Communication device, control method, and program

Abstract

An embodiment of the present invention provides a communication device including an acquisition unit for acquiring obstacle information including a distance from an emission unit that emits a beam to an obstacle that blocks the beam, a derivation unit for deriving a beam width of the beam emitted from the emission unit according to the distance to the obstacle acquired by the acquisition unit, and a beam control unit for controlling the emission unit to emit the beam with the beam width derived by the derivation unit.

Description

[Technical Field]

[0001] The present invention relates to a communication device, a control method, and a program technology. [Background technology]

[0002] Communication systems such as 5G use high-frequency millimeter wave bands. In order to achieve even higher speeds and larger capacities in future wireless communication systems such as 6G, it is expected that even higher frequency bands will be used, which will allow for wider bandwidths.

[0003] Because high frequency bands have large propagation losses and short wavelengths, increasing the number of antenna elements and performing beamforming ensures gain and covers the communication area. Before a connection is established between the base station and the terminal, or when the connection is lost (initial connection), the appropriate beam direction is unknown, so a beam search is required to estimate the appropriate beam direction.

[0004] Figure 7 shows beam search in 5G NR (New Radio). Figure 7 shows the base station, the terminal, and the terminal's received power. It also shows the relative positions of the base station and the terminal. The terminal is located slightly to the right as seen from the base station. It also shows the changes in the beam radiation direction and received power from time t1 to t5. As shown in Figure 7, the closer the beam direction is to the terminal, the greater the terminal's received power.

[0005] In this way, at the time of initial connection in 5G NR, a full-search type beam search is performed in which a comprehensive beam sweep is performed within the coverage area and the beam with the highest received power is selected (see Non-Patent Document 1).

[0006] Fig. 8 is a diagram showing a hierarchical beam search. As in Fig. 7, Fig. 8 shows a base station, a terminal, and the received power of the terminal. It also shows the positional relationship between the base station and the terminal. The terminal is located slightly to the right as seen from the base station. It also shows the change in the beam radiation direction and the change in received power from time t1 to t5.

[0007] As shown in Fig. 8, in hierarchical beam search, a sweep is performed in the first stage (t1, t2, t3) with a beam having a wide beam width. Then, in the second stage (t4, t5), a sweep is performed with a beam having a narrower beam width than the beam in the first stage. In this way, a technology has been proposed that performs hierarchical beam search to reduce the number of beam searches. In hierarchical beam search, the second stage of beam search can be performed individually for each user, or it can be performed simultaneously for all terminals in a multicast manner (see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Takeda et al., "NR Physical Layer Specifications for 5G," NTT DOCOMO Technical Journal, Vol. 26, No. 3, pp. 47-58, Nov. 2018. [Non-patent document 2] Kojima et al., "Study and Evaluation of Two-Stage Beam Search Method for Millimeter-Wave Communications," IEICE Technical Report, vol.116, no.396, RCS2016-237, pp.7-11, January 2017. Summary of the Invention [Problem to be solved by the invention]

[0009] Since propagation attenuation increases with increasing frequency, it is necessary to increase the beamforming gain by narrowing the beam width. One way to narrow the beam width is to increase the number of antenna elements or to use lenses to widen the antenna aperture area.

[0010] On the other hand, narrowing the beam width increases the directivity, and the overhead associated with beam search increases because the number of searches increases when performing a beam sweep to cover a spatial region. Widening the beam width to reduce overhead reduces the beamforming gain, leading to a reduction in coverage.

[0011] Furthermore, in the above-mentioned hierarchical beam search, if the second-stage beam search is performed for each terminal, the number of beam searches increases according to the number of terminals. If the second-stage beam search is performed simultaneously for all terminals, if users are uniformly distributed within the coverage area, the beam search must be performed comprehensively, and the number of beam searches becomes the same as for the full search type. As such, it has been difficult to reduce the overhead of beam search while ensuring coverage at the same time.

