Master station apparatus and analog signal transmission method

Abstract

This master station apparatus is capable of transmitting / receiving an analog signal to / from a plurality of slave station apparatus, and comprises: an acquisition unit for acquiring beam information indicating a beamforming pattern from the outside of the master station apparatus; a selection unit for selecting at least one slave station apparatus among the plurality of slave station apparatuses on the basis of the beam information; a transmission unit for performing transmission processing for transmitting a downlink analog signal to the slave station apparatus; and a reception unit for performing reception processing for receiving an uplink analog signal from the slave station apparatus. The transmission unit performs processing for reflecting the result of selecting the slave station apparatus by the selection unit in the transmission processing, and the reception unit performs processing for reflecting the result of selecting the slave station apparatus by the selection unit in the reception processing.

Description

Master station device and analog signal transmission method

[0001] This application claims priority based on Japanese Patent Application No. 2024-48857, filed March 26, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0002] Non-Patent Document 1 ("NR SSB Beam Sweeping", [online], [searched February 27, 2024], Internet <URL: https: / / jp.mathworks.com / help / 5g / ug / nr-ssb-beam-sweeping.html>) discloses a beamforming technique.

[0003] Furthermore, a distributed antenna system (DAS) is known as a technology for eliminating radio wave blindness caused by obstacles.

[0004] "NR SSB Beam Sweeping", [online], [searched February 27, 2024], Internet <URL: https: / / jp.mathworks.com / help / 5g / ug / nr-ssb-beam-sweeping.html> "5G / NR-Beam Management", [online], [searched February 27, 2024], Internet <URL: https: / / www.sharetechnote.com / html / 5G / 5G_Phy_BeamManagement.html> "5G NR Beam Managament SA, NSA | Beam Management In 5G NR”, [online], [retrieved February 27, 2024], Internet〈URL: https: / / www.rfwireless-world.com / 5G / 5G-NR-Beam-Management.html〉

[0005] The parent station device of the present disclosure is a parent station device capable of transmitting and receiving analog signals to and from a plurality of child station devices, each of which transmits and receives RF (Radio Frequency) signals via antennas arranged at intervals, and includes an acquisition unit that acquires beam information indicating a beamforming pattern from outside the parent station device, a selection unit that selects at least one of the plurality of child station devices based on the beam information acquired by the acquisition unit, a transmission unit that performs transmission processing to transmit a downstream analog signal to the child station device, and a reception unit that performs reception processing to receive an upstream analog signal from the child station device, wherein the transmission unit performs downstream signal processing to reflect the selection result of the child station device by the selection unit in the transmission processing, and the reception unit performs upstream signal processing to reflect the selection result of the child station device by the selection unit in the reception processing.

[0006] One aspect of the present disclosure may be realized not only as a master station device having such a characteristic processing unit, but also as a program for causing a computer to execute the steps of such a characteristic process. Furthermore, one aspect of the present disclosure may be realized as a semiconductor integrated circuit that realizes part or all of the master station device, or as a system including the master station device.

[0007] FIG. 1 is a diagram illustrating a configuration of a communication system according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of an arrangement of remote nodes in the communication system according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating a configuration of a center node in the communication system according to the first embodiment of the present disclosure. FIG. 4 is a diagram illustrating a configuration of a remote node in the communication system according to the first embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of a correspondence table stored in a storage unit in the remote node according to the first embodiment of the present disclosure. FIG. 6 is a flowchart illustrating an example of an operation procedure when the center node according to the first embodiment of the present disclosure transmits and receives an analog signal. FIG. 7 is a diagram illustrating a configuration of a communication system according to a second embodiment of the present disclosure. FIG. 8 is a diagram illustrating a configuration of a center node in the communication system according to the second embodiment of the present disclosure. FIG. 9 is a diagram illustrating an example of a correspondence table stored in a storage unit in the remote node according to the second embodiment of the present disclosure. FIG. 10 is a diagram illustrating a configuration of a remote node in the communication system according to the second embodiment of the present disclosure. FIG. 11 is a diagram illustrating a configuration of a communication system according to a third embodiment of the present disclosure. FIG. 12 is a diagram illustrating a configuration of a center node in the communication system according to the third embodiment of the present disclosure. Fig. 13 is a diagram illustrating a configuration of a communication system according to a fourth embodiment of the present disclosure. Fig. 14 is a diagram illustrating a configuration of a center node in the communication system according to the fourth embodiment of the present disclosure.

[0008] Conventionally, techniques have been developed to improve communication quality in communication systems.

[0009] [Problem to be Solved by the Present Disclosure] In a distributed antenna system, RF signals are transmitted and received via a plurality of antennas, and therefore communication quality may be degraded due to superposition of noise caused by multiplexing of uplink signals.

[0010] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a master station device and an analog signal transmission method that can further improve communication quality in a communication system.

[0011] Effect of the Present Disclosure According to the present disclosure, it is possible to further improve communication quality in a communication system.

[0012] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. (1) A master station device according to an embodiment of the present disclosure is a master station device capable of transmitting and receiving analog signals to and from a plurality of slave station devices, each of which transmits and receives RF signals via antennas arranged at intervals, and includes an acquisition unit that acquires beam information indicating a beamforming pattern from outside the master station device, a selection unit that selects at least one of the plurality of slave station devices based on the beam information acquired by the acquisition unit, a transmission unit that performs transmission processing to transmit a downstream analog signal to the slave station device, and a reception unit that performs reception processing to receive an upstream analog signal from the slave station device, wherein the transmission unit performs downstream signal processing to reflect the selection result of the slave station device by the selection unit in the transmission processing, and the reception unit performs upstream signal processing to reflect the selection result of the slave station device by the selection unit in the reception processing.

[0013] In this way, by selecting a slave station device based on beam information and reflecting the selection result in the transmission and reception processes, it is possible to selectively transmit and receive analog signals to and from the selected slave station device, which makes it possible to suppress ingress noise caused by noise contained in the RF signals received via each antenna, compared to a configuration in which analog signals are transmitted in parallel to all slave station devices, thereby further improving the communication quality in the communication system.

[0014] (2) In the above (1), the transmitting unit may adjust the level of the downstream analog signal to be transmitted to the slave station equipment based on the selection result of the slave station equipment by the selecting unit as the downstream signal processing, and the receiving unit may adjust the level of the upstream analog signal received from the slave station equipment based on the selection result of the slave station equipment by the selecting unit as the upstream signal processing.

[0015] With this configuration, the level of the analog signal transmitted and received with the slave station device can be finely adjusted compared to a configuration in which the on state and off state of the transmission and reception of analog signals with the slave station device are switched based on the selection result of the slave station device.

[0016] (3) In the above (2), the transmitter may be capable of adjusting levels of the downstream analog signals to be transmitted to the slave station devices selected by the selector to different values.

[0017] With this configuration, the level of the downstream analog signal can be adjusted according to the size of the coverage area of ​​the slave station device, for example. Therefore, the level of the downstream analog signal addressed to a slave station device with a large coverage area can be adjusted to a higher value to transmit an RF signal of sufficient level from that slave station device, while the level of the downstream analog signal addressed to a slave station device with a small coverage area can be adjusted to a lower value to reduce the power consumption of that slave station device.

[0018] (4) In the above (2) or (3), the receiving unit may attenuate the upstream analog signals having a level equal to or higher than a predetermined value among the upstream analog signals received from the plurality of slave station devices.

[0019] With this configuration, even if an excessive RF signal input occurs in some slave station devices, it is possible to prevent a deterioration in the communication quality of the upstream communication caused by combining multiple upstream analog signals received from multiple slave station devices.

[0020] (5) In the above (1), the transmitting unit may selectively transmit the downstream analog signal to a slave station device selected by the selecting unit from among the plurality of slave station devices as the downstream signal processing, and the receiving unit may selectively receive the upstream analog signal from the slave station device selected by the selecting unit from among the plurality of slave station devices as the upstream signal processing.

