ANALOG RoF SYSTEM, MASTER STATION DEVICE, SLAVE STATION DEVICE, DATA STRUCTURE, AND OPTICAL COMMUNICATION METHOD

Abstract

To provide an analog RoF system that transmits control information at a desired transmission frequency.SOLUTION: In an analog RoF system, a master station device generates a frame storing destination information, first control information corresponding to a first slave station device that is a slave station device indicated by the destination information, and second control information corresponding to a second slave station device that is a slave station device other than the slave station device indicated by the destination information, and transmits an optical signal including a digital signal including the generated frame and a main signal to a plurality of slave station devices. The first slave station device obtains the first control information from the digital signal included in the optical signal received from the master station device, and the second slave station device obtains the second control information from the digital signal included in the optical signal received from the master station device.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an analog Radio over Fiber (RoF) system, a master station device, a slave station device, a data structure, and an optical communication method. [Background technology]

[0002] 2. Description of the Related Art In a conventional optical communication system in which an analog signal including communication data is transmitted between devices via an optical fiber, a technique has been developed in which control information for controlling the operation of one of the devices is multiplexed onto the analog signal and then transmitted.

[0003] For example, Patent Document 1 (JP 2021-64861 A) discloses an optical transmission device as follows: That is, the optical transmission device includes a multiplexing means for frequency-multiplexing a first electrical signal carrying information and a plurality of tone signals to generate a multiplexed signal, and a modulation means for performing carrier suppression amplitude modulation of continuous light with the multiplexed signal.

[0004] Also, Patent Document 2 (JP 2020-43488 A) discloses an amplifier unit as follows. That is, the amplifier unit includes a digital signal generating unit that generates a digital signal of a modulation frequency fm and outputs the digital signal, an analog signal generating unit that generates an analog signal of a frequency fc having information in the amplitude and outputs the analog signal, a superposition unit that generates a superposed signal by superposing the digital signal and the analog signal and outputs the superposed signal, an amplifier unit that generates an amplified signal by amplifying the superposed signal and outputs the amplified signal, a detection unit that detects information regarding the voltage of the amplified signal, and an amplification degree determination unit that determines the amplification degree of the amplifier unit based on the information detected by the detection unit. The relationship between the input voltage of the input signal input to the amplifier unit and the output voltage of the output signal output from the amplifier unit has a relationship having a region in which the amplification degree changes from a region in which the output voltage increases as the input voltage increases to a region in which the amplification degree changes so that the output voltage becomes a predetermined constant value. Also, the input voltage of the digital signal input to the amplifier unit is a voltage at which the output voltage of the digital signal amplified at the amplification degree becomes the constant value. Moreover, the input voltage of the analog signal input to the amplifier is a voltage at which the output voltage of the analog signal amplified with the amplification degree becomes a value proportional to the amplification degree. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-64861 [Patent Document 2] JP 2020-43488 A Summary of the Invention [Problem to be solved by the invention]

[0006] Beyond the techniques described in Patent Documents 1 and 2, a technique is desired that allows control information to be transmitted at a desired transmission frequency in an analog RoF system.

[0007] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide an analog RoF system, a master station device, a slave station device, a data structure, and an optical communication method capable of transmitting control information at a desired transmission frequency. [Means for solving the problem]

[0008] The analog RoF system of the present disclosure is an analog RoF system comprising a parent station device and a plurality of child station devices, wherein the parent station device generates a frame addressed to the child station device, the frame including control information, the frame including destination information indicating the destination of the frame, first control information corresponding to a first child station device which is the child station device indicated by the destination information, and second control information corresponding to a second child station device which is the child station device other than the child station device indicated by the destination information, and transmits an optical signal including a digital signal including the generated frame and an analog main signal to the plurality of child station devices, wherein the first child station device acquires the first control information from the digital signal included in the optical signal received from the parent station device, and the second child station device acquires the second control information from the digital signal included in the optical signal received from the parent station device. Effect of the Invention

[0009] According to the present disclosure, in an analog RoF system, control information can be transmitted at a desired transmission frequency. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an analog RoF system according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram illustrating a frame transmitted from a master station device to a slave station device in an analog RoF system according to a comparative example of the first embodiment of the present disclosure. [Diagram 3] FIG. 3 is a diagram illustrating a frame transmitted from a master station device to a slave station device in an analog RoF system according to the first embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram illustrating a configuration of a master station device according to the first embodiment of the present disclosure. [Diagram 5] FIG. 5 is a diagram illustrating an example of a data structure of a frame generated by a generating unit of a master station device according to the first embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram illustrating a configuration of a slave station device according to the first embodiment of the present disclosure. [Figure 7] FIG. 7 is a diagram illustrating an example of a communication sequence in the analog RoF system according to the first embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram illustrating an example of a data structure of a frame generated by a generating unit of a master station device according to a modified example of the first embodiment of the present disclosure. [Figure 9] FIG. 9 is a diagram illustrating a configuration of an analog RoF system according to the second embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating a configuration of a master station device according to the second embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram illustrating a configuration of a slave station device according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] First, the contents of the embodiments of the present disclosure will be listed and described.

[0012] (1) An analog RoF system according to an embodiment of the present disclosure includes a parent station device and a plurality of child station devices, wherein the parent station device generates a frame addressed to the child station device and including control information, the frame including destination information indicating a destination of the frame, first control information corresponding to a first child station device that is the child station device indicated by the destination information, and second control information corresponding to a second child station device that is the child station device other than the child station device indicated by the destination information, and transmits an optical signal including a digital signal including the generated frame and an analog main signal to the plurality of child station devices, wherein the first child station device acquires the first control information from the digital signal included in the optical signal received from the parent station device, and the second child station device acquires the second control information from the digital signal included in the optical signal received from the parent station device.

[0013] In this manner, the parent station device transmits an optical signal including a frame in which destination information, first control information, and second control information are stored to multiple child station devices, the first child station device indicated by the destination information acquires the first control information, and the second child station device other than the child station device indicated by the destination information acquires the second control information. This configuration allows the parent station device to transmit the first control information to the first child station device while transmitting the second control information to the multiple child station devices using multiple frames with different destination information, making it possible to more flexibly set the transmission frequency of the control information to each child station device. Therefore, in an analog RoF system, control information can be transmitted at a desired transmission frequency.

[0014] (2) In the above (1), the parent station device may generate the frame in which the second control information corresponding to the first child station device and the second child station device is stored, and the first child station device may further acquire the second control information from the digital signal included in the optical signal received from the parent station device.

[0015] With this configuration, it is possible to transmit the second control information to each of the slave station devices including the first slave station device using one frame.

[0016] (3) In the above (1) or (2), the master station device may generate the frame in which the second control information is stored, the second control information corresponding one-to-one to the slave station device.

[0017] With this configuration, it is possible to transmit second control information that is individual to each slave station device by using a frame addressed to each slave station device.

[0018] (4) In any of (1) to (3) above, the frame may include a first field in which the first control information is stored, a second field in which the second control information is stored, and a third field in which third control information common to the multiple child station devices is stored.

[0019] With this configuration, it is possible to further transmit common third control information to all the slave station equipment units using frames addressed to each slave station equipment unit.

