WO2022163242A1 - Base station and method for controlling antenna - Google Patents

Base station and method for controlling antenna Download PDF

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Publication number
WO2022163242A1
WO2022163242A1 PCT/JP2021/047917 JP2021047917W WO2022163242A1 WO 2022163242 A1 WO2022163242 A1 WO 2022163242A1 JP 2021047917 W JP2021047917 W JP 2021047917W WO 2022163242 A1 WO2022163242 A1 WO 2022163242A1
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Prior art keywords
antenna
base station
bbu
radio
hub
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PCT/JP2021/047917
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French (fr)
Japanese (ja)
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直樹 本江
良治 武鎗
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株式会社日立国際電気
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Priority to JP2022578168A priority Critical patent/JPWO2022163242A1/ja
Publication of WO2022163242A1 publication Critical patent/WO2022163242A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/28—Cell structures using beam steering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices

Definitions

  • the present invention relates to a base station with multiple radio antenna units.
  • the fifth generation requires ultra-low delay and multiple simultaneous connectivity in addition to high speed.
  • it is effective to broaden the bandwidth, and because the frequency usage situation is tight, from the 5th generation onwards, the use of high frequency bands such as the millimeter wave band will be effective.
  • the 5th generation uses the 28 MHz band, which is close to the millimeter wave band.
  • the reception area of one planar antenna becomes smaller, which poses a problem of larger propagation loss than in the microwave band. If the propagation loss increases, the area covered by each wireless device will decrease, resulting in an increase in cost.
  • the 5th generation adopts beam forming technology (BF: Beam Forming).
  • BF technology can obtain sharp antenna directivity by arranging (arraying) a plurality of antennas and controlling the amplitude and phase of the transmission signal of each antenna element. Also, radio wave propagation loss can be compensated for by the antenna gain.
  • transmission BF by controlling the phases of transmission signals radiated from a plurality of antennas and spatially combining them, the phases of the radio waves radiated from each antenna are close to the same phase at a certain location, and the power is strengthened. radio waves emitted from each antenna cancel out the power. As a result, a combined gain can be obtained in a place where electric power is strengthened, so that radio wave propagation loss can be compensated for and long-distance transmission becomes possible.
  • the desired signal power-to-noise power ratio in the receiver becomes large, high-speed transmission becomes possible by increasing the multilevel number of the quadrature amplitude modulation.
  • FIG. 1(a) is an example in the case of one subarray (or one element), and the antenna beam has the directivity of a planar antenna.
  • FIG. 1(b) is an example in the case of four subarrays, in which the directivity of the antenna beam is sharper and the combined power in the front direction is greater than in the case of one subarray.
  • FIG. 1(c) is an example in the case of 16 sub-arrays, where the directivity of the antenna beam becomes even sharper and the combined power in the front direction becomes even greater.
  • FIG. 1(b) is an example in the case of four subarrays, in which the directivity of the antenna beam is sharper and the combined power in the front direction is greater than in the case of one subarray.
  • FIG. 1(c) is an example in the case of 16 sub-arrays, where the directivity of the antenna beam becomes even sharper and the combined power in the front direction becomes even greater.
  • FIG. 1(d) shows 16 sub-arrays, but FIG. 1(c) is an example in which the phase of the transmission signal of each antenna element is different. It is By sharpening the directivity of the antenna, it is possible to reduce the interference given to other wireless devices, and there is also the advantage of improving the utilization efficiency of the frequency. Since the principle of the BF technique, the directivity control method, and the like are well-known techniques in many documents, a detailed description thereof will be omitted. Also, as shown in Patent Document 1, the development of a hybrid BF that combines an analog BF and a digital BF is underway.
  • the reception BF includes a method of maximizing the gain in the direction of arrival of the desired wave and a method of minimizing the gain in the direction of arrival of the interference wave when combining the signals received by each antenna. It is also known that the reception performance is improved by providing a plurality of antennas and performing spatial diversity. Also, various researches and practical applications have been made on algorithms for automatically selecting and executing the optimum method from among the above reception techniques according to changes in the propagation environment.
  • FIG. 2 shows a configuration example of a distributed antenna system.
  • a base station connected to a core network comprises a CU (Central Unit) 100 and a plurality of DUs (Distributed Units) 201 connected to the CU100.
  • the CU 100 is a centralized control device that mainly executes data processing and network control.
  • the DU 200 is a unit that mainly executes radio signal processing, and includes an RF unit, an antenna, and the like.
  • centralized control of a plurality of DUs 200 by one CU 100 can provide an economic advantage.
  • FIG. 3 shows a configuration example of the DU 200 in the distributed antenna system of FIG.
  • FIG. 4 shows an arrangement example of the DU 200 in the distributed antenna system of FIG.
  • the DU 200 comprises a BBU (Base Band Unit) 201 and a plurality of RUs (Radio Units) 202 connected to the BBU 201 .
  • BBU Base Band Unit
  • RUs Radio Units
  • the BBU 201 is a unit that centrally performs baseband signal processing and control of the distributed antenna system.
  • the RUs 202 are units corresponding to the radio section of a general radio, and are spaced apart from each other so as to complement each other's coverage areas 204 .
  • the CU 100 and BBU 201, and the BBU 201 and RU 202 are connected by a connection cable 203 such as an optical fiber.
  • RU 202 includes a transmitting/receiving antenna, a power amplifier, an LNA (Low Noise Amplifier), a frequency filter, a D/A (Digital to Analog) converter, an A/D (Analog to Digital) converter, and an OFDM (Orthogonal Frequency Division Multiplexing) modulation section, OFDM demodulation section, O/E (Optical to Electronic) conversion section, E/O (Electronic to Optical) conversion section, and the like.
  • LNA Low Noise Amplifier
  • the BBU 201 optically transmits downlink signals optically transmitted from the CU 100 to a plurality of RUs 202 .
  • Each of the plurality of RUs 202 transmits the same downlink signal distributed from the BBU 201 from transmission/reception antennas.
  • the BBU 201 also receives uplink signals optically transmitted from each of the plurality of RUs 202 and combines them. Uplink signals from a plurality of RUs 202 differ depending on the positional relationship between the mobile station serving as a communication partner and the RUs 202, the radio wave environment, noise, and the like.
  • the BBU 201 optically transmits the combined uplink signal to the CU 100 .
  • the coverage area of the base station can be expanded. Moreover, since the number of BBUs 201 can be relatively suppressed with respect to the size of the coverage area, it is economical. Since the distributed antenna system aims to expand the coverage area, the signal transmitted from the BBU 201 to each RU 202 through the connection cable 203 and transmitted from the antenna of each RU 202 is 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 BBU 201 through connection cable 203 are different for each RU 202 , and are combined by BBU 201 and transmitted to CU 100 .
  • FIG. 5 shows another configuration example of the DU 200 in the distributed antenna system of FIG.
  • the DU 200 in the figure further comprises a HUB (divider/combiner) 205 for dividing the transmission signal and combining the received signal in order to reduce the overall cable length.
  • HUB 205 relays communication between BBU 201 and RU 202 , distributes downlink signals to multiple RUs 202 like BBU 201 , and combines uplink signals transmitted from multiple RUs 202 .
  • the BBU 201 and HUB 205 distribute downlink signals to all connected RUs 202, and all the RUs 202 transmit radio waves from their antennas. As a result, radio waves are transmitted even to areas where mobile stations do not exist, resulting in wasted power consumption. Also, in the conventional method, in the uplink, the BBU 201 and HUB 205 combine uplink signals transmitted from all connected RUs 202 . As a result, received signals in areas where mobile stations do not exist, that is, noise signals are also combined, resulting in deterioration of communication quality.
  • the transmission loss from outdoor radios to the inside of a building is greater than in the microwave band, and the area where radio waves can be received is smaller. Therefore, it is necessary to expand the indoor coverage area using a DAS system or the like.
  • a DAS system or the like.
  • the maximum area expansion effect and maximum radio communication performance cannot always be obtained due to the dynamic control of the antenna beam with sharp directivity. be.
  • Another problem is that there are restrictions on the installation of the radio antenna unit.
  • the figure shows an example in which the RU 202 is installed on the wall 301 of the building.
  • the RU 202 has a BF function, which increases the propagation distance of radio waves but sharpens the directivity of the antenna beam. Therefore, if there is a shielding object (e.g., the pillar 302), the radio wave is blocked by the shielding object, and the radio wave does not reach beyond the shielding object.
  • a dead zone 304 is generated within the range of the area 303 .
  • the height at which the RU202 is installed is limited by the height of the walls and ceiling of the building. radio waves are also blocked.
  • FIG. 3 shows an example in which the RU 202 is installed on the ceiling 305 of the building.
  • the shielding object is in contact with the floor, and the RU 202 installed on the ceiling is in a substantially line-of-sight environment, so the first problem is solved.
  • the coverage area 303 is reduced. For example, if the directivity half-value width of a planar antenna is calculated as a general 90°, the coverage area 303 remains a circle with a radius equal to the installation height h.
  • the configuration in which the RU 202 with the BF function is installed on the ceiling has a significantly low cost performance.
  • the present invention has been made in view of the conventional circumstances as described above, and provides a base station capable of reducing power consumption and improving communication quality while realizing expansion of the coverage area. for the purpose.
  • a base station configured as follows. That is, a base station that includes a plurality of spaced-apart wireless antenna units and performs antenna control based on a control signal that includes identification information for beamforming, wherein for each of the identification information for beamforming: At least one of the plurality of radio antenna units is associated in advance, and in antenna control, the radio antenna unit associated with the identification information for beamforming included in the control signal is selected for use in radio communication. do.
  • the base station has a configuration comprising a central unit that outputs control signals and a baseband unit interposed between the central unit and the plurality of radio antenna units, the baseband unit: It may have the function of performing antenna control.
  • the hub may have the function of performing antenna control.
  • the present invention it is possible to provide a base station capable of reducing power consumption and improving communication quality while expanding the coverage area.