[0021] With this configuration, it is possible to more reliably suppress the occurrence of ingress noise.

[0022] (6) In any of (1) to (5) above, the parent station device may further include a storage unit that stores correspondence information indicating the correspondence between the beamforming patterns and the child station devices, and the selection unit may select at least one of the plurality of child station devices based on the correspondence information and the beam information, and the correspondence information may include the child station devices with which the plurality of beamforming patterns are associated.

[0023] With this configuration, when selecting a slave station device associated with a plurality of beam forming patterns, it is possible to make a decision on the slave station device depending on the beam forming pattern indicated by the beam information, for example.

[0024] (7) In the above (6), the transmitter may further transmit a control signal for controlling a beamforming pattern of the RF signal to the slave station devices associated with the plurality of beamforming patterns.

[0025] With this configuration, the beam forming pattern in the slave station device can be controlled depending on the beam forming pattern indicated by the beam information.

[0026] (8) In any of (1) to (5) above, the parent station device may further include a storage unit that stores correspondence information indicating a correspondence relationship between the beamforming pattern and the child station device, and the selection unit may select at least one of the plurality of child station devices based on the correspondence information and the beam information, and the correspondence information may provide a one-to-one correspondence between the beamforming pattern and the child station device.

[0027] With this configuration, it is possible to select slave station devices that transmit and receive analog signals, for example, from among a larger number of slave station devices using a limited number of beamforming patterns.

[0028] (9) In any of (1) to (8) above, the parent station device may further include a delay processing unit that imparts a delay amount to the downstream analog signal and the upstream analog signal, and the delay processing unit may impart a delay amount to the downstream analog signal transmitted by the transmitting unit according to the transmission distance of the downstream analog signal between the parent station device and the child station device that is the destination of the downstream analog signal, and the delay processing unit may impart a delay amount to the upstream analog signal received by the receiving unit according to the transmission distance of the upstream analog signal between the parent station device and the child station device that is the source of the upstream analog signal.

[0029] This configuration can suppress variations in the transmission timing of RF signals at each slave station device, which may be caused by the transmission distance of the downstream analog signal, and can also suppress variations in the reception timing of upstream analog signals at the destination device, which may be caused by the transmission distance of the upstream analog signal.

[0030] (10) In the above (9), the delay processing unit may notify a base station device outside the parent station device of a representative value of the transmission delay amount of the plurality of downstream analog signals corresponding to each of the plurality of child station devices, and the transmitting unit may transmit the downstream analog signals, the transmission timing of which has been controlled in the base station device based on the representative value, to the child station device.

[0031] With this configuration, while distributing the antennas to multiple locations, it is possible to make the transmission timing of the RF signal closer to the transmission timing of the RF signal when the antennas are directly connected to the base station device.

[0032] (11) An analog signal transmission method according to an embodiment of the present disclosure is an analog signal transmission method in a master station device capable of transmitting and receiving analog signals to and from a plurality of slave station devices that transmit and receive RF signals via distributed antennas, and includes the steps of acquiring beam information indicating a beamforming pattern, selecting at least one of the plurality of slave station devices based on the acquired beam information, performing a transmission process to transmit a downstream analog signal to the slave station device, and performing a reception process to receive an upstream analog signal from the slave station device, wherein in the transmission process, downstream signal processing is performed to reflect the selection result of the slave station device in the transmission process, and in the reception process, upstream signal processing is performed to reflect the selection result of the slave station device in the reception process.

[0033] In this way, by selecting a slave station device based on beam information and reflecting the selection result in the transmission and reception processes, it is possible to selectively transmit and receive analog signals to and from the selected slave station device, which makes it possible to suppress ingress noise caused by noise contained in the RF signals received via each antenna, compared to a method in which analog signals are transmitted in parallel to all slave station devices, thereby further improving the communication quality in the communication system.

[0034] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and their description will not be repeated. Furthermore, at least some of the embodiments described below may be combined in any manner.

[0035] First Embodiment [Configuration and Basic Operation] Fig. 1 is a diagram illustrating a configuration of a communication system according to a first embodiment of the present disclosure. Referring to Fig. 1, a communication system 401 includes a center node 101 and a plurality of remote nodes 201. The center node 101 is an example of a master station device. The remote nodes 201 are an example of slave station devices. The communication system 401 is a distributed antenna system. The center node 101 and the remote nodes 201 are connected to each other via an optical fiber 191. The center node 101 is connected to a base station device 301 via a transmission line 181. The transmission line 181 is, for example, a coaxial cable.

[0036] Each remote node 201 includes an antenna 211. For example, the antenna 211 is an omnidirectional antenna. The antennas 211 are arranged at intervals. More specifically, the antennas 211 are arranged in a spatially dispersed manner.

[0037] 2 is a diagram illustrating an example of an arrangement of remote nodes in a communication system according to the first embodiment of the present disclosure. Referring to FIG. 2, a plurality of remote nodes 201 are provided on the ceilings of a plurality of rooms 82 in a building 81. Note that a plurality of remote nodes 201 may be provided in one room 82. The remote node 201 transmits and receives RF signals to and from a communication terminal 111 via an antenna 211. The communication terminal 111 may be a mobile terminal or a fixed terminal.

[0038] 1 again, the center node 101 and the remote node 201 transmit and receive optical signals including analog signals via an optical fiber 191. Hereinafter, an optical signal transmitted from the center node 101 to the remote node 201 will also be referred to as a downstream optical signal, and an optical signal transmitted from the remote node 201 to the center node 101 will also be referred to as an upstream optical signal.

[0039] For example, the communication system 401 is used as a fronthaul in a mobile communication system conforming to the TDD (Time Division Duplex) method. In this case, in the communication system 401, a downlink period Pd for downlink communication in which the remote node 201 transmits an RF signal to the communication terminal 111 and an uplink period Pu for uplink communication in which the remote node 201 receives an RF signal from the communication terminal 111 are switched and alternately repeated.

[0040] More specifically, the center node 101 receives an analog signal SId in the intermediate frequency (IF) band, which includes communication data, from the base station device 301 via the transmission line 181. The center node 101 transmits a downstream optical signal, which includes the received analog signal SId, to the remote node 201 via the optical fiber 191. The analog signal SId is an example of a downstream analog signal.

[0041] The remote node 201 receives a downstream optical signal from the center node 101 via the optical fiber 191. The remote node 201 acquires an analog signal SId from the received downstream optical signal and generates an RF signal SRd by frequency-converting the acquired analog signal SId. The remote node 201 transmits the generated RF signal SRd to the communication terminal 111 via the antenna 211 during a downstream period Pd.

[0042] Furthermore, during the upstream period Pu, the remote node 201 receives an RF signal SRu containing communication data from the communication terminal 111. The remote node 201 generates, for example, an IF band analog signal SIu by frequency-converting the RF signal SRu received from the communication terminal 111. The remote node 201 transmits an upstream optical signal containing the generated analog signal SIu to the center node 101 via the optical fiber 191. The analog signal SIu is an example of an upstream analog signal.

[0043] The center node 101 receives an upstream optical signal from the remote node 201 via the optical fiber 191. The center node 101 acquires an analog signal SIu from the received upstream optical signal and transmits the acquired analog signal SIu to the base station device 301 via the transmission line 181.

[0044] [Problem] In a distributed antenna system, RF signals are transmitted and received via multiple antennas, and therefore communication quality may be degraded due to superposition of noise caused by multiplexing of uplink signals.

[0045] More specifically, in a distributed antenna system, ingress noise occurs due to noise contained in the RF signal SRu received via each remote node 201. This causes a decrease in the communication quality of upstream communication.

[0046] Therefore, the communication system 401 according to the first embodiment of the present disclosure solves the above problem by adopting the following configuration.

