Analog RoF system, master station device, slave station device, and optical communication method

Abstract

The present invention relates to an analog RoF system comprising: a master station device; and a slave station device that transmits and receives a wireless signal via an antenna, the master station device generating control information to be used for controlling the transmission and reception of the wireless signal, and transmitting an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber. The first digital signal includes the generated control information, and the slave station device acquires the control information from the first digital signal included in the optical signal received from the master station device via the optical fiber, and transmits the control information to the master station device on the basis of the acquired control information. A switching process between a transmission operation and a reception operation of the wireless signal via the antenna is performed.

Description

Technical Field

[0001] The present invention relates to a simulated RoF (Radio over Fiber) system, a master station device, a slave station device and an optical communication method.

[0002] This application claims the priority of Japanese Patent Application No. 2022-166626 filed on October 18, 2022, and incorporates all the contents disclosed therein into this application. Background Art

[0003] Patent document 1 (Japanese Patent Publication No. 2016-158062) discloses the following communication device. That is, the communication device includes: a data packet receiving unit that receives a data packet storing a divided continuous signal; a signal holding unit that receives and holds a received continuous signal, the received continuous signal being a continuous signal stored in the data packet received by the data packet receiving unit; a transmission timing control unit that, when the data packet receiving unit receives a data packet different from a subsequent data packet of a data packet received previously, instructs the signal holding unit to output the received continuous signal at a timing determined based on a timestamp inserted in a header of the data packet received this time, and instructs the signal holding unit to output the received continuous signal at a timing predetermined based on the size of the divided continuous signal when the data packet receiving unit receives a subsequent data packet of a data packet received previously; and a continuous signal transmitting unit that transmits the continuous signal output from the signal holding unit to a network for continuous signal transmission.

[0004] Furthermore, Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-166278) discloses the following wireless communication system. That is, the wireless communication system is a wireless communication system composed of a master station device, a slave station device, a network connecting the master station device and the slave station device, and a wireless terminal, the master station device has: a wireless modulation circuit, which modulates data; a wireless demodulation circuit, which demodulates data; and a processing unit, which converts a digital wireless signal input from the wireless modulation circuit into a packet and sends it to the network, and receives a packet from the network, converts the received packet into a digital wireless signal and forwards it to the wireless demodulation circuit, the slave station device has: a wireless transmission circuit, which sends a wireless signal to the wireless terminal; a wireless reception circuit, which receives a wireless signal from the wireless terminal; and a processing unit, which converts a digital wireless signal input from the wireless reception circuit into a packet and sends it to the network, and receives a packet from the network, extracts a digital wireless signal from the received packet and forwards it to the wireless transmission circuit, the processing units of the master station device and the slave station device synchronize the time and clock frequency of the master station device and the slave station device, and add time information to the packet transmitted in the network to transmit the digital wireless signal.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-158062;

[0008] Patent document 2: Japanese Patent Application Publication No. 2007-166278. Summary of the invention

[0009] The analog RoF system of the present invention comprises: a master station device; and a slave station device, which transmits and receives wireless signals via an antenna, the master station device generates control information used in controlling the transmission and reception of the wireless signal, and transmits an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber, the first digital signal including the generated control information, the slave station device obtains the control information from the first digital signal included in the optical signal received from the master station device via the optical fiber, and performs switching processing of the transmission and reception of the wireless signal via the antenna based on the obtained control information.

[0010] The master station device of the present invention comprises: a control information generating unit, which generates control information used in controlling the transmission and reception of wireless signals by a slave station device via an antenna; and a transmitting unit, which transmits an optical signal including a digital signal and an analog master signal to the slave station device via an optical fiber, wherein the digital signal includes the control information generated by the control information generating unit.

[0011] The slave station device of the present invention comprises: a wireless transceiver unit, which transmits and receives wireless signals via an antenna; a receiving unit, which receives an optical signal including a digital signal and an analog main signal from a master station device via an optical fiber, wherein the digital signal includes control information; an acquisition unit, which acquires the control information from the digital signal included in the optical signal received by the receiving unit; and a control unit, which switches the sending and receiving operations of the wireless transceiver unit via the antenna based on the control information acquired by the acquisition unit.

[0012] The optical communication method of the present invention is an optical communication method in an analog RoF system having a master station device and a slave station device that transmits and receives wireless signals via an antenna, comprising: the master station device generates control information used in controlling the transmission and reception of the wireless signal, and sends an optical signal containing a first digital signal and an analog master signal to the slave station device via an optical fiber, wherein the first digital signal contains the generated control information; and the slave station device obtains the control information from the first digital signal contained in the optical signal received from the master station device via the optical fiber, and performs switching processing of the transmission and reception of the wireless signal via the antenna based on the obtained control information.

[0013] One embodiment of the present invention can be implemented not only as a master station device having such a characteristic processing unit, but also as an optical communication method having the characteristic processing as steps, or as a program for causing a computer to execute the steps. In addition, one embodiment of the present invention can be implemented as a semiconductor integrated circuit that implements part or all of the master station device.

[0014] Furthermore, one aspect of the present invention can be implemented not only as a slave station device having such a characteristic processing unit, but also as an optical communication method having the characteristic processing as a step, or as a program for causing a computer to execute the step. Furthermore, one aspect of the present invention can be implemented as a semiconductor integrated circuit that implements a part or all of the slave station device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing the configuration of a simulated RoF system according to the first embodiment of the present invention.

[0016] Figure 2This is a diagram showing an example of a timing diagram of a communication frame in a mobile wireless communication system.

[0017] Figure 3 It is a diagram showing the configuration of a master station device according to the first embodiment of the present invention.

[0018] Figure 4 It is a diagram showing the configuration of a slave device according to the first embodiment of the present invention.

[0019] Figure 5 This is a diagram showing an example of a TDD signal transmitted by a base station apparatus according to the first embodiment of the present invention.

[0020] Figure 6 This is a diagram showing an example of a TDD signal generated by a TDD processing unit in a slave station device according to the first embodiment of the present invention.

[0021] Figure 7 This is a diagram showing an example of a communication sequence of a simulated RoF system according to the first embodiment of the present invention.

[0022] Figure 8 It is a diagram showing a configuration of a simulated RoF system according to a second embodiment of the present invention.

[0023] Fig. 9 It is a diagram showing the configuration of a master station device according to a second embodiment of the present invention.

[0024] Fig.10 This is a diagram showing an example of a correspondence table held by the information storage unit in the master station device according to the second embodiment of the present invention.

[0025] Fig.11 It is a diagram showing the configuration of a slave device according to the second embodiment of the present invention.

[0026] Fig.12 It is a diagram showing a configuration of a simulated RoF system according to a third embodiment of the present invention.

[0027] Fig.13 It is a diagram showing the configuration of a master station device according to a third embodiment of the present invention.

[0028] Fig.14 It is a diagram showing a configuration of a slave device according to a third embodiment of the present invention.

[0029] Fig.15 This is a diagram showing an example of a communication sequence simulating a RoF system according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0030] Conventionally, technologies have been developed for improving the communication performance of optical communication systems.

[0031] [Problems to be Solved by the Invention]

[0032] There is a demand for a technology that exceeds the technologies described in Patent Documents 1 and 2 and can realize TDD (Time Division Duplex) with a simple configuration in a pseudo RoF system having a master device and slave devices.

[0033] The present invention is made to solve the above-mentioned problems, and its purpose is to provide a simulated RoF system, a master station device, a slave station device and an optical communication method, which can realize TDD with a simple structure in the simulated RoF system having a master station device and a slave station device.

[0034] [Effects of the Invention]

[0035] According to the present invention, TDD can be realized with a simple configuration in a pseudo RoF system including a master station device and slave station devices.

[0036] [Description of Embodiments of the Invention]

[0037] First, the contents of the embodiments of the present invention are listed and described.

[0038] (1) An analog RoF system according to an embodiment of the present invention comprises: a master station device; and a slave station device, which transmits and receives wireless signals via an antenna, wherein the master station device generates control information used in controlling the transmission and reception of the wireless signal, and transmits an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber, wherein the first digital signal includes the generated control information, and the slave station device obtains the control information from the first digital signal included in the optical signal received from the master station device via the optical fiber, and performs switching processing of the transmission and reception of the wireless signal via the antenna based on the obtained control information.

[0039] In this way, the master station device transmits a downlink optical signal including the first digital signal and the master signal to the slave station device via the optical fiber, and the slave station device obtains control information from the first digital signal included in the downlink optical signal and performs a switching process of transmitting and receiving the wireless signal. According to such a structure, the switching process of transmitting and receiving can be performed without performing detailed calculation processing for determining the switching timing of transmitting and receiving in the slave station device. Therefore, in the analog RoF system having the master station device and the slave station device, TDD can be realized with a simple structure.