[0020] (5) A parent station device according to an embodiment of the present disclosure is a parent station device that transmits control information to a plurality of child station devices in an analog RoF system, and includes: a generation unit that generates a frame addressed to the child station devices, the frame including control information, the frame including destination information indicating a destination of the frame, a first control information corresponding to the child station device indicated by the destination information, and a second control information corresponding to the child station device other than the child station device indicated by the destination information; and a transmission unit that transmits an optical signal including a digital signal including the frame generated by the generation unit and an analog main signal to the plurality of child station devices.

[0021] In this manner, by generating frames in which destination information, first control information, and second control information are stored, and transmitting optical signals including the generated frames to multiple child station devices, it is possible to transmit the first control information to a child station device indicated by the destination information while transmitting the second control information to the multiple child station devices using multiple frames with different destination information, so that the transmission frequency of the control information to each child station device can be set more flexibly. Therefore, in an analog RoF system, control information can be transmitted at a desired transmission frequency.

[0022] (6) A slave station device according to an embodiment of the present disclosure is a slave station device in an analog RoF system, and includes a receiving unit that receives an optical signal including an analog main signal and a digital signal including the frame in which destination information, first control information, and second control information are stored, and an acquiring unit that acquires the second control information from the digital signal included in the optical signal received by the receiving unit, wherein the acquiring unit further acquires the first control information from the digital signal when the device indicated by the destination information is the slave station device.

[0023] In this way, a slave station device receives an optical signal including a frame storing destination information, first control information, and second control information, acquires the second control information from a digital signal included in the received optical signal, and if the device indicated by the destination information is the slave station device, further acquires the first control information from the digital signal. This makes it possible to transmit the first control information to the slave station device using a frame addressed to the slave station device, while transmitting the second control information to multiple slave station devices using multiple frames with different destination information, thereby making it possible to more flexibly set the transmission frequency of the control information to each slave station device. Therefore, in an analog RoF system, control information can be transmitted at a desired transmission frequency.

[0024] (7) A data structure according to an embodiment of the present disclosure is a data structure of a frame transmitted from a parent station device to multiple child station devices in an analog RoF system including a parent station device and the multiple child station devices, and includes a destination address field in which destination information indicating the child station device to which the frame is addressed is stored, a first field in which first control information corresponding to the child station device indicated by the destination information is stored, and a second field in which second control information corresponding to the child station device other than the child station device indicated by the destination information is stored.

[0025] In this way, the data structure of the frame includes a destination address field, a first field in which first control information corresponding to the child station device indicated by the destination information is stored, and a plurality of second fields in which second control information corresponding to child station devices other than the child station device indicated by the destination information is stored, so that the first control information can be transmitted to the child station device using the frame addressed to the child station device, while the second control information can be transmitted to a plurality of child station devices using a plurality of frames with different destination information, making it possible to more flexibly set the transmission frequency of the control information to each child station device. Therefore, in an analog RoF system, control information can be transmitted at a desired transmission frequency.

[0026] (8) An optical communication method according to an embodiment of the present disclosure is an optical communication method in an analog RoF system including a parent station device and a plurality of child station devices, the method including the steps of: generating a frame addressed to the child station device, the frame including control information, the frame including destination information indicating a destination of the frame, first control information corresponding to a first child station device that is the child station device indicated by the destination information, and second control information corresponding to a second child station device that is the child station device other than the child station device indicated by the destination information; transmitting an optical signal including a digital signal including the generated frame and an analog main signal to the plurality of child station devices; acquiring the first control information from the digital signal included in the optical signal received from the parent station device, and acquiring the second control information from the digital signal included in the optical signal received from the parent station device, by the second child station device.

[0027] In this way, the parent station device transmits an optical signal including a frame storing destination information, first control information, and second control information to multiple child station devices, the first child station device indicated by the destination information acquires the first control information, and the second child station device other than the child station device indicated by the destination information acquires the second control information. This method allows the parent station device to transmit the first control information to the first child station device while transmitting the second control information to the multiple child station devices using multiple frames with different destination information, making it possible to more flexibly set the transmission frequency of the control information to each child station device. Therefore, in an analog RoF system, control information can be transmitted at a desired transmission frequency.

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated. In addition, at least some of the embodiments described below may be arbitrarily combined.

[0029] <First embodiment> [Configuration and basic operation] FIG. 1 is a diagram showing a configuration of an analog RoF system according to a first embodiment of the present disclosure. Referring to FIG. 1, an analog RoF system 301 includes a master station device 101 and slave station devices 201A, 201B, and 201C. The slave station devices 201A, 201B, and 201C are connected to antennas 161A, 161B, and 161C, respectively. Hereinafter, each of the slave station devices 201A, 201B, and 201C will also be referred to as a slave station device 201, and each of the antennas 161A, 161B, and 161C will also be referred to as an antenna 161. The slave station device 201 is an example of a first slave station device and an example of a second slave station device. The analog RoF system 301 may include two or four or more slave station devices 201. Each slave station device 201 is assigned a slave station ID.

[0030] The master station device 101 and the slave station devices 201 are connected to the master station device 101 via an optical fiber 191 and an optical coupler (not shown). The master station device 101 and the slave station devices 201 transmit and receive optical signals including communication data via the optical fiber 191.

[0031] When the analog RoF system 301 is applied to mobile wireless communication, for example, a TDD (Time Division Duplex) method is adopted in the mobile wireless communication. In this case, in the analog RoF system 301, an upstream transmission period for transmitting communication data from the slave station device 201 to the master station device 101 and a downstream transmission period for transmitting communication data from the master station device 101 to the slave station device 201 are switched and alternately repeated.

[0032] More specifically, the master station device 101 receives an analog signal modulated by Orthogonal Frequency Division Multiplexing (OFDM) including communication data from a base station device (not shown). The master station device 101 generates an intermediate frequency (IF) signal by frequency-converting the received analog signal. The IF signal is an example of a main signal. During a downstream transmission period, the master station device 101 transmits an optical signal including the generated IF signal to each slave station device 201 via the optical fiber 191.

[0033] Each slave station device 201 receives an optical signal from the master station device 101 via an optical fiber 191. Each slave station device 201 acquires an IF signal from the received optical signal, and transmits a millimeter wave band RF (Radio Frequency) signal based on the acquired IF signal to a mobile communication terminal (not shown) via a corresponding antenna 161. Note that the slave station device 201 may be configured to transmit a signal based on the acquired IF signal to another device via a wire.

[0034] Furthermore, each slave station device 201 receives an OFDM-modulated millimeter waveband RF signal including communication data from a mobile communication terminal (not shown) via the corresponding antenna 161. Each slave station device 201 generates an IF signal by frequency-converting the received RF signal. During an upstream transmission period, each slave station device 201 transmits an optical signal including the generated IF signal to the master station device 101 via the optical fiber 191. Note that the slave station device 201 may be configured to receive a signal including communication data via a wired connection and transmit an optical signal including the received signal to the master station device 101 via the optical fiber 191.

[0035] The master station device 101 receives optical signals from each slave station device 201 via an optical fiber 191. The master station device 101 acquires an IF signal from the received optical signals, and transmits a signal based on the acquired IF signal to the base station device.