[0047] (Configuration of Center Node and Remote Node) FIG. 3 is a diagram illustrating the configuration of a center node in a communication system according to the first embodiment of the present disclosure. Referring to FIG. 3, the center node 101 includes a transceiver 1, a control unit 2, and a storage unit 3. The transceiver 1 is an example of a transmitter and an example of a receiver. The control unit 2 is an example of an acquirer and an example of a selector. Some or all of the functions of the transceiver 1 and the control unit 2 are realized, for example, by a processing circuit (circuitry) including one or more processors. The storage unit 3 is, for example, a non-volatile memory included in the processing circuit.

[0048] The transceiver 1 includes a downstream processing unit 11, an upstream processing unit 12, a switching unit 20, and a plurality of optical transceivers 30. The switching unit 20 has switches 21 and 22. The optical transceivers 30 include a multiplexer 31, a demultiplexer 32, an optical modulator 33, an optical demodulator 34, and an optical coupler 35. The optical couplers 35 in each optical transceiver 30 are connected to different remote nodes 201 via optical fibers 191. The transceiver 1 performs a transmission process of transmitting an analog signal SId to the remote node 201 and a reception process of receiving an analog signal SIu from the remote node 201. Details of the transmission process and the reception process will be described later.

[0049] The switch 21 has an input terminal connected to the downstream processing unit 11 and a plurality of output terminals respectively connected to the plurality of optical transceivers 30. The switch 21 is capable of switching the optical transceiver 30 connected to the downstream processing unit 11.

[0050] The switch 22 has a plurality of input terminals connected to the plurality of optical transceivers 30, respectively, and an output terminal connected to the upstream processing unit 12. The switch 22 is capable of switching the optical transceiver 30 connected to the upstream processing unit 12.

[0051] 4 is a diagram illustrating a configuration of a remote node in a communication system according to the first embodiment of the present disclosure. Referring to FIG. 4, the remote node 201 includes an optical coupler 41, an optical demodulator 42, an optical modulator 43, a separator 44, a multiplexer 45, frequency converters 46 and 47, amplifiers 48 and 49, an RF transmitter / receiver 50, a controller 51, and an antenna 211. Some or all of the functions of the controller 51 are implemented by, for example, a processing circuit including one or more processors.

[0052] 3 , in the center node 101, the control unit 2 acquires beam information indicating a beamforming pattern from outside the center node 101. For example, the control unit 2 receives the beam information from the base station device 301.

[0053] More specifically, the base station device 301 generates beam information for beamforming control in accordance with the beamforming techniques described in Non-Patent Documents 1, 2, and 3. For example, the beam information includes a BeamID, which is an identifier of a beamforming pattern in accordance with the specifications of the O-RAN (Open Radio Access Network). The base station device 301 generates beam information periodically or irregularly and transmits the generated beam information to the center node 101.

[0054] When the control unit 2 receives the beam information from the base station device 301, the control unit 2 selects, based on the received beam information, at least one remote node 201 from among the plurality of remote nodes 201. For example, based on the beam information, the control unit 2 selects, from among the plurality of remote nodes 201, one remote node 201 that transmits and receives the analog signals SId and SIu.

[0055] 5 is a diagram illustrating an example of a correspondence table stored in a storage unit in the remote node according to the first embodiment of the present disclosure. Referring to Fig. 5, the storage unit 3 stores a correspondence table T1 indicating a correspondence relationship between a Beam ID of a beamforming pattern and a remote ID that is an identifier of the remote node 201. The correspondence table T1 is an example of correspondence information.

[0056] 5 , there is a one-to-one correspondence between beamforming patterns and remote nodes 201. More specifically, in the correspondence table T1, the remote ID of "AAA" is associated with the beam ID of "aaa," the remote ID of "BBB" is associated with the beam ID of "bbb," the remote ID of "CCC" is associated with the beam ID of "ccc," and the remote ID of "DDD" is associated with the beam ID of "ddd."

[0057] The control unit 2 selects a remote node 201 that transmits and receives the analog signals SId and SIu from among the multiple remote nodes 201, based on the correspondence table T1 and the beam information. More specifically, when the control unit 2 receives beam information from the base station device 301, it acquires a beam ID from the beam information. The control unit 2 refers to the correspondence table T1 in the storage unit 3, and determines the remote node 201 having a remote ID that corresponds to the acquired beam ID as the remote node 201 that transmits and receives the analog signals SId and SIu.

[0058] Referring again to Figure 3, when the control unit 2 selects a remote node 201 that transmits and receives analog signals SId and SIu, it outputs a switching signal to the transceiver unit 1 to connect the optical transceiver unit 30 corresponding to the selected remote node 201 to the base station device 301.

[0059] (Downstream Communication) In the center node 101, the transmitter / receiver 1 performs downstream signal processing to reflect in the transmission processing the selection result of the remote node 201 by the controller 2. For example, as the downstream signal processing, the transmitter / receiver 1 selectively transmits the analog signal SId to the remote node 201 selected by the controller 2 from among the multiple remote nodes 201.

[0060] More specifically, the switch 21 in the switching unit 20 receives a switching signal from the control unit 2 and, in accordance with the received switching signal, switches the optical transceiver 30 among the multiple optical transceivers 30 that is connected to the base station device 301 via the downlink processing unit 11.

[0061] The downstream processing unit 11 receives an analog signal SId including communication data from the base station device 301. During a downstream period Pd, the downstream processing unit 11 outputs the received analog signal SId to the optical transceiver unit 30 via the switch 21. More specifically, the downstream processing unit 11 outputs the analog signal SId to one of the multiple optical transceivers 30 connected via the switch 21.

[0062] The control unit 2 receives TDD information indicating the uplink period Pu and the downlink period Pd, as well as synchronization information, from the base station device 301. The control unit 2 generates a digital signal Sdd including the received TDD information and synchronization information, and outputs the generated digital signal Sdd to the optical transceiver unit 30 corresponding to the remote node 201 that transmits and receives the analog signals SId and SIu.

[0063] The multiplexing unit 31 in the optical transceiver 30 connected to the downstream processing unit 11 via the switch 21 frequency-multiplexes the analog signal SId received from the downstream processing unit 11 via the switch 21 and the digital signal Sdd received from the control unit 2. The multiplexing unit 31 generates an electrical signal in which the analog signal SId and the digital signal Sdd are frequency-multiplexed, and outputs the electrical signal to the optical modulation unit 33.

[0064] The optical modulation unit 33 in the optical transceiver 30 connected to the downstream processing unit 11 via the switch 21 receives the electrical signal from the multiplexer 31 and generates a downstream optical signal of wavelength λ1 by optically modulating the received electrical signal. The optical modulation unit 33 transmits the downstream optical signal to the corresponding remote node 201 via the optical coupler 35 and the optical fiber 191. The optical modulation unit 33 in the optical transceiver 30 not connected to the downstream processing unit 11 via the switch 21 may be configured to transmit a downstream optical signal of a predetermined intensity that does not include the analog signal SId to the corresponding remote node 201 via the optical coupler 35 and the optical fiber 191, or may be configured not to transmit a downstream optical signal.

[0065] 4 again, in the remote node 201, the optical demodulator 42 receives a downstream optical signal from the center node 101 via the optical fiber 191 and the optical coupler 41. The optical demodulator 42 generates an electrical signal at a level corresponding to the intensity of the received downstream optical signal and outputs the electrical signal to the separator 44.

[0066] The separator 44 separates the analog signal SId and the digital signal Sdd contained in the electrical signal received from the optical demodulator 42. The separator 44 outputs the separated analog signal SId to the frequency converter 46 and outputs the separated digital signal Sdd to the controller 51.

[0067] The frequency conversion unit 46 generates an RF signal SRd by frequency-converting the analog signal SId received from the separation unit 44 and outputs the RF signal SRd to the amplification unit 48 .

[0068] Amplifying unit 48 amplifies RF signal SRd received from frequency converting unit 46 and outputs the amplified RF signal SRd to RF transmitting / receiving unit 50 .