[0040] (2) In the above (1), the master station device can be connected between the base station device and the slave station device, and the master station device can receive a mode signal representing the uplink communication period and the downlink communication period in TDD from the base station device, and generate the control information based on the received mode signal.

[0041] With such a structure, the control information can be generated by simple processing in the master station device, and the switching processing of transmission and reception can be performed in synchronization with the uplink communication period and the downlink communication period set in the base station device in the slave station device. In addition, when the downlink communication period and the uplink communication period are changed by the base station device, the switching processing in the slave station device can be changed by transmitting the control information reflecting the changed content from the master station device to the slave station device, so that the change of the downlink communication period and the uplink communication period can be flexibly responded to.

[0042] (3) In the above (2), the master station device can generate a switching pattern for the transmission and reception of the wireless signal based on the mode signal, and generate the control information, wherein the control information includes the generated switching pattern and the start timing of the switching process using the switching pattern.

[0043] With such a configuration, for example, it is possible to set the start timing in consideration of the transmission delay of the control information between the master station device and the slave station device, and to perform a stable switching process in the slave station device.

[0044] (4) In the above (2), the master station device and the slave station device can maintain corresponding information, wherein the corresponding information indicates the correspondence between the type of the mode signal and the identification information of the mode signal. The master station device can refer to the corresponding information to obtain the identification information corresponding to the mode signal received from the base station device, and generate the control information, wherein the control information includes the obtained identification information and the start timing of the switching process using the identification information.

[0045] With this configuration, the uplink communication period and the downlink communication period set in the base station device can be notified to the slave station device with a simple configuration compared to a configuration in which control information including a switching mode of wireless signal transmission and reception operations is transmitted from the master station device to the slave station device.

[0046] (5) In the above (3) or (4), the pseudo RoF system may include a plurality of slave station devices, and the master station device may generate the control information including a different start timing for each slave station device.

[0047] With such a configuration, for example, the start timing can be set in consideration of different processing delays for each slave station device, and therefore interference between wireless signals transmitted from each slave station device via an antenna can be suppressed.

[0048] (6) In any one of (3) to (5) above, the slave station device may correct the start timing included in the control information, and start the switching process based on the control information at the corrected start timing.

[0049] With such a configuration, it is possible to correct the start timing to be more accurate based on the actual transmission delay of the control information received in the slave station device, and perform a stable switching process in the slave station device.

[0050] (7) In any of the above (1) to (6), the slave station device can receive mode information representing the uplink communication period and the downlink communication period in TDD from a device other than the master station device outside the slave station device, generate a second digital signal including the received mode information, and send an optical signal including the generated second digital signal and the simulated main signal to the master station device via the optical fiber. The master station device can obtain the mode information from the second digital signal included in the optical signal received from the slave station device via the optical fiber, and generate the control information reflecting the content of the obtained mode information.

[0051] With such a configuration, when the downlink communication period and the uplink communication period in TDD adopted in the mobile wireless communication system are changed according to the communication status of the mobile communication terminal, for example, the change of the downlink communication period and the uplink communication period can be flexibly handled.

[0052] (8) The master station device of an embodiment of the present invention comprises: a control information generating unit, which generates control information used in controlling the transmission and reception of wireless signals by the slave station device via an antenna; and a transmitting unit, which transmits an optical signal including a digital signal and an analog master signal to the slave station device via an optical fiber, wherein the digital signal includes the control information generated by the control information generating unit.

[0053] In this way, a downlink optical signal including a digital signal and a main signal is transmitted to a slave device via an optical fiber, and the digital signal includes control information. With such a structure, the switching process of transmission and reception can be performed without performing detailed calculation processing for determining the switching timing of transmission and reception of wireless signals in the slave device. Therefore, in an analog RoF system having a master device and a slave device, TDD can be implemented with a simple structure.

[0054] (9) The slave station device of an embodiment of the present invention comprises: a wireless transceiver unit, which transmits and receives wireless signals via an antenna; a receiving unit, which receives an optical signal including a digital signal and an analog main signal from a master station device via an optical fiber, wherein the digital signal includes control information; an acquisition unit, which acquires the control information from the digital signal included in the optical signal received by the receiving unit; and a control unit, which switches the sending and receiving operations of the wireless transceiver unit via the antenna based on the control information acquired by the acquisition unit.

[0055] In this way, by acquiring control information from a digital signal included in an optical signal to perform a switching process of transmitting and receiving a wireless signal, it is possible to perform a switching process of transmitting and receiving a wireless signal without performing detailed calculations and processing for determining the switching timing of transmitting and receiving a wireless signal. Therefore, in an analog RoF system having a master station device and a slave station device, TDD can be implemented with a simple structure.

[0056] (10) The communication method of an embodiment of the present invention is an optical communication method in an analog RoF system having a master station device and a slave station device that transmits and receives wireless signals via an antenna, comprising: the master station device generates control information used in controlling the transmission and reception of the wireless signal, and sends an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber, wherein the first digital signal includes the generated control information; and the slave station device obtains the control information from the first digital signal included in the optical signal received from the master station device via the optical fiber, and performs switching processing of the transmission and reception of the wireless signal via the antenna based on the obtained control information.

[0057] In this way, the master station device transmits a downlink optical signal including the first digital signal and the master signal to the slave station device via the optical fiber, and the slave station device obtains control information from the first digital signal included in the downlink optical signal and performs a switching process of transmitting and receiving the wireless signal. In this method, the switching process of transmitting and receiving can be performed without performing detailed calculation processing for determining the switching timing of transmitting and receiving the wireless signal in the slave station device. Therefore, in the analog RoF system having the master station device and the slave station device, TDD can be realized with a simple structure.

[0058] Hereinafter, the embodiments of the present invention will be described using the accompanying drawings. In addition, the same or corresponding parts in the figures are marked with the same symbols, and their description is not repeated. In addition, at least a part of the embodiments described below can also be arbitrarily combined.

[0059] <First Embodiment>

[0060] [Structure and basic work]

[0061] Figure 1 1 is a diagram showing a configuration of a simulated RoF system according to a first embodiment of the present invention. Figure 1 , the simulated RoF system 301 has a master station device 101 and a plurality of slave station devices 201. Figure 1 , one slave station device 201 is representatively shown. The master station device 101 and the slave station device 201 are connected to each other via the optical fiber 191. The master station device 101 is connected between the base station device 111 and the slave station device 201. In addition, the master station device 101 and the plurality of slave station devices 201 may be connected via the optical fiber 191 and an optical coupler. In addition, the simulated RoF system 301 may also be a structure having one slave station device 201.

[0062] The master station device 101 and the slave station device 201 transmit and receive optical signals via the optical fiber 191, and the optical signals include communication data generated in the base station device 111. Hereinafter, the optical signal sent from the master station device 101 to the slave station device 201 is also referred to as a downlink optical signal, and the optical signal sent from the slave station device 201 to the master station device 101 is also referred to as an uplink optical signal.

[0063] The simulated RoF system 301 is used for a mobile wireless communication system using TDD. For example, the simulated RoF system 301 is used for mobile fronthaul and local 5G in a fifth generation mobile communication system (hereinafter also referred to as 5G) using TDD.

[0064] Figure 2 FIG. 1 is a diagram showing an example of a timing diagram of a communication frame of a mobile wireless communication system. Figure 2 In TDD, a communication frame F consisting of 10 subframes SF#0 to SF#9 is repeated. Each subframe SF includes two time slots S. For example, the period of a communication frame F is 10 milliseconds, the period of a subframe SF is 1 millisecond, and the period of a time slot S is 0.5 milliseconds.

[0065] Any of an uplink communication time slot US constituting an uplink communication period UP in TDD, a downlink communication time slot DS constituting a downlink communication period DP in TDD, and a special time slot SS as a switching period between the uplink communication period UP and the downlink communication period DP is allocated to the time slot S. The uplink communication period UP and the downlink communication period DP are repeated alternately.