  • FIG. 3 is a diagram showing an example of directivity of a planar antenna and beamforming; 1 is a diagram showing a configuration example of a distributed antenna system; FIG. 3 is a diagram showing a configuration example of a DU in the distributed antenna system of FIG. 2; FIG. FIG. 3 is a diagram showing an arrangement example of DUs in the distributed antenna system of FIG. 2; 3 is a diagram showing another configuration example of DUs in the distributed antenna system of FIG. 2; FIG. It is a figure which shows the example of the 1st problem in a conventional method. It is a figure which shows the example of the 2nd problem in a conventional method.
  • FIG. 4 is a diagram showing a configuration example of DUs in the distributed antenna system according to one embodiment of the present invention; FIG.
  • FIG. 10 is a diagram showing an example of beam scanning of a multi-element antenna by the BF function;
  • FIG. 2 is a diagram schematically showing how a plurality of RUs are installed on the ceiling of a building;
  • FIG. 11 is a plan view showing areas covered by a plurality of RUs installed as 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; 9 is a diagram showing a configuration example 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. FIG. 9 is a diagram showing a configuration example of an RU in the distributed antenna system of FIG. 8;
  • O-RAN Open Radio Access Network
  • C-plane the format of the control signal
  • Split 7 defined in the O-RAN specifications (for example, non-patent literature 1).
  • BeamID is BF control information for selecting one from a plurality of BF patterns preset in the RU.
  • BeamID which is BF control information
  • RUID which is identification information for identifying each RU. Then, instead of forming a narrow beam by the BF according to the BeamID specified by the control signal, an RU having an RUID corresponding to the BeamID is selected, and wireless communication with the mobile station is performed using the selected RU. It is a mechanism to control to A distributed antenna system according to an embodiment of the present invention will be specifically described below.
  • FIG. 8 shows a configuration example of a DU in a distributed antenna system according to one embodiment of the present invention.
  • DU400 connected to CU100 is provided with BBU401, RU402, and HUB405. Note that when the number of RUs 402 is small, the HUB 405 may not be provided.
  • a plurality of RUs 402 are connected to the BBU 401 via a HUB 405 or not via an RU 405 .
  • CU 100 and BBU 401, BBU 401 and RU 402, BBU 401 and HUB 405, and HUB 405 and RU 402 are connected by connection cables 403 such as optical fibers.
  • the RU 402 of this example does not have a BF function, and has the directivity of a planar antenna as shown in FIG. 1(a).
  • an RU selector 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 the RU 402 having the RUID corresponding to the BeamID based on the BF control information (that is, the BeamID) among 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 manner as the conventional RU 202 .
  • RUs 402 that are not selected by the RU selection unit 410 do not perform operations such as transmission and reception of RF signals.
  • the BBU 401 and HUB 405 do not synthesize signals from a plurality of RUs 402 unlike the conventional technology, and use only the signal from the selected RU 402 . That is, the RU selection unit 410 performs control to perform radio communication with the mobile station using only the RU 402 corresponding to the BF control information. As a result, it is possible to substantially expand the coverage area of the base station, reduce power consumption in the downlink, and improve communication quality in the uplink.
  • FIG. 9 shows an example of beam scanning of a multi-element antenna using the BF function.
  • the base station searches for a BeamID suitable for wireless communication with the mobile station while sequentially changing the BeamID, and selects the optimum BeamID. wireless communication with the mobile station.
  • the BeamID is transmitted to the BBU using, for example, control signals defined by O-RAN. Since the mobile station is a mobile radio device and the optimum BeamID changes with the passage of time, the base station repeats the above process after a predetermined period of time.
  • all RUs 202 perform BF operations based on the optimum BeamID identified by searching to perform wireless communication with mobile stations.
  • the base station of this example uses only the RU 402 corresponding to the optimum BeamID identified by the search to perform wireless communication with the mobile station. That is, as shown in FIGS. 10 and 11, there is one RU 402 that performs radio signals with mobile stations at a certain time.
  • FIG. 10 schematically shows how a plurality of RUs 402 are installed at intervals on the ceiling of a building.
  • FIG. 11 shows the area covered by each RU 402 two-dimensionally.
  • FIG. 12 shows an example of functional division of the base station in the distributed antenna system of this example.
  • Base station functions include RRC (Radio Resource Control) 501, PDCP (Packet Data Convergence Protocol) 502, RLC (Radio Link Control) 503, MAC (Medium Access Control) 504, PHY (PHYsical 505 layer) Frequency) 506 functions.
  • RRC Radio Resource Control
  • PDCP Packet Data Convergence Protocol
  • RLC Radio Link Control
  • MAC Medium Access Control
  • PHY Physical 505 layer Frequency
  • the functions of the PHY 505 are split.
  • the CU 100 side is defined as PHY-high 505H
  • the DU 400 side is defined as PHY-low 505L.
  • the functions of PHY-high505H include [encoding / decoding], [scrambling / descrambling], [modulation / demodulation], [layer mapping / equivalent processing, IDFT], [ precoding/channel estimation] and [resource element mapping/resource element demapping].
  • the functions of the PHY-Low 505L include [transmitting digital BF/receiving digital BF] and [IFFT/FFT].
  • the functions of the RF 506 include [D/A conversion/A/D conversion] and [transmitting analog BF/receiving analog BF].
  • the 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 includes mapped transmission data and FFT (Fast Fourier Transform) reception data.
  • the C-plane (Control-plane) in the interface of the connection cable 403 includes BF identification information (BeamID).
  • FIG. 13 shows a configuration example of the BBU and HUB in the distributed antenna system of this example.
  • BBU 401 includes RU selector 410 and PHY-low 505L.
  • the PHY-low 505L processes U-plane signals from the CU 100 and generates transmission signals.
  • 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 slave unit (RU 402) pre-assigned to the BF control information (BeamID) included in the C-plane signal from the CU 100.
  • BeamID BF control information
  • the selected RU 202 converts the transmission signal received from the BBU 401 into an electric signal and outputs it from the antenna.
  • an uplink signal on the same path as RU 202 selected in downlink by RU selection section 410 is transmitted to CU 100 in the U-plane.
  • the HUB 405 exists between the BBU 401 and the RU 402, the HUB 405 is also connected to a plurality of RUs 402, so the RU selector 410 in the HUB 405 performs similar processing.
  • FIG. 14 shows an example of a route selection table.
  • the BBU 401 refers to the BBU Table and selects a route corresponding to the BeamID.
  • the BBU Table contains two routes (route 1, route 2) for each of the two RUs 402 directly connected to the BBU 401, and a common route (route 3) for the two RUs 402 connected to the BBU 401 via a HUB. is set.
  • the HUB 405 refers to the HUB Table #1 and selects the path corresponding to the BeamID. Two routes (route 1 and route 2) for each of the two RUs 402 directly connected to the HUB 405 are set in the HUB Table #1.
  • FIG. 15 shows a configuration example of RUs in the distributed antenna system of this example.
  • RU 402 includes the components of RF 506 shown in FIG.
  • RF 506 in the figure includes a selection determination unit 601, an O/E converter 602, a D/A converter 603, a frequency conversion unit 604, a power amplifier (PA) 605, and a TDD-SW (Time Division Duplex-Switch) 606 , antenna 607 , LNA (Low Noise Amplifier) 608 , frequency converter 609 , A/D converter 610 , and E/O converter 611 .
  • PPA power amplifier
  • the selection determination unit 601 determines whether or not its own RU has been selected. As an example, there is a method of obtaining selection/non-selection flag information from the RU selection unit 410 and making a determination. RU 402 performs the following operations only when it is selected (ie, it does not perform the following operations when it is not 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 .
  • a D/A converter 603 converts the digital signal obtained by the O/E conversion into an analog signal. Note that the D/A converter 603 is not required in the case of analog Rof.
  • a frequency converter 604 converts the IF signal obtained by the D/A conversion into an RF signal.
  • a power amplifier 605 amplifies the power of the frequency-converted RF signal.
  • the TDD-SW 606 switches paths on the downlink (transmission) or uplink (reception). An RF signal is transmitted from the antenna 607 on the downlink.
  • antenna 607 receives RF signals from mobile stations.
  • LNA 608 amplifies the RF signal received by antenna 607 .
  • a frequency converter 609 frequency-converts the amplified RF signal into an IF signal.
  • A/D converter 610 converts the frequency-converted IF signal from an analog signal to a digital signal.
  • the E/O converter 611 converts the electrical signal obtained by A/D conversion into an optical signal. Note that the A/D converter 611 is not required in the case of analog Rof.
  • FIG. 15 shows only the functional blocks necessary for simplification of the explanation, various functions such as a bandpass filter, AGC (Automatic Gain Control), AFC (Automatic Frequency Control), etc., which are well known to those skilled in the art, are shown. Functional blocks may be interposed between illustrated functional blocks.
  • AGC Automatic Gain Control
  • AFC Automatic Frequency Control
  • the base station of this example includes a plurality of RUs 402 arranged at intervals and performs antenna control based on BF control information including BeamID.
  • the unit 410 performs a process of selecting an RU 402 pre-associated with the BeamID included in the BF control information for use in wireless communication.
  • CU 100 corresponds to the central unit according to the present invention
  • BBU 401 corresponds to the baseband unit according to the present invention
  • RU 402 corresponds to the radio antenna unit according to the present invention
  • HUB 405 corresponds to the hub according to the present invention. handle.
  • the RU 402 does not require a BF function, does not need to be provided with a large number of antenna elements, and a single or a small number of antenna elements with wide directivity are sufficient, so the device cost can be reduced.
  • the signal between BBU 401 and RU 402, the signal between BB 401 and HUB 405, and the signal between HUB 405 and RU 402 may be optical signals or electrical signals. Further, when these signals are optical signals, the same signals as the signals of CU100 and BBU401 may be used, or the signals of CU100 and BBU401 may be replaced with different signals. Also, a distributed antenna having a function of selecting one RU 402 according to BF identification information may be used.
  • one RU 402 is associated with one BeamID, but multiple (for example, two) RUs 402 may be associated with one BeamID. This is effective when a mobile station exists in the middle part of two RUs 402, or when a mobile station moves and the serving RU 402 switches.
  • the present invention has been described based on one embodiment, it goes without saying that the present invention is not limited to the wireless communication system described here, and can be widely applied to other wireless communication systems.