[0036] Furthermore, during the downstream transmission period, the master station device 101 transmits control information Cnt for controlling the operation of the slave station device 201 to the slave station device 201. In detail, the master station device 101 generates a frame F1 addressed to the slave station device 201, including a destination ID indicating the destination slave station device 201 and the control information Cnt, and transmits the generated frame F1 to each slave station device 201. More specifically, the master station device 101 generates an optical signal based on an electrical signal in which an NRZ (Non Return to Zero) digital signal and an IF signal are frequency-multiplexed, including the frame F1, and transmits the generated optical signal to each slave station device 201 via the optical fiber 191.

[0037] For example, the master station device 101 transmits beamforming information, TDD (Time Division Duplex) information, health check information, synchronization information, and the like as the control information Cnt to the slave station device 201. The beamforming information is information for controlling the transmission direction of an RF signal in the slave station device 201. The TDD information is information for controlling the transmission timing of an RF signal according to TDD. The health check information is information indicating that the master station device 101 is operating normally. If a state in which the health check information from the master station device 101 has been interrupted continues for a certain period of time or more, the slave station device 201 stops operating until the master station device 101 recovers to normal in order to prevent interference with the transmission and reception of RF signals in other slave station devices 201. The synchronization information is information for performing synchronization processing between the master station device 101 and the slave station device 201.

[0038] Each slave station device 201 acquires a frame F1 from a digital signal included in an optical signal received from the master station device 101 via the optical fiber 191, and acquires a destination ID from the frame F1. If the acquired destination ID matches the slave station ID of the slave station device 201, the slave station device 201 acquires control information Cnt from the frame F1, and operates according to the acquired control information Cnt.

[0039] [assignment] 2 is a diagram showing frames transmitted from a master station device to a slave station device in an analog RoF system according to a comparative example of the first embodiment of the present disclosure. Frames F1A, F1B, and F1C are shown in FIG. Frame F1A is a frame F1 addressed to the slave station device 201A and storing control information Cnt for controlling the operation of the slave station device 201A. Frame F1B is a frame F1 addressed to the slave station device 201B and storing control information Cnt for controlling the operation of the slave station device 201B. Frame F1C is a frame F1 addressed to the slave station device 201C and storing control information Cnt for controlling the operation of the slave station device 201C.

[0040] 2, for example, the master station device 101 transmits a frame F1 to each slave station device 201 at a transmission timing according to a predetermined transmission cycle Pt. More specifically, the master station device 101 repeatedly transmits frames F1A, F1B, and F1C in this order to each slave station device 201 at each transmission timing.

[0041] The slave station device 201 acquires control information Cnt from the frame F1 that includes the slave station ID of the slave station device 201 as the destination ID, out of the frames F1A, F1B, and F1C received from the master station device 101.

[0042] Here, the control information Cnt is classified into short cycle information that needs to be updated at short cycles and long cycle information that does not need to be updated at short cycles. The short cycle information needs to be transmitted to the slave station device 201 at high frequency, whereas the long cycle information does not need to be transmitted to the slave station device 201 at high frequency.

[0043] For example, beamforming information is classified as short cycle information in order to realize RF signal transmission following the movement of a mobile communication terminal in the slave station device 201. Also, for example, health check information is classified as short cycle information in order to prevent interference with transmission and reception of RF signals between the slave station devices 201 when an abnormality occurs in the master station device 101. On the other hand, periodically changing TDD information and synchronization information are classified as long cycle information.

[0044] In the future, in optical communication systems, it is expected that the number of slave station devices connected to a master station device will increase in order to build an economical or efficient network. Meanwhile, in an analog RoF system 301, the frequency of transmission of control information Cnt from the master station device 101 to the slave station devices 201 is inversely proportional to the number of slave station devices 201 connected to the master station device 101. Therefore, if the number of slave station devices 201 connected to the master station device 101 becomes, for example, 100 or more, the limited transmission band for transmitting the control information Cnt may not be able to transmit the short-period information at a predetermined transmission frequency, and the short-period information may not be able to be updated at a set period.

[0045] In the parent station device 101, if the bit rate is increased to improve the transmission frequency of short-period information, the transmission frequency of long-period information will become higher than necessary, resulting in a waste of transmission bandwidth and an increase in the cost of the hardware configuration of the optical modulation unit, signal processing circuit, etc. in the parent station device 101.

[0046] Therefore, the analog RoF system 301 according to the first embodiment of the present disclosure solves the above problem by adopting the following configuration.

[0047] FIG. 3 is a diagram illustrating a frame transmitted from a master station device to a slave station device in an analog RoF system according to the first embodiment of the present disclosure.

[0048] 3, the master station device 101 generates a frame F1 in which a destination ID, low-speed control information CL corresponding to the slave station device 201 indicated by the destination ID, and high-speed control information CH corresponding to the slave station device 201 other than the slave station device 201 indicated by the destination ID are stored. For example, the master station device 101 generates a frame F1 in which a destination ID, low-speed control information CL, and high-speed control information CH corresponding one-to-one to the slave station devices 201A, 201B, and 201C are stored. The master station device 101 transmits an optical signal including a digital signal including the generated frame F1 and an analog main signal to each slave station device 201. The low-speed control information CL is an example of first control information. The high-speed control information CH is an example of second control information. For example, the high-speed control information CH is control information Cnt classified as short-period information by an administrator of the analog RoF system 301. The low-speed control information CL is control information Cnt other than the high-speed control information CH.

[0049] Of the slave station devices 201, the slave station device 201 indicated by the destination ID acquires the low-speed control information CL and the high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. Also, of the slave station devices 201, the slave station devices 201 other than the slave station device 201 indicated by the destination ID acquire the high-speed control information CH from the digital signal included in the optical signal received from the master station device 101.

[0050] The processing in the master station device 101 and the slave station device 201 will be described in detail below.

[0051] Fig. 4 is a diagram showing a configuration of a master station device according to the first embodiment of the present disclosure. Referring to Fig. 4, the master station device 101 includes a signal receiving unit 11, a frequency conversion unit 12, an acceptance unit 13, a generation unit 14, an 8B / 10B modulation unit 15, an LPF 16, a multiplexing unit 17, and an optical modulation unit 18. The optical modulation unit 18 is an example of a transmission unit. A part or all of the signal receiving unit 11, the frequency conversion unit 12, the acceptance unit 13, the generation unit 14, and the 8B / 10B modulation unit 15 are realized, for example, by a processing circuit including one or more processors.

[0052] The reception unit 13 receives, from the administrator of the analog RoF system 301, setting contents of enabling or disabling the transmission of high-speed control information CH, setting contents of control information Cnt to be transmitted as the high-speed control information CH, and setting contents of control information Cnt to be transmitted as the low-speed control information CL. For example, the reception unit 13 receives setting contents to enable the transmission of high-speed control information CH, transmit beamforming information and health check information as the high-speed control information CH, and transmit periodically changing TDD information and synchronization information as the low-speed control information CL. The reception unit 13 outputs setting information indicating the received setting contents to the generation unit 14.