[0069] The control unit 51 acquires TDD information and synchronization information from the digital signal Sdd received from the separation unit 44, and based on the acquired TDD information and synchronization information, switches between the transmission and reception of RF signals by the RF transceiver unit 50. More specifically, based on the TDD information and synchronization information, the control unit 51 generates a TDD switching signal for switching between the transmission and reception of RF signals by the RF transceiver unit 50, and outputs the generated TDD switching signal to the RF transceiver unit 50.

[0070] In accordance with the TDD switching signal received from the control unit 51, the RF transceiver unit 50 transmits the RF signal SRd received from the amplifier unit 48 to the communication terminal 111 via the antenna 211 during the downlink period Pd.

[0071] (Uplink Communication) In accordance with the TDD switching signal received from the control unit 51, the RF transceiver 50 receives the RF signal SRu from the communication terminal 111 via the antenna 211 during the uplink period Pu. The RF transceiver 50 outputs the received RF signal SRu to the amplifier 49.

[0072] Amplifying unit 49 amplifies RF signal SRu received from RF transmitting / receiving unit 50 and outputs the amplified RF signal SRu to frequency converting unit 47 .

[0073] The frequency converter 47 converts the frequency of the RF signal SRu received from the amplifier 49 to generate an analog signal SIu, and outputs the analog signal SIu to the multiplexer 45 .

[0074] The multiplexing unit 45 receives a digital signal Sdu including monitoring results such as the temperature of the remote node 201 from a monitoring unit (not shown). The multiplexing unit 45 frequency-multiplexes the analog signal SIu received from the frequency conversion unit 47 and the digital signal Sdu received from the monitoring unit (not shown). The multiplexing unit 45 generates an electrical signal in which the analog signal SIu and the digital signal Sdu are frequency-multiplexed, and outputs the electrical signal to the optical modulation unit 43.

[0075] The optical modulation unit 43 receives the electrical signal from the multiplexing unit 45 and generates an upstream optical signal with wavelength λ2 by optically modulating the received electrical signal. Wavelength λ2 may be the same as or different from wavelength λ1. The optical modulation unit 43 transmits the upstream optical signal to the center node 101 via the optical coupler 41 and the optical fiber 191.

[0076] 3 again, in the center node 101, the transmitter / receiver 1 performs upstream signal processing to reflect in the reception processing the selection result of the remote node 201 by the controller 2. For example, as the upstream signal processing, the transmitter / receiver 1 selectively receives the analog signal SIu from the remote node 201 selected by the controller 2 from among the multiple remote nodes 201.

[0077] More specifically, the switch 22 in the switching unit 20 receives a switching signal from the control unit 2 and, in accordance with the received switching signal, switches the optical transceiver 30 out of the multiple optical transceivers 30 that is connected to the base station device 301 via the upstream processing unit 12.

[0078] The optical demodulator 34 in the optical transmitter / receiver 30 receives an upstream optical signal from the corresponding remote node 201 via the optical fiber 191 and the optical coupler 35. The optical demodulator 34 generates an electrical signal at a level corresponding to the intensity of the received upstream optical signal and outputs the electrical signal to the separator 32.

[0079] The separator 32 separates the analog signal SIu and the digital signal Sdu contained in the electrical signal received from the optical demodulator 34. The separator 44 outputs the separated analog signal SIu to the upstream processor 12 via the switch 22, and outputs the separated digital signal Sdu to the controller 2.

[0080] The upstream processing unit 12 receives the analog signal SIu from the optical transceiver 30 via the switch 22 and transmits it to the base station device 301. More specifically, the upstream processing unit 12 receives the analog signal SIu from one of the multiple optical transceivers 30 that is connected via the switch 22, and transmits the received analog signal SIu to the base station device 301.

[0081] The control unit 2 acquires the monitoring result from the digital signal Sdu received from the demultiplexing unit 32, and processes the acquired monitoring result. Note that the control unit 2 may transmit the acquired monitoring result to the base station device 301.

[0082] [Operation Flow] FIG. 6 is a flowchart defining an example of an operation procedure when the center node according to the first embodiment of the present disclosure transmits and receives an analog signal.

[0083] Referring to FIG. 6, first, the center node 101 starts a transmission process for transmitting the analog signal SId and a reception process for receiving the analog signal SIu (step S11).

[0084] Next, the center node 101 waits for the arrival of beam information (NO in step S12), and when it receives beam information from the base station device 301 (YES in step S12), it selects a remote node 201 from the multiple remote nodes 201 that will transmit and receive analog signals SId and SIu based on the received beam information and the correspondence table T1 in the memory unit 3 (step S13).

[0085] Next, the center node 101 performs downstream signal processing to reflect the selection result of the remote node 201 in transmission processing, and upstream signal processing to reflect the selection result of the remote node 201 in reception processing. More specifically, the center node 101 connects the optical transceiver 30 corresponding to the selected remote node 201 to the base station device 301 via the downstream processing unit 11, the upstream processing unit 12 and the switches 21 and 22, thereby transmitting downstream optical signals to the selected remote node 201 and receiving upstream optical signals from the selected remote node 201 (step S14).

[0086] Next, the center node 101 continues transmitting downstream optical signals to the remote node 201 selected in step S13 and receiving upstream optical signals from the remote node 201 until new beam information arrives (NO in step S12).

[0087] In the communication system 401 according to the first embodiment of the present disclosure, the center node 101 and the remote nodes 201 are configured to transmit and receive optical signals via the optical fiber 191, but this is not limiting. The center node 101 and the remote nodes 201 may be configured to transmit and receive analog signals via a transmission line. In this case, the transmitter / receiver 1 in the center node 101 transmits an electrical signal including the analog signal SId to one remote node 201 via the transmission line, and receives an electrical signal including the analog signal SIu from one remote node 201 via the transmission line.

[0088] Furthermore, in the center node 101 according to the first embodiment of the present disclosure, the control unit 2 is configured to select one remote node 201 that transmits and receives the analog signals SId and SIu, but this is not limited to this. The control unit 2 may be configured to select two or more remote nodes 201 that transmit and receive the analog signals SId and SIu from among the multiple remote nodes 201 in the communication system 401. In this case, the center node 101 further includes a power splitter combined with the switches 21 and 22.

[0089] Furthermore, although the remote node 201 according to the first embodiment of the present disclosure is configured to include the frequency converters 46 and 47, this is not limiting. The remote node 201 may also be configured without the frequency converters 46 and 47. In this case, for example, the optical transceiver 30 in the center node 101 further includes a frequency converter provided before the multiplexer 31 that generates an RF signal SRd by frequency-converting the analog signal SId, and a frequency converter provided after the demultiplexer 32 that generates an analog signal SIu by frequency-converting the RF signal SRu. Note that, if the optical transceiver 30 does not include a frequency converter, the downstream processing unit 11 may receive the RF signal SRd from the base station device 301 and output the received RF signal SRd to the optical transceiver 30 via the switch 21. Note that, if the optical transceiver 30 does not include a frequency converter, the upstream processing unit 12 may receive the RF signal SRu from the optical transceiver 30 and transmit the received RF signal SRu to the base station device 301. In this case, the base station apparatus 301 generates an analog signal SIu or a baseband signal by frequency-converting the RF signal SRu received from the center node 101 .

[0090] As described above, in the center node 101 according to the first embodiment of the present disclosure, the control unit 2 acquires beam information indicating a beamforming pattern from outside the center node 101. The control unit 2 selects at least one remote node 201 from among the multiple remote nodes 201 based on the acquired beam information. The transceiver unit 1 performs downlink signal processing and uplink signal processing to reflect the selection result of the remote node 201 by the control unit 2 in the transmission processing.