[0012] In view of the above circumstances, an object of the present invention is to provide a technology that can reduce the overhead of beam search while ensuring coverage. [Means for solving the problem]

[0013] One aspect of the present invention is a communication device that includes an acquisition unit that acquires obstruction information including the distance from an emission unit that emits a beam to an obstruction that blocks the beam, a derivation unit that derives the beam width of the beam emitted from the emission unit in accordance with the distance to the obstruction acquired by the acquisition unit, and a beam control unit that controls the emission unit to emit the beam with the beam width derived by the derivation unit.

[0014] One aspect of the present invention is a control method for a communication device, comprising: an acquisition step of acquiring obstruction information including the distance from an emission unit that emits a beam to an obstruction that blocks the beam; a derivation step of deriving the beam width of the beam emitted from the emission unit in accordance with the distance to the obstruction acquired in the acquisition step; and a beam control step of controlling the emission unit to emit the beam with the beam width derived in the derivation step.

[0015] One aspect of the present invention is a program for causing a computer to function as a communication device, the program causing the computer to function as an acquisition unit that acquires obstruction information including the distance from an emission unit that emits a beam to an obstruction that blocks the beam, a derivation unit that derives the beam width of the beam emitted from the emission unit in accordance with the distance to the obstruction acquired by the acquisition unit, and a beam control unit that controls the emission unit to emit the beam with the beam width derived by the derivation unit. [Effects of the Invention]

[0016] The present invention can reduce the overhead of beam searching. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a configuration of a communication device 100. FIG. [Figure 2] FIG. 1 is a diagram showing a shield and a beam. [Figure 3] FIG. 10 is a diagram illustrating an example of a combination stored in a storage unit. [Figure 4] 10 is a flowchart showing a flow of processing by the communication device. [Figure 5] FIG. 10 is a diagram showing the state of a beam when the antenna is installed on the ceiling. [Figure 6] FIG. 10 is a diagram illustrating an example of a combination stored in a storage unit. [Figure 7] FIG. 1 illustrates a conventional technique. [Figure 8] FIG. 1 illustrates a conventional technique. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. 1 is a block diagram showing the configuration of a communication device 100 according to this embodiment. The communication device 100 includes an acquisition unit 110, a derivation unit 120, a storage unit 130, a signal processing unit 140, a beam control unit 150, and an antenna 160.

[0019] The acquisition unit 110 acquires obstruction information including the distance from the antenna 160 to an obstruction that blocks a beam. Specifically, the acquisition unit 110 acquires, as the obstruction information, the distance from the antenna 160 to the obstruction in a predetermined area (hereinafter referred to as the "communication area"), the direction from the antenna 160 to the obstruction, the size of the obstruction, and the like. Methods for acquiring the obstruction information include methods for acquiring the information from sensing information obtained by sensing using radio waves, light waves, sound waves, etc., video captured by a camera, 3D map data, etc. The sensing information, video captured by a camera, and 3D map data may be input by, for example, the operator of the communication device 100.

[0020] The derivation unit 120 derives the beam width of the beam radiated from the antenna 160 according to the distance to the obstruction acquired by the acquisition unit 110. Specifically, the derivation unit 120 calculates the difference between the beam's reach at maximum beamforming gain and the distance to the obstruction. The derivation unit 120 calculates the required allowable gain reduction in each direction using a theoretical value of distance attenuation for this difference. The derivation unit 120 calculates the number of antenna elements that can be reduced in the antenna 160 from the required allowable gain reduction, and derives the beam width when the number of antenna elements is reduced. From the above, the derivation unit 120 derives the beam width that makes the communication distance using the beam radiated from the antenna 160 equal to or greater than the distance to the obstruction. Furthermore, the derivation unit 120 determines the narrowest beam width to be the beam width of the beam in a direction where there are no obstructions.

[0021] Note that if it is possible to create a beam width that makes the beam's reach exactly the same as the distance to the obstruction, the derivation unit 120 may derive the beam width that makes the beam's reach exactly the same as the distance to the obstruction, but because the beam width can be discretely controlled to reduce the number of antenna elements, it is not always possible to create a beam width that makes the beam's reach exactly the same as the distance to the obstruction. Therefore, if it is not possible to create a beam width that makes the beam's reach exactly the same as the distance to the obstruction, the derivation unit 120 derives a beam width that makes the beam's reach greater than the distance to the obstruction and less than the beam's reach at maximum beamforming gain.

