JP7518215B2 - Base station and antenna control method - Google Patents

Description

The present invention relates to a base station equipped with multiple radio antenna units.

In recent years, wireless access systems have become widespread and are indispensable for living a rich life. Looking back at the first to fourth generation of mobile phones, technology has mainly evolved to increase the speed of wireless communication. In the fifth generation, in addition to high speed, ultra-low latency and multiple simultaneous connections are required. In order to achieve these, a wide bandwidth is effective, and since the usage situation of frequencies is tight, the use of high frequency bands such as the millimeter wave band is effective from the fifth generation onwards. For example, the fifth generation uses the 28 MHz band, which is close to the millimeter wave band. As the frequency increases (i.e., the wavelength becomes shorter), the receiving area of one planar antenna becomes smaller, for example, so there is a problem that the propagation loss is larger compared to the microwave band. If the propagation loss increases, the coverage area per wireless device becomes smaller, which leads to an increase in costs.

To solve this problem, the fifth generation will adopt beamforming technology (BF). BF technology arranges multiple antennas (array) and controls the amplitude and phase of the transmission signal of each antenna element to obtain sharp antenna directivity. In addition, the antenna gain can compensate for radio wave propagation loss.

In the transmission BF, the phase of the transmission signals radiated from multiple antennas is controlled and spatially combined, so that in some places the phases of the radio waves radiated from each antenna are close to the same phase, reinforcing their power, and in other places the radio waves radiated from each antenna cancel each other out. As a result, in places where the power is reinforced, a combined gain can be obtained, compensating for radio wave propagation loss and enabling long-distance transmission. Alternatively, the desired signal power to noise power ratio at the receiver increases, making high-speed transmission possible by increasing the number of multi-levels of quadrature amplitude modulation.

With reference to FIG. 1, the directivity when a narrow beam is formed by BF will be described. Here, the example is a planar antenna, which is widely used in the microwave and millimeter wave bands. FIG. 1(a) is an example of one subarray (or one element), and the antenna beam has the directivity of a planar antenna. FIG. 1(b) is an example of four subarrays, and the directivity of the antenna beam is sharper than that of one subarray, and the composite power in the front direction is larger. FIG. 1(c) is an example of 16 subarrays, and the directivity of the antenna beam is even sharper, and the composite power in the front direction is also larger. FIG. 1(d) is an example of 16 subarrays, but is an example of a case where the phase of the transmission signal of each antenna element is different from that of FIG. 1(c), and the directivity of the antenna beam is controlled to face leftward rather than forward. By making the antenna directivity sharp, it is possible to reduce interference with other wireless devices, and there is also the advantage that the frequency utilization efficiency is improved. The principle of BF technology and the directivity control method are well known technologies in many documents, so a detailed explanation will be omitted. Furthermore, as disclosed in Patent Document 1, development of a hybrid BF that combines an analog BF and a digital BF is also underway.

When combining the received signals of each antenna, the receiving BF can be used to maximize the gain in the direction of arrival of the desired wave or minimize the gain in the direction of arrival of the interference wave. It is also known that reception performance can be improved by providing multiple antennas and implementing spatial diversity. Various research and practical applications are also being conducted on algorithms that automatically select and execute the optimal method from the above receiving techniques in response to changes in the propagation environment.

Another technology that solves the above problems is a distributed antenna system (DAS: Distributed Antenna System) in a base station. Figure 2 shows an example of the configuration of a distributed antenna system. A base station connected to a core network includes a CU (Central Unit) 100 and multiple DUs (Distributed Units) 201 connected to the CU 100. The CU 100 is a centralized control device that mainly performs data processing and network control. The DU 200 is a unit that mainly performs wireless signal processing, and is composed of an RF unit, an antenna, etc. In a distributed antenna system, economic benefits can be obtained by centrally controlling multiple DUs 200 with one CU 100.