[0053] The signal receiving unit 11 receives an OFDM-modulated analog signal including communication data from a base station device (not shown). The signal receiving unit 11 may be configured to receive an RF signal or a baseband signal as the analog signal. The signal receiving unit 11 outputs the received analog signal to the frequency conversion unit 12.

[0054] The frequency conversion unit 12 up-converts or down-converts the analog signal received from the signal receiving unit 11 to generate an IF signal having a center frequency fa, and outputs the generated IF signal to the multiplexing unit 17 .

[0055] The generating unit 14 receives setting information from the receiving unit 13. The generating unit 14 also receives, from a base station device (not shown), a plurality of pieces of control information Cnt to be transmitted to the plurality of slave station devices 201, respectively. For example, the generating unit 14 receives, as the control information Cnt, beamforming information, periodically changing TDD information, health check information, and synchronization information from the base station device.

[0056] The generation unit 14 generates a frame addressed to the slave station device 201, in which the control information Cnt received from the base station device is stored, in accordance with the setting information received from the reception unit 13. For example, the generation unit 14 generates a frame F1 at a generation timing according to the transmission period Pt.

[0057] Fig. 5 is a diagram showing an example of a data structure of a frame generated by a generation unit of a master station device according to the first embodiment of the present disclosure. Referring to Fig. 5, a frame F1 includes a preamble, a start frame delimiter (SFD), a destination address field, a sequence number, a high-speed transmission field, a source address field, a low-speed transmission field, an end frame delimiter (EFD), and a cyclic redundancy check (CRC). The low-speed transmission field is an example of a first field.

[0058] The high-speed transmission field includes high-speed subfields SF1, SF2, and SF3 and a common subfield SFC. Hereinafter, each of the high-speed subfields SF1, SF2, and SF3 is also referred to as a high-speed subfield SFn. The high-speed subfield SFn is an example of a second field. The common subfield SFC is an example of a third field. The high-speed transmission field in the frame F1 is not limited to a configuration including three high-speed subfields SFn, and may include four or more high-speed subfields SFn in preparation for a case in which a new slave station device 201 is added to the analog RoF system 301.

[0059] A destination address field in the frame F1 stores a destination ID indicating the slave station device 201 that is the destination of the frame F1. A low-speed transmission field stores low-speed control information CL corresponding to the slave station device 201 indicated by the destination ID stored in the destination address field. A high-speed subfield SFn in the high-speed information field stores three pieces of high-speed control information CH corresponding to the slave station devices 201A, 201B, and 201C, respectively.

[0060] The common subfield SFC stores common control information Cemr, which is control information Cnt common to the slave station devices 201A, 201B, and 201C. For example, the common subfield SFC is a spare field provided in the high-speed information field for transmitting the common control information Cemr.

[0061] The generation unit 14 generates a frame F1 addressed to a slave station device 201 and including control information Cnt, in which a destination ID indicating the destination of the frame F1, low-speed control information CL corresponding to the slave station device 201 indicated by the destination ID, and high-speed control information CH corresponding to the slave station devices 201A, 201B, and 201C are stored.

[0062] More specifically, at the generation timing of the frame F1A addressed to the slave station device 201A, the generation unit 14 generates a frame F1A in which the slave station ID of the slave station device 201A is stored as the destination ID in the destination address field, low-speed control information CL addressed to the slave station device 201A is stored in the low-speed transmission field, high-speed control information CH addressed to the slave station device 201A is stored in the high-speed sub-field SF1, high-speed control information CH addressed to the slave station device 201B is stored in the high-speed sub-field SF2, and high-speed control information CH addressed to the slave station device 201C is stored in the high-speed sub-field SF3.

[0063] Furthermore, at the timing of generating a frame F1B addressed to the slave station device 201B, the generation unit 14 generates a frame F1B in which the slave station ID of the slave station device 201B is stored as the destination ID in the destination address field, low-speed control information CL addressed to the slave station device 201B is stored in the low-speed transmission field, high-speed control information CH addressed to the slave station device 201A is stored in the high-speed subfield SF1, high-speed control information CH addressed to the slave station device 201B is stored in the high-speed subfield SF2, and high-speed control information CH addressed to the slave station device 201C is stored in the high-speed subfield SF3.

[0064] Furthermore, at the timing of generating a frame F1C addressed to the slave station device 201C, the generation unit 14 generates a frame F1C in which the slave station ID of the slave station device 201C is stored as a destination ID in the destination address field, low-speed control information CL addressed to the slave station device 201C is stored in the low-speed transmission field, high-speed control information CH addressed to the slave station device 201A is stored in the high-speed subfield SF1, high-speed control information CH addressed to the slave station device 201B is stored in the high-speed subfield SF2, and high-speed control information CH addressed to the slave station device 201C is stored in the high-speed subfield SF3.

[0065] For example, the generating unit 14 generates a frame F1 in which NULL data is stored in the common subfield SFC during normal operation. Also, for example, in an emergency such as when a disaster occurs, the generating unit 14 generates a frame F1 in which a predetermined message addressed to the slave station device 201 and a partial stop instruction for turning off a predetermined function in the slave station device 201 to reduce power consumption are stored in the common subfield SFC.

[0066] When the generating unit 14 receives setting information from the receiving unit 13 to disable the transmission of high-speed control information CH, the generating unit 14 generates a frame F1 in which NULL data is stored in the high-speed subfields SF1, SF2, and SF3.

[0067] Referring back to FIG. 4, after generating the frame F1, the generating unit 14 outputs to the 8B / 10B modulating unit 15 a binary digital signal having a bandwidth fd and including the generated frame.

[0068] The 8B / 10B modulation unit 15 performs 8B / 10 modulation on the digital signal received from the generation unit 14 and outputs the modulated signal to the LPF 16. That is, the 8B / 10B modulation unit 15 converts the 8-bit digital signal received from the generation unit 14 into a 10-bit digital signal and outputs the converted signal to the LPF 16.

[0069] The LPF 16 receives the digital signal from the 8B / 10B modulation unit 15 and attenuates frequency components equal to or higher than a predetermined frequency in the received digital signal. For example, the LPF 16 is a Bessel filter with a filter order of 4 or higher that attenuates frequency components equal to or higher than a cutoff frequency fc. The cutoff frequency fc is lower than the center frequency fa of the IF signal generated by the frequency conversion unit 12. The LPF 16 outputs the digital signal with frequency components equal to or higher than the cutoff frequency fc attenuated to the multiplexing unit 17.

[0070] For example, the multiplexing unit 17 frequency-multiplexes the passing signal of the LPF 16 and the IF signal. More specifically, the multiplexing unit 17 frequency-multiplexes the digital signal received from the LPF 16 and the IF signal received from the frequency conversion unit 12. The multiplexing unit 17 generates an electrical signal M1 in which the digital signal and the IF signal are frequency-multiplexed, and outputs the electrical signal M1 to the optical modulation unit 18.

[0071] The master station device 101 may be configured to receive an IF signal from the base station device and transmit an optical signal including the received IF signal to the slave station device 201 via the optical fiber 191. More specifically, the master station device 101 may be configured not to include the frequency conversion unit 12. In this case, the signal receiving unit 11 receives the IF signal from the base station device and outputs the received IF signal to the multiplexing unit 17. The multiplexing unit 17 receives the IF signal from the signal receiving unit 11 and frequency-multiplexes the digital signal received from the LPF 16 and the IF signal received from the signal receiving unit 11.