[0066] exist Figure 2In the example shown, the downlink communication time slot DS is allocated to the time slots S#0 and S#1 in the subframe SF#0 and the time slots S#2 and S#3 in the subframe SF#1. The special time slot SS is allocated to the first time slot S#4 in the subframe SF#2. The uplink communication time slot US is allocated to the second time slot S#5 in the subframe SF#2, the time slots S#6 and S#7 in the subframe SF#3, and the first time slot S#8 in the subframe SF#4. The special time slot SS is allocated to the second time slot S#9 in the subframe SF#4. The downlink communication time slot DS is allocated to the time slots S#10 and S#11 in the subframe SF#5 and the time slots S#12 and S#13 in the subframe SF#6. The special time slot SS is allocated to the first time slot S#14 in the subframe SF#7. The uplink communication time slot US is allocated to the second time slot S#15 in subframe SF#7, time slots S#16 and S#17 in subframe SF#8, and the first time slot S#18 in subframe SF#9. The special time slot SS is allocated to the second time slot S#19 in subframe SF#9.

[0067] In the simulated RoF system 301 , the slave device 201 transmits communication data to the master device 101 in the uplink communication period UP, and the master device 101 transmits communication data to the slave device 201 in the downlink communication period DP.

[0068] More specifically, the master station device 101 receives an analog signal modulated by OFDM (Orthogonal Frequency Division Multiplexing) containing communication data from the base station device 111. The master station device 101 generates an IF (Intermediate Frequency) signal Fa by frequency converting the received analog signal. The IF signal Fa is an example of a master signal. The master station device 101 transmits a downlink optical signal containing the generated IF signal Fa to the slave station device 201 via the optical fiber 191 in the downlink communication period DP.

[0069] The slave station device 201 transmits and receives RF (Radio Frequency) signals via the switch device 151 and the antenna 161. More specifically, the slave station device 201 receives a downlink optical signal from the master station device 101 via the optical fiber 191. Then, the slave station device 201 obtains an IF signal Fa from the received downlink optical signal, and transmits a millimeter wave band RF signal based on the obtained IF signal Fa via the switch device 151 and the antenna 161.

[0070] In addition, the slave station device 201 receives an OFDM-modulated millimeter wave band RF signal containing communication data from a mobile communication terminal (not shown) via the antenna 161 and the switch device 151, and generates an IF signal Fb by frequency converting the received RF signal. The slave station device 201 transmits an uplink optical signal containing the generated IF signal Fb to the master station device 101 via the optical fiber 191 in the uplink communication period UP.

[0071] The master station device 101 receives an uplink optical signal from the slave station device 201 via the optical fiber 191. The master station device 101 acquires an IF signal Fb from the received uplink optical signal, and transmits a signal based on the acquired IF signal Fb to the base station device 111.

[0072] The slave station device 201 transmits a TDD signal Std2 for controlling the state of the switch device 151 to the switch device 151. The switch device 151 switches between a transmission state in which the antenna 161 is connected to a transmission circuit of an RF signal in the slave station device 201 and a reception state in which the antenna 161 is connected to a reception circuit of an RF signal in the slave station device 201, according to the TDD signal Std2 received from the slave station device 201.

[0073] Figure 3 1 is a diagram showing the configuration of a master station device according to a first embodiment of the present invention. Figure 3 The master station device 101 includes a synchronization processing unit 11, a TDD processing unit 12, a frame processing unit 13, a frequency conversion unit 14, a multiplexing unit 15, a separation unit 16, an optical modulation unit 17, an optical demodulation unit 18, and an optical coupler CP1. The TDD processing unit 12 is an example of a control information generation unit. The optical modulation unit 17 is an example of a transmission unit.

[0074] The synchronization processing unit 11 receives a reference clock from an oscillator external to or internal to the master station device 101, and generates a local clock CL1 by dividing or multiplying the received reference clock. The synchronization processing unit 11 counts according to the timing of the generated local clock CL1 and holds the count value. Each unit in the master station device 101 operates based on the local clock CL1.

[0075] The synchronization processing unit 11 receives a reference signal from the base station device 111. For example, the synchronization processing unit 11 receives a clock signal, a GNSS (Global Navigation Satellite System) signal, or a grandmaster clock signal as a reference signal from the base station device 111. The synchronization processing unit 11 performs a base station synchronization process for synchronizing the count value of the local clock CL1 with the base station device 111 based on the received reference signal. For example, when the wiring between the base station device 111 and the master station device 101 is short, the synchronization processing unit 11 performs the base station synchronization process based on the reference signal without considering the transmission delay of the reference signal between the base station device 111 and the master station device 101.

[0076] The frame processing unit 13 generates an Ethernet (registered trademark) frame addressed to the slave device 201, in which information to be transmitted to the slave device 201 is stored in a payload. The frame processing unit 13 outputs the digital signal Da including the generated Ethernet frame to the multiplexing unit 15.

[0077] The frequency converter 14 receives an OFDM-modulated analog signal including communication data from the base station device 111. The frequency converter 14 may be configured to receive an analog signal in an RF band or a baseband. The frequency converter 14 generates an IF signal Fa by up-converting or down-converting the received analog signal, and outputs the generated IF signal Fa to the multiplexing unit 15.

[0078] The multiplexing unit 15 frequency-multiplexes the digital signal Da received from the frame processing unit 13 and the IF signal Fa received from the frequency conversion unit 14. The multiplexing unit 15 generates an electrical signal by frequency-multiplexing the digital signal Da and the IF signal Fa, and outputs the signal to the optical modulation unit 17.

[0079] The optical modulator 17 receives the electrical signal from the multiplexer 15 and generates a downstream optical signal having a wavelength λ1 by optically modulating the received electrical signal. The optical modulator 17 outputs the downstream optical signal to the optical fiber 191 via the optical coupler CP1 in the downstream communication period DP.

[0080] In this way, by generating the digital signal Da and the IF signal Fa in different units and transmitting the downstream optical signal including the generated digital signal Da and the IF signal Fa to the slave station device 201, it is possible to suppress the degradation of the signal quality of the IF signal Fa and the transmission delay of the IF signal Fa.

[0081] In addition, the master station device 101 may also be a structure that receives the IF signal Fa from the base station device 111 and transmits the downlink optical signal including the received IF signal Fa to the slave station device 201 via the optical fiber 191. More specifically, the master station device 101 may also be a structure that does not include the frequency conversion unit 14. In this case, the multiplexing unit 15 receives the IF signal Fa from the base station device 111, and frequency-multiplexes the digital signal Da received from the frame processing unit 13 and the IF signal Fa received from the base station device 111.

[0082] Figure 4 1 is a diagram showing a configuration of a slave device according to a first embodiment of the present invention. Figure 4 The slave station device 201 has a synchronization processing unit 21, a TDD processing unit 22, a frame processing unit 23, an RF transceiver unit 24, a separation unit 25, a multiplexing unit 26, an optical demodulation unit 27, an optical modulation unit 28, and an optical coupler CP2. The RF transceiver unit 24 is an example of a wireless transceiver. The RF transceiver 24 includes a receiving circuit (not shown) for receiving an RF signal and a transmitting circuit (not shown) for transmitting an RF signal. The optical demodulation unit 27 is an example of a receiving unit. The frame processing unit 23 is an example of an acquisition unit. The TDD processing unit 22 is an example of a control unit.

[0083] The synchronization processing unit 21 receives a reference clock from an external or internal oscillator of the slave device 201, for example, and generates a local clock CL2 by dividing or multiplying the received reference clock. The synchronization processing unit 21 counts according to the timing of the generated local clock CL2 and holds the count value. Each unit in the slave device 201 operates based on the local clock CL2. The frequency of the local clock CL2 is set to be equal to the local clock CL1 of the master device 101.

[0084] The optical demodulator 27 receives a downstream optical signal from the master station 101 via the optical fiber 191 and the optical coupler CP2 , and generates an electrical signal based on the received downstream optical signal. More specifically, the optical demodulator 27 generates an electrical signal of a level corresponding to the intensity of the received downstream optical signal, and outputs it to the separator 25 .

[0085] The separator 25 receives the electrical signal from the optical demodulator 27, separates the IF signal Fa and the digital signal Da contained in the received electrical signal, outputs the IF signal Fa to the RF transceiver 24, and outputs the digital signal Da to the frame processor 23. For example, the separator 25 is a duplexer composed of an HPF (High Pass Filter) and an LPF. The separator 25 outputs the frequency components above the frequency Fx in the electrical signal received from the optical demodulator 27 as the IF signal Fa to the RF transceiver 24, and outputs the frequency components below the frequency Fx as the digital signal Da to the frame processor 23. Here, the frequency Fx is lower than the center frequency of the IF signal Fa.

[0086] For example, the RF transceiver 24 amplifies the IF signal Fa received from the separator 25. The RF transceiver 24 generates an RF signal by up-converting the amplified IF signal Fa, and outputs the generated RF signal to the antenna 161 via the switch device 151.