Figure 3 shows an example of the configuration of DU200 in the distributed antenna system of Figure 2. Figure 4 shows an example of the arrangement of DU200 in the distributed antenna system of Figure 2. DU200 includes BBU (Base Band Unit) 201 and a plurality of RUs (Radio Units) 202 connected to BBU201.

BBU201 is a unit that centralizes baseband signal processing and control of the distributed antenna system. RU202 is a unit that corresponds to the radio section of a general radio, and is placed at intervals from each other so as to complement each other's coverage area 204. CU100 and BBU201, and BBU201 and RU202 are connected by connection cables 203 such as optical fibers.

RU202 has a transmitting/receiving antenna, a power amplifier, an LNA (Low Noise Amplifier), a frequency filter, a D/A (Digital to Analog) conversion unit, an A/D (Analog to Digital) conversion unit, an OFDM (Orthogonal Frequency Division Multiplexing) modulation unit, an OFDM demodulation unit, an O/E (Optical to Electronic) conversion unit, an E/O (Electronic to Optical) conversion unit, etc.

The BBU201 optically transmits the downlink signal optically transmitted from the CU100 to the multiple RUs202. Each of the multiple RUs202 transmits the same downlink signal distributed from the BBU201 from a transmitting/receiving antenna. The BBU201 also receives the uplink signals optically transmitted from each of the multiple RUs202 and combines them. The uplink signals from the multiple RUs202 differ depending on the positional relationship between the mobile station with which it is communicating and the RU202, the radio wave environment, noise, etc. The BBU201 optically transmits the combined uplink signal to the CU100.

By connecting multiple RUs 202 to the BBU 201 and controlling them centrally, the coverage area of the base station can be expanded. In addition, the number of BBUs 201 can be kept relatively small compared to the size of the coverage area, which is economical. Since the purpose of the distributed antenna system is to expand the coverage area, the signals transmitted from the BBU 201 to each RU 202 via the connection cable 203 and transmitted from the antenna of each RU 202 are the same for all RUs 202 connected to the BBU 201. On the other hand, the signals received by the antenna of each RU 202 and transmitted to the BBU 201 via the connection cable 203 are different for each RU 202, and are synthesized in the BBU 201 and transmitted to the CU 100.

Figure 5 shows another example configuration of DU200 in the distributed antenna system of Figure 2. The DU200 in the figure further includes a HUB (distributor/combiner) 205 that distributes transmit signals and combines receive signals in order to reduce the overall cable length. Some of the multiple RUs 202 are connected to BBU201 via HUB205. HUB205 relays communications between BBU201 and RU202, and distributes downlink signals to multiple RUs 202 in the same way as BBU201, and also combines uplink signals transmitted from multiple RUs 202.

JP 2018-107594 A

Umesh Anil and 3 others, "O-RAN Fronthaul Specifications Overview," NTT DOCOMO Technical Journal Vol. 27 No. 1, April 2019, pp. 43-55

In the conventional method, in the downlink, BBU201 and HUB205 distribute the downlink signal to all connected RU202, and all RU202 transmit radio waves from their antennas. As a result, radio waves are transmitted to areas where there are no mobile stations, resulting in a problem of wasted power consumption. Also, in the conventional method, in the uplink, BBU201 and HUB205 combine the uplink signals transmitted from all connected RU202. As a result, the received signals from areas where there are no mobile stations, i.e., noise signals, are also combined, resulting in a problem of degraded communication quality.

Millimeter wave bands have a larger transmission loss from an outdoor radio device to the inside of a building (i.e., indoors) than microwave bands, resulting in a smaller area in which radio waves can be received. For this reason, it is necessary to expand the indoor coverage area using a DAS system or the like. However, when constructing a DAS using radio devices with BF functionality, there is a problem that the maximum area expansion effect and maximum wireless communication performance are not necessarily obtained because the sharply directional antenna beam is dynamically controlled. There is also the problem that there are restrictions on the installation of wireless antenna units.