  • the present invention provides, for example, a method including technical procedures related to the above processing, a program for causing a processor to execute the above processing, and a storage medium storing such a program in a computer-readable manner. is also possible.
  • the present invention can be used in a base station equipped with multiple radio antenna units.
  • CU 100: CU, 200: DU, 201: BBU, 202: RU, 203: Connection cable, 205: HUB, 301: Wall, 302: Pillar, 303: Cover area, 304: Dead zone, 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 converter, 610: A/D converter, 611: E/O converter

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

[Problem]　To provide a base station with which it is possible to reduce power consumption and to improve communication quality while achieving expansion of a coverage area.　[Solution]　A base station according to the present example comprises a plurality of RUs 402 arranged at intervals and performs antenna control on the basis of BF control information including a Beam ID. In the base station, as the antenna control, RU selection units 410 of a BBU 401 and a HUB 405 select an RU 402 preliminarily associated with the Beam ID included in the BF control information to use the RU 402 for wireless communication.

Description

基地局及びアンテナ制御方法Base station and antenna control method
　本発明は、複数の無線アンテナユニットを備えた基地局に関する。 The present invention relates to a base station with multiple radio antenna units.
　近年、無線アクセスシステムが普及し、豊かな生活を送るためには無くてはならないものとなっている。携帯電話の第１世代から第４世代までを振り返ると、主に無線通信の高速化のための技術が進化してきた。第５世代では、高速化に加えて超低遅延及び多数同時接続性が要求される。これらの実現のためには広帯域化が有効であること、また、周波数の利用状況がひっ迫していることから、第５世代以降では、ミリ波帯をはじめとする高周波帯の利用が効果的である。例えば、第５世代ではミリ波帯に近い２８ＭＨｚ帯が使用される。周波数が高くなる（すなわち、波長が短くなる）と、例えば１つの平面アンテナの受信面積が小さくなるため、マイクロ波帯と比較して伝搬損失が大きくなるという課題がある。伝搬損失が大きくなると、無線機あたりのカバーエリアが小さくなるため、コストの増大を招いてしまう。 In recent years, wireless access systems have become widespread and have become indispensable for leading a prosperous life. Looking back on the first to fourth generations of mobile phones, technologies for increasing the speed of wireless communication have evolved. The fifth generation requires ultra-low delay and multiple simultaneous connectivity in addition to high speed. In order to achieve these goals, it is effective to broaden the bandwidth, and because the frequency usage situation is tight, from the 5th generation onwards, the use of high frequency bands such as the millimeter wave band will be effective. be. For example, the 5th generation uses the 28 MHz band, which is close to the millimeter wave band. As the frequency becomes higher (that is, the wavelength becomes shorter), for example, the reception area of one planar antenna becomes smaller, which poses a problem of larger propagation loss than in the microwave band. If the propagation loss increases, the area covered by each wireless device will decrease, resulting in an increase in cost.
　この課題を解決するために、第５世代ではビームフォーミング技術(ＢＦ：Ｂｅａｍ　Ｆｏｒｍｉｎｇ)が採用される。ＢＦ技術は、複数のアンテナを配置（アレー）し、各アンテナ素子の送信信号の振幅と位相を制御することで鋭いアンテナ指向性を得ることができる。また、アンテナ利得によって電波伝搬損失を補償することができる。 In order to solve this problem, the 5th generation adopts beam forming technology (BF: Beam Forming). BF technology can obtain sharp antenna directivity by arranging (arraying) a plurality of antennas and controlling the amplitude and phase of the transmission signal of each antenna element. Also, radio wave propagation loss can be compensated for by the antenna gain.
　送信ＢＦでは、複数のアンテナから放射する送信信号の位相を制御して空間合成することで、或る場所では各アンテナから放射された電波の位相が同相に近くなって電力を強め合い、また或る場所では各アンテナから放射された電波が電力を打ち消し合う。その結果、電力を強め合う場所では合成利得を得ることができるため、電波伝搬損失を補償し、長距離伝送が可能となる。あるいは、受信機での所望信号電力対雑音電力比が大きくなるため、直交振幅変調の多値数を大きくすることで高速伝送が可能となる。 In transmission BF, by controlling the phases of transmission signals radiated from a plurality of antennas and spatially combining them, the phases of the radio waves radiated from each antenna are close to the same phase at a certain location, and the power is strengthened. radio waves emitted from each antenna cancel out the power. As a result, a combined gain can be obtained in a place where electric power is strengthened, so that radio wave propagation loss can be compensated for and long-distance transmission becomes possible. Alternatively, since the desired signal power-to-noise power ratio in the receiver becomes large, high-speed transmission becomes possible by increasing the multilevel number of the quadrature amplitude modulation.
　図１を参照して、ＢＦによって狭小ビームを形成する場合の指向性について説明する。ここでは、アンテナとして、マイクロ波帯やミリ波帯において多く採用されている平面アンテナを用いる場合を例とした。図１（ａ）は１サブアレイ（または１素子）の場合の例であり、アンテナビームは平面アンテナの指向性を有する。図１（ｂ）は４サブアレイの場合の例であり、１サブアレイと比較してアンテナビームの指向性は鋭くなり、正面方向の合成電力は大きくなる。図１（ｃ）は１６サブアレイの場合の例であり、アンテナビームの指向性は更に鋭くなり、正面方向の合成電力も更に大きくなる。図１（ｄ）は１６サブアレイであるが、図１（ｃ）とは各アンテナ素子の送信信号の位相が異なる場合の例であり、正面よりも左側にアンテナビームの指向性が向くように制御されている。アンテナ指向性を鋭くすることによって、他の無線機に与える干渉を小さくすることができ、周波数の利用効率が良くなるという利点もある。ＢＦ技術の原理や指向性制御方法などは多くの文献で公知の技術となっているので、具体的な説明を省略する。また、特許文献１に示すように、アナログＢＦとデジタルＢＦを組み合わせたハイブリッドＢＦの開発も進められている。 Directivity when narrow beams are formed by BF will be described with reference to FIG. Here, as an antenna, a case of using a planar antenna that is widely used in the microwave band and the millimeter wave band is taken as an example. FIG. 1(a) is an example in the case of one subarray (or one element), and the antenna beam has the directivity of a planar antenna. FIG. 1(b) is an example in the case of four subarrays, in which the directivity of the antenna beam is sharper and the combined power in the front direction is greater than in the case of one subarray. FIG. 1(c) is an example in the case of 16 sub-arrays, where the directivity of the antenna beam becomes even sharper and the combined power in the front direction becomes even greater. FIG. 1(d) shows 16 sub-arrays, but FIG. 1(c) is an example in which the phase of the transmission signal of each antenna element is different. It is By sharpening the directivity of the antenna, it is possible to reduce the interference given to other wireless devices, and there is also the advantage of improving the utilization efficiency of the frequency. Since the principle of the BF technique, the directivity control method, and the like are well-known techniques in many documents, a detailed description thereof will be omitted. Also, as shown in Patent Document 1, the development of a hybrid BF that combines an analog BF and a digital BF is underway.
　受信ＢＦは、各アンテナの受信信号を合成する際に、所望波の到来方向のゲインを最大化する方法や、干渉波の到来方向のゲインを最小化する方法などがある。また、複数のアンテナを備えて空間ダイバーシティを行うことで、受信性能が良くなることも知られている。また、伝搬環境の変化に応じて上記受信技術の中から最適な方法を自動的に選択して実行するアルゴリズムについても、種々の研究や実用化が行われている。 The reception BF includes a method of maximizing the gain in the direction of arrival of the desired wave and a method of minimizing the gain in the direction of arrival of the interference wave when combining the signals received by each antenna. It is also known that the reception performance is improved by providing a plurality of antennas and performing spatial diversity. Also, various researches and practical applications have been made on algorithms for automatically selecting and executing the optimum method from among the above reception techniques according to changes in the propagation environment.
　上記の課題を解決する別の技術として、基地局における分散アンテナシステム（ＤＡＳ：Ｄｉｓｔｒｉｂｕｔｅｄ　Ａｎｔｅｎｎａ　Ｓｙｓｔｅｍ）がある。図２には、分散アンテナシステムの構成例を示してある。コアネットワークと接続される基地局は、ＣＵ（Ｃｅｎｔｒａｌ　Ｕｎｉｔ）１００と、ＣＵ１００に接続された複数のＤＵ（Ｄｉｓｔｒｉｂｕｔｅｄ　Ｕｎｉｔ）２０１とを備える。ＣＵ１００は、データ処理やネットワーク制御を主に実行する集中制御装置である。ＤＵ２００は、無線信号処理を主に実行するユニットであり、ＲＦユニットやアンテナなどで構成される。分散アンテナシステムでは、１つのＣＵ１００で複数のＤＵ２００を集中的に制御することで、経済的なメリットを得ることができる。 Another technology that solves the above problems is a distributed antenna system (DAS: Distributed Antenna System) in a base station. FIG. 2 shows a configuration example of a distributed antenna system. A base station connected to a core network comprises a CU (Central Unit) 100 and a plurality of DUs (Distributed Units) 201 connected to the CU100. The CU 100 is a centralized control device that mainly executes data processing and network control. The DU 200 is a unit that mainly executes radio signal processing, and includes an RF unit, an antenna, and the like. In a distributed antenna system, centralized control of a plurality of DUs 200 by one CU 100 can provide an economic advantage.
　図３には、図２の分散アンテナシステムにおけるＤＵ２００の構成例を示してある。また、図４には、図２の分散アンテナシステムにおけるＤＵ２００の配置例を示してある。ＤＵ２００は、ＢＢＵ（Ｂａｓｅ　Ｂａｎｄ　Ｕｎｉｔ）２０１と、ＢＢＵ２０１に接続された複数のＲＵ（Ｒａｄｉｏ　Ｕｎｉｔ）２０２とを備える。 FIG. 3 shows a configuration example of the DU 200 in the distributed antenna system of FIG. Also, FIG. 4 shows an arrangement example of the DU 200 in the distributed antenna system of FIG. The DU 200 comprises a BBU (Base Band Unit) 201 and a plurality of RUs (Radio Units) 202 connected to the BBU 201 .