[0022] Furthermore, if there is a need to leave some margin in the communication area, adjacent beams may be partially overlapped at a distance greater than the distance to the obstruction, or the beam width may be set so that the half-width (e.g., a beam width 3 dB lower) rather than the peak of the beam fills the communication area in the distance direction.

[0023] The storage unit 130 stores combinations of beam directions that can cover a communication area with beams and beam widths of beams radiated in the beam directions. The signal processing unit 140 performs signal processing for wireless communication.

[0024] The beam control unit 150 converts signals received from the signal processing unit 140 into radio signals and outputs them to the antenna 160, and also converts radio signals received from the antenna into electrical signals and outputs them to the signal processing unit 140. The beam control unit 150 also controls the antenna 160 to transmit a beam with the beam width derived by the derivation unit 120. Furthermore, the beam control unit 150 performs beam forming and beam search using the combinations stored in the storage unit 130. The antenna 160 is an example of a radiating unit. The antenna 160 is composed of multiple antenna elements.

[0025] Note that the storage unit 130 is not required in a configuration in which the derived beam width is directly passed from the derivation unit 120 to the beam control unit 150. An example of such a configuration is a configuration in which the acquisition unit 110 periodically acquires obstruction information and derives the beam width accordingly.

[0026] Fig. 2 is a diagram showing obstructions and beams. Shown in Fig. 2 are an antenna 160, six beams B1 to B6, and two obstructions A and B (for example, structures such as buildings). The fan-shaped area indicated by the dotted line indicates the communication area. Furthermore, (θ, W) indicate the angle of the beam direction and the beam width.

[0027] If there is an obstruction, radio waves are blocked by the obstruction, and there is a high probability that the area on the opposite side of the obstruction from antenna 160 will be an area where communication is not possible. This tendency is particularly strong for radio waves in the high frequency band, as they tend to travel in a straight line and are highly attenuated, and there is little detouring or reflection.

[0028] Therefore, if there is an obstruction within the communication area, the distance coverage will be narrower in the direction of the obstruction, and it is expected that the required gain from beamforming will also be reduced. If the required gain from beamforming is reduced, the antenna aperture length can be narrowed by thinning out the number of antenna elements used for beamforming, and the beam width can be widened. Widening the beam width reduces the number of beam searches.

[0029] 2, beams B1, B4, and B5 have the narrowest beam widths because they are not blocked by any obstructions. Beams B1, B4, and B5 represent beams with the longest distances (referred to as "longest beams") that can be communicated by antenna 160. On the other hand, even if the longest beams are emitted in the direction of obstructions A and B, there is a high probability that the areas on the opposite sides of obstructions A and B will be areas where communication is not possible, for the reasons described above.

[0030] Therefore, for the directions of the obstructions A and B, the derivation unit 120 derives a beam width such that the communication distance of the beam emitted by the antenna 160 is equal to or greater than the distance to the obstructions. Beams B2, B3, and B6 are beams emitted from the antenna 160 controlled to have the derived beam width. As shown in FIG. 2, the beam widths of beams B2, B3, and B6 are wider than the beam widths of beams B1, B4, and B5. Therefore, compared to conventional technology that searches using the beam widths of beams B1, B4, and B5, the number of beams covering the communication area can be reduced. This reduction in the number of beams reduces the number of beam searches, thereby reducing overhead compared to conventional technology. Furthermore, even if the number of beams is reduced, the communication area remains unchanged because the area on the other side of the obstructions is an area where communication is not possible even with conventional technology. Note that while FIG. 2 depicts beams and obstructions on a two-dimensional plane, the same can be considered in three-dimensional space.