The first problem in the conventional method will be described with reference to FIG. 6. The figure shows an example in which RU202 is installed on the wall 301 of a building. RU202 has a BF function, which increases the propagation distance of radio waves, but sharpens the directivity of the antenna beam. Therefore, if there is an obstruction (e.g., a pillar 302), the radio waves are blocked by the obstruction and cannot reach beyond that point, and since millimeter waves are difficult to diffract, a dead zone 304 occurs within the planned coverage area 303. In particular, indoors, the height at which RU202 is installed is limited by the height of the building's walls and ceiling, so if the beam is directed far away, the angle between the floor and the beam becomes small, and the radio waves are blocked even by relatively low obstructions such as people.

The second problem in the conventional method will be described with reference to FIG. 7. The figure shows an example in which RU202 is installed on the ceiling 305 of a building. In many cases, the obstruction is in contact with the floor, and the ceiling-installed RU202 provides a nearly line-of-sight environment, so the first problem is solved. However, despite the ability to propagate radio waves over long distances using BF, the installation height is limited by the height of the ceiling indoors, resulting in a small coverage area 303. For example, if the directivity half-width of a planar antenna is calculated as a general 90°, the coverage area 303 will be limited to a circle with a radius of the installation height h. In this way, the configuration in which RU202 with BF function is installed on the ceiling has significantly low performance relative to the cost.

The present invention has been made in consideration of the above-mentioned conventional circumstances, and aims to provide a base station that can expand the coverage area while reducing power consumption and improving communication quality.

In order to achieve the above object, a base station according to the present invention is configured as follows.
That is, the base station is provided with a plurality of radio antenna units arranged at intervals, and performs antenna control based on a control signal including identification information for beamforming, in which at least one of the plurality of radio antenna units is pre-assigned to each of the identification information for beamforming, and in the antenna control, the radio antenna unit associated with the identification information for beamforming included in the control signal is selected for use in wireless communication.

Here, when the base station according to the present invention is configured to include a central unit that outputs control signals and a baseband unit interposed between the central unit and multiple radio antenna units, the baseband unit may have the function of performing antenna control.

In addition, when the base station according to the present invention is configured with a hub interposed between the central unit and at least one of the multiple radio antenna units, the hub may have the function of performing antenna control.

According to the present invention, it is possible to provide a base station that can expand the coverage area while reducing power consumption and improving communication quality.

1A and 1B are diagrams illustrating examples of planar antennas and beamforming directivity. FIG. 1 is a diagram illustrating a configuration example of a distributed antenna system. A diagram showing an example of the configuration of a DU in the distributed antenna system of Figure 2. A diagram showing an example of DU placement in the distributed antenna system of Figure 2. A figure showing another example configuration of a DU in the distributed antenna system of Figure 2. FIG. 1 is a diagram illustrating an example of a first problem in a conventional method. FIG. 13 is a diagram illustrating an example of a second problem in the conventional method. A figure showing an example of the configuration of a DU in a distributed antenna system according to one embodiment of the present invention. FIG. 1 is a diagram showing an example of beam scanning of a multi-element antenna using the BF function. FIG. 1 is a diagram showing a schematic diagram of a plurality of RUs installed on the ceiling of a building. FIG. 11 is a plan view showing a coverage area provided by a plurality of RUs installed as shown in FIG. 10. FIG. 9 is a diagram showing an example of functional division of a base station in the distributed antenna system of FIG. 8 . FIG. 9 is a diagram showing an example of the configuration of a BBU and a HUB in the distributed antenna system of FIG. 8 . FIG. 9 is a diagram showing an example of a route selection table used in the distributed antenna system of FIG. 8 . FIG. 9 is a diagram showing an example of the configuration of an RU in the distributed antenna system of FIG. 8 .