　ＢＢＵ２０１は、分散アンテナシステムのベースバンド信号処理や制御などを集中的に行うユニットである。ＲＵ２０２は、一般的な無線機の無線部に相当するユニットであり、各々のカバーエリア２０４を補い合うように互いに間隔を置いて配置される。ＣＵ１００とＢＢＵ２０１、及び、ＢＢＵ２０１とＲＵ２０２は、光ファイバなどの接続ケーブル２０３で接続される。 The BBU 201 is a unit that centrally performs baseband signal processing and control of the distributed antenna system. The RUs 202 are units corresponding to the radio section of a general radio, and are spaced apart from each other so as to complement each other's coverage areas 204 . The CU 100 and BBU 201, and the BBU 201 and RU 202 are connected by a connection cable 203 such as an optical fiber.
　ＲＵ２０２は、送受信アンテナ、電力増幅部、ＬＮＡ（Ｌｏｗ　Ｎｏｉｓｅ　Ａｍｐｌｉｆｉｅｒ）、周波数フィルタ、Ｄ／Ａ（Ｄｉｇｉｔａｌ　ｔｏ　Ａｎａｌｏｇ）変換部、Ａ／Ｄ（Ａｎａｌｏｇ　ｔｏ　Ｄｉｇｉｔａｌ）変換部、ＯＦＤＭ（Ｏｒｔｈｏｇｏｎａｌ　Ｆｒｅｑｕｅｎｃｙ　Ｄｉｖｉｓｉｏｎ　Ｍｕｌｔｉｐｌｅｘｉｎｇ）変調部、ＯＦＤＭ復調部、Ｏ／Ｅ（Ｏｐｔｉｃａｌ　ｔｏ　Ｅｌｅｃｔｒｏｎｉｃ）変換部、Ｅ／Ｏ（Ｅｌｅｃｔｒｏｎｉｃ　ｔｏ　Ｏｐｔｉｃａｌ）変換部などを有する。 RU 202 includes a transmitting/receiving antenna, a power amplifier, an LNA (Low Noise Amplifier), a frequency filter, a D/A (Digital to Analog) converter, an A/D (Analog to Digital) converter, and an OFDM (Orthogonal Frequency Division Multiplexing) modulation section, OFDM demodulation section, O/E (Optical to Electronic) conversion section, E/O (Electronic to Optical) conversion section, and the like.
　ＢＢＵ２０１は、ＣＵ１００から光伝送された下りリンクの信号を複数のＲＵ２０２に光伝送する。複数のＲＵ２０２の各々は、ＢＢＵ２０１から分配された同一の下りリンクの信号を送受信アンテナから送信する。また、ＢＢＵ２０１は、複数のＲＵ２０２の各々から光伝送された上りリンクの信号を受信し、これらを合成する。複数のＲＵ２０２からの上りリンクの信号は、通信相手となる移動局とＲＵ２０２との位置関係、電波環境、雑音等により異なる。ＢＢＵ２０１は、合成した上りリンクの信号をＣＵ１００へ光伝送する。 The BBU 201 optically transmits downlink signals optically transmitted from the CU 100 to a plurality of RUs 202 . Each of the plurality of RUs 202 transmits the same downlink signal distributed from the BBU 201 from transmission/reception antennas. The BBU 201 also receives uplink signals optically transmitted from each of the plurality of RUs 202 and combines them. Uplink signals from a plurality of RUs 202 differ depending on the positional relationship between the mobile station serving as a communication partner and the RUs 202, the radio wave environment, noise, and the like. The BBU 201 optically transmits the combined uplink signal to the CU 100 .
　ＢＢＵ２０１に複数のＲＵ２０２を接続して集中制御することで、基地局のカバーエリアを拡大することができる。また、カバーエリアの広さに対してＢＢＵ２０１の数を相対的に抑えることができるため、経済的である。分散アンテナシステムはカバーエリアの拡大を目的としているため、ＢＢＵ２０１から接続ケーブル２０３を通じて各ＲＵ２０２に伝送して各ＲＵ２０２のアンテナから送信する信号は、ＢＢＵ２０１に接続された全てのＲＵ２０２で同一である。一方、各ＲＵ２０２のアンテナで受信して接続ケーブル２０３を通じてＢＢＵ２０１に伝送する信号は、ＲＵ２０２毎に異なっており、ＢＢＵ２０１で合成してＣＵ１００に送信される。 By connecting multiple RUs 202 to the BBU 201 and centrally controlling them, the coverage area of the base station can be expanded. Moreover, since the number of BBUs 201 can be relatively suppressed with respect to the size of the coverage area, it is economical. Since the distributed antenna system aims to expand the coverage area, the signal transmitted from the BBU 201 to each RU 202 through the connection cable 203 and transmitted from the antenna of each RU 202 is 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 BBU 201 through connection cable 203 are different for each RU 202 , and are combined by BBU 201 and transmitted to CU 100 .
　図５には、図２の分散アンテナシステムにおけるＤＵ２００の別の構成例を示してある。同図のＤＵ２００は、総合的なケーブルの長さを抑えるために、送信信号の分配及び受信信号の合成を行うＨＵＢ（分配／合成装置）２０５を更に備えている。複数のＲＵ２０２のうちの一部は、ＨＵＢ２０５を介してＢＢＵ２０１と接続される。ＨＵＢ２０５は、ＢＢＵ２０１とＲＵ２０２の間の通信を中継するものであり、ＢＢＵ２０１と同様に下りリンクの信号を複数のＲＵ２０２に分配し、また、複数のＲＵ２０２から伝送された上りリンクの信号を合成する。 FIG. 5 shows another configuration example of the DU 200 in the distributed antenna system of FIG. The DU 200 in the figure further comprises a HUB (divider/combiner) 205 for dividing the transmission signal and combining the received signal in order to reduce the overall cable length. Some of the multiple RUs 202 are connected to the BBU 201 via the HUB 205 . HUB 205 relays communication between BBU 201 and RU 202 , distributes downlink signals to multiple RUs 202 like BBU 201 , and combines uplink signals transmitted from multiple RUs 202 .
特開２０１８－１０７５９４号公報JP 2018-107594 A
　従来の方法では、下りリンクにおいて、ＢＢＵ２０１及びＨＵＢ２０５は、接続されている全てのＲＵ２０２へ下りリンクの信号を分配し、全てのＲＵ２０２がアンテナから電波を送信する。その結果、移動局が存在しないエリアに対しても電波が送信されるので、消費電力に無駄が生じるという問題があった。また、従来の方法では、上りリンクにおいて、ＢＢＵ２０１及びＨＵＢ２０５は、接続されている全てのＲＵ２０２から伝送された上りリンクの信号を合成する。その結果、移動局が存在しないエリアの受信信号、すなわち雑音信号も合成してしまうので、通信品質が劣化するという問題があった。 In the conventional method, in the downlink, the BBU 201 and HUB 205 distribute downlink signals to all connected RUs 202, and all the RUs 202 transmit radio waves from their antennas. As a result, radio waves are transmitted even to areas where mobile stations do not exist, resulting in wasted power consumption. Also, in the conventional method, in the uplink, the BBU 201 and HUB 205 combine uplink signals transmitted from all connected RUs 202 . As a result, received signals in areas where mobile stations do not exist, that is, noise signals are also combined, resulting in deterioration of communication quality.
　ミリ波帯は、屋外にある無線機から建物の中（すなわち、屋内）への透過損失がマイクロ波帯と比較して大きく、電波を受信できるエリアが小さくなる。このため、ＤＡＳシステムなどを用いて屋内のカバーエリアを拡大する必要がある。しかしながら、ＢＦ機能を備えた無線機でＤＡＳを構築する場合、鋭い指向性のアンテナビームを動的に制御するために、最大のエリア拡張効果および最大の無線通信性能を必ずしも得られないという問題がある。また、無線アンテナユニットの設置に制約があるという問題もある。 In the millimeter wave band, the transmission loss from outdoor radios to the inside of a building (that is, indoors) is greater than in the microwave band, and the area where radio waves can be received is smaller. Therefore, it is necessary to expand the indoor coverage area using a DAS system or the like. However, when constructing a DAS with radios equipped with a BF function, there is the problem that the maximum area expansion effect and maximum radio communication performance cannot always be obtained due to the dynamic control of the antenna beam with sharp directivity. be. Another problem is that there are restrictions on the installation of the radio antenna unit.
　図６を参照して、従来方式における第１の課題を説明する。同図には、建物の壁３０１にＲＵ２０２を設置した例を示してある。ＲＵ２０２はＢＦ機能を備えており、電波の伝搬距離が大きくなるが、アンテナビームの指向性が鋭くなる。そのため、遮蔽物（例えば、柱３０２）がある場合には、遮蔽物によって電波が阻害されてそこから先には電波が届かず、また、ミリ波では電波が回折しにくいので、予定されたカバーエリア３０３の範囲内に不感地帯３０４が発生してしまう。特に、屋内ではＲＵ２０２を設置する高さが建物の壁や天井の高さによって制限されるので、遠方にビームを向けると床とビームのなす角が小さくなり、人などの比較的低い遮蔽物によっても電波が阻害されてしまう。 A first problem in the conventional method will be described with reference to FIG. The figure shows an example in which the RU 202 is installed on the wall 301 of the building. The RU 202 has a BF function, which increases the propagation distance of radio waves but sharpens the directivity of the antenna beam. Therefore, if there is a shielding object (e.g., the pillar 302), the radio wave is blocked by the shielding object, and the radio wave does not reach beyond the shielding object. A dead zone 304 is generated within the range of the area 303 . Especially indoors, the height at which the RU202 is installed is limited by the height of the walls and ceiling of the building. radio waves are also blocked.