[0091] In this manner, by using a configuration in which a remote node 201 is selected based on beam information and the selection result is reflected in the transmission and reception processes, it is possible to selectively transmit and receive analog signals SId and SIu to and from, for example, a selected remote node 201. This makes it possible to suppress ingress noise due to noise contained in the RF signal SRu received via each antenna 211, compared to a configuration in which analog signals SId and SIu are transmitted in parallel to all remote nodes 201. This further improves the communication quality in the communication system 401. Furthermore, since the remote node 201 can be selected using an existing mechanism in which beam information is transmitted from the base station device 301 to perform beamforming, it is possible to switch the content of the transmission and reception processes of the analog signals SId and SIu without significantly changing the configuration of the conventional base station device 301.

[0092] Furthermore, in the center node 101, the transceiver unit 1 transmits an analog signal SId only to the remote node 201 selected by the control unit 2, and receives an analog signal SIu only from the remote node 201 selected by the control unit 2. More specifically, the control unit 2 outputs a switching signal to the switching unit 20 for connecting the optical transceiver unit 30 corresponding to the remote node 201 that transmits and receives the analog signals SId and SIu to the downstream processing unit 11 and the upstream processing unit 12. The switch 21 in the switching unit 20 switches, in accordance with the switching signal received from the control unit 2, the optical transceiver unit 30 that is connected to the base station device 301 via the downstream processing unit 11, among the plurality of optical transceivers 30. The switch 22 in the switching unit 20 switches, in accordance with the switching signal received from the control unit 2, the optical transceiver unit 30 that is connected to the base station device 301 via the upstream processing unit 12, among the plurality of optical transceivers 30.

[0093] With this configuration, it is possible to selectively transmit the analog signal SId received from the base station device 301 to the remote node 201 selected by the control unit 2, and selectively transmit the analog signal SIu received from the remote node 201 selected by the control unit 2 to the base station device 301, without notifying the remote node 201 of the selection result by the control unit 2. Therefore, it is not necessary to install a configuration for reflecting the selection result by the control unit 2 in the remote node 201, and the configuration of the remote node 201 can be simplified.

[0094] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and their description will not be repeated.

[0095] Second Embodiment This embodiment relates to a communication system 402 that controls a beamforming pattern, as compared to the communication system 401 according to the first embodiment. The communication system 402 is the same as the communication system 401 according to the first embodiment except for the contents described below.

[0096] 7 is a diagram illustrating a configuration of a communication system according to a second embodiment of the present disclosure. Referring to FIG. 7, a communication system 402 includes a center node 102 instead of the center node 101 and a remote node 202 instead of the remote node 201, as compared to the communication system 401. The remote node 202 includes an antenna 212 instead of the antenna 211, as compared to the remote node 201. For example, the antenna 212 is a directional antenna.

[0097] 8 is a diagram illustrating a configuration of a center node in a communication system according to the second embodiment of the present disclosure. Compared to the center node 101, the center node 102 includes a control unit 4 instead of the control unit 2 and a storage unit 5 instead of the storage unit 3.

[0098] 9 is a diagram illustrating an example of a correspondence table stored in a storage unit in a remote node according to the second embodiment of the present disclosure. Referring to FIG. 9, the storage unit 5 stores a correspondence table T2 indicating a correspondence relationship between a Beam ID, a remote ID, and a pattern ID indicating a beamforming pattern. The correspondence table T2 is an example of correspondence information.

[0099] 9 includes remote nodes 202 associated with a plurality of beamforming patterns. More specifically, in the correspondence table T2, a remote ID of "CCC" is associated with a beam ID of "ccc" and a beam ID of "ddd." Also, in the correspondence table T2, a pattern ID of "111" is associated with the beam ID of "ccc," and a pattern ID of "222" is associated with the beam ID of "ddd."

[0100] Based on the correspondence table T2 and the beam information, the control unit 4 selects a remote node 202 that transmits and receives the analog signals SId and SIu from among the multiple remote nodes 202. More specifically, when the control unit 4 receives the beam information from the base station device 301, the control unit 4 acquires a Beam ID from the beam information. The control unit 4 refers to the correspondence table T2 in the storage unit 5 and selects a remote node 202 that has a remote ID that corresponds to the acquired Beam ID.

[0101] When the Beam ID acquired from the beam information is "ccc," the control unit 4 determines the remote node 202 with the remote ID "CCC" as the remote node 202 that transmits and receives the analog signals SId and SIu, and acquires the pattern ID "111" from the correspondence table T2. The control unit 4 then outputs a switching signal to the switches 21 and 22 to connect the optical transceiver 30 corresponding to the remote node 202 with the remote ID "CCC" to the downlink processing unit 11 and the uplink processing unit 12. The control unit 4 also outputs a digital signal Sdd to the optical transceiver 30, which includes beam control information indicating the acquired pattern ID in addition to the TDD information and synchronization information. The beam control information is an example of a control signal that controls the beamforming pattern of the RF signals SRd and SRu.

[0102] Furthermore, when the Beam ID acquired from the beam information is "ddd," the control unit 4 determines the remote node 202 with the remote ID "CCC" as the remote node 202 that will transmit and receive the analog signals SId and SIu, and acquires the pattern ID of "222" from the correspondence table T2. The control unit 4 then outputs a switching signal to the switches 21 and 22 to connect the optical transceiver 30 corresponding to the remote node 202 with the remote ID "DDD" to the downstream processing unit 11 and the upstream processing unit 12. The control unit 4 also outputs a digital signal Sdd to the optical transceiver 30 that further includes beam control information indicating the acquired pattern ID in addition to the TDD information and synchronization information.

[0103] 8 again, the transceiver 1 further transmits the beam control information to the remote node 202. More specifically, the multiplexer 31 in the optical transceiver 30 frequency-multiplexes the analog signal SId received from the downstream processing unit 11 via the switch 21 and the digital signal Sdd received from the control unit 4. The multiplexer 31 generates an electrical signal in which the analog signal SId and the digital signal Sdd are frequency-multiplexed, and outputs the electrical signal to the optical modulator 33.

[0104] The optical modulation unit 33 receives the electrical signal from the multiplexing unit 31 and generates a downstream optical signal having a wavelength λ1 by optically modulating the received electrical signal. The optical modulation unit 33 transmits the downstream optical signal to the remote node 202 having the remote ID “CCC” via the optical coupler 35 and the optical fiber 191.

[0105] 10 is a diagram illustrating a configuration of a remote node in a communication system according to the second embodiment of the present disclosure. Compared to the remote node 201, the remote node 202 includes a control unit 52 instead of the control unit 51.

[0106] In the remote node 202 whose remote ID is "CCC", the control unit 52 receives the digital signal Sdd from the separation unit 44 and obtains beam control information from the received digital signal Sdd.

[0107] The control unit 52 determines the transmission / reception range, i.e., coverage area, of the RF signals Sru and Srd by the antenna 212 in accordance with the acquired beam control information, within a range that does not increase power consumption in the remote node 202, for example.

[0108] More specifically, when the pattern ID included in the acquired beam control information is "111," the control unit 52 controls the antenna 212 to transmit and receive the RF signals Sru and Srd in coverage area R1. When the pattern ID included in the acquired beam control information is "222," the control unit 52 controls the antenna 212 to transmit and receive the RF signals Sru and Srd in coverage area R2, which is different from coverage area R1.

[0109] In the center node 102 according to the second embodiment of the present disclosure, the transceiver 1 is configured to transmit beam control information to the remote node 202, but this is not limiting. The transceiver 1 may be configured not to transmit beam control information to the remote node 202. In this case, the control unit 4 outputs a digital signal Sdd to the optical transceiver 30 that includes TDD information and synchronization information but does not include beam control information. In this case, the control unit 4 may be configured to output a digital signal Sdd to the optical transceiver 30 that includes control information for performing control other than beamforming on the remote node 202 according to the pattern ID, instead of the beam control information.

[0110] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and their description will not be repeated.

[0111] Third Embodiment This embodiment relates to a communication system 403 that performs timing control of analog signals SId and SIu, as compared with the communication system 401 according to the first embodiment. Except for the contents described below, the communication system 403 is the same as the communication system 401 according to the first embodiment.