Before describing one embodiment of the present invention, the interface between the BBU and the RU will be described. For example, in RRHs (Remote Radio Heads) up to the fourth generation, signal transmission between the CU and the BBU or between the BBU and the RU was mainly performed using RoF (Radio over Fiber). However, in 5G, the signal bandwidth is as wide as several hundred MHz, and the transmission capacity of optical fiber becomes huge and unrealistic. Therefore, a method is adopted in which a digital signal before OFDM modulation is optically transmitted during transmission, and a digital signal after OFDM demodulation is optically transmitted during reception to reduce the transmission capacity. In addition, since high frequency bands such as millimeter waves are used for the radio frequency of 5G, it is assumed that BF is performed using a multi-element antenna, and a signal related to BF is included as a control signal in the digital signal to be optically transmitted.

One example of the 5G system architecture is O-RAN (Open Radio Access Network), where the format of the control signal (C-plane) is specified in Split 7 defined in the O-RAN specifications (see, for example, Non-Patent Document 1). In O-RAN, there is a parameter called "Beam ID" in the control signal of the interface between the BBU and the RU. Beam ID is BF control information for selecting one of multiple BF patterns preset in the RU.

In one embodiment of the present invention, which will be described later, a BeamID, which is BF control information, is pre-associated with a RUID, which is identification information for identifying each RU. Then, instead of forming a narrow beam by the BF according to the BeamID specified in the control signal, an RU having a RUID corresponding to the BeamID is selected, and wireless communication with a mobile station is performed using the selected RU. A specific description of a distributed antenna system according to one embodiment of the present invention is given below.

Figure 8 shows an example of the configuration of a DU in a distributed antenna system according to one embodiment of the present invention. In the distributed antenna system of this example, the DU 400 connected to the CU 100 includes a BBU 401, an RU 402, and a HUB 405. If the number of RUs 402 is small, the HUB 405 may not be included. A plurality of RUs 402 are connected to the BBU 401 via the HUB 405 or without the RU 405. The CU 100 and the BBU 401, the BBU 401 and the RU 402, the BBU 401 and the HUB 405, and the HUB 405 and the RU 402 are connected by a connection cable 403 such as an optical fiber. The RU 402 in this example does not include a BF function and has the directivity of a planar antenna as shown in Figure 1 (a).

In the distributed antenna system of this example, an RU selection unit 410 is added after the BBU 401 (or inside the BBU 401) and after the HUB 405 (or inside the HUB 405). The RU selection unit 410 selects an RU 402 having an RUID corresponding to the BeamID based on the BF control information (i.e., BeamID) from the information transmitted from the CU 100 through the connection cable 403. The RU 402 selected by the RU selection unit 410 transmits and receives RF signals in the same way as the conventional RU 202. The RU 402 not selected by the RU selection unit 410 does not perform operations including transmitting and receiving RF signals. Also, unlike the conventional method, the BBU 401 and HUB 405 do not combine signals from multiple RUs 402 in the uplink, but only use the signal from the selected RU 402. In other words, the RU selection unit 410 controls wireless communication with the mobile station to be performed using only the RU 402 corresponding to the BF control information, thereby making it possible to substantially expand the coverage area of the base station while suppressing power consumption in the downlink and improving communication quality in the uplink.

A method for determining RU402 that transmits and receives in a target area where a mobile station is present will be described. FIG. 9 shows an example of beam scanning of a multi-element antenna using the BF function. As shown in FIG. 9, in the case of a multi-element antenna that applies 5G BF technology, the base station searches for a BeamID suitable for wireless communication with a mobile station while sequentially changing the BeamID, selects the optimal BeamID, and performs wireless communication with the mobile station. As described above, the BeamID is transmitted to the BBU using a control signal specified in O-RAN, for example. Since a mobile station is a moving radio device and the optimal BeamID changes over time, the base station repeats the above process after a predetermined time has elapsed.