[0087] The frame processing unit 23 receives the digital signal Da from the separation unit 25, and obtains an Ethernet frame from the received digital signal Da. When the destination MAC address included in the obtained Ethernet frame does not match the MAC address of the slave station device 201, the frame processing unit 23 discards the Ethernet frame. On the other hand, when the destination MAC address included in the obtained Ethernet frame matches the MAC address of the slave station device 201, the frame processing unit 23 obtains information from the payload of the Ethernet frame.

[0088] Furthermore, the frame processing unit 23 generates an Ethernet frame addressed to the master station device 101 and storing information to be transmitted to the master station device 101 in a payload. The frame processing unit 23 outputs the digital signal Db including the generated Ethernet frame to the multiplexing unit 26 .

[0089] The RF transceiver 24 receives an OFDM-modulated analog signal in the RF band including communication data from a mobile communication terminal (not shown) via the antenna 161 and the switch device 151. The RF transceiver 24 generates an IF signal Fb by down-converting the received analog signal and outputs the generated IF signal Fb to the multiplexer 26.

[0090] The multiplexer 26 frequency-multiplexes the digital signal Db received from the frame processor 23 and the IF signal Fb received from the RF transceiver 24. The multiplexer 26 generates an electrical signal by frequency-multiplexing the digital signal Db and the IF signal Fb, and outputs the signal to the optical modulator 28.

[0091] The optical modulation unit 28 transmits the uplink optical signal including the digital signal Db and the IF signal Fb to the master station device 101 via the optical fiber 191. More specifically, the optical modulation unit 28 receives the electrical signal from the multiplexing unit 26, and generates an uplink optical signal of wavelength λ2 by optically modulating the received electrical signal. The optical modulation unit 28 outputs the uplink optical signal to the optical fiber 191 via the optical coupler CP2 in the uplink communication period UP.

[0092] Refer again Figure 3 The optical demodulator 18 in the master station device 101 receives the uplink optical signal from the slave station device 201 via the optical fiber 191 and the optical coupler CP1, and generates an electrical signal based on the received uplink optical signal. More specifically, the optical demodulator 18 generates an electrical signal of a level corresponding to the intensity of the received uplink optical signal, and outputs it to the separator 16.

[0093] The separator 16 receives the electrical signal from the optical demodulator 18, separates the IF signal Fb and the digital signal Db contained in the received electrical signal, outputs the IF signal Fb to the frequency converter 14, and outputs the digital signal Db to the frame processor 13. For example, the separator 16 is a duplexer composed of an HPF and an LPF. The separator 16 outputs the frequency components above the frequency Fy in the electrical signal received from the optical demodulator 18 as the IF signal Fb to the frequency converter 14, and outputs the frequency components below the frequency Fy as the digital signal Db to the frame processor 13. Here, the frequency Fy is lower than the center frequency of the IF signal Fb.

[0094] For example, the frequency converter 14 generates an RF signal by up-converting the IF signal Fb received from the separator 16, and transmits the generated RF signal to the base station apparatus 111. Alternatively, the frequency converter 14 generates a baseband signal by down-converting the IF signal Fb received from the separator 16, and transmits the generated baseband signal to the base station apparatus 111. In addition, as described above, the master station apparatus 101 may also be configured not to include the frequency converter 14. In this case, the separator 16 transmits the IF signal Fb to the base station apparatus 111.

[0095] The frame processing unit 13 receives the digital signal Db from the separation unit 16, obtains an Ethernet frame from the received digital signal Db, and obtains information from the payload of the Ethernet frame.

[0096] (Inter-station synchronization processing)

[0097] The synchronization processing unit 11 in the master station device 101 and the synchronization processing unit 21 in the slave station device 201 perform inter-station synchronization processing to synchronize the count value of the local clock CL1 of the master station device 101 with the count value of the local clock CL2 of the slave station device 201 at synchronization processing timing according to a predetermined cycle, for example.

[0098] More specifically, the synchronization processing unit 11 acquires the current count value of the local clock CL1 in the inter-station synchronization process, generates count information indicating the acquired count value, and outputs the count information to the frame processing unit 13 .

[0099] The frame processing unit 13 receives the count information from the synchronization processing unit 11, generates an Ethernet frame to be sent to the slave station device 201 in which the received count information is stored in the payload, and outputs the digital signal Da1 including the generated Ethernet frame to the multiplexing unit 15. The digital signal Da1 output from the frame processing unit 13 to the multiplexing unit 15 is frequency-multiplexed with the IF signal Fa by the multiplexing unit 15, is included in the downstream optical signal by the optical modulation unit 17, and is sent to the slave station device 201.

[0100] Refer again Figure 4 , the frame processing unit 23 in the slave station device 201 loops back the counting information generated in the master station device 101 in the inter-station synchronization process. More specifically, the frame processing unit 23 obtains an Ethernet frame from the digital signal Da1 received from the separation unit 25, and obtains the counting information from the payload of the Ethernet frame. The frame processing unit 23 generates an Ethernet frame to be sent to the master station device 101, storing the obtained counting information in the payload, and outputs the digital signal Db1 containing the generated Ethernet frame to the multiplexing unit 26. The digital signal Db1 output by the frame processing unit 23 to the multiplexing unit 26 is frequency-multiplexed with the IF signal Fb by the multiplexing unit 26, and is included in the uplink optical signal by the optical modulation unit 28, and is sent to the master station device 101.

[0101] Refer again Figure 3 The frame processing unit 13 in the master station device 101 receives the digital signal Db1 from the separation unit 25 , obtains an Ethernet frame from the received digital signal Db1 , and obtains count information from the payload of the Ethernet frame. The frame processing unit 13 outputs the obtained count information to the synchronization processing unit 11 .

[0102] The synchronization processing unit 11 receives the count information from the frame processing unit 13, and calculates the difference between the count value indicated by the count information and the current count value of the local clock CL1 as the RTT (Round Trip Time) of the count information. In addition, the synchronization processing unit 11 calculates 1 / 2 of the RTT as the transmission delay time DT between the master station device 101 and the slave station device 201.

[0103] When calculating the transmission delay time DT, the synchronization processing unit 11 obtains the current count value of the local clock CL1 and generates synchronization information including the synchronization time ST1 obtained by adding the transmission delay time DT to the obtained count value. The synchronization processing unit 11 outputs the generated synchronization information to the frame processing unit 13.

[0104] The frame processing unit 13 receives the synchronization information from the synchronization processing unit 11, generates an Ethernet frame to be sent to the slave station device 201, storing the received synchronization information in the payload, and outputs the digital signal Da2 including the generated Ethernet frame to the multiplexing unit 15. The digital signal Da2 output from the frame processing unit 13 to the multiplexing unit 15 is frequency-multiplexed with the IF signal Fa by the multiplexing unit 15, and is included in the downstream optical signal by the optical modulation unit 17, and is sent to the slave station device 201.

[0105] Refer again Figure 4 The frame processing unit 23 in the slave station device 201 obtains an Ethernet frame from the digital signal Da2 received from the separation unit 25 and obtains synchronization information from the payload of the Ethernet frame. The frame processing unit 23 outputs the obtained synchronization information to the synchronization processing unit 21.

[0106] The synchronization processing unit 21 receives the synchronization information from the frame processing unit 23, and updates the count value of the local clock CL2 based on the received synchronization information. That is, the synchronization processing unit 21 sets the count value of the local clock CL2 to the synchronization time ST1 included in the synchronization information. As a result, the count value of the local clock CL2 of the slave station device 201 is synchronized with the count value of the local clock CL2 of the master station device 101.

[0107] Furthermore, the synchronization processing unit 11 in the master station device 101 and the synchronization processing unit 21 in the slave station device 201 may be configured to synchronize the count value of the local clock CL1 and the count value of the local clock CL2 in accordance with IEEE 1588.

[0108] (Switch Process)

[0109] Refer again Figure 1 The master station device 101 generates control information used in controlling the transmission and reception of the RF signal, and sends a downlink optical signal including a digital signal Da3 containing the generated control information and an IF signal Fa to the slave station device 201 via the optical fiber 191.

[0110] The slave station device 201 obtains control information from the digital signal Da3 included in the downstream optical signal received from the master station device 101 via the optical fiber 191 , and performs switching processing for switching the transmission and reception of RF signals via the antenna 161 based on the obtained control information.

[0111] Figure 5 FIG. 1 is a diagram showing an example of a TDD signal transmitted by a base station apparatus according to the first embodiment of the present invention. Figure 5, the base station device 111 continuously transmits a rectangular wave TDD signal Std1 indicating an uplink communication period UP and a downlink communication period DP in TDD to the master station device 101. The TDD signal Std1 is an example of a mode signal.