[0112] 11 is a diagram illustrating a configuration of a communication system according to the third embodiment of the present disclosure. Referring to FIG. 11, a communication system 403 includes a center node 103 instead of the center node 101 in the communication system 401.

[0113] 12 is a diagram illustrating a configuration of a center node in a communication system according to a third embodiment of the present disclosure. Referring to FIG. 12, compared to the center node 101, the center node 103 includes a transceiver unit 6 instead of the transceiver unit 1 and a control unit 7 instead of the control unit 2. The control unit 7 is an example of an acquisition unit, an example of a selection unit, and an example of a delay processing unit. Compared to the transceiver unit 1, the transceiver unit 6 includes a downlink processing unit 13 instead of the downlink processing unit 11 and an uplink processing unit 14 instead of the uplink processing unit 12.

[0114] The control unit 7 selects at least one remote node 201 from the plurality of remote nodes 201 based on the correspondence table T1 and the beam information. More specifically, when the control unit 7 receives the beam information from the base station device 301, it acquires a Beam ID from the beam information. The control unit 7 refers to the correspondence table T1 in the storage unit 3, and determines the remote node 201 having the remote ID corresponding to the acquired Beam ID as the remote node 201 that transmits and receives the analog signals SId and SIu.

[0115] (Delay Control) The control unit 7 performs delay control, as timing control for the analog signal SId, to give the analog signal SId transmitted by the transmitting / receiving unit 6 a delay amount Dt corresponding to the transmission distance of the analog signal SId between the remote node 201, which is the transmission destination of the analog signal SId, and the center node 103. Furthermore, the control unit 7 performs delay control, as timing control for the analog signal SIu, to give the analog signal SIu received by the transmitting / receiving unit 6 a delay amount Dt corresponding to the transmission distance of the analog signal SIu between the remote node 201, which is the transmission source of the analog signal SIu, and the center node 103.

[0116] For example, the storage unit 3 stores a delay table indicating the correspondence between the remote nodes 201 and the delay amount Dt. The delay amount Dt in the delay table is set in advance based on, for example, the length of the optical fiber 191 between the center node 103 and the corresponding remote node 201. More specifically, the delay amount Dt in the delay table is set so that the sum of the delay amount Dt applied to the analog signals SId and SIu by the control unit 7 and the transmission delay amount Df of the analog signals SId and SIu on the optical fiber 191 is equal to the transmission delay amount Dfmax of the analog signals SId and SIu on the longest optical fiber 191 among the multiple optical fibers 191 in the communication system 403.

[0117] When the control unit 7 determines the remote node 201 that transmits and receives the analog signals SId and SIu, it references the delay table in the storage unit 3 and obtains the delay amount Dt corresponding to the determined remote node 201. Then, the control unit 7 outputs switching signals to the switches 21 and 22 to connect the optical transceiver 30 corresponding to the determined remote node 201 to the downstream processing unit 11 and the upstream processing unit 14. The control unit 7 also outputs a delay instruction indicating the obtained delay amount Dt to the downstream processing unit 13 and the upstream processing unit 14.

[0118] The downstream processing unit 13 delays the analog signal SId received from the base station device 301 by a delay amount Dt in accordance with the delay instruction received from the control unit 7. More specifically, the downstream processing unit 13 includes a circuit such as a delay line for delaying the analog signal SId. The downstream processing unit 13 performs delay processing to delay the analog signal SId by the delay amount Dt during the downstream period Pd, and outputs the delayed analog signal SId to the optical transceiver unit 30 via the switch 21. This makes it possible to suppress variations in the transmission timing of the RF signal SRd at each remote node 201, which are based on the length of the optical fiber 191.

[0119] The upstream processing unit 14 delays the analog signal SIu received from the optical transceiver 30 via the switch 22 by a delay amount Dt in accordance with a delay instruction received from the control unit 7. More specifically, the upstream processing unit 14 includes a circuit such as a delay line for delaying the analog signal SIu. During the upstream period Pu, the upstream processing unit 14 performs delay processing to delay the analog signal SIu by a delay amount Dt, and transmits the delayed analog signal SIu to the base station device 301. This makes it possible to suppress variations in the reception timing of the analog signal SIu at the base station device 301, which are based on the length of the optical fiber 191.

[0120] (Transmission and Reception Timing Control) The control unit 7 notifies the base station device 301 of representative values ​​of a plurality of transmission delay amounts Df corresponding to the plurality of remote nodes 201. For example, the control unit 7 notifies the base station device 301 of a transmission delay amount Dfmax as the representative value of the transmission delay amounts Df.

[0121] The base station device 301 controls the transmission timing of the analog signal SId and the reception timing of the analog signal SIu based on the transmission delay amount Dfmax notified by the control unit 7 .

[0122] More specifically, as a transmission timing control, the base station device 301 transmits the analog signal SId to the center node 103 at a timing Tt that is earlier by a transmission delay amount Dfmax than the transmission timing of the RF signal SRd when the antenna 211 is directly connected to the base station device 301, for example.

[0123] The transmitter / receiver 6 in the center node 103 transmits to the remote node 201 an analog signal SId whose transmission timing has been controlled based on the transmission delay amount Df in the base station device 301. More specifically, the downlink processing unit 13 in the transmitter / receiver 6 receives the analog signal SId whose transmission timing has been controlled from the base station device 301, and outputs the received analog signal SId to the optical transmitter / receiver 30 via the switch 21. This makes it possible to make the transmission timing of the RF signal SRd in the remote node 201 closer to the transmission timing of the RF signal SRd when the antenna 211 is directly connected to the base station device 301.

[0124] Furthermore, as a reception timing control, the base station device 301 performs reception processing of the analog signal SIu at timing Tr that is later by a transmission delay amount Dfmax than the reception timing of the RF signal SRu when the antenna 211 is directly connected to the base station device 301. More specifically, the base station device 301 receives, as the analog signal SIu, a signal arriving from the center node 103 at this timing Tr. This allows the base station device 301 to receive the analog signal SIu more accurately.

[0125] In the center node 103 according to the third embodiment of the present disclosure, the delay amount Dt in the delay table is configured to be set in advance based on the length of the optical fiber 191 between the center node 103 and the corresponding remote node 201, but this is not limiting. The delay amount Dt may be configured to be set in advance based on, for example, a round trip time (RTT) between the center node 103 and the remote node 201.

[0126] More specifically, before the communication system 403 is put into operation, the control unit 7 generates a digital signal Sdd including a predetermined test signal and outputs the generated digital signal Sdd to the optical transceiver 30. The remote node 201 acquires the test signal from the digital signal Sdd, generates a digital signal Sdu including the acquired test signal, and transmits an upstream signal including the digital signal Sdu to the center node 103 via the optical fiber 191. The control unit 7 acquires the test signal from the digital signal Sdu received from the demultiplexer 32 and calculates the RTT based on the difference between the output timing of the test signal and the acquisition timing of the test signal. The control unit 7 calculates the RTT for each remote node 201 and calculates a transmission delay Df for each remote node 201 based on the calculated RTT. The control unit 7 then sets a delay Dt for each remote node 201 based on the calculated transmission delay Df.

[0127] Furthermore, in the communication system 403 according to the third embodiment of the present disclosure, the control unit 7 in the center node 103 performs delay control and the base station device 301 performs transmission and reception timing control, but this is not limited to this. The communication system 403 may be configured such that the control unit 7 performs delay control while the base station device 301 does not perform transmission and reception timing control. Furthermore, the communication system 403 may be configured such that the base station device 301 performs transmission and reception timing control while the control unit 7 does not perform delay control.

[0128] However, a configuration that performs both delay control and transmission / reception timing control makes it possible to roughly adjust the transmission timing of the RF signal Srd based on a representative value of the transmission delay amount Df, and to finely adjust the transmission timing of the RF signal Srd based on the transmission delay amount Df in each optical fiber 191. Therefore, it is possible to more accurately match the transmission timing of the RF signal Srd in each remote node 201 with the transmission timing of the RF signal Srd when the antenna 211 is directly connected to the base station device 301.