　図７を参照して、従来方式における第２の課題を説明する。同図には、建物の天井３０５にＲＵ２０２を設置した例を示してある。遮蔽物は床に接している場合が多く、天井設置のＲＵ２０２からは略見通し環境となるため、第１の課題は解決される。しかしながら、ＢＦによって遠方まで電波を伝搬させる能力があるにも関わらず、屋内では天井の高さによって設置高さが制限されるため、カバーエリア３０３が小さくなってしまう。例えば、平面アンテナの指向性半値幅を一般的な９０°として計算すると、カバーエリア３０３は設置高さｈを半径とする円に留まってしまう。このように、ＢＦ機能付きのＲＵ２０２を天井に設置する構成は、コストに対してのパフォーマンスが著しく低い。 A second problem in the conventional method will be described with reference to FIG. The figure shows an example in which the RU 202 is installed on the ceiling 305 of the building. In many cases, the shielding object is in contact with the floor, and the RU 202 installed on the ceiling is in a substantially line-of-sight environment, so the first problem is solved. However, despite the ability of the BF to propagate radio waves over long distances, indoors the installation height is limited by the height of the ceiling, so the coverage area 303 is reduced. For example, if the directivity half-value width of a planar antenna is calculated as a general 90°, the coverage area 303 remains a circle with a radius equal to the installation height h. Thus, the configuration in which the RU 202 with the BF function is installed on the ceiling has a significantly low cost performance.
　本発明は、上記のような従来の事情に鑑みて為されたものであり、カバーエリアの拡大を実現しつつ、消費電力の抑制、通信品質の向上を図ることが可能な基地局を提供することを目的とする。 SUMMARY OF THE INVENTION The present invention has been made in view of the conventional circumstances as described above, and provides a base station capable of reducing power consumption and improving communication quality while realizing expansion of the coverage area. for the purpose.
　上記の目的を達成するために、本発明に係る基地局は、以下のように構成される。
　すなわち、間隔を置いて配置された複数の無線アンテナユニットを備え、ビームフォーミング用の識別情報を含む制御信号に基づくアンテナ制御を行う基地局であって、ビームフォーミング用の識別情報の各々に対して複数の無線アンテナユニットのうちの少なくとも１つが予め対応付けられており、アンテナ制御では、制御信号に含まれるビームフォーミング用の識別情報に対応付けられた無線アンテナユニットを無線通信に使用するために選択する。 In order to achieve the above objects, a base station according to the present invention is configured as follows.
That is, a base station that includes a plurality of spaced-apart wireless antenna units and performs antenna control based on a control signal that includes identification information for beamforming, wherein for each of the identification information for beamforming: At least one of the plurality of radio antenna units is associated in advance, and in antenna control, the radio antenna unit associated with the identification information for beamforming included in the control signal is selected for use in radio communication. do.
　ここで、本発明に係る基地局は、制御信号を出力する中央ユニットと、中央ユニットと複数の無線アンテナユニットとの間に介在するベースバンドユニットとを備えた構成の場合、ベースバンドユニットが、アンテナ制御を行う機能を有し得る。 Here, if the base station according to the present invention has a configuration comprising a central unit that outputs control signals and a baseband unit interposed between the central unit and the plurality of radio antenna units, the baseband unit: It may have the function of performing antenna control.
　また、本発明に係る基地局は、中央ユニットと複数の無線アンテナユニットのうちの少なくとも１つとの間に介在するハブを備えた構成の場合、ハブが、アンテナ制御を行う機能を有し得る。 Also, if the base station according to the present invention has a configuration including a hub interposed between the central unit and at least one of the plurality of radio antenna units, the hub may have the function of performing antenna control.
　本発明によれば、カバーエリアの拡大を実現しつつ、消費電力の抑制、通信品質の向上を図ることが可能な基地局を提供することができる。 According to the present invention, it is possible to provide a base station capable of reducing power consumption and improving communication quality while expanding the coverage area.
平面アンテナとビームフォーミングの指向性の例を示す図である。FIG. 3 is a diagram showing an example of directivity of a planar antenna and beamforming; 分散アンテナシステムの構成例を示す図である。1 is a diagram showing a configuration example of a distributed antenna system; FIG. 図２の分散アンテナシステムにおけるＤＵの構成例を示す図である。3 is a diagram showing a configuration example of a DU in the distributed antenna system of FIG. 2; FIG. 図２の分散アンテナシステムにおけるＤＵの配置例を示す図である。FIG. 3 is a diagram showing an arrangement example of DUs in the distributed antenna system of FIG. 2; 図２の分散アンテナシステムにおけるＤＵの別の構成例を示す図である。3 is a diagram showing another configuration example of DUs in the distributed antenna system of FIG. 2; FIG. 従来方式における第１の課題の例を示す図である。It is a figure which shows the example of the 1st problem in a conventional method. 従来方式における第２の課題の例を示す図である。It is a figure which shows the example of the 2nd problem in a conventional method. 本発明の一実施形態に係る分散アンテナシステムにおけるＤＵの構成例を示す図である。FIG. 4 is a diagram showing a configuration example of DUs in the distributed antenna system according to one embodiment of the present invention; ＢＦ機能による多素子アンテナのビームスキャンの例を示す図である。FIG. 10 is a diagram showing an example of beam scanning of a multi-element antenna by the BF function; 建物の天井に複数のＲＵが設置された様子を概略的に示す図である。FIG. 2 is a diagram schematically showing how a plurality of RUs are installed on the ceiling of a building; 図１０のように設置された複数のＲＵによるカバーエリアを平面的に示す図である。FIG. 11 is a plan view showing areas covered by a plurality of RUs installed as in FIG. 10; 図８の分散アンテナシステムにおける基地局の機能分割の例を示す図である。FIG. 9 is a diagram showing an example of functional division of a base station in the distributed antenna system of FIG. 8; 図８の分散アンテナシステムにおけるＢＢＵ及びＨＵＢの構成例を示す図である。9 is a diagram showing a configuration example of a BBU and a HUB in the distributed antenna system of FIG. 8; FIG. 図８の分散アンテナシステムで使用する経路選択用テーブルの例を示す図である。9 is a diagram showing an example of a route selection table used in the distributed antenna system of FIG. 8; FIG. 図８の分散アンテナシステムにおけるＲＵの構成例を示す図である。FIG. 9 is a diagram showing a configuration example of an RU in the distributed antenna system of FIG. 8;
　本発明の一実施形態について説明するに先立ち、ＢＢＵとＲＵとのインタフェースについて説明する。例えば第４世代までのＲＲＨ（Ｒｅｍｏｔｅ　Ｒａｄｉｏ　Ｈｅａｄ）では、ＣＵとＢＢＵ間やＢＢＵとＲＵ間の信号の伝送は、ＲｏＦ（Ｒａｄｉｏ　ｏｖｅｒ　Ｆｉｂｅｒ）にて行うことが主流であった。しかしながら、５Ｇでは信号帯域幅が数百ＭＨｚと広帯域であり、光ファイバの伝送容量が膨大になって現実的でない。そのため、送信時はＯＦＤＭ変調前のデジタル信号を光伝送し、受信時はＯＦＤＭ復調後のデジタル信号を光伝送することで、伝送容量を抑える方法が採用されている。また、５Ｇの無線周波数にはミリ波などの高周波帯が使用されるため、多素子アンテナを用いてＢＦを行うことが前提とされており、光伝送するデジタル信号の中に、ＢＦに関する信号が制御信号として含まれる。 Before describing one embodiment of the present invention, the interface between the BBU and RU will be described. For example, in RRHs (Remote Radio Heads) up to the fourth generation, transmission of signals between CU and BBU and between BBU and RU was mainly performed by RoF (Radio over Fiber). However, in 5G, the signal bandwidth is as wide as several hundred MHz, and the transmission capacity of optical fibers is enormous, which is not realistic. Therefore, a method of optically transmitting a digital signal before OFDM modulation at the time of transmission, and optically transmitting a digital signal after OFDM demodulation at the time of reception, thereby suppressing the transmission capacity is adopted. In addition, since high-frequency bands such as millimeter waves are used for 5G radio frequencies, it is assumed that BF is performed using a multi-element antenna, and BF-related signals are included in optically transmitted digital signals. Included as a control signal.
　５Ｇシステムのアーキテクチャの一例としてＯ－ＲＡＮ（Ｏｐｅｎ　Ｒａｄｉｏ　Ａｃｃｅｓｓ　Ｎｅｔｗｏｒｋ）があり、Ｏ－ＲＡＮ仕様で規定されたＳｐｌｉｔ７にて制御信号（Ｃ－ｐｌａｎｅ）のフォーマットが規定されている（例えば、非特許文献１参照）。Ｏ－ＲＡＮでは、ＢＢＵとＲＵとのインタフェースの制御信号の中に「ＢｅａｍＩＤ」と呼ばれるパラメータがある。ＢｅａｍＩＤは、ＲＵにプリセットされた複数のＢＦパタンの中から１つを選択するためのＢＦ制御情報である。 O-RAN (Open Radio Access Network) is an example of the architecture of the 5G system, and the format of the control signal (C-plane) is defined in Split 7 defined in the O-RAN specifications (for example, non-patent literature 1). In O-RAN, there is a parameter called "BeamID" in the control signal of the interface between BBU and RU. BeamID is BF control information for selecting one from a plurality of BF patterns preset in the RU.
　後述する本発明の一実施形態では、ＢＦ制御情報であるＢｅａｍＩＤを、各ＲＵを識別する識別情報であるＲＵＩＤに予め対応付けておく。そして、制御信号にて指定されたＢｅａｍＩＤに従ってＢＦにより狭小ビームを形成するのではなく、ＢｅａｍＩＤに対応するＲＵＩＤを持つＲＵを選択し、選択されたＲＵを用いて移動局との無線通信を行うように制御する仕組みとなっている。以下、本発明の一実施形態に係る分散アンテナシステムについて具体的に説明する。 In one embodiment of the present invention, which will be described later, BeamID, which is BF control information, is associated in advance with RUID, which is identification information for identifying each RU. Then, instead of forming a narrow beam by the BF according to the BeamID specified by the control signal, an RU having an RUID corresponding to the BeamID is selected, and wireless communication with the mobile station is performed using the selected RU. It is a mechanism to control to A distributed antenna system according to an embodiment of the present invention will be specifically described below.
