatter communication elements 21 and the number of second backscatter communication elements 22 may be the minimum number required for backscatter communication. In this case, the number of downlink communication elements 25 is obtained by subtracting the number of first backscatter communication elements 21 and the number of second backscatter communication elements 22 from the total number of reflecting elements provided by RIS20.

[0038] Furthermore, the RIS 20A may also be capable of broadcasting automated driving support information to an automated driving vehicle located at a position other than both the first position P1 and the second position P2. In that case, the RIS 20A may further include backscatter communication elements other than the first backscatter communication element 21 and the second backscatter communication element 22 for broadcasting automated driving support information to the automated driving vehicle located at that other position. In that case, the other position may be single or multiple. In other words, there is no particular limit to the number of positions to which the RIS 20A broadcasts automated driving support information to an automated driving vehicle.

[0039] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0040] 20, 20A RIS 21 First backscatter communication element 22 Second backscatter communication element 25 Downlink communication element 100, 200 Mobile communication system

Claims

1. A Reconfigurable Intelligent Surface (RIS) for extending cell coverage in a mobile communication network, comprising: a downlink communication element that reflects radio waves of downlink communication from a base station to a terminal in the cell; and a first backscatter communication element that performs backscatter communication with an autonomous vehicle located at a first position on the road surface near the installation location of the RIS, wherein the first backscatter communication element broadcasts first autonomous driving support information to the autonomous vehicle located at the first position by performing on / off keying in response to radio waves incident from the base station.

2. The RIS according to claim 1, wherein the first backscatter communication element adds a header to the signal of the first automated driving support information to distinguish it from the signal of the downlink communication, and broadcasts the first automated driving support information to an automated driving vehicle located at the first position.

3. The RIS according to claim 1 or 2, wherein the first backscatter communication elements are a plurality of, and the plurality of first backscatter communication elements perform the same on / off keying to each other.

4. The RIS according to any one of claims 1 to 3, wherein the first backscatter communication elements are a plurality, and the plurality of first backscatter communication elements are arranged so as not to be adjacent to one another.

5. The RIS according to any one of claims 1 to 4, further comprising a second backscatter communication element that performs backscatter communication with an autonomous vehicle located at a second position different from the first position on the road surface located near the installation position of the RIS, wherein the second backscatter communication element broadcasts second autonomous driving support information to the autonomous vehicle located at the second position by performing on / off keying in response to radio waves incident from the base station.

6. A mobile communication system comprising the RIS described in any one of claims 1 to 5.

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