[0072] The optical modulation unit 18 transmits an optical signal including a digital signal including the frame F1 generated by the generation unit 14 and an analog IF main signal to the slave station device 201 via the optical fiber 191. More specifically, the optical modulation unit 18 receives the electric signal M1 from the multiplexing unit 17, generates an optical signal by optically modulating the received electric signal M1, and outputs the generated optical signal to the optical fiber 191.

[0073] (Slave station device) Fig. 6 is a diagram showing a configuration of a slave station device according to the first embodiment of the present disclosure. Referring to Fig. 6, the slave station device 201 includes an optical demodulator 21, a separator 22, amplifiers 23A and 23B, a frequency converter 24, an 8B / 10B demodulator 25, an LPF 26, and a control information processor 27. The optical demodulator 21 is an example of a receiver. The control information processor 27 is an example of an acquirer. The frequency converter 24, the 8B / 10B demodulator 25, and the control information processor 27 are partly or entirely realized by a processing circuit including one or more processors.

[0074] The optical demodulator 21 receives a digital signal including the frame F1 and an optical signal including an IF signal from the master station 101 via the optical fiber 191. The optical demodulator 21 generates an electrical signal M2 based on the received optical signal. More specifically, the optical demodulator 21 generates an electrical signal M2 at a level corresponding to the intensity of the received optical signal and outputs the electrical signal M2 to the separator 22.

[0075] The separator 22 receives the electrical signal M2 from the optical demodulator 21 and separates a digital signal including the frame F1 from the received electrical signal M2. More specifically, the separator 22 outputs some of the frequency components of the electrical signal M2 to the amplifier 23A and outputs the remaining frequency components to the amplifier 23B.

[0076] For example, the separator 22 is a diplexer composed of an HPF (High Pass Filter) and an LPF. The separator 22 outputs an electric signal M2a, which is a frequency component of the electric signal M2 that is equal to or higher than the frequency Fx, to the amplifier 23A, and outputs an electric signal M2b, which is a frequency component less than the frequency Fx, to the amplifier 23B. Here, the frequency Fx is smaller than the center frequency fa of the IF signal. The electric signal M2a includes an IF signal generated by the frequency converter 12 in the master station device 101. The electric signal M2b includes a digital signal that has passed through the LPF 16 in the master station device 101.

[0077] The amplifier 23A receives the electrical signal M2a from the separator 22 and amplifies the received electrical signal M2a. For example, the amplifier 23A is a linear amplifier. The amplifier 23A outputs the amplified electrical signal M2a to the frequency converter 24.

[0078] The amplifier 23B receives the electrical signal M2b from the separator 22 and amplifies the received electrical signal M2b. For example, the amplifier 23B is a limiting amplifier. The amplifier 23B outputs the amplified electrical signal M2b to the 8B / 10B demodulator 25.

[0079] In this manner, by separating the electric signal M2 into the electric signal M2a and the electric signal M2b and amplifying the electric signals M2a and M2b using the amplifiers 23A and 23B, a linear amplifier can be used as the amplifier 23A, and a limiting amplifier can be used as the amplifier 23B. This makes it possible to avoid waveform distortion of the digital signal that occurs when a linear amplifier is used as the amplifier 23B. Furthermore, compared to the technique described in Patent Document 2 in which the electric signal M2 is amplified without separating the electric signal M2a and the electric signal M2b, the circuit scale of the slave station device 201 can be made smaller.

[0080] For example, the frequency conversion unit 24 generates an RF signal by up-converting the electrical signal M2a received from the amplification unit 23A, and outputs the generated RF signal to the antenna 161. Note that the frequency conversion unit 24 may generate a baseband signal by down-converting the electrical signal M2a received from the amplification unit 23A, and transmit the generated baseband signal to a device external to the slave station device 201.

[0081] The 8B / 10B demodulation unit 25 8B / 10B demodulates the electrical signal M2b received from the amplification unit 23B and outputs it to the LPF 26. That is, the 8B / 10B demodulation unit 25 converts the 10-bit electrical signal M2b received from the amplification unit 23B into an 8-bit electrical signal M2b and outputs it to the LPF 26.

[0082] The LPF 26 receives the electrical signal M2b from the 8B / 10B demodulation unit 25 and attenuates components of a predetermined frequency or higher in the received electrical signal M2b. For example, the LPF 26 is a Bessel filter with a filter order of 4 or higher that attenuates frequency components of a cutoff frequency fc or higher. The LPF 26 outputs the electrical signal M2b, in which components of the cutoff frequency fc or higher have been attenuated, to the control information processing unit 27.

[0083] The control information processing unit 27 acquires high-speed control information CH from the digital signal included in the optical signal received by the optical demodulation unit 21. More specifically, the control information processing unit 27 receives the electrical signal M2b from the LPF 26 and acquires a frame F1 from the received electrical signal M2b. The control information processing unit 27 acquires high-speed control information CH from a predetermined high-speed subfield SFn in the high-speed transmission field of the acquired frame F1. As an example, the control information processing unit 27 in the slave station device 201A acquires high-speed control information CH from the high-speed subfield SF1, the control information processing unit 27 in the slave station device 201B acquires high-speed control information CH from the high-speed subfield SF2, and the control information processing unit 27 in the slave station device 201C acquires high-speed control information CH from the high-speed subfield SF3.

[0084] When the device indicated by the destination ID stored in the frame F1 is the slave station device 201, the control information processing unit 27 in the slave station device 201 further acquires low-speed control information CL from the digital signal included in the optical signal received by the optical demodulation unit 21. More specifically, the control information processing unit 27 acquires the destination ID from the destination address field of the acquired frame F1. When the acquired destination ID matches the slave station ID of the slave station device 201, the control information processing unit 27 acquires the low-speed control information CL from the low-speed transmission field in the frame F1.

[0085] The control information processing unit 27 processes the acquired control information Cnt. For example, the control information processing unit 27 receives beamforming information, which is an example of high-speed control information CH, and performs processing to control the direction of the beam output from the antenna 161 in accordance with the received beamforming information.

[0086] [Operation flow] FIG. 7 is a diagram illustrating an example of a communication sequence in the analog RoF system according to the first embodiment of the present disclosure.

[0087] Referring to FIG. 7, first, the master station device 101 generates a frame F1A in which the slave station ID of the slave station device 201A is stored in the destination address field, low-speed control information CL addressed to the slave station device 201A is stored in the low-speed transmission field, and high-speed control information CH addressed to the slave station devices 201A, 201B, and 201C are stored in the high-speed subfields SF1, SF2, and SF3 (step S11).

[0088] Next, the master station device 101 transmits an optical signal including a digital signal containing the generated frame F1A and an analog IF main signal to each slave station device 201 via the optical fiber 191 (step S12).

[0089] Next, the slave station device 201A acquires the low-speed control information CL and the high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201A acquires a frame F1A from the digital signal, acquires the low-speed control information CL from the low-speed transmission field in the frame F1A, and acquires the high-speed control information CH from the high-speed subfield SF1 in the high-speed transmission field of the frame F1A (step S13).