[0112] As an example, the TDD signal Std1 is set to a high level in the downlink communication time slot DS, and is set to a low level in the uplink communication time slot US. For example, the TDD signal Std1 changes from a high level to a low level at the timing of switching from the downlink communication time slot DS to the special time slot SS, and changes from a low level to a high level at the timing of switching from the special time slot SS to the downlink communication time slot DS.

[0113] The TDD processing unit 12 in the master station device 101 receives the TDD signal Std1 from the base station device 111, and generates control information based on the received TDD signal Std1. As an example, the TDD processing unit 12 generates control information at the generation timing of the predetermined generation cycle Cy. For example, the length of the generation cycle Cy is 10 milliseconds, which is equivalent to one cycle of the communication frame F. In addition, the length of the generation cycle Cy may also be equivalent to the length of multiple cycles of the communication frame F.

[0114] For example, the TDD processing unit 12 determines the transition time tr which is the timing when the TDD signal Std1 transitions from the low level to the high level and the transition time tf which is the timing when the TDD signal Std1 transitions from the high level to the low level.

[0115] In more detail, when the TDD processing unit 12 detects that the TDD signal Std1 changes from a low level to a high level, it obtains the current count value of the local clock CL1 held by the synchronization processing unit 11 as the first transition time tr, that is, the transition time tr1. Next, when the TDD processing unit 12 detects that the TDD signal Std1 changes from a high level to a low level, it obtains the current count value of the local clock CL1 held by the synchronization processing unit 11 as the first transition time tf, that is, the transition time tf1. Next, when the TDD processing unit 12 detects that the TDD signal Std1 changes from a low level to a high level, it obtains the current count value of the local clock CL1 held by the synchronization processing unit 11 as the second transition time tr, that is, the transition time tr2. Next, when the TDD processing unit 12 detects that the TDD signal Std1 changes from a high level to a low level, it obtains the current count value of the local clock CL1 held by the synchronization processing unit 11 as the second transition time tf, that is, the transition time tf2. In addition, the TDD processing unit 12 may be configured to obtain an absolute time instead of a count value as the transition time tr, tf.

[0116] Then, the TDD processing unit 12 generates a switching pattern of the transmission and reception operation of the RF signal via the antenna 161 in the slave station device 201 including the transition times tr1 , tf1 , tr2 , and tf2 determined within the previous 10 milliseconds.

[0117] When generating a switching pattern, the TDD processing unit 12 sets the start timing ts of the switching process using the switching pattern. As an example, the TDD processing unit 12 sets the start timing ts to the time obtained by adding the transition time tr1, which is the earliest time among the transition times tr1, tf1, tr2, and tf2, and the margin time Tm of a predetermined length. The margin time Tm is, for example, 10 milliseconds corresponding to one cycle of the communication frame F.

[0118] Refer again Figure 3 The TDD processing unit 12 generates a switching pattern and sets a start timing ts at a generation timing based on the generation cycle Cy, and generates control information including the generated switching pattern and start timing ts. For example, the TDD processing unit 12 generates control information including a different start timing ts for each slave station device 201. More specifically, the TDD processing unit 12 sets a start timing ts added with a margin time Tm of a different length for each slave station device 201. The TDD processing unit 12 outputs the generated control information to the frame processing unit 13.

[0119] The frame processing unit 13 receives the control information from the TDD processing unit 12 , generates an Ethernet frame addressed to the slave station device 201 in which the received control information is stored in a payload, and outputs a digital signal Da3 including the generated Ethernet frame to the multiplexing unit 15 .

[0120] The multiplexing unit 15 frequency-multiplexes the digital signal Da3 received from the frame processing unit 13 and the IF signal Fa received from the frequency conversion unit 14. The multiplexing unit 15 generates an electrical signal by frequency-multiplexing the digital signal Da3 and the IF signal Fa, and outputs the signal to the optical modulation unit 17.

[0121] The optical modulation unit 17 transmits the downstream optical signal including the digital signal Da3 and the IF signal Fa to the slave station device 201 via the optical fiber 191. More specifically, the optical modulation unit 17 receives the electrical signal from the multiplexing unit 15, and generates a downstream optical signal by optically modulating the received electrical signal. The optical modulation unit 17 outputs the downstream optical signal to the optical fiber 191 via the optical coupler CP1 in the downstream communication period DP.

[0122] Refer again Figure 4The optical demodulator 27 in the slave station device 201 receives the downstream optical signal including the digital signal Da3 and the IF signal Fa from the master station device 101 via the optical fiber 191. The optical demodulator 27 generates an electrical signal of a level corresponding to the intensity of the received downstream optical signal and outputs it to the separator 25.

[0123] The separator 25 receives the electrical signal from the optical demodulator 27 , separates the IF signal Fa and the digital signal Da3 included in the received electrical signal, outputs the IF signal Fa to the RF transceiver 24 , and outputs the digital signal Da3 to the frame processor 23 .

[0124] The frame processing unit 23 obtains control information from the digital signal Da3 included in the downstream optical signal received by the optical modulation unit 17. More specifically, the frame processing unit 23 receives the digital signal Da3 from the separation unit 25, obtains an Ethernet frame from the received digital signal Da3, and obtains control information from the payload of the Ethernet frame. The frame processing unit 23 outputs the obtained control information to the TDD processing unit 22.

[0125] The TDD processing unit 22 performs a switching process for the RF transceiver unit 24 to perform the transmission operation and the reception operation of the RF signal based on the control information acquired by the frame processing unit 23 .

[0126] Figure 6 FIG. 1 is a diagram showing an example of a TDD signal generated by a TDD processing unit in a slave station device according to the first embodiment of the present invention. Figure 6 The TDD processing unit 22 receives control information from the frame processing unit 23, generates a TDD signal Std2 based on the switching pattern included in the received control information, and sends the generated TDD signal Std2 to the switching device 151 at the start timing ts included in the control information.

[0127] Here, the length of the optical fiber 191 connecting the master station device 101 and the slave station device 201 is, for example, about 30 km, and a transmission delay corresponding to the length of the optical fiber 191 may occur between the master station device 101 and the slave station device 201. By setting the time obtained by adding the transition time tr1 and the margin time Tm to the start timing ts in the master station device 101, the control information can be received in the slave station device 201 before the set start timing ts, and the TDD signal Std2 can be sent to the switch device 151 at the start timing ts.

[0128] The switch device 151 connects the antenna 161 and the transmitting circuit in the RF transceiver unit 24 while the TDD signal Std2 received from the slave station device 201 is at a high level, and connects the antenna 161 and the receiving circuit in the RF transceiver unit 24 while the TDD signal Std2 received from the slave station device 201 is at a low level.

[0129] In addition, the TDD processing unit 22 may also be configured to correct the start timing ts included in the control information and start the switching process based on the control information at the corrected start timing tsx. More specifically, the TDD processing unit 22 determines the start timing tsx by adding the delay time required for processing the control information to the start timing ts, and sends the generated TDD signal Std2 to the switch device 151 at the determined start timing tsx.

[0130] [Work flow]

[0131] Each device in the simulated RoF system of the embodiment of the present invention includes a computer including a memory, and a CPU or other processing unit in the computer reads and executes a program including a part or all of each step of the following flowchart and sequence from the memory. The programs of these multiple devices can be installed from the outside. The programs of these multiple devices are circulated in a state stored in a recording medium or via a communication line.

[0132] Figure 7 This is a diagram showing an example of a communication sequence in a simulated RoF system according to the first embodiment of the present invention.

[0133] Reference Figure 7 First, the master station device 101 performs a base station synchronization process to synchronize the count value of the local clock CL1 with that of the base station device 111 (step S11).

[0134] Next, the master station 101 and the slave station 201 perform an inter-station synchronization process to synchronize the count value of the local clock CL1 in the master station 101 with the count value of the local clock CL2 in the slave station 201 at synchronization process timing in a predetermined cycle (step S12).

[0135] Next, the master station device 101 determines the transition times tr1 and tr2, which are the timings at which the TDD signal Std1 received from the base station device 111 changes from a low level to a high level, and the transition times tf1 and tf2, which are the timings at which the TDD signal Std1 changes from a high level to a low level, and generates control information including a switching pattern including the transition times tr1, tf1, tr2, and tf2 and a start timing ts (step S13).

[0136] Next, the master device 101 generates an Ethernet frame to be addressed to the slave device 201 in which the generated control information is stored in a payload, and generates a digital signal Da3 including the generated Ethernet frame (step S14).