　図８には、本発明の一実施形態に係る分散アンテナシステムにおけるＤＵの構成例を示してある。本例の分散アンテナシステムでは、ＣＵ１００に接続されたＤＵ４００は、ＢＢＵ４０１と、ＲＵ４０２と、ＨＵＢ４０５とを備える。なお、ＲＵ４０２の台数が少ない場合は、ＨＵＢ４０５を備えなくてもよい。ＢＢＵ４０１には、ＨＵＢ４０５を介して、又は、ＲＵ４０５を介さずに、複数のＲＵ４０２が接続される。ＣＵ１００とＢＢＵ４０１、ＢＢＵ４０１とＲＵ４０２、ＢＢＵ４０１とＨＵＢ４０５、及び、ＨＵＢ４０５とＲＵ４０２は、光ファイバなどの接続ケーブル４０３で接続される。なお、本例のＲＵ４０２はＢＦ機能を備えておらず、図１（ａ）のような平面アンテナの指向性を有する。 FIG. 8 shows a configuration example of a DU in a distributed antenna system according to one embodiment of the present invention. In the distributed antenna system of this example, DU400 connected to CU100 is provided with BBU401, RU402, and HUB405. Note that when the number of RUs 402 is small, the HUB 405 may not be provided. A plurality of RUs 402 are connected to the BBU 401 via a HUB 405 or not via an RU 405 . CU 100 and BBU 401, BBU 401 and RU 402, BBU 401 and HUB 405, and HUB 405 and RU 402 are connected by connection cables 403 such as optical fibers. Note that the RU 402 of this example does not have a BF function, and has the directivity of a planar antenna as shown in FIG. 1(a).
　本例の分散アンテナシステムでは、ＢＢＵ４０１の後段（或いはＢＢＵ４０１の内部）及びＨＵＢ４０５の後段（或いはＨＵＢ４０５の内部）に、ＲＵ選択部４１０を追加してある。ＲＵ選択部４１０は、ＣＵ１００から接続ケーブル４０３を通じて伝送された情報のうちのＢＦ制御情報（すなわち、ＢｅａｍＩＤ）に基づいて、ＢｅａｍＩＤに対応するＲＵＩＤを持つＲＵ４０２を選択する。ＲＵ選択部４１０によって選択されたＲＵ４０２は、従来のＲＵ２０２と同様にＲＦ信号の送受信を行う。ＲＵ選択部４１０によって選択されていないＲＵ４０２は、ＲＦ信号の送受信をはじめとした動作を行わない。また、ＢＢＵ４０１及びＨＵＢ４０５は上りリンクにおいて、従来とは異なって複数のＲＵ４０２からの信号を合成せず、選択されＲＵ４０２からの信号のみを使用する。つまり、ＲＵ選択部４１０は、ＢＦ制御情報に対応するＲＵ４０２のみを用いて移動局との無線通信を行うよう制御する。これにより、基地局のカバーエリアを実質的に拡大しつつ、下りリンクでは消費電力を抑えることができ、上りリンクでは通信品質を改善することができる。 In the distributed antenna system of this example, an RU selector 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 the RU 402 having the RUID corresponding to the BeamID based on the BF control information (that is, the BeamID) among 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 manner as the conventional RU 202 . RUs 402 that are not selected by the RU selection unit 410 do not perform operations such as transmission and reception of RF signals. Also, in the uplink, the BBU 401 and HUB 405 do not synthesize signals from a plurality of RUs 402 unlike the conventional technology, and use only the signal from the selected RU 402 . That is, the RU selection unit 410 performs control to perform radio communication with the mobile station using only the RU 402 corresponding to the BF control information. As a result, it is possible to substantially expand the coverage area of the base station, reduce power consumption in the downlink, and improve communication quality in the uplink.
　移動局が存在する対象エリアの送受信を行うＲＵ４０２の決定方法について説明する。図９には、ＢＦ機能による多素子アンテナのビームスキャンの例を示してある。図９に示すように、５ＧのＢＦ技術を適用した多素子アンテナの場合、基地局は、ＢｅａｍＩＤを順次変更しながら移動局との無線通信に適したＢｅａｍＩＤをサーチし、最適なＢｅａｍＩＤを選択して移動局との無線通信を行う。前述したように、ＢｅａｍＩＤは、例えばＯ－ＲＡＮで規定された制御信号を用いてＢＢＵに伝達される。移動局は移動する無線機であり、時間経過に伴って最適なＢｅａｍＩＤが変化するため、基地局は所定時間の経過後に上記の処理を繰り返す。 A method for determining the RU 402 that performs transmission and reception in the target area where the mobile station is located will be explained. 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 applying 5G BF technology, the base station searches for a BeamID suitable for wireless communication with the mobile station while sequentially changing the BeamID, and selects the optimum BeamID. wireless communication with the mobile station. As described above, the BeamID is transmitted to the BBU using, for example, control signals defined by O-RAN. Since the mobile station is a mobile radio device and the optimum BeamID changes with the passage of time, the base station repeats the above process after a predetermined period of time.
　従来の基地局では、サーチによって特定された最適なＢｅａｍＩＤに基づくＢＦ動作を全てのＲＵ２０２が行って、移動局との無線通信を行っていた。しかしながら、移動局はいずれかのＲＵ２０２のカバーエリア内にしか存在しないため、他の移動局は無駄な動作をすることになる。これに対し、本例の基地局では、サーチによって特定された最適なＢｅａｍＩＤに対応するＲＵ４０２のみを使用して、移動局との無線通信を行う。つまり、図１０及び図１１に示すように、或る時刻に移動局との無線信号を行うＲＵ４０２は１つである。図１０は、建物の天井に複数のＲＵ４０２が間隔を置いて設置された様子を概略的に示したものである。図１１は、各ＲＵ４０２によるカバーエリアを平面的に示したものである。このように、移動局が存在するエリアをサーチし、移動局との通信に最適なＲＵＩＤ＃２を持つＲＵ４０２のみを使用して、移動局との無線通信を行う。本例では、ＢＢＵ４０１やＨＵＢ４０５がＲＵ選択部４１０を備えることで、ＣＵ１００とＢＢＵ４０１の間のインタフェースを変更する必要が無い。 In a conventional base station, all RUs 202 perform BF operations based on the optimum BeamID identified by searching to perform wireless communication with mobile stations. However, since the mobile station exists only within the coverage area of one of the RUs 202, the other mobile stations will operate in vain. On the other hand, the base station of this example uses only the RU 402 corresponding to the optimum BeamID identified by the search to perform wireless communication with the mobile station. That is, as shown in FIGS. 10 and 11, there is one RU 402 that performs radio signals with mobile stations at a certain time. FIG. 10 schematically shows how a plurality of RUs 402 are installed at intervals on the ceiling of a building. FIG. 11 shows the area covered by each RU 402 two-dimensionally. In this way, the area where the mobile station exists is searched, and only the RU 402 having RUID#2 that is most suitable for communication with the mobile station is used to perform wireless 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. FIG.
　次に、基地局機能のＣＵ１００およびＤＵ４００への機能分割について説明する。以下では、基地局機能のＣＵ１００およびＤＵ４００への機能分割について、広く用いられているＯ－ＲＡＮ仕様のインタフェース「ｓｐｌｉｔ７」を例にして説明するが、これに限定するものではない。 Next, functional division of base station functions into CU100 and DU400 will be described. The division of the base station functions into the CU 100 and the DU 400 will be described below using the widely used O-RAN specification interface "split7" as an example, but the present invention is not limited to this.
　図１２には、本例の分散アンテナシステムにおける基地局の機能分割の例を示してある。基地局の機能としては、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、ＲＦ（Ｒａｄｉｏ　Ｆｒｅｑｕｅｎｃｙ）５０６の各機能がある。 FIG. 12 shows an example of functional division of the base station in the distributed antenna system of this example. Base station functions include RRC (Radio Resource Control) 501, PDCP (Packet Data Convergence Protocol) 502, RLC (Radio Link Control) 503, MAC (Medium Access Control) 504, PHY (PHYsical 505 layer) Frequency) 506 functions.
　Ｏ－ＲＡＮ「ｓｐｌｉｔ７」では、ＰＨＹ５０５の機能が分割される。分割されたＰＨＹ５０５の機能のうち、ＣＵ１００側をＰＨＹ－ｈｉｇｈ５０５Ｈ、ＤＵ４００側をＰＨＹ－ｌｏｗ５０５Ｌと定義される。ＰＨＹ－ｈｉｇｈ５０５Ｈの機能には、［下りリンク／上りリンク］表現で、［符号化／復号］、［スクランブリング／デスクランブリング］、［変調／復調］、［レイヤマッピング／等価処理，ＩＤＦＴ］、［プリコーディング／チャネル推定］、［リソースエレメントマッピング／リソースエレメントデマッピング］がある。ＰＨＹ－Ｌｏｗ５０５Ｌの機能には、［送信デジタルＢＦ／受信デジタルＢＦ］、［ＩＦＦＴ／ＦＦＴ］がある。ＲＦ５０６の機能には、［Ｄ／Ａ変換／Ａ／Ｄ変換］、［送信アナログＢＦ／受信アナログＢＦ］がある。 In the O-RAN "split7", the functions of the PHY 505 are split. Among the functions of the divided PHY 505, 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-high505H include [encoding / decoding], [scrambling / descrambling], [modulation / demodulation], [layer mapping / equivalent processing, IDFT], [ precoding/channel estimation] and [resource element mapping/resource element demapping]. The functions of the PHY-Low 505L include [transmitting digital BF/receiving digital BF] and [IFFT/FFT]. The functions of the RF 506 include [D/A conversion/A/D conversion] and [transmitting analog BF/receiving analog BF].
　ＰＨＹ－ｈｉｇｈ５０５ＨとＰＨＹ－ｌｏｗ５０５Ｌは、接続ケーブル４０３により接続される。接続ケーブル４０３のインタフェース中のＵ－ｐｌａｎｅ（Ｕｓｅｒ－ｐｌａｎｅ）には、マッピングされた送信データ、及び、ＦＦＴ（Ｆａｓｔ　Ｆｏｕｒｉｅｒ　Ｔｒａｎｓｆｏｒｍ）された受信データが含まれる。接続ケーブル４０３のインタフェース中のＣ－ｐｌａｎｅ（Ｃｏｎｔｒｏｌ－ｐｌａｎｅ）には、ＢＦ識別情報（ＢｅａｍＩＤ）が含まれる。 The 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 includes mapped transmission data and FFT (Fast Fourier Transform) reception data. The C-plane (Control-plane) in the interface of the connection cable 403 includes BF identification information (BeamID).