[0090] Furthermore, the slave station device 201B acquires high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201B acquires a frame F1A from the digital signal, and acquires the high-speed control information CH from the high-speed subfield SF2 in the high-speed transmission field of the frame F1A (step S14).

[0091] Furthermore, the slave station device 201C acquires high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201C acquires a frame F1A from the digital signal, and acquires the high-speed control information CH from the high-speed subfield SF3 in the high-speed transmission field of the frame F1A (step S15).

[0092] Next, the master station device 101 generates a frame F1B in which the slave station ID of the slave station device 201B is stored in the destination address field, low-speed control information CL addressed to the slave station device 201B is stored in the low-speed transmission field, and high-speed control information CH addressed to the slave station devices 201A, 201B, and 201C is stored in the high-speed subfields SF1, SF2, and SF3 (step S16).

[0093] Next, the master station device 101 transmits an optical signal including a digital signal containing the generated frame F1B and an analog IF main signal to each slave station device 201 via the optical fiber 191 (step S17).

[0094] Next, the slave station device 201A acquires high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201A acquires a frame F1B from the digital signal, and acquires the high-speed control information CH from the high-speed subfield SF1 in the high-speed transmission field of the frame F1B (step S18).

[0095] Furthermore, the slave station device 201B acquires low-speed control information CL and high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201B acquires a frame F1B from the digital signal, acquires low-speed control information CL from the low-speed transmission field in the frame F1B, and acquires high-speed control information CH from the high-speed subfield SF2 in the high-speed transmission field of the frame F1B (step S19).

[0096] Furthermore, the slave station device 201C acquires high-speed control information CH from a digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201C acquires a frame F1B from the digital signal, and acquires the high-speed control information CH from a high-speed subfield SF3 in the high-speed transmission field of the frame F1B (step S20).

[0097] Next, the master station device 101 generates a frame F1C in which the slave station ID of the slave station device 201C is stored in the destination address field, low-speed control information CL addressed to the slave station device 201C is stored in the low-speed transmission field, and high-speed control information CH addressed to the slave station devices 201A, 201B, and 201C is stored in the high-speed subfields SF1, SF2, and SF3 (step S21).

[0098] Next, the master station device 101 transmits an optical signal including a digital signal containing the generated frame F1C and an analog IF main signal to each slave station device 201 via the optical fiber 191 (step S22).

[0099] Next, the slave station device 201A acquires high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201A acquires a frame F1C from the digital signal, and acquires the high-speed control information CH from the high-speed subfield SF1 in the high-speed transmission field of the frame F1C (step S23).

[0100] Furthermore, the slave station device 201B acquires high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201B acquires a frame F1C from the digital signal, and acquires the high-speed control information CH from the high-speed subfield SF2 in the high-speed transmission field of the frame F1C (step S24).

[0101] Furthermore, the slave station device 201C acquires low-speed control information CL and high-speed control information CH from the digital signal included in the optical signal received from the master station device 101. More specifically, the slave station device 201C acquires a frame F1C from the digital signal, acquires the low-speed control information CL from the low-speed transmission field in the frame F1C, and acquires the high-speed control information CH from the high-speed subfield SF3 in the high-speed transmission field of the frame F1C (step S25).

[0102] In the master station device 101 according to the first embodiment of the present disclosure, the generation unit 14 is configured to generate the frame F1 including the common subfield SFC, but this is not limiting. The generation unit 14 may be configured to generate the frame F1 that does not include the common subfield SFC.

[0103] In addition, in the master station device 101 according to the first embodiment of the present disclosure, the generating unit 14 is configured to generate a frame F1 in which a destination ID, low-speed control information CL corresponding to the slave station device 201 indicated by the destination ID, and high-speed control information CH corresponding to the slave station device 201A, 201B, and 201C are stored, but this is not limited thereto. The generating unit 14 may be configured to generate a frame F1 in which high-speed control information CH corresponding to the slave station device 201 indicated by the destination ID is not stored. That is, the generating unit 14 may be configured to generate a frame F1A in which high-speed control information CH addressed to the slave station device 201A is not stored in the high-speed information field, a frame F1B in which high-speed control information CH addressed to the slave station device 201B is not stored in the high-speed information field, and a frame F1C in which high-speed control information CH addressed to the slave station device 201C is not stored in the high-speed information field.

[0104] <Modification> The slave station devices 201 in the analog RoF system 301 are divided into a plurality of groups G, each consisting of one or a plurality of slave station devices 201, according to the installation location of each slave station device 201, for example, by an administrator of the analog RoF system 301.

[0105] In this case, the parent station device 101 generates a frame F2 that stores a destination ID, low-speed control information CL corresponding to the child station device 201 indicated by the destination ID, and multiple pieces of high-speed control information CH that correspond one-to-one to multiple groups G.

[0106] For example, the slave station devices 201 are installed in a building and grouped according to the floors they are installed on. Alternatively, the slave station devices 201 may be grouped according to the rooms they are installed in.

[0107] Also, for example, the slave station devices 201 are divided into groups according to installation areas that share at least a part of a line-of-sight area, which is an area in which RF signals can be transmitted and received via the corresponding antennas 161 .

[0108] As an example, in the analog RoF system 301, the slave station devices 201A and 201B are classified into a group G1 which is part of group G, and the slave station device 201C is classified into a group G2 which is part of group G.

[0109] 8 is a diagram showing an example of a data structure of a frame generated by a generation unit of a master station device according to a modified example of the first embodiment of the present disclosure. Referring to FIG. 8, compared to frame F1, frame F2 includes high-speed subfields SFG1 and SFG2 instead of high-speed subfields SF1, SF2, and SF3. Hereinafter, each of high-speed subfields SFG1 and SFG2 is also referred to as high-speed subfield SFGn. High-speed subfield SFGn is an example of a second field. The high-speed transmission field in frame F2 is not limited to a configuration including two high-speed subfields SFGn, and may include three or more high-speed subfields SFGn in preparation for a case where a new group G is added to the analog RoF system 301.

[0110] In the high-speed subfield SFGn, two pieces of high-speed control information CH corresponding to the groups G1 and G2, respectively, are stored.

[0111] The generation unit 14 generates a frame F2 addressed to a child station device 201 including control information Cnt, in which a destination ID indicating the destination of the frame F2, low-speed control information CL corresponding to the child station device 201 indicated by the destination ID, and two pieces of high-speed control information CH corresponding to groups G1 and G2, respectively, are stored.

[0112] More specifically, at the generation timing of frame F2A, which is frame F2 addressed to the slave station device 201A, the generation unit 14 generates frame F2A in which the slave station ID of the slave station device 201A is stored as the destination ID in the destination address field, low-speed control information CL addressed to the slave station device 201A is stored in the low-speed transmission field, high-speed control information CH addressed to the slave station device 201A, 201B belonging to group G1 is stored in the high-speed subfield SFG1, and high-speed control information CH addressed to the slave station device 201C belonging to group G2 is stored in the high-speed subfield SFG2.