In a conventional base station, all RUs 202 perform BF operations based on the optimal BeamID identified by the search to perform wireless communication with a mobile station. However, since a mobile station exists only within the coverage area of one of the RUs 202, other mobile stations perform unnecessary operations. In contrast, in the base station of this example, wireless communication with a mobile station is performed using only the RU 402 corresponding to the optimal BeamID identified by the search. In other words, as shown in Figures 10 and 11, there is only one RU 402 that transmits wireless signals with a mobile station at a certain time. Figure 10 is a schematic diagram showing a state in which multiple RUs 402 are installed at intervals on the ceiling of a building. Figure 11 is a plan view showing the coverage area of each RU 402. In this way, the area in which the mobile station exists is searched, and wireless communication with the mobile station is performed using only the RU 402 having the optimal RUID #2 for communication with the mobile station. In this example, since the BBU 401 and the HUB 405 are provided with the RU selection unit 410, there is no need to change the interface between the CU 100 and the BBU 401.

Next, the functional division of the base station functions into CU100 and DU400 will be explained. Below, the functional division of the base station functions into CU100 and DU400 will be explained using the widely used O-RAN specification interface "split7" as an example, but is not limited to this.

Figure 12 shows an example of the functional division of a base station in the distributed antenna system of this example. The functions of the base station are RRC (Radio Resource Control) 501, PDCP (Packet Data Convergence Protocol) 502, RLC (Radio Link Control) 503, MAC (Medium Access Control) 504, PHY (PHYsical layer) 505, and RF (Radio Frequency) 506.

In O-RAN "split 7", the functions of PHY 505 are split. Of the split PHY 505 functions, the CU 100 side is defined as PHY-high 505H, and the DU 400 side is defined as PHY-low 505L. The functions of PHY-high 505H are expressed as [downlink/uplink], and include [encoding/decoding], [scrambling/descrambling], [modulation/demodulation], [layer mapping/equalization processing, IDFT], [precoding/channel estimation], and [resource element mapping/resource element demapping]. The functions of PHY-Low 505L include [transmit digital BF/receive digital BF] and [IFFT/FFT]. The functions of RF 506 include [D/A conversion/A/D conversion] and [transmit analog BF/receive analog BF].

PHY-high 505H and PHY-low 505L are connected by a connection cable 403. The U-plane (User-plane) in the interface of the connection cable 403 contains the mapped transmission data and the received data that has been subjected to FFT (Fast Fourier Transform). The C-plane (Control-plane) in the interface of the connection cable 403 contains BF identification information (BeamID).

Figure 13 shows an example of the configuration of the BBU and HUB in the distributed antenna system of this example. The BBU 401 includes an RU selection unit 410 and a PHY-low 505L. In the downlink, the PHY-low 505L processes the U-plane signal from the CU 100 and generates a transmission signal. The transmission signal is output as a digital or analog RoF (Radio over Fiber) signal. The RU selection unit 410 selects a route to a child unit (RU 402) that has been pre-assigned to the BF control information (Beam ID) included in the C-plane signal from the CU 100. The selected RU 202 converts the transmission signal received from the BBU 401 into an electrical signal and outputs it from an antenna. In the uplink, an uplink signal of the same route as that of the RU 202 selected in the downlink by the RU selection unit 410 is transmitted to the CU 100 in the U-plane. If a HUB 405 exists between the BBU 401 and the RU 402, the HUB 405 is also connected to a plurality of RUs 402, and therefore the same processing is performed by the RU selection unit 410 in the HUB 405.

Next, the route selection method by the RU selection unit 410 will be described. FIG. 14 shows an example of a route selection table. The table in the figure is an example in which two RUs, RU402 (#1) and RU402 (#2), are directly connected to the BU401, and two RUs, RU402 (#3) and RU402 (#4), are further connected via the HUB405, as shown in FIG. 13. The BBU401 refers to the BBU Table and selects a route corresponding to the BeamID. The BBU Table has two routes (route 1, route 2) for each of the two RUs 402 directly connected to the BBU401, and a route (route 3) common to the two RUs 402 connected to the BBU401 via the HUB. The HUB405 refers to the HUB Table #1 and selects a route corresponding to the BeamID. In the HUB Table #1, two routes (route 1 and route 2) are set for each of the two RUs 402 directly connected to the HUB 405. By using such a route selection table, it is possible to easily identify the RU 402 corresponding to the Beam ID.