　図１３には、本例の分散アンテナシステムにおけるＢＢＵ及びＨＵＢの構成例を示してある。ＢＢＵ４０１は、ＲＵ選択部４１０と、ＰＨＹ－ｌｏｗ５０５Ｌとを含む。下りリンクでは、ＰＨＹ－ｌｏｗ５０５Ｌは、ＣＵ１００からのＵ－ｐｌａｎｅの信号を処理し、送信信号を生成する。送信信号は、デジタル又はアナログのＲｏＦ（Ｒａｄｉｏ　ｏｖｅｒ　Ｆｉｂｅｒ）信号として出力される。ＲＵ選択部４１０は、ＣＵ１００からのＣ－ｐｌａｎｅの信号に含まれるＢＦ制御情報（ＢｅａｍＩＤ）に対して予め割り当てられた子機（ＲＵ４０２）への経路を選択する。選択されたＲＵ２０２は、ＢＢＵ４０１から受信した送信信号を電気信号に変換し、アンテナより出力する。上りリンクでは、ＲＵ選択部４１０で下りリンクで選択したＲＵ２０２と同一の経路の上り信号を、Ｕ－ｐｌａｎｅでＣＵ１００へ送信する。ＢＢＵ４０１とＲＵ４０２の間にＨＵＢ４０５が存在する場合には、ＨＵＢ４０５も複数のＲＵ４０２と接続されるため、ＨＵＢ４０５内のＲＵ選択部４１０によって同様の処理を行う。 FIG. 13 shows a configuration example of the BBU and HUB in the distributed antenna system of this example. BBU 401 includes RU selector 410 and PHY-low 505L. In the downlink, the PHY-low 505L processes U-plane signals from the CU 100 and generates transmission signals. 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 slave unit (RU 402) pre-assigned to the BF control information (BeamID) included in the C-plane signal from the CU 100. FIG. The selected RU 202 converts the transmission signal received from the BBU 401 into an electric signal and outputs it from the antenna. In uplink, an uplink signal on the same path as RU 202 selected in downlink by RU selection section 410 is transmitted to CU 100 in the U-plane. When the HUB 405 exists between the BBU 401 and the RU 402, the HUB 405 is also connected to a plurality of RUs 402, so the RU selector 410 in the HUB 405 performs similar processing.
　次に、ＲＵ選択部４１０による経路選択方法について説明する。図１４には、経路選択用テーブルの例を示してある。同図のテーブルは、図１３に示したように、ＢＵ４０１にＲＵ４０２（＃１）及びＲＵ４０２（＃２）の２台が直接接続され、更にＲＵ４０２（＃３）及びＲＵ４０２（＃４）の２台がＨＵＢ４０５を介して接続されている場合の例である。ＢＢＵ４０１は、ＢＢＵ　Ｔａｂｌｅを参照して、ＢｅａｍＩＤに対応した経路を選択する。ＢＢＵ　Ｔａｂｌｅには、ＢＢＵ４０１に直接接続された２台のＲＵ４０２それぞれに対する２つの経路（経路１，経路２）と、ＢＢＵ４０１にＨＵＢを介して接続された２台のＲＵ４０２に共通の経路（経路３）が設定されている。ＨＵＢ４０５は、ＨＵＢ　Ｔａｂｌｅ♯１を参照して、ＢｅａｍＩＤに対応した経路を選択する。ＨＵＢ　Ｔａｂｌｅ♯１には、ＨＵＢ４０５に直接接続された２台のＲＵ４０２のそれぞれに対する２つの経路（経路１，経路２）が設定されている。このような経路選択用テーブルを用いることで、ＢｅａｍＩＤに対応するＲＵ４０２を容易に特定することができる。 Next, a route selection method by the RU selection unit 410 will be described. FIG. 14 shows an example of a route selection table. As shown in FIG. 13, the table in FIG. are connected via a HUB 405. FIG. The BBU 401 refers to the BBU Table and selects a route corresponding to the BeamID. The BBU Table contains two routes (route 1, route 2) for each of the two RUs 402 directly connected to the BBU 401, and a common route (route 3) for the two RUs 402 connected to the BBU 401 via a HUB. is set. The HUB 405 refers to the HUB Table #1 and selects the path corresponding to the BeamID. Two routes (route 1 and route 2) for each of the two RUs 402 directly connected to the HUB 405 are set in the HUB Table #1. By using such a route selection table, it is possible to easily identify the RU 402 corresponding to the BeamID.
　図１５には、本例の分散アンテナシステムにおけるＲＵの構成例を示してある。ＲＵ４０２は、図１５に示すＲＦ５０６の構成要素を含む。同図のＲＦ５０６は、選択判別部６０１と、Ｏ／Ｅ変換器６０２と、Ｄ／Ａ変換器６０３と、周波数変換部６０４と、電力増幅器（ＰＡ：Ｐｏｗｅｒ　Ａｍｐｌｉｆｉｅｒ）６０５と、ＴＤＤ－ＳＷ（Ｔｉｍｅ　Ｄｉｖｉｓｉｏｎ　Ｄｕｐｌｅｘ－Ｓｗｉｔｃｈ）６０６と、アンテナ６０７と、ＬＮＡ（Ｌｏｗ　Ｎｏｉｓｅ　Ａｍｐｌｉｆｉｅｒ）６０８と、周波数変換部６０９と、Ａ／Ｄ変換器６１０と、Ｅ／Ｏ変換器６１１とを有する。 FIG. 15 shows a configuration example of RUs in the distributed antenna system of this example. RU 402 includes the components of RF 506 shown in FIG. RF 506 in the figure includes a selection determination unit 601, an O/E converter 602, a D/A converter 603, a frequency conversion unit 604, a power amplifier (PA) 605, and a TDD-SW (Time Division Duplex-Switch) 606 , antenna 607 , LNA (Low Noise Amplifier) 608 , frequency converter 609 , A/D converter 610 , and E/O converter 611 .
　選択判別部６０１は、自ＲＵが選択されたか否かの判断を行う。一例として、ＲＵ選択部４１０から選択／非選択のフラグ情報を得て判断する方法がある。ＲＵ４０２は、自己が選択された場合にのみ下記の動作を行う（すなわち、自己が選択されていない場合は下記の動作を行わない）。 The selection determination unit 601 determines whether or not its own RU has been selected. As an example, there is a method of obtaining selection/non-selection flag information from the RU selection unit 410 and making a determination. RU 402 performs the following operations only when it is selected (ie, it does not perform the following operations when it is not selected).
　自ＲＵが選択されている場合、ＢＢＵ４０１又はＨＵＢ４０５からの信号は、Ｏ／Ｅ変換器６０２で光信号から電気信号に変換される。Ｄ／Ａ変換器６０３は、Ｏ／Ｅ変換によって得られたデジタル信号をアナログ信号に変換する。なお、アナログＲｏｆの場合はＤ／Ａ変換器６０３は不要となる。周波数変換部６０４は、Ｄ／Ａ変換によって得られたＩＦ信号をＲＦ信号に変換する。電力増幅器６０５は、周波数変換後のＲＦ信号の電力を増幅する。ＴＤＤ－ＳＷ６０６は、下りリンク（送信）又は上りリンク（受信）で経路を切り替える。下りリンクでは、アンテナ６０７からＲＦ信号が送信される。 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 . A D/A converter 603 converts the digital signal obtained by the O/E conversion into an analog signal. Note that the D/A converter 603 is not required in the case of analog Rof. A frequency converter 604 converts the IF signal obtained by the D/A conversion into an RF signal. A power amplifier 605 amplifies the power of the frequency-converted RF signal. The TDD-SW 606 switches paths on the downlink (transmission) or uplink (reception). An RF signal is transmitted from the antenna 607 on the downlink.
　上りリンクでは、アンテナ６０７で移動局からのＲＦ信号を受信する。ＬＮＡ６０８は、アンテナ６０７によって受信されたＲＦ信号を増幅する。周波数変換部６０９は、増幅後のＲＦ信号をＩＦ信号に周波数変換する。Ａ／Ｄ変換器６１０は、周波数変換後のＩＦ信号をアナログ信号からデジタル信号に変換する。Ｅ／Ｏ変換器６１１は、Ａ／Ｄ変換によって得られた電気信号を光信号に変換する。なお、アナログＲｏｆの場合はＡ／Ｄ変換器６１１は不要となる。 In the uplink, antenna 607 receives RF signals from mobile stations. LNA 608 amplifies the RF signal received by antenna 607 . A frequency converter 609 frequency-converts the amplified RF signal into an IF signal. A/D converter 610 converts the frequency-converted IF signal from an analog signal to a digital signal. The E/O converter 611 converts the electrical signal obtained by A/D conversion into an optical signal. Note that the A/D converter 611 is not required in the case of analog Rof.
　図１５では、説明を簡潔にするために必要な機能ブロックのみを示したが、当業者には周知である、バンドパスフィルタ、ＡＧＣ（Ａｕｔｏｍａｔｉｃ　Ｇａｉｎ　Ｃｏｎｔｒｏｌ）、ＡＦＣ（Ａｕｔｏｍａｔｉｃ　Ｆｒｅｑｕｅｎｃｙ　Ｃｏｎｔｒｏｌ）などの種々の機能ブロックが、図示した機能ブロックの間に挿入されてもよい。 Although FIG. 15 shows only the functional blocks necessary for simplification of the explanation, various functions such as a bandpass filter, AGC (Automatic Gain Control), AFC (Automatic Frequency Control), etc., which are well known to those skilled in the art, are shown. Functional blocks may be interposed between illustrated functional blocks.