[0113] Furthermore, at the timing of generating frame F2B, which is frame F2 addressed to the slave station device 201B, the generation unit 14 generates frame F2B in which the slave station ID of the slave station device 201B is stored as the destination ID in the destination address field, low-speed control information CL addressed to the slave station device 201B is stored in the low-speed transmission field, high-speed control information CH addressed to the slave station device 201A, 201B belonging to group G1 is stored in the high-speed subfield SFG1, and high-speed control information CH addressed to the slave station device 201C belonging to group G2 is stored in the high-speed subfield SFG2.

[0114] Furthermore, at the timing of generating frame F2C, which is frame F2 addressed to the slave station device 201C, the generation unit 14 generates frame F2C in which the slave station ID of the slave station device 201C is stored as the destination ID in the destination address field, low-speed control information CL addressed to the slave station device 201C is stored in the low-speed transmission field, high-speed control information CH addressed to the slave station device 201A, 201B belonging to group G1 is stored in the high-speed subfield SFG1, and high-speed control information CH addressed to the slave station device 201C belonging to group G2 is stored in the high-speed subfield SFG2.

[0115] Next, another embodiment 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 characters and the description thereof will not be repeated.

[0116] <Second embodiment> [Configuration and basic operation] This embodiment is different from the analog RoF system 301 according to the first embodiment in that it relates to an analog RoF system 302 that transmits wavelength-multiplexed optical signals via an optical fiber 191. Contents other than those described below are the same as those of the analog RoF system 301 according to the first embodiment.

[0117] Fig. 9 is a diagram showing a configuration of an analog RoF system according to a second embodiment of the present disclosure. With reference to Fig. 9, compared to the analog RoF system 301 shown in Fig. 1, an analog RoF system 302 includes a master station device 102 instead of the master station device 101, and includes slave station devices 202A, 202B, and 202C instead of the slave station devices 201A, 201B, and 201C. Hereinafter, each of the slave station devices 202A, 202B, and 202C will also be referred to as a slave station device 202. The analog RoF system 302 may be configured to include two or four or more slave station devices 202.

[0118] The master station device 102 generates a frame F1 that contains a destination ID, low-speed control information CL corresponding to the slave station device 202 indicated by the destination ID, and high-speed control information CH that corresponds one-to-one to the slave station devices 202A, 202B, and 202C. During a downstream transmission period, the master station device 102 generates an optical signal based on a digital signal including the frame F1, wavelength-multiplexes the generated optical signal with an optical signal based on the IF signal, and transmits the multiplexed optical signal to each slave station device 202 via the optical fiber 191.

[0119] Of the slave station devices 202, the slave station device 202 indicated by the destination ID acquires the low-speed control information CL and the high-speed control information CH from the digital signal included in the optical signal received from the master station device 102. Also, of the slave station devices 202, the slave station devices 202 other than the slave station device 202 indicated by the destination ID acquire the high-speed control information CH from the digital signal included in the optical signal received from the master station device 102.

[0120] (Master station device) Fig. 10 is a diagram showing a configuration of a master station device according to a second embodiment of the present disclosure. With reference to Fig. 10, compared to the master station device 101 shown in Fig. 4, the master station device 102 includes optical modulation units 31A and 31B and a multiplexing unit 32 instead of the LPF 16, the multiplexing unit 17, and the optical modulation unit 18. The multiplexing unit 32 is an example of a transmission unit.

[0121] The frequency conversion unit 12 receives an analog signal from the signal receiving unit 11, up-converts or down-converts the received analog signal to generate an IF signal, and outputs the generated IF signal to the optical modulation unit 31A.

[0122] The optical modulation section 31A receives the IF signal from the frequency conversion section 12, generates an optical signal with a wavelength of λ1 by optically modulating the received IF signal, and outputs the generated optical signal to the multiplexing section 32.

[0123] The 8B / 10B modulation section 15 receives a digital signal including the frame F1 from the generation section 14, 8B / 10 modulates the received digital signal, and outputs the 8B / 10 modulated signal to the optical modulation section 31B.

[0124] The optical modulation section 31B receives the digital signal from the 8B / 10B modulation section 15, generates an optical signal with a wavelength of λ2 by optically modulating the received digital signal, and outputs the generated optical signal to the multiplexing section 32.

[0125] The multiplexing unit 32 wavelength-multiplexes the optical signal having the wavelength λ1 received from the optical modulation unit 31A and the optical signal having the wavelength λ2 received from the optical modulation unit 31B. For example, the multiplexing unit 32 is an optical coupler. The multiplexing unit 32 outputs the wavelength-multiplexed optical signal to the optical fiber 191.

[0126] (Slave station device) Fig. 11 is a diagram showing a configuration of a slave station device according to a second embodiment of the present disclosure. With reference to Fig. 11, compared to the slave station device 201 shown in Fig. 6, the slave station device 202 includes a separator 41 and optical demodulators 42A and 42B instead of the optical demodulator 21, separator 22, and LPF 26. The separator 41 is an example of a receiver.

[0127] The separator 41 receives an optical signal including a digital signal including a frame F1 and an IF signal from the master station device 102 via the optical fiber 191. The separator 41 separates the received optical signal according to wavelength. For example, the separator 41 is an optical coupler. Of the received optical signals, the separator 41 outputs an optical signal with a wavelength λ1 to the optical demodulator 42A and outputs an optical signal with a wavelength λ2 to the optical demodulator 42B. The optical signal with a wavelength λ1 includes an IF signal generated by the frequency converter 12 in the master station device 102. The optical signal with a wavelength λ2 includes a digital signal modulated by the 8B / 10B modulator 15 in the master station device 102.

[0128] The optical demodulator 42A receives the optical signal of wavelength λ1 from the separator 41, generates an electrical signal M2a at a level corresponding to the intensity of the received optical signal, and outputs the electrical signal M2a to the amplifier 23A.

[0129] The amplifier 23A receives the electrical signal M2a from the separator 41, amplifies the received electrical signal M2a, and outputs the amplified electrical signal M2a to the frequency converter 24.

[0130] For example, the frequency conversion unit 24 generates an RF signal by up-converting the electrical signal M2a received from the amplification unit 23A, and outputs the generated RF signal to a mobile communication terminal (not shown) via the antenna 161. Note that the frequency conversion unit 24 may generate a baseband signal by down-converting the electrical signal M2a received from the amplification unit 23A, and transmit the generated baseband signal to a device external to the slave station device 202.

[0131] The optical demodulator 42B receives the optical signal with wavelength λ2 from the separator 41, generates an electrical signal M2b at a level corresponding to the intensity of the received optical signal, and outputs the electrical signal M2b to the amplifier 23B.

[0132] The amplifier 23B receives the electrical signal M2b from the separator 41, amplifies the received electrical signal M2b, and outputs the amplified electrical signal M2b to the 8B / 10B demodulator 25.

[0133] The 8B / 10B demodulation unit 25 8B / 10B demodulates the electrical signal M2b received from the amplification unit 23B and outputs it to the control information processing unit 27. That is, the 8B / 10B demodulation unit 25 converts the 10-bit electrical signal M2b received from the amplification unit 23B into an 8-bit electrical signal M2b and outputs it to the control information processing unit 27.