[0129] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and their description will not be repeated.

[0130] Fourth Embodiment This embodiment relates to a communication system 404 that, unlike the communication system 401 according to the first embodiment, adjusts the levels of analog signals SId and SIu in accordance with the selection result of the remote node 201. The details other than those described below are the same as those of the communication system 401 according to the first embodiment.

[0131] 13 is a diagram illustrating a configuration of a communication system according to a fourth embodiment of the present disclosure. Referring to FIG. 13, a communication system 404 includes a center node 104 instead of the center node 101 in the communication system 401.

[0132] 14 is a diagram illustrating a configuration of a center node in a communication system according to a fourth embodiment of the present disclosure. Referring to FIG. 14 , the center node 104 includes a transceiver 8 instead of the transceiver 1, as compared to the center node 101. The transceiver 8 includes an optical transceiver 60 instead of the optical transceiver 30, does not include the switching unit 20, and further includes a distributor 71 and a multiplexer 72, as compared to the transceiver 1. The optical transceiver 60 further includes variable ATTs 61 and 62 and a setting unit 63, as compared to the optical transceiver 30. The transceiver 8 performs a transmission process of transmitting an analog signal SId to a remote node 201 and a reception process of receiving an analog signal SIu from the remote node 201.

[0133] (Downstream Communication) The downstream processing unit 11 receives an analog signal SId including communication data from the base station device 301. The downstream processing unit 11 outputs the received analog signal SId to the distributor 71 during a downstream period Pd.

[0134] The distributor 71 distributes the analog signal SId received from the downstream processing unit 11 to each optical transceiver 60 .

[0135] The variable ATT 61 in the optical transceiver 60 attenuates the analog signal SId received from the downstream processor 11. The amount of attenuation of the analog signal SId in the variable ATT 61 is set by a setting unit 63.

[0136] The multiplexing unit 31 frequency-multiplexes the analog signal SId that has passed through the variable ATT 61 and the digital signal Sdd that has been received from the control unit 2. The multiplexing unit 31 generates an electrical signal in which the analog signal SId and the digital signal Sdd are frequency-multiplexed, and outputs the electrical signal to the optical modulation unit 33.

[0137] The optical modulation unit 33 receives the electrical signal from the multiplexing unit 31 and generates a downstream optical signal with wavelength λ1 by optically modulating the received electrical signal. The optical modulation unit 33 transmits the downstream optical signal to the corresponding remote node 201 via the optical coupler 35 and the optical fiber 191.

[0138] (Upstream Communication) The optical demodulator 34 receives an upstream optical signal from the corresponding remote node 201 via the optical fiber 191 and the optical coupler 35. The optical demodulator 34 generates an electrical signal at a level corresponding to the intensity of the received upstream optical signal and outputs the electrical signal to the separator 32.

[0139] The separation unit 32 separates the analog signal SIu and the digital signal Sdu contained in the electrical signal received from the optical demodulation unit 34, outputs the separated analog signal SIu to the variable ATT 62 and the setting unit 63, and outputs the separated digital signal Sdu to the control unit 2.

[0140] The variable ATT 62 attenuates the analog signal SIu received from the separator 32. The amount of attenuation of the analog signal SIu in the variable ATT 62 is set by a setting unit 63.

[0141] The multiplexer 72 multiplexes the analog signals SIu that have passed through the variable ATTs 62 in the optical transmitters and receivers 60 , and outputs the multiplexed analog signal SIu to the upstream processing unit 12 .

[0142] The uplink processing unit 12 transmits the analog signal SIu received from the multiplexer 72 to the base station apparatus 301 .

[0143] (Adjustment of Attenuation Amount) When the control unit 2 receives beam information from the base station device 301, the control unit 2 selects at least one remote node 201 from the multiple remote nodes 201 based on the received beam information. The control unit 2 outputs selection information indicating a remote ID, which is an identifier of the selected remote node 201, to each optical transceiver 60 in the transceiver 8.

[0144] The transmitter / receiver 8 performs downstream signal processing and upstream signal processing to reflect the selection result of the remote node 201 by the control unit 2 in the transmission processing. For example, as the downstream signal processing, the transmitter / receiver 8 adjusts the level of the analog signal SId to be transmitted to the remote node 201 based on the selection result of the remote node 201 by the control unit 2. Furthermore, as the upstream signal processing, the transmitter / receiver 8 adjusts the level of the analog signal SIu received from the remote node 201 based on the selection result of the remote node 201 by the control unit 2.

[0145] More specifically, the setting unit 63 in the optical transceiver 60 receives selection information from the control unit 2 and determines, based on the received selection information, whether the remote node 201 corresponding to the optical transceiver 60 has been selected by the control unit 2.

[0146] When the control unit 2 selects the remote node 201 corresponding to the optical transceiver 60, the setting unit 63 in the optical transceiver 60 sets the attenuation amount of the variable ATTs 61 and 62 in the optical transceiver 60 to a predetermined setting value Von. The setting value Von is, for example, zero. The variable ATT 61 with the attenuation amount set to zero passes the analog signal SId received from the downstream processing unit 11 without attenuating it.

[0147] On the other hand, if the remote node 201 corresponding to the optical transceiver 60 is not selected by the control unit 2, the setting unit 63 in the optical transceiver 60 sets the attenuation amount of the variable ATTs 61, 62 in the optical transceiver 60 to a predetermined setting value Voff. The setting value Voff is a value greater than zero. The variable ATT 61, whose attenuation amount is set to the setting value Voff, attenuates the analog signal SId received from the downstream processing unit 11 and passes it.

[0148] For example, the transceiver 8 can adjust the levels of the multiple analog signals SId to different values, respectively, to be transmitted to the multiple remote nodes 201 selected by the control unit 2. More specifically, when the control unit 2 selects a remote node 201 corresponding to the optical transceiver 60, the setting unit 63 in the optical transceiver 60 sets the attenuation amount of the variable ATT 61 in the optical transceiver 60 to a setting value Von according to the size of the coverage area of ​​the remote node 201.

[0149] Specifically, when the size of the coverage area of ​​the corresponding remote node 201 is equal to or larger than a predetermined value Vs, the setting unit 63 in the optical transceiver 60 sets the attenuation amount of the variable ATT 61 in the optical transceiver 60 to a setting value Von1. When the size of the coverage area of ​​the corresponding remote node 201 is smaller than the predetermined value Vs, the setting unit 63 in the optical transceiver 60 sets the attenuation amount of the variable ATT 61 in the optical transceiver 60 to a setting value Von2 that is larger than the setting value Von1.

[0150] For example, the transceiver 8 attenuates an analog signal SIu having a level equal to or greater than a predetermined value among a plurality of analog signals SIu received from a plurality of remote nodes 201. More specifically, the setting unit 63 in the optical transceiver 60 corresponding to the remote node 201 selected by the control unit 2 compares the level of the analog signal SIu received from the demultiplexer 32 with a predetermined threshold Vth. When the level of the analog signal SIu received from the demultiplexer 32 is equal to or greater than the threshold Vth, the setting unit 63 adjusts the attenuation amount of the variable ATT 62 so that the level of the analog signal SIu after attenuation by the variable ATT 62 becomes equal to the threshold Vth.

[0151] In the center node 104 according to the fourth embodiment of the present disclosure, the optical transceiver 60 in the transceiver 8 has been described as having the variable ATTs 61 and 62, but this is not limiting. The optical transceiver 60 may have, instead of the variable ATTs 61 and 62, a variable amplifier that amplifies the analog signal SId received from the downstream processing unit 11 and a variable amplifier that amplifies the analog signal SIu received from the demultiplexer 32. In this case, the setting unit 63 sets the amplification amount of the variable amplifier.