　以上のように、本例の基地局は、間隔を置いて配置された複数のＲＵ４０２を備え、ＢｅａｍＩＤを含むＢＦ制御情報に基づくアンテナ制御を行う基地局であって、ＢＢＵ４０１及びＨＵＢ４０５が有するＲＵ選択部４１０が、上記アンテナ制御として、ＢＦ制御情報に含まれるＢｅａｍＩＤに予め対応付けられたＲＵ４０２を無線通信に使用するために選択する処理を行う。ＣＵ１００は、本発明に係る中央ユニットに対応し、ＢＢＵ４０１は、本発明に係るベースバンドユニットに対応し、ＲＵ４０２は、本発明に係る無線アンテナユニットに対応し、ＨＵＢ４０５は、本発明に係るハブに対応する。 As described above, the base station of this example includes a plurality of RUs 402 arranged at intervals and performs antenna control based on BF control information including BeamID. As the antenna control, the unit 410 performs a process of selecting an RU 402 pre-associated with the BeamID included in the BF control information for use in wireless communication. CU 100 corresponds to the central unit according to the present invention, BBU 401 corresponds to the baseband unit according to the present invention, RU 402 corresponds to the radio antenna unit according to the present invention, and HUB 405 corresponds to the hub according to the present invention. handle.
　このような構成によれば、基地局のカバーエリアを実質的に拡大できるだけでなく、下りリンクでは、選択されなかったＲＵ４０２はＲＦ信号を送信しないので消費電力を抑えることができ、上りリンクでは、選択されなかったＲＵ４０２の受信信号（雑音信号）を合成しないので通信品質を向上させることができる。また、ＲＵ４０２は、ＢＦ機能が不要であり、多数のアンテナ素子を備える必要もなく、指向性が広い単一又は少数素子のアンテナで十分なため、装置コストを抑えることが可能である。 According to such a configuration, it is possible not only to substantially expand the coverage area of the base station, but also to reduce power consumption in the downlink because the RUs 402 that have not been selected do not transmit RF signals. Since the received signals (noise signals) of the RUs 402 that have not been selected are not combined, the communication quality can be improved. In addition, the RU 402 does not require a BF function, does not need to be provided with a large number of antenna elements, and a single or a small number of antenna elements with wide directivity are sufficient, so the device cost can be reduced.
　なお、上述した構成は、屋内での利用に特に効果的であるが、屋外で利用しても構わない。また、ＢＢＵ４０１とＲＵ４０２間の信号、ＢＢ４０１とＨＵＢ４０５間の信号、及び、ＨＵＢ４０５とＲＵ４０２間の信号は、光信号でもよく、電気信号でもよい。また、これらの信号を光信号とする場合、ＣＵ１００とＢＢＵ４０１の信号と同じ信号を用いてもよく、ＣＵ１００とＢＢＵ４０１の信号とは異なる信号に置き換えてもよい。また、ＢＦ識別情報に応じて１つのＲＵ４０２を選択する機能を持つ分散アンテナを使用してもよい。 Although the above configuration is particularly effective for indoor use, it may also be used outdoors. Also, the signal between BBU 401 and RU 402, the signal between BB 401 and HUB 405, and the signal between HUB 405 and RU 402 may be optical signals or electrical signals. Further, when these signals are optical signals, the same signals as the signals of CU100 and BBU401 may be used, or the signals of CU100 and BBU401 may be replaced with different signals. Also, a distributed antenna having a function of selecting one RU 402 according to BF identification information may be used.
　また、上記の説明では、１つのＢｅａｍＩＤに対して１つのＲＵ４０２を対応付けているが、１つのＢｅａｍＩＤに対して複数（例えば、２つ）のＲＵ４０２を対応付けてもよい。これは、２つのＲＵ４０２の中間部分に移動局が存在する場合や、移動局が移動して在圏のＲＵ４０２が切り替わる場合などに有効である。 Also, in the above description, one RU 402 is associated with one BeamID, but multiple (for example, two) RUs 402 may be associated with one BeamID. This is effective when a mobile station exists in the middle part of two RUs 402, or when a mobile station moves and the serving RU 402 switches.
　以上、本発明について一実施形態に基づいて説明したが、本発明はここに記載された無線通信システムに限定されるものではなく、他の無線通信システムに広く適用することができることは言うまでもない。
　また、本発明は、例えば、上記の処理に関する技術的手順を含む方法や、上記の処理をプロセッサにより実行させるためのプログラム、そのようなプログラムをコンピュータ読み取り可能に記憶する記憶媒体などとして提供することも可能である。 Although the present invention has been described based on one embodiment, it goes without saying that the present invention is not limited to the wireless communication system described here, and can be widely applied to other wireless communication systems.
In addition, the present invention provides, for example, a method including technical procedures related to the above processing, a program for causing a processor to execute the above processing, and a storage medium storing such a program in a computer-readable manner. is also possible.
　なお、本発明の範囲は、図示され記載された例示的な実施形態に限定されるものではなく、本発明が目的とするものと均等な効果をもたらす全ての実施形態をも含む。更に、本発明の範囲は、全ての開示されたそれぞれの特徴のうち特定の特徴のあらゆる所望する組み合わせによって画され得る。 It should be noted that the scope of the present invention is not limited to the illustrated and described exemplary embodiments, but includes all embodiments that achieve effects equivalent to those intended by the present invention. Moreover, the scope of the invention may be defined by any desired combination of the specific features of each and every disclosed feature.
　この出願は、２０２１年１月２７日に出願された日本出願特願２０２１－０１１００５を基礎として優先権の利益を主張するものであり、その開示の全てを引用によってここに取り込む。 This application claims the benefit of priority based on Japanese Patent Application No. 2021-011005 filed on January 27, 2021, the entire disclosure of which is hereby incorporated by reference.
　本発明は、複数の無線アンテナユニットを備えた基地局に利用することが可能である。 The present invention can be used in a base station equipped with multiple radio antenna units.
　１００：ＣＵ、　２００：ＤＵ、　２０１：ＢＢＵ、　２０２：ＲＵ、　２０３：接続ケーブル、　２０５：ＨＵＢ、　３０１：壁、　３０２：柱、　３０３：カバーエリア、　３０４：不感地帯、　３０５：天井、　４０１：ＢＢＵ、　４０２：ＲＵ、　４０３：接続ケーブル、　４０５：ＨＵＢ、　４０６：ＲＵ選択部、　５０１：ＲＰＣ、　５０２：ＰＤＣＰ、　５０３：ＲＬＣ、　５０４：ＭＡＣ、　５０５Ｈ：ＰＨＹ－ｈｉｇｈ、　５０５Ｌ：ＰＨＹ－Ｌｏｗ、　５０６：ＲＦ、　６０１：選択判定部、　６０２：Ｏ／Ｅ変換器、　６０３：Ｄ／Ａ変換器、　６０４：周波数変換部、　６０５：電力増幅器、　６０６：ＴＤＤ－ＳＷ、　６０７：アンテナ、　６０８：ＬＮＡ、　６０９：周波数変換部、　６１０：Ａ／Ｄ変換器、　６１１：Ｅ／Ｏ変換器 100: CU, 200: DU, 201: BBU, 202: RU, 203: Connection cable, 205: HUB, 301: Wall, 302: Pillar, 303: Cover area, 304: Dead zone, 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 converter, 610: A/D converter, 611: E/O converter

Claims (4)

  1. 　間隔を置いて配置された複数の無線アンテナユニットを備え、ビームフォーミング用の識別情報を含む制御信号に基づくアンテナ制御を行う基地局であって、
    　前記ビームフォーミング用の識別情報の各々に対して前記複数の無線アンテナユニットのうちの少なくとも１つが予め対応付けられており、
    　前記アンテナ制御では、前記制御信号に含まれるビームフォーミング用の識別情報に対応付けられた無線アンテナユニットを無線通信に使用するために選択することを特徴とする基地局。     A base station comprising a plurality of spaced apart radio antenna units and performing antenna control based on a control signal containing identification information for beamforming,
    At least one of the plurality of radio antenna units is associated in advance with each of the identification information for beamforming,
    The base station, wherein in the antenna control, a radio antenna unit associated with identification information for beamforming included in the control signal is selected for use in radio communication.
  2. 　請求項１に記載の基地局において、
    　前記制御信号を出力する中央ユニットと、前記中央ユニットと前記複数の無線アンテナユニットとの間に介在するベースバンドユニットとを備え、
    　前記ベースバンドユニットが、前記アンテナ制御を行う機能を有することを特徴とする基地局。     In the base station of claim 1,
    A central unit that outputs the control signal, and a baseband unit interposed between the central unit and the plurality of radio antenna units,
    A base station, wherein the baseband unit has a function of performing the antenna control.
  3. 　請求項２に記載の基地局において、
    　前記中央ユニットと前記複数の無線アンテナユニットのうちの少なくとも１つとの間に介在するハブを備え、
    　前記ハブが、前記アンテナ制御を行う機能を有することを特徴とする基地局。     In the base station according to claim 2,
    a hub interposed between the central unit and at least one of the plurality of radio antenna units;
    The base station, wherein the hub has a function of performing the antenna control.
  4. 　間隔を置いて配置された複数の無線アンテナユニットを備えた基地局において、ビームフォーミング用の識別情報を含む制御信号に基づくアンテナ制御を行うアンテナ制御方法であって、
    　前記ビームフォーミング用の識別情報の各々に対して前記複数の無線アンテナユニットのうちの少なくとも１つが予め対応付けられており、
    　前記アンテナ制御では、前記制御信号に含まれるビームフォーミング用の識別情報に対応付けられた無線アンテナユニットを無線通信に使用するために選択することを特徴とするアンテナ制御方法。     An antenna control method for performing antenna control based on a control signal including identification information for beamforming in a base station equipped with a plurality of wireless antenna units arranged at intervals,
    At least one of the plurality of radio antenna units is associated in advance with each of the identification information for beamforming,
    The antenna control method, wherein in the antenna control, a radio antenna unit associated with identification information for beamforming included in the control signal is selected for use in radio communication.
PCT/JP2021/047917 2021-01-27 2021-12-23 Base station and method for controlling antenna WO2022163242A1 (en)

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WO2009151893A2 (en) * 2008-05-21 2009-12-17 Samplify Systems, Inc. Compression of baseband signals in base transceiver systems
WO2020095460A1 (en) * 2018-11-09 2020-05-14 株式会社Ｎｔｔドコモ Signal processing device, radio device, front haul multiplexer, beam control method, and signal combining method

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