[0137] Next, the master station device 101 frequency-multiplexes the digital signal Da3 and the IF signal Fa, and transmits a downstream optical signal including the digital signal Da3 and the IF signal Fa to the slave station device 201 via the optical fiber 191 (step S15).

[0138] Next, the slave station device 201 receives the downstream optical signal from the master station device 101 via the optical fiber 191, and acquires the digital signal Ds3 from the received downstream optical signal (step S16).

[0139] Next, the slave device 201 acquires control information from the digital signal Ds3 (step S17).

[0140] Next, the slave device 201 performs a switching process based on the acquired control information. More specifically, the slave device 201 generates the TDD signal Std2 based on the switching pattern included in the control information, and transmits the TDD signal Std2 to the switch device 151 at the start timing ts included in the control information (step S18).

[0141] In the pseudo RoF system 301 of the first embodiment of the present invention, the slave station device 201 transmits and receives RF signals via the switch device 151 and the antenna 161 , but the present invention is not limited thereto.

[0142] However, in the pseudo RoF system 301 including the master station device 101 and the slave station device 201 , a technology capable of realizing TDD with a simple configuration is desired.

[0143] For example, in a mobile wireless communication system adopting TDD, it is desirable to control the transmission timing of an RF signal with high accuracy in order to suppress radio wave interference.

[0144] In addition, for example, in a mobile wireless communication system using a millimeter wave band, since the coverage area of ​​the antenna 161 is small, it is necessary to densely install more slave station devices 201 and antennas 161. Therefore, in order to realize a mobile wireless communication system using a millimeter wave band with a low cost and a simple structure, it is desirable to simplify the structure of the slave station device 201.

[0145] In this regard, in the analog RoF system 301 of the first embodiment of the present invention, the master station device 101 generates control information used for controlling the transmission and reception operation of the RF signal, and transmits a downstream optical signal including a digital signal Ds3 including the generated control information and an IF signal Fa to the slave station device 201 via the optical fiber 191. The slave station device 201 acquires the control information from the digital signal Ds3 included in the downstream optical signal received from the master station device 101 via the optical fiber 191, and performs switching processing of the transmission operation and the reception operation of the RF signal via the antenna 161 based on the acquired control information.

[0146] In this way, the master station device 101 transmits a downlink optical signal including the digital signal Ds3 and the IF signal Fa to the slave station device 201 via the optical fiber 191, and the slave station device 201 obtains control information from the digital signal Ds3 included in the downlink optical signal, and performs switching processing of the transmission operation and the reception operation of the RF signal via the antenna 161 based on the obtained control information. According to such a structure, the control information can be transmitted from the master station device 101 to the slave station device 201 via the optical fiber 191, and the transmission and reception operation of the slave station device 201 can be switched. Therefore, in the analog RoF system 301 having the master station device 101 and the slave station device 201, TDD can be realized with a simple structure.

[0147] Furthermore, by changing the content of the control information generated in the master station device 101 , the content of the switching process of the transmission and reception operations in the slave station device 201 can be flexibly changed.

[0148] Next, other embodiments of the present invention will be described using the accompanying drawings. In addition, the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0149] <Second Embodiment>

[0150] Compared with the pseudo RoF system 301 of the first embodiment, the present embodiment relates to a pseudo RoF system 302 that transmits control information further including a configuration number indicating the type of a TDD signal Std1. Except for the following contents, the present embodiment is the same as the pseudo RoF system 301 of the first embodiment.

[0151] Figure 8 2 is a diagram showing a configuration of a simulated RoF system according to a second embodiment of the present invention. Figure 8 ,and Figure 1 Compared with the simulated RoF system 301 shown, the simulated RoF system 302 has a master station device 102 instead of the master station device 101 , and has a slave station device 202 instead of the slave station device 201 .

[0152] Fig. 92 is a diagram showing the configuration of a master station device according to a second embodiment of the present invention. Fig. 9 ,and Figure 3 Compared with the master station device 101 shown, the master station device 102 includes a TDD processing unit 32 instead of the TDD processing unit 12 , and further includes an information storage unit 31 .

[0153] Fig.10 FIG. 2 is a diagram showing an example of a correspondence table held by an information storage unit in a master station device according to a second embodiment of the present invention. Fig.10 The information storage unit 31 holds a correspondence table TB1 indicating the correspondence between the allocation pattern PT of the time slot S in the communication frame F and the configuration number as the identification information of the TDD signal Std1. The correspondence table TB1 is an example of the correspondence information. The pattern of the time slot S in the communication frame F indicates the type of the TDD signal Std1.

[0154] The correspondence table TB1 shows that the TDD signal Std1 with the configuration number "C1" corresponds to the allocation pattern PT of 4 downlink communication time slots DS and 4 uplink communication time slots US, which are repeated alternately with special time slots SS. In addition, the correspondence table TB1 shows that the TDD signal Std1 with the configuration number "C2" corresponds to the allocation pattern PT of 9 downlink communication time slots DS and 9 uplink communication time slots US, which are repeated alternately with special time slots SS. In addition, the correspondence table TB1 shows that the TDD signal Std1 with the configuration number "C3" corresponds to the allocation pattern PT of 4 downlink communication time slots DS and 2 uplink communication time slots US, which are repeated alternately with special time slots SS. In addition, the correspondence table TB1 shows that the TDD signal Std1 with the configuration number "C4" corresponds to the allocation pattern PT of 4 uplink communication time slots US and 2 downlink communication time slots DS, which are repeated alternately with special time slots SS. Furthermore, the correspondence table TB1 shows that the TDD signal Std1 with the configuration number "C11" corresponds to the allocation pattern PT in which the time slots S#3 to S#5 are changed from the downlink communication time slots DS to the uplink communication time slots US in the allocation pattern PT of the TDD signal Std1 with the configuration number "C2".

[0155] The correspondence table TB1 stored in the information storage unit 31 may be updated by a control device (not shown). When the correspondence table TB1 in the information storage unit 31 is updated, the master device 102 transmits the updated correspondence table TB1 to the slave device 202 .

[0156] When acquiring the transition times tr and tf of the TDD signal Std1 received from the base station apparatus 111 , the TDD processing unit 32 generates a switching pattern including the acquired transition times tr and tf and sets a start timing ts.

[0157] Furthermore, the TDD processing unit 32 refers to the correspondence table TB1 in the information storage unit 31 to obtain the configuration number corresponding to the TDD signal Std1 received from the base station apparatus 111. More specifically, the TDD processing unit 32 obtains the configuration number corresponding to the type of the TDD signal Std1 indicated by the obtained transition times tr, tf.

[0158] Then, the TDD processing unit 32 generates control information including the switching pattern, the start timing ts, and the acquired configuration number, and outputs the generated control information to the frame processing unit 13 .

[0159] The frame processing unit 13 receives the control information from the TDD processing unit 32 , generates an Ethernet frame to be addressed to the slave station device 201 in which the received control information is stored in a payload, and outputs a digital signal Da4 including the generated Ethernet frame to the multiplexing unit 15 .

[0160] The multiplexing unit 15 frequency-multiplexes the digital signal Da4 received from the frame processing unit 13 and the IF signal Fa received from the frequency conversion unit 14. The multiplexing unit 15 generates an electrical signal by frequency-multiplexing the digital signal Da4 and the IF signal Fa, and outputs the signal to the optical modulation unit 17.

[0161] The optical modulation unit 17 transmits the downstream optical signal including the digital signal Da4 and the IF signal Fa to the slave station device 202 via the optical fiber 191. More specifically, the optical modulation unit 17 receives the electrical signal from the multiplexing unit 15, and generates a downstream optical signal by optically modulating the received electrical signal. The optical modulation unit 17 outputs the downstream optical signal to the optical fiber 191 via the optical coupler CP1 in the downstream communication period DP.

[0162] Fig.11 2 is a diagram showing a configuration of a slave device according to a second embodiment of the present invention. Fig.11 ,and Figure 4 Compared with the slave station device 201 shown, the slave station device 202 includes a TDD processing unit 42 instead of the TDD processing unit 22 , and further includes an information storage unit 41 .

[0163] Similar to the information storage unit 31 in the master station device 102 , the information storage unit 41 holds a correspondence table TB1 .

[0164] The optical demodulator 27 receives a downstream optical signal including the digital signal Da4 and the IF signal Fa from the master station device 101 via the optical fiber 191 , generates an electrical signal of a level corresponding to the intensity of the received downstream optical signal, and outputs the electrical signal to the separator 25 .

[0165] The separator 25 receives the electrical signal from the optical demodulator 27 , separates the IF signal Fa and the digital signal Da4 included in the received electrical signal, outputs the IF signal Fa to the RF transceiver 24 , and outputs the digital signal Da4 to the frame processor 23 .