[0031] FIG. 3 is a diagram showing example combinations stored in the storage unit 130. The example combinations shown in FIG. 3 correspond to the beams in FIG. 2. A combination is composed of a direction θ and a width W. The direction θ indicates the angle between the line segment L shown in FIG. 2 and the direction of the beam. In other words, it is the angle between the line segment L on the ground and the direction of the beam projected onto the ground, with the ground being considered as a plane. The width W indicates the beam width. Note that the beam width is determined by the gain or the number of antenna elements, as described above. Therefore, the gain or the number of antenna elements may be used in the combinations instead of the beam width. Note that the elevation angle may also be used as an angle indicating the direction.

[0032] In addition, indexes (e.g., numbers) are assigned in advance to beam patterns (e.g., patterns indicating the beam direction and width) that can be generated by the communication device 100. Then, the storage unit 130 may store combinations using only these indexes. In this way, combinations can be stored without storing the beam direction and width.

[0033] 4 is a flowchart showing the processing flow of the communication device 100. The acquisition unit 110 acquires shielding object information (step S101). The acquisition unit 110 determines whether the shielding object information acquired in step S101 has been updated from the shielding object information acquired previously (step S102). Note that if the shielding object information acquired previously does not exist, such as when the shielding object information is acquired for the first time in step S101, the shielding object information is deemed to have been updated.

[0034] If the information has not been updated from the obstruction information (step S102: NO), the communication device 100 proceeds to step S105. If the information has been updated from the obstruction information (step S102: YES), the derivation unit 120 derives the beam width for each direction in the communication area according to the obstruction information such as distance (step S103).

[0035] The storage unit 130 stores a combination of a beam direction and a beam width of a beam radiated in the beam direction using the beam width derived by the derivation unit 120 (step S104). If a combination has already been stored, the storage unit 130 updates the combination by overwriting it. The beam control unit 150 performs a beam search by referring to the stored combination (step S105) (step S106).

[0036] In beam search, communication device 100 generates a beam sweep signal in which a beam ID that can uniquely identify each beam is embedded as digital information. Communication device 100 transmits this beam sweep signal on each beam that is generated by switching over time. The terminal measures the received power of each beam and reads the beam ID embedded in the beam sweep signal to determine which transmitting beam has the best quality, and feeds this back to communication device 100. Communication device 100 selects the beam with the best quality.

[0037] In the flowchart described above, the acquisition of the obstruction information in step S101 may be performed periodically, or may be performed only once before the communication device 100 starts operating.

[0038] In the above-described embodiment, the obstruction is assumed to be an outdoor structure such as a building, but obstructions also exist indoors. For example, if an antenna is installed on the ceiling, the floor also acts as an obstruction because it blocks radio waves. Fig. 5 is a diagram showing the state of beams when antenna 160 is installed on the ceiling. Fig. 5 shows five beams b1 to b5, the ceiling, and the floor.

[0039] Indoors, the farther the floor surface is from the antenna 160, the longer the distance from the antenna 160. Therefore, the derivation unit 120 derives the beam width according to the distance, so the embodiment for the outdoor case can be applied as is. Indoors, the farther the floor surface is from the antenna 160, the narrower the beam width.

[0040] FIG. 6 is a diagram illustrating an example of combinations stored in the storage unit 130. The example combinations shown in FIG. 6 correspond to the beams in FIG. 5. Each combination is composed of two angles τ and φ, and a width w. The angle τ indicates the angle between the beam direction and a line segment M perpendicular to the line segment L. The angle φ indicates the angle between the line segment L on the floor surface and the direction of the beam projected onto the floor surface. Similarly, in the case of FIG. 6, the combinations may use gain or the number of antenna elements instead of beam width. Also, indexes (e.g., numbers) may be assigned in advance to beam patterns (e.g., patterns indicating the beam direction and width) that the communication device 100 can generate. The storage unit 130 may then store the combinations using only these indexes. This allows the combinations to be stored without storing the beam direction and width.

[0041] In the embodiment described above, the communication device 100 includes the signal processing unit 140. However, the signal processing unit may be divided into devices such as a CU (Centralized Unit), a DU (Distributed Unit), and an RU (Radio Unit) in 5G NR. The acquisition unit 110 may be provided outside the communication device 100.