Figure 15 shows an example of the configuration of an RU in the distributed antenna system of this example. RU 402 includes the components of RF 506 shown in Figure 15. RF 506 in the figure has a selection discrimination unit 601, an O/E converter 602, a D/A converter 603, a frequency conversion unit 604, a power amplifier (PA: Power Amplifier) 605, a TDD-SW (Time Division Duplex-Switch) 606, an antenna 607, an LNA (Low Noise Amplifier) 608, a frequency conversion unit 609, an A/D converter 610, and an E/O converter 611.

The selection discrimination unit 601 judges whether or not its own RU has been selected. One example is a method of making this judgment by obtaining selected/non-selected flag information from the RU selection unit 410. RU 402 performs the following operations only when it has been selected (i.e., it does not perform the following operations when it has not been selected).

When the own RU is selected, the signal from the BBU 401 or HUB 405 is converted from an optical signal to an electrical signal by the O/E converter 602. The D/A converter 603 converts the digital signal obtained by the O/E conversion into an analog signal. Note that in the case of an analog Rof, the D/A converter 603 is not required. The frequency conversion unit 604 converts the IF signal obtained by the D/A conversion into an RF signal. The power amplifier 605 amplifies the power of the RF signal after frequency conversion. The TDD-SW 606 switches the path between the downlink (transmission) and the uplink (reception). In the downlink, an RF signal is transmitted from the antenna 607.

In the uplink, an antenna 607 receives an RF signal from a mobile station. An LNA 608 amplifies the RF signal received by the antenna 607. A frequency conversion unit 609 frequency converts the amplified RF signal to an IF signal. An A/D converter 610 converts the frequency-converted IF signal from an analog signal to a digital signal. An E/O converter 611 converts the electrical signal obtained by the A/D conversion into an optical signal. Note that in the case of an analog Rof, the A/D converter 611 is not required.

In FIG. 15, only the functional blocks necessary for simplicity of explanation are shown, but various functional blocks such as a bandpass filter, AGC (Automatic Gain Control), AFC (Automatic Frequency Control), etc., which are well known to those skilled in the art, may be inserted between the illustrated functional blocks.

As described above, the base station in this example is a base station that has multiple RUs 402 arranged at intervals and performs antenna control based on BF control information including a BeamID, and the RU selection unit 410 of the BBU 401 and HUB 405 performs a process of selecting an RU 402 that is pre-associated with a BeamID included in the BF control information for use in wireless communication as the above-mentioned antenna control. The CU 100 corresponds to the central unit according to the present invention, the BBU 401 corresponds to the baseband unit according to the present invention, the RU 402 corresponds to the wireless antenna unit according to the present invention, and the HUB 405 corresponds to the hub according to the present invention.

With this configuration, not only can the coverage area of the base station be substantially expanded, but in the downlink, the unselected RUs 402 do not transmit RF signals, so power consumption can be reduced, and in the uplink, the received signals (noise signals) of the unselected RUs 402 are not combined, so communication quality can be improved. In addition, the RUs 402 do not require a BF function and do not need to be equipped with many antenna elements; a single or small number of antenna elements with wide directivity is sufficient, so that equipment costs can be reduced.

The above-mentioned configuration is particularly effective for indoor use, but may also be used outdoors. The signals between BBU401 and RU402, between BB401 and HUB405, and between HUB405 and RU402 may be optical signals or electrical signals. If these signals are optical signals, the same signals as those between CU100 and BBU401 may be used, or may be replaced with signals different from those between CU100 and BBU401. A distributed antenna having the function of selecting one RU402 according to BF identification information may also be used.