[0166] The frame processing unit 23 receives the digital signal Da4 from the separation unit 25 , obtains an Ethernet frame from the received digital signal Da4 , and obtains control information from the payload of the Ethernet frame. The frame processing unit 23 outputs the obtained control information to the TDD processing unit 42 .

[0167] The TDD processing unit 42 receives control information from the frame processing unit 23, and obtains the configuration number from the received control information. The TDD processing unit 42 refers to the correspondence table TB1 in the information storage unit 41, and obtains the allocation pattern PT corresponding to the obtained configuration number. The TDD processing unit 42 generates a TDD signal Std2 based on the obtained allocation pattern PT, and transmits the generated TDD signal Std2 to the switch device 151 at the start timing ts included in the control information.

[0168] In addition, the TDD processing unit 42 may also be configured to correct the start timing ts included in the control information and start the switching process based on the control information at the corrected start timing tsx. For example, the TDD processing unit 42 corrects the start timing ts included in the control information received from the frame processing unit 23 based on the acquired allocation pattern PT. More specifically, when the difference between the transition time tr, tf included in the control information and the transition time tr, tf estimated based on the acquired allocation pattern PT is greater than a predetermined value, the TDD processing unit 42 corrects the start timing ts included in the control information so that the difference becomes smaller.

[0169] Furthermore, for example, the TDD processing unit 42 may be configured to perform error correction on the TDD signal Std2 generated based on the switching pattern based on the acquired allocation pattern PT, or may be configured to perform distortion correction on the duty ratio of the generated TDD signal Std2.

[0170] In addition, in the simulated RoF system 302 of the second embodiment of the present invention, the TDD processing unit 32 in the master station device 102 adopts a structure that obtains the configuration number corresponding to the TDD signal Std1 received from the base station device 111, but is not limited to this. The TDD processing unit 32 may also be a structure that receives notification of the configuration number from the base station device 111. In this case, the TDD processing unit 32 generates control information including the notified configuration number and outputs it to the frame processing unit 23. In addition, in this case, the TDD processing unit 32 may also be a structure that does not receive the TDD signal Std1 from the base station device 111.

[0171] Next, other embodiments of the present invention will be described using the accompanying drawings. In addition, the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated.

[0172] <Third Embodiment>

[0173] Compared with the simulated RoF system 302 of the second embodiment, this embodiment relates to a simulated RoF system 303 that generates control information based on the mode information received from the management device 171 in the mobile wireless communication system. Except for the following contents, it is the same as the simulated RoF system 302 of the second embodiment.

[0174] Fig.12 2 is a diagram showing a configuration of a simulated RoF system according to a third embodiment of the present invention. Fig.12 ,and Figure 8 Compared with the simulated RoF system 302 shown, the simulated RoF system 303 has the master station device 103 instead of the master station device 102 , and has the slave station device 203 instead of the slave station device 202 .

[0175] The slave station device 203 receives pattern information indicating the uplink communication period UP and the downlink communication period DP in TDD from a device other than the master station device 103 outside the slave station device 203. For example, the slave station device 203 receives the pattern information from the management device 171 in the mobile wireless communication system.

[0176] In more detail, in order to improve the link speed of uplink communication according to the communication status of the mobile communication terminal in the mobile wireless communication system, the management device 171 sometimes changes a part of the downlink communication period DP in TDD to the uplink communication period UP in, for example, a part of the slave station device 203. In the case of changing a part of the downlink communication period DP to the uplink communication period UP, the management device 171 generates pattern information including a configuration number corresponding to the allocation pattern PT of the time slot S of the uplink communication period UP and the downlink communication period DP after the change. And the management device 171 generates a frame to the slave station device 203 storing the generated pattern information, and transmits an RF signal including the generated frame. In addition, in order to improve the link speed of downlink communication, the management device 171 may also change a part of the uplink communication period UP to the downlink communication period DP, and generate pattern information including a configuration number corresponding to the allocation pattern PT of the time slot S of the uplink communication period UP and the downlink communication period DP after the change. In addition, the management device 171 may also be a structure that transmits the frame including the pattern information to the slave station device 203 via a wired transmission path.

[0177] Fig.13 2 is a diagram showing a configuration of a master station device according to a third embodiment of the present invention. Fig.13 ,and Fig. 9 Compared with the master station device 102 shown in FIG. 1 , the master station device 103 includes a TDD processing unit 52 instead of the TDD processing unit 32 .

[0178] Fig.14 2 is a diagram showing a configuration of a slave device according to a third embodiment of the present invention. Fig.14 ,and Fig.11 Compared with the slave station device 202 shown in the figure, the slave station device 203 includes a TDD processing unit 62 instead of the TDD processing unit 42 .

[0179] The TDD processing unit 62 receives the RF signal including the mode information from the management device 171 via the antenna 161 and the switch device 151. The TDD processing unit 62 acquires the mode information from the received RF signal and outputs the acquired mode information to the frame processing unit 23.

[0180] The frame processing unit 23 receives the mode information from the TDD processing unit 62, generates an Ethernet frame to be sent to the master station device 103 in which the received mode information is stored in the payload, and outputs the digital signal Db2 including the generated Ethernet frame to the multiplexing unit 26. The digital signal Db2 is an example of a second digital signal. The digital signal Db2 output by the frame processing unit 23 to the multiplexing unit 26 is frequency-multiplexed with the IF signal Fb by the multiplexing unit 26, and is included in the uplink optical signal by the optical modulation unit 28, and is sent to the master station device 103.

[0181] Refer again Fig.13 The master station device 103 acquires the pattern information from the digital signal Db2 included in the uplink optical signal received from the slave station device 203, and generates control information reflecting the content of the acquired pattern information.

[0182] More specifically, the frame processing unit 13 in the master station device 103 receives the digital signal Db2 from the separator 25 , obtains an Ethernet frame from the received digital signal Db2 , and obtains mode information from the payload of the Ethernet frame. The frame processing unit 13 outputs the obtained mode information to the TDD processing unit 52 .

[0183] The TDD processing unit 52 receives the mode information from the frame processing unit 13 and acquires the configuration number from the received mode information. The TDD processing unit 52 refers to the correspondence table TB1 in the information storage unit 31 and acquires the allocation pattern PT corresponding to the acquired configuration number. The TDD processing unit 52 generates control information reflecting the acquired allocation pattern PT.

[0184] Refer again Fig.10For example, when the TDD processing unit 52 receives mode information including the configuration number "C11" from the frame processing unit 13, it obtains the allocation pattern PT corresponding to the configuration number "C11" and determines whether the obtained allocation pattern PT is in a quasi-synchronous state relative to the TDD signal Std1 received from the base station device 111.

[0185] Specifically, when the acquired allocation mode PT corresponds to an allocation mode in which a portion of the high-level period in the TDD signal Std1 is changed to a low-level period, the TDD processing unit 52 determines that the acquired allocation mode PT is in a quasi-synchronous state relative to the TDD signal Std1, generates control information including the configuration number "C11" and the start timing ts, and outputs the generated control information to the frame processing unit 13.

[0186] On the other hand, when the TDD processing unit 52 determines that the acquired allocation pattern PT is not in a quasi-synchronous state with respect to the TDD signal Std1 , it does not generate control information including the configuration number “ C11 ”.

[0187] The frame processing unit 13 receives the control information from the TDD processing unit 52, generates an Ethernet frame to be sent to the slave station device 203, storing the received control information in the payload, and outputs the digital signal Da3 including the generated Ethernet frame to the multiplexing unit 15. The digital signal Da1 output by the frame processing unit 13 to the multiplexing unit 15 is frequency-multiplexed with the IF signal Fa by the multiplexing unit 15, and is included in the downlink optical signal by the optical modulation unit 17, and is sent to the slave station device 203.

[0188] Fig.15 FIG. 1 is a diagram showing an example of a communication sequence in a simulated RoF system according to the third embodiment of the present invention. Fig.15 , the master station device 103 and the slave station device 203 communicate with Figure 7 The same processing as steps S11 to S18 shown above is the processing of steps S21 to S28.

[0189] Next, the slave station device 203 receives the mode information from the management device 171 in the mobile wireless communication system (step S29).

[0190] Next, the slave station device 203 generates an Ethernet frame that stores the received mode information in the payload and is sent to the master station device 103, performs frequency multiplexing on the digital signal Db2 and the IF signal Fb containing the generated Ethernet frame, and sends the uplink optical signal containing the digital signal Db2 and the IF signal Fb to the master station device 103 via the optical fiber 191 (step S30).