[0042] Furthermore, the beam search according to this embodiment can be applied not only to communication devices etc. in the downlink but also to terminals etc. in the uplink. Furthermore, the beam search according to this embodiment can be applied not only to full-search beam search but also to beam search at each layer of hierarchical beam search. When applied to hierarchical beam search, shadowing information is acquired, and for example, a range of half the distance of the longest beam is set as the communication area, and beam widths for each direction are derived, and a first-stage search is performed using these combinations. Next, a range of the distance of the longest beam is set as the communication area, and beam widths for each direction are derived, and a second-stage search is performed using these combinations.

[0043] The acquisition unit 110, derivation unit 120, storage unit 130, signal processing unit 140, and beam control unit 150 may be configured using a processor such as a CPU (Central Processing Unit) and a memory. In this case, the acquisition unit 110, derivation unit 120, storage unit 130, signal processing unit 140, and beam control unit 150 function as the acquisition unit 110, derivation unit 120, storage unit 130, signal processing unit 140, and beam control unit 150 by the processor executing a program. Note that all or part of the functions of the acquisition unit 110, derivation unit 120, storage unit 130, signal processing unit 140, and beam control unit 150 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The above program may be recorded on a computer-readable recording medium. The computer-readable recording medium may be, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a semiconductor storage device (e.g., an SSD (Solid State Drive)), or a storage device such as a hard disk or semiconductor storage device built into a computer system. The above program may be transmitted via a telecommunications line.

[0044] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0045] The present invention is applicable to communication devices that perform beam search. [Explanation of symbols]

[0046] 100... communication device, 110... acquisition unit, 120... derivation unit, 130... storage unit, 140... signal processing unit, 150... beam control unit, 160... antenna

Claims

1. an acquisition unit that acquires obstruction information including a distance from an emission unit that emits a beam to an obstruction that blocks the beam; a derivation unit that derives a beam width of the beam radiated from the radiation unit in a direction where the shielding object is present, the beam width being wider than that in a direction where the shielding object is not present, in accordance with the distance to the shielding object acquired by the acquisition unit; a beam control unit that controls the radiation unit to radiate the beam with the beam width derived by the derivation unit in the direction of the obstruction and reduce the number of beams, thereby reducing the number of beam searches; A communication device comprising:

2. The communication device according to claim 1 , wherein the derivation unit derives a beam width such that a distance over which communication is possible using the beam radiated by the radiation unit is equal to or greater than a distance to the obstruction.

3. The communication device according to claim 1 or 2, wherein the obstruction information further includes a direction from the radiation unit to the obstruction.

4. The communication device according to claim 3 , wherein the derivation unit sets the beam width of the beam in a direction where no obstruction is present to the narrowest beam width.

5. 5. The communication device according to claim 4, further comprising a storage unit that stores a combination of the direction of the beam that can cover a predetermined area with the beam and the beam width of the beam radiated in the direction of the beam.

6. The communication device according to claim 5 , wherein the beam control unit performs a beam search using the combination stored in the storage unit.

7. A method for controlling a communication device, comprising: an acquisition step of acquiring obstruction information including a distance from an emission unit that emits a beam to an obstruction that blocks the beam; a derivation step of deriving a beam width of the beam radiated from the radiation unit in a direction where the shielding object is present, the beam width being wider than that in a direction where the shielding object is not present, according to the distance to the shielding object acquired in the acquisition step; a beam control step of controlling the radiation unit so that the number of beams is reduced by radiating the beams with the beam width derived in the derivation step in the direction of the obstruction, thereby reducing the number of beam searches; A control method comprising:

8. A program for causing a computer to function as a communication device, The computer an acquisition unit that acquires obstruction information including a distance from an emission unit that emits a beam to an obstruction that blocks the beam; a derivation unit that derives a beam width of the beam radiated from the radiation unit in a direction where the shielding object is present, the beam width being wider than that in a direction where the shielding object is not present, in accordance with the distance to the shielding object acquired by the acquisition unit; A program for causing the program to function as a beam control unit that controls the radiation unit to emit the beam with the beam width derived by the derivation unit in the direction of the obstruction, thereby reducing the number of beams and thereby reducing the number of beam searches.

Images