[0152] Furthermore, in the center node 104 according to the fourth embodiment of the present disclosure, the setting unit 63 in the optical transceiver 60 is configured to set the attenuation amount of the variable ATT 61 in the optical transceiver 60 to the setting value Von according to the size of the coverage area of ​​the remote node 201, but this is not limited to this. When the corresponding remote node 201 is selected by the control unit 2, the setting unit 63 may be configured to set the attenuation amount of the variable ATT 61 in the optical transceiver 60 to a predetermined value regardless of the size of the coverage area of ​​the remote node 201.

[0153] Furthermore, in the center node 104 according to the fourth embodiment of the present disclosure, the setting unit 63 in the optical transceiver 60 is configured to adjust the attenuation amount of the variable ATT 62 when the level of the analog signal SIu received from the separator 32 is equal to or higher than the threshold Vth so that the level of the analog signal SIu after attenuation by the variable ATT 62 becomes equal to the threshold Vth. However, this is not limiting. The setting unit 63 may be configured not to adjust the attenuation amount of the variable ATT 62 according to the level of the analog signal SIu received from the separator 32.

[0154] Furthermore, instead of adjusting the attenuation amount of the variable ATT 62 so that the level of the analog signal SIu received from the demultiplexer 32 becomes equal to the threshold value Vth, the setting unit 63 may be configured to adjust the attenuation amount of at least one of the variable ATTs 61, 62 in accordance with the quality of the analog signal SIu received from the demultiplexer 32. This makes it possible to adjust the levels of the analog signals SId, SIu corresponding to the remote node 201 in accordance with the occurrence of interference in the remote node 201, thereby improving communication quality.

[0155] The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0156] Each process (each function) in the above-described embodiments is realized by a processing circuit (circuitry) including one or more processors. The processing circuit may be configured as an integrated circuit or the like that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the processes. The one or more processors may execute each of the processes according to the program read from the one or more memories, or may execute each of the processes according to a logic circuit designed in advance to execute each of the processes. The processor may be any of various processors suitable for computer control, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit). Note that the physically separated processors may cooperate with each other to execute the processes. For example, the processors installed in the physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet to execute the processes. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor memory, and then installed into the memory from the recording medium.

[0157] The above description includes the following additional features: [Supplementary Note 1] A master station device capable of transmitting and receiving analog signals to and from a plurality of slave station devices, each of which transmits and receives RF signals via antennas arranged at intervals, comprising a processing circuit, the processing circuit: acquires beam information indicating a beamforming pattern from outside the master station device, selects at least one of the plurality of slave station devices based on the acquired beam information, performs transmission processing to transmit a downstream analog signal to the slave station device, performs reception processing to receive an upstream analog signal from the slave station device, performs downstream signal processing to reflect the selection result of the slave station device in the transmission processing, and performs upstream signal processing to reflect the selection result of the slave station device in the reception processing.

[0158] 1, 6, 8 Transmitter / receiver 2, 4, 7 Control unit 3, 5 Memory unit 11, 13 Downstream processing unit 12, 14 Upstream processing unit 20 Switching unit 21, 22 Switch 30, 60 Optical transmitter / receiver 31 Multiplexer 32 Separator 33 Optical modulator 34 Optical demodulator 35 Optical coupler 41 Optical coupler 42 Optical demodulator 43 Optical modulator 44 Separator 45 Multiplexer 46, 47 Frequency converter 48, 49 Amplifier 50 RF transmitter / receiver 51, 52 Control unit 61, 62 Variable ATT 63 Setting unit 71 Distributor 72 Multiplexer 81 Building 82 Room 101, 102, 103, 104 Center node 111 Communication terminal 181 Transmission line 191 Optical fiber 201, 202 Remote nodes 211, 212 Antennas 301 Base station device 401, 402, 403, 404 Communication system T1, T2 Correspondence table R1, R2 Coverage area

Claims

1. A master station device capable of transmitting and receiving analog signals to and from a plurality of slave station devices, each of which transmits and receives RF signals via antennas arranged at intervals, comprising: an acquisition unit that acquires beam information indicating a beamforming pattern from outside the master station device; a selection unit that selects at least one of the plurality of slave station devices based on the beam information acquired by the acquisition unit; a transmission unit that performs transmission processing to transmit downstream analog signals to the slave station devices; and a reception unit that performs reception processing to receive upstream analog signals from the slave station devices, wherein the transmission unit performs downstream signal processing to reflect the selection result of the slave station device by the selection unit in the transmission processing, and the reception unit performs upstream signal processing to reflect the selection result of the slave station device by the selection unit in the reception processing.

2. The master station device according to claim 1, wherein the transmitting unit, as the downstream signal processing, adjusts the level of the downstream analog signal to be transmitted to the slave station device based on the selection result of the slave station device by the selecting unit, and the receiving unit, as the upstream signal processing, adjusts the level of the upstream analog signal received from the slave station device based on the selection result of the slave station device by the selecting unit.

3. The master station device according to claim 2, wherein the transmitting section is capable of adjusting the levels of the plurality of downstream analog signals to be transmitted to the plurality of slave station devices selected by the selecting section to mutually different values.

4. A master station device according to claim 2 or 3, wherein the receiving section attenuates the upstream analog signals having a level equal to or higher than a predetermined value among the upstream analog signals received from the slave station devices.

5. The master station device according to claim 1, wherein the transmitting unit selectively transmits the downstream analog signal to the slave station device selected by the selecting unit from among the plurality of slave station devices as the downstream signal processing, and the receiving unit selectively receives the upstream analog signal from the slave station device selected by the selecting unit from among the plurality of slave station devices as the upstream signal processing.

6. The master station device according to any one of claims 1 to 5, further comprising: a memory unit that stores correspondence information indicating the correspondence between the beamforming patterns and the slave station devices; the selection unit selects at least one of the plurality of slave station devices based on the correspondence information and the beam information; and the correspondence information includes the slave station devices with which the plurality of beamforming patterns are associated.

7. The master station device according to claim 6, wherein the transmitter further transmits a control signal for controlling a beamforming pattern of the RF signal to the slave station devices associated with the plurality of beamforming patterns.

8. The master station device according to any one of claims 1 to 5, further comprising: a storage unit that stores correspondence information indicating the correspondence between the beamforming patterns and the slave station devices; the selection unit selects at least one of the plurality of slave station devices based on the correspondence information and the beam information; and the correspondence information provides a one-to-one correspondence between the beamforming patterns and the slave station devices.

9. A master station device according to any one of claims 1 to 8, further comprising a delay processing unit that imparts a delay amount to the downstream analog signal and the upstream analog signal, wherein the delay processing unit imparts a delay amount to the downstream analog signal transmitted by the transmitting unit according to a transmission distance of the downstream analog signal between the master station device and the slave station device that is the destination of the downstream analog signal, and the delay processing unit imparts a delay amount to the upstream analog signal received by the receiving unit according to a transmission distance of the upstream analog signal between the master station device and the slave station device that is the source of the upstream analog signal.

10. The master station device according to claim 9, wherein the delay processing unit notifies a base station device outside the master station device of a representative value of the transmission delay amount of the plurality of downstream analog signals corresponding to each of the plurality of slave station devices, and the transmitting unit transmits the downstream analog signals, the transmission timing of which has been controlled in the base station device based on the representative value, to the slave station device.

11. An analog signal transmission method in a master station device capable of transmitting and receiving analog signals to and from a plurality of slave station devices that transmit and receive RF signals via distributed antennas, comprising: a step of acquiring beam information indicating a beamforming pattern; a step of selecting at least one of the plurality of slave station devices based on the acquired beam information; a step of performing transmission processing to transmit downstream analog signals to the slave station device; and a step of receiving processing to receive upstream analog signals from the slave station device, wherein in the step of performing transmission processing, downstream signal processing is performed to reflect the selection result of the slave station device in the transmission processing, and in the step of receiving processing, upstream signal processing is performed to reflect the selection result of the slave station device in the reception processing.

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