[0191] Next, the master station device 103 generates control information reflecting the content of the mode information received from the slave station device 203 (step S31).

[0192] Next, the master device 103 generates an Ethernet frame to be addressed to the slave device 203 in which the generated control information is stored in a payload, and generates a digital signal Da3 including the generated Ethernet frame (step S32 ).

[0193] Next, the master station device 103 frequency-multiplexes the digital signal Da3 and the IF signal Fa, and transmits a downstream optical signal including the digital signal Da3 and the IF signal Fa to the slave station device 203 via the optical fiber 191 (step S33).

[0194] Next, the slave station device 203 receives the downstream optical signal from the master station device 103 via the optical fiber 191, and acquires the digital signal Ds3 from the received downstream optical signal (step S34).

[0195] Next, the slave device 203 acquires control information from the digital signal Ds3 (step S35).

[0196] Next, the slave device 203 performs switching processing based on the acquired control information. More specifically, the slave device 203 generates the TDD signal Std2 based on the switching pattern included in the control information, and transmits the TDD signal Std2 to the switch device 151 at the start timing ts included in the control information (step S36).

[0197] In addition, in the simulated RoF system 303 of the third embodiment of the present invention, the TDD processing unit 52 in the master station device 103 adopts a structure that generates control information including the configuration number when the allocation pattern PT corresponding to the configuration number included in the mode information is in a quasi-synchronous state with respect to the TDD signal Std1, but is not limited to this. The TDD processing unit 52 may also be a structure that generates a switching pattern including transition times tr and tf based on the allocation pattern PT corresponding to the configuration number included in the mode information and the TDD signal Std1, and generates control information including the generated switching pattern. In this case, the TDD processing unit 52 may also generate a new switching pattern accompanied by a change in the length of the time slot S.

[0198] Each process (function) of the above-mentioned embodiment is implemented by a processing circuit (Circuitry) including one or more processors. The above-mentioned processing circuit can also be composed of an integrated circuit that combines one or more memories, various analog circuits, and various digital circuits in addition to the above-mentioned one or more processors. The above-mentioned one or more memories store programs (instructions) that enable the above-mentioned one or more processors to perform the above-mentioned processes. The above-mentioned one or more processors can perform the above-mentioned processes according to the above-mentioned programs read from the above-mentioned one or more memories, or they can perform the above-mentioned processes according to the logic circuits pre-designed to perform the above-mentioned processes. The above-mentioned processor can be a CPU (Central Processing Unit: Central Processing Unit), GPU (Graphics Processing Unit: Graphics Processing Unit), DSP (Digital Signal Processor: Digital Signal Processor), FPGA (Field Programmable Gate Array: Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit: Application Specific Integrated Circuit), etc., various processors suitable for controlling computers. In addition, the above-mentioned multiple processors that are physically separated can also cooperate with each other to perform the above-mentioned processes. For example, the processors installed in physically separated computers can cooperate with each other through a network such as a LAN (Local Area Network), a WAN (Wide Area Network), and the Internet to perform the above-mentioned processing. The program can be installed into the memory from an external server device through the network, or can be circulated in a state stored in a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), and a semiconductor memory, and installed from the recording medium into the memory.

[0199] The above embodiments should be considered as illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0200] The above description includes the following additional features.

[0201] [Note 1]

[0202] A simulated RoF system having:

[0203] a master station device; and

[0204] A slave station device transmits and receives wireless signals via an antenna.

[0205] The master station device generates control information used in controlling the transmission and reception of the wireless signal, and transmits an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber, wherein the first digital signal includes the generated control information.

[0206] The slave station device acquires the control information from the first digital signal, and performs switching processing of sending and receiving the wireless signal via the antenna based on the acquired control information, wherein the first digital signal is included in the optical signal received from the master station device via the optical fiber.

[0207] The master station device and the slave station device perform an inter-station synchronization process of synchronizing a count value of a local clock of the master station device with a count value of a local clock of the slave station device at a timing in accordance with a predetermined cycle.

[0208] Description of Reference Numerals

[0209] 11: Synchronous processing unit;

[0210] 12, 32, 52: TDD processing unit;

[0211] 13: frame processing unit;

[0212] 14: frequency conversion unit;

[0213] 15: Multiplexing Department;

[0214] 16: separation part;

[0215] 17: light modulation unit;

[0216] 18: optical demodulation unit;

[0217] 21: Synchronous processing unit;

[0218] 22, 42, 62: TDD processing unit;

[0219] 23: frame processing unit;

[0220] 24: RF transceiver;

[0221] 25: separation part;

[0222] 26: Multiplexing Department;

[0223] 27: optical demodulation unit;

[0224] 28: light modulation unit;

[0225] 31: information storage unit;

[0226] 41: information storage unit;

[0227] 101, 102, 103: master station device;

[0228] 111: base station device;

[0229] 151: switch device;

[0230] 161: Antenna;

[0231] 171: Management device;

[0232] 191: optical fiber;

[0233] 201, 202, 203: slave devices;

[0234] 301, 302, 303: simulated RoF system;

[0235] CP1, CP2: Optocoupler;

[0236] TB1: Correspondence table.

Claims

1. A simulated RoF (Radio over Fiber) system having: a master station device; and A slave station device transmits and receives wireless signals via an antenna. The master station device generates control information used in controlling the transmission and reception of the wireless signal, and transmits an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber, wherein the first digital signal includes the generated control information. The slave station device acquires the control information from the first digital signal included in the optical signal received from the master station device via the optical fiber, and performs switching processing of sending and receiving the wireless signal via the antenna based on the acquired control information.

2. The simulated RoF system according to claim 1, wherein: The master station device is connected between the base station device and the slave station device. The master station device receives a mode signal indicating an uplink communication period and a downlink communication period in TDD (Time Division Duplex) from the base station device, and generates the control information based on the received mode signal.

3. The simulated RoF system according to claim 2, wherein: The master station device generates a switching pattern of the transmission and reception operation of the wireless signal based on the mode signal, and generates the control information including the generated switching pattern and a start timing of the switching process using the switching pattern.

4. The simulated RoF system according to claim 2, wherein: The master station device and the slave station device hold corresponding information, wherein the corresponding information indicates a corresponding relationship between the type of the mode signal and the identification information of the mode signal. The master station device refers to the corresponding information, acquires the identification information corresponding to the pattern signal received from the base station device, and generates the control information including the acquired identification information and a start timing of the switching process using the identification information.

5. The simulated RoF system according to claim 3 or claim 4, wherein: The simulated RoF system has a plurality of slave devices. The master station device generates the control information including the different start timing for each of the slave station devices.

6. The simulated RoF system according to any one of claims 3 to 5, wherein: The slave station device corrects the start timing included in the control information, and starts the switching process based on the control information at the corrected start timing.

7. The simulated RoF system according to any one of claims 1 to 6, wherein: The slave station device receives mode information indicating an uplink communication period and a downlink communication period in TDD from a device other than the master station device outside the slave station device, generates a second digital signal including the received mode information, and transmits an optical signal including the generated second digital signal and a simulated master signal to the master station device via the optical fiber. The master station device acquires the pattern information from the second digital signal included in the optical signal received from the slave station device via the optical fiber, and generates the control information reflecting the content of the acquired pattern information.

8. A master station device, comprising: a control information generating unit that generates control information used to control the transmission and reception of wireless signals by the slave station device via the antenna; and A transmitting unit transmits an optical signal including a digital signal and an analog master signal to the slave station device via an optical fiber, wherein the digital signal includes the control information generated by the control information generating unit.

9. A slave station device, comprising: A wireless transceiver unit that transmits and receives wireless signals via an antenna; a receiving unit that receives an optical signal including a digital signal and an analog main signal from a master station device via an optical fiber, wherein the digital signal includes control information; an acquisition unit configured to acquire the control information from the digital signal included in the optical signal received by the receiving unit; and A control unit performs switching processing of the wireless transmission and reception operation of the wireless transmission and reception unit via the antenna based on the control information acquired by the acquisition unit.

10. An optical communication method in a simulated RoF system, the simulated RoF system having a master station device and a slave station device for transmitting and receiving wireless signals via an antenna, the optical communication method comprising: The master station device generates control information used in controlling the transmission and reception of the wireless signal, and transmits an optical signal including a first digital signal and an analog master signal to the slave station device via an optical fiber, wherein the first digital signal includes the generated control information; and The slave station device obtains the control information from the first digital signal contained in the optical signal received from the master station device via the optical fiber, and performs switching processing of sending and receiving the wireless signal via the antenna based on the obtained control information.

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