In the above description, one RU 402 is associated with one Beam ID, but multiple (e.g., two) RUs 402 may be associated with one Beam ID. This is effective when a mobile station is located between two RUs 402, or when a mobile station moves and switches the RU 402 in its area.

The present invention has been described above based on one embodiment, but it goes without saying that the present invention is not limited to the wireless communication system described herein and can be widely applied to other wireless communication systems.
Furthermore, the present invention can also be provided as, for example, a method including technical procedures related to the above-mentioned processing, a program for causing a processor to execute the above-mentioned processing, or a storage medium for storing such a program in a computer-readable manner.

The scope of the present invention is not limited to the exemplary embodiments shown and described, but includes all embodiments that have equivalent effects to those intended by the present invention. Furthermore, the scope of the present invention can be defined by any desired combination of specific features among all the respective features disclosed.

This application claims the benefit of priority from Japanese Patent Application No. 2021-011005, filed on January 27, 2021, the entire disclosure of which is incorporated herein by reference.

The present invention can be used in base stations equipped with multiple radio antenna units.

100: CU, 200: DU, 201: BBU, 202: RU, 203: Connection cable, 205: HUB, 301: Wall, 302: Pillar, 303: Coverage area, 304: Blind area, 305: Ceiling, 401: BBU, 402: RU, 403: Connection cable, 405: HUB, 406: RU selection unit, 501: RPC, 502: PDCP, 503: RLC, 504: MAC, 505H: PHY-high, 505L: PHY-low, 506: RF, 601: Selection determination unit, 602: O/E converter, 603: D/A converter, 604: Frequency conversion unit, 605: Power amplifier, 606: TDD-SW, 607: Antenna, 608: LNA, 609: Frequency conversion section, 610: A/D converter, 611: E/O converter

Claims (3)

A base station including: a distributed unit having a plurality of radio antenna units each having a single directivity and a baseband unit to which the plurality of radio antenna units are connected; and a central unit that outputs a control signal including identification information for beamforming to the distributed unit,
The plurality of wireless antenna units are spaced apart from one another to complement each other's coverage areas,
At least one of the plurality of radio antenna units is previously associated with each of the beamforming identification information,
The baseband unit uses beamforming identification information included in the control signal received from the central unit to select a radio antenna unit corresponding to the beamforming identification information from among the multiple radio antenna units, and controls the selected radio antenna unit to perform transmission and reception operations while controlling the unselected radio antenna units not to perform transmission and reception operations, and further, in the uplink, combines only signals from the selected radio antenna units without combining signals from the unselected radio antenna units. 2. The base station according to claim 1,
the distributed unit includes a hub interposed between the baseband unit and at least one radio antenna unit of the plurality of radio antenna units;
The hub uses beamforming identification information contained in the control signal received from the central unit via the baseband unit to select a radio antenna unit corresponding to the beamforming identification information from among the at least one radio antenna unit, and controls the selected radio antenna unit to perform transmission and reception operations while controlling the unselected radio antenna units not to perform transmission and reception operations, and further, in the uplink, combines only signals from the selected radio antenna unit without combining signals from the unselected radio antenna units. 1. An antenna control method implemented by a base station including: distributed units having a plurality of radio antenna units each having a single directivity and a baseband unit to which the plurality of radio antenna units are connected; and a central unit that outputs a control signal including identification information for beamforming to the distributed units, the method comprising:
The plurality of wireless antenna units are spaced apart from one another to complement each other's coverage areas,
At least one of the plurality of radio antenna units is previously associated with each of the beamforming identification information,
The antenna control method is characterized in that the baseband unit uses beamforming identification information included in the control signal received from the central unit to select a radio antenna unit corresponding to the beamforming identification information from among the multiple radio antenna units, causes the selected radio antenna unit to perform transmission and reception operations while controlling unselected radio antenna units not to perform transmission and reception operations, and further, in an uplink, combines only signals from the selected radio antenna unit without combining signals from unselected radio antenna units.

Images