[0134] The control information processing unit 27 acquires high-speed control information CH from the digital signal included in the optical signal received by the demultiplexer 41. More specifically, the control information processing unit 27 receives the electrical signal M2b from the 8B / 10B demodulator 25, and acquires a frame F1 from the received electrical signal M2b. The control information processing unit 27 acquires high-speed control information CH from a predetermined high-speed subfield SFn in the high-speed transmission field of the acquired frame F1.

[0135] When the device indicated by the destination ID stored in the frame F1 is the slave station device 202, the control information processing unit 27 in the slave station device 202 further acquires low-speed control information CL from the digital signal included in the optical signal received by the demultiplexer 41. More specifically, the control information processing unit 27 acquires the destination ID from the destination address field of the acquired frame F1. When the acquired destination ID matches the slave station ID of the slave station device 202, the control information processing unit 27 acquires the low-speed control information CL from the low-speed transmission field in the frame F1.

[0136] The above-described embodiments should be considered as illustrative and not restrictive in all respects. 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.

[0137] Each process (each function) of the above-mentioned embodiment is realized by a processing circuit (circuitry) including one or more processors. The above-mentioned processing circuit may be composed of an integrated circuit or the like in which one or more memories, various analog circuits, and various digital circuits are combined in addition to the above-mentioned one or more processors. The above-mentioned one or more memories store programs (instructions) that cause the above-mentioned one or more processors to execute each of the above-mentioned processes. The above-mentioned one or more processors may execute each of the above-mentioned processes according to the programs read from the above-mentioned one or more memories, or may execute each of the above-mentioned processes according to a logic circuit designed in advance to execute each of the above-mentioned processes. The above-mentioned processors may be 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). The above-mentioned physically separated processors may execute each of the above-mentioned processes in cooperation with each other. For example, the processors mounted on each of a plurality of physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), the Internet, etc. The program may be installed in the memory from an external server device or the like via the network, or may be distributed in a state stored in 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 installed in the memory from the recording medium.

[0138] The above description includes the following additional features. [Appendix 1] 1. An analog RoF system, comprising: A master station device; A plurality of slave station devices, the parent station device generates a frame addressed to the child station device, the frame including control information, the frame storing destination information indicating a destination of the frame, first control information corresponding to a first child station device which is the child station device indicated by the destination information, and second control information corresponding to a second child station device which is the child station device other than the child station device indicated by the destination information, and transmits an optical signal including a digital signal including the generated frame and an analog main signal to the multiple child station devices; the first slave station device acquires the first control information from the digital signal included in the optical signal received from the master station device; the second slave station device acquires the second control information from the digital signal included in the optical signal received from the master station device; An analog RoF system, wherein the second control information includes at least one of beamforming information for controlling a transmission direction of an RF signal in the slave station device and health check information indicating that the master station device is operating normally.

[0139] [Appendix 2] In an analog RoF system including a master station device and a plurality of slave station devices, a data structure of a frame transmitted from the master station device to the plurality of slave station devices, a destination address field in which destination information indicating the child station device to which the frame is addressed is stored; a first field in which first control information corresponding to the slave station device indicated by the destination information is stored; a second field in which second control information corresponding to the slave station device other than the slave station device indicated by the destination information is stored; A data structure in which the first control information and the second control information are information for controlling an operation of the slave station device. [Explanation of symbols]

[0140] 11 Signal receiving section 12 Frequency conversion section 13 Reception 14 Generation part 15 8B / 10B modulation section 16 LPF 17 Multiplex section 18 Optical modulation section 21 Optical demodulation section 22 Separation part 23A, 23B Amplification section 24 Frequency conversion section 25 8B / 10B demodulation section 26 LPF 27 Control information processing section 31A, 31B Optical modulation section 32 Multiplex section 41 Separation part 42A, 42B Optical demodulation section 101,102 Master station device 161, 161A, 161B, 161C Antenna 191 Optical Fiber 201,201A,201B,201C,202,202A,202B,202C Slave station device 301,302 Analog RoF system F1, F1A, F1B, F1C, F2 frames CH High-speed control information CL Low speed control information

Claims

1. An analog Radio over Fiber (RoF) system, comprising: A master station device; A plurality of slave station devices, the parent station device generates a frame addressed to the child station device, the frame including control information, the frame storing destination information indicating a destination of the frame, first control information corresponding to a first child station device which is the child station device indicated by the destination information, and second control information corresponding to a second child station device which is the child station device other than the child station device indicated by the destination information, and transmits an optical signal including a digital signal including the generated frame and an analog main signal to the multiple child station devices; the first slave station device acquires the first control information from the digital signal included in the optical signal received from the master station device; An analog RoF system, wherein the second slave station device acquires the second control information from the digital signal included in the optical signal received from the master station device.

2. the master station device generates the frame in which the second control information corresponding to the first slave station device and the second slave station device is stored; The analog RoF system according to claim 1 , wherein the first slave station device further acquires the second control information from the digital signal included in the optical signal received from the master station device.

3. 3. The analog RoF system according to claim 1, wherein the master station device generates the frame in which the second control information is stored, the second control information corresponding to the slave station device in a one-to-one correspondence.

4. 3. The analog RoF system according to claim 1, wherein the frame includes a first field in which the first control information is stored, a second field in which the second control information is stored, and a third field in which third control information common to the multiple slave station devices is stored.

5. A master station device that transmits control information to a plurality of slave station devices in an analog RoF system, a generating unit that generates a frame addressed to the child station device including control information, the frame storing destination information indicating a destination of the frame, first control information corresponding to the child station device indicated by the destination information, and second control information corresponding to the child station device other than the child station device indicated by the destination information; a transmitter that transmits, to the plurality of slave station devices, an optical signal that includes a digital signal including the frame generated by the generator and an analog main signal.

6. A slave station device in an analog RoF system, a receiving unit that receives an optical signal including a digital signal including a frame in which destination information, first control information, and second control information are stored, and an analog main signal; an acquisition unit that acquires the second control information from the digital signal included in the optical signal received by the receiving unit, The acquisition unit further acquires the first control information from the digital signal when the device indicated by the destination information is the slave station device.

7. In an analog RoF system including a master station device and a plurality of slave station devices, a data structure of a frame transmitted from the master station device to the plurality of slave station devices, a destination address field in which destination information indicating the child station device to which the frame is addressed is stored; a first field in which first control information corresponding to the slave station device indicated by the destination information is stored; a second field in which second control information corresponding to the slave station equipment other than the slave station equipment indicated by the destination information is stored.

8. An optical communication method in an analog RoF system including a master station device and a plurality of slave station devices, comprising: a step of the parent station device generating a frame addressed to the child station device, the frame including control information, the frame storing destination information indicating a destination of the frame, first control information corresponding to a first child station device which is the child station device indicated by the destination information, and second control information corresponding to a second child station device which is the child station device other than the child station device indicated by the destination information, and transmitting an optical signal including a digital signal including the generated frame and an analog main signal to the multiple child station devices; acquiring, by the first slave station device, the first control information from the digital signal included in the optical signal received from the master station device; and acquiring, by the second slave station device, the second control information from the digital signal included in the optical signal received from the master station device.

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