IF channel allocation device, IFoF transmission system, and IF channel allocation method

Abstract

To dynamically allocate an IF channel in accordance with transmission quality.SOLUTION: An IF (Intermediate Frequency) channel allocation device 150 is applied to an IFoF (IF-over Fiber) transmission system 1 which performs optical fiber transmission of a radio wave emitted from an antenna 210 as an IF signal. The IF channel allocation device comprises: an IF channel allocation information calculation section for calculating IF channel allocation information indicating an IF channel to be allocated to one or more antenna devices 200; and an IF channel signal generation section for generating an IF channel allocation signal based on the IF channel allocation information, transmitting the IF channel allocation signal to a base station 110, and disposing the IF channel allocation signal for each antenna device 200 to a downlink IF signal string transmitted from the base station 110 to the one or more antenna devices 200.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an IF channel allocation device, an IF channel allocation method, and an IFoF transmission system that are applied to an IF-over-Fiber (IFoF) transmission system in which radio waves emitted from an antenna are transmitted over optical fiber as IF (Intermediate Frequency) signals. [Background technology]

[0002] Analog RoF (Radio over Fiber) transmission technology has been known for some time. Analog RoF transmission technology separates the signal processing device that processes the radio signal from the antenna device that outputs the radio signal, and transmits the analog waveform of the radio signal directly from the signal processing device to the antenna device via optical fiber, making it possible to extract the original radio signal simply by performing optical-to-electrical (O / E) conversion on the transmitted optical signal. In analog RoF, in order to transmit large-capacity radio signals using low-bandwidth, inexpensive optical equipment, IFoF (Intermediate Frequency over Fiber) transmission systems are being considered. IFoF down-converts the radio signal to an IF signal, which is an electrical signal with an intermediate frequency (IF), and transmits the IF signal via optical fiber.

[0003] Patent Document 1 discloses a device that uses a digital-to-analog converter (DAC) / analog-to-digital converter (ADC) for frequency conversion in an IFoF transmission system, thereby reducing the influence of harmonic components generated by frequency conversion.

[0004] Patent Document 2 discloses a method for collectively monitoring the status of relay stations, antenna devices, and optical transmission paths of an IFoF transmission system using a monitoring device installed on the base station side by placing a monitoring signal in the IF signal of the IFoF transmission system. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-26984 [Patent Document 2] Japanese Patent Application Publication No. 2019-212983 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the transmission quality of an IF channel deteriorates due to the effects of reflections and nonlinearities in the optical transmission path (MFH: Mobile Fronthaul), the effects of frequency characteristics in the RF circuit, etc. The inventions described in Patent Documents 1 and 2 do not take into consideration changing the allocation of IF channels, and it is conceivable that when the transmission quality of an IF channel deteriorates, some IF channels may become unusable.

[0007] The present invention has been made in view of the above circumstances, and aims to provide an IF channel allocation device, an IF channel allocation method, and an IFoF transmission system that enable dynamic allocation of IF channels according to transmission quality. [Means for solving the problem]

[0008] (1) In order to achieve the above object, the present invention provides the following means: That is, an IF channel allocation device of the present invention is an IF channel allocation device applicable to an IF-over-Fiber (IFoF) transmission system in which radio waves emitted from antennas are transmitted over optical fiber as IF (Intermediate Frequency) signals, and includes: an IF channel allocation information calculation unit that calculates IF channel allocation information indicating IF channels to be allocated to one or more antenna devices; and an IF channel signal generation unit that generates IF channel allocation signals based on the IF channel allocation information, transmits the IF channel allocation signals to a base station, and allocates the IF channel allocation signals for each of the antenna devices in a downlink IF signal sequence transmitted from the base station to one or more of the antenna devices, wherein the IF channel allocation information calculation unit calculates the IF channel allocation information based on information acquired from the antenna devices so that an IF channel with degraded transmission quality has a bit rate corresponding to the transmission quality.

[0009] This allows IF channels to be dynamically allocated according to transmission quality, and IF channels with degraded transmission quality can be effectively utilized.

[0010] (2) Furthermore, in the IF channel allocation device described in (1) above, the IF channel allocation device further comprises: a pilot signal receiving unit that receives a pilot signal that is generated in a relay station that relays optical fiber transmission between the base station and the antenna device or in the antenna device and that is placed in an uplink IF signal sequence that is transmitted from the relay station or the antenna device to the base station; and a quality evaluation unit that evaluates the transmission quality of each of the IF channels using the received pilot signal, and the IF channel allocation information calculation unit calculates the IF channel allocation information based on the evaluation in the quality evaluation unit.

[0011] This allows the transmission quality of each IF channel to be grasped by evaluating the pilot signal, making it possible to dynamically allocate IF channels more appropriately.

[0012] (3) The IFoF transmission system of the present invention is an IF-over-Fiber (IFoF) transmission system that transmits radio waves emitted from an antenna as IF (Intermediate Frequency) signals over optical fiber, and includes at least a base station, an accommodating station including the IF channel allocation device according to claim 1, and one or more antenna devices. The base station receives IF channel allocation signals from the IF channel allocation device. signal The antenna device modulates a radio signal based on the modulated signal to generate a BB (BaseBand) signal. Note A The antenna device is characterized by comprising an IF channel monitoring device that places a pilot signal in an uplink IF signal sequence transmitted from the antenna device to the base station.

[0013] This enables dynamic allocation of IF channels according to transmission quality, and enables effective use of IF channels with degraded transmission quality.

[0014] (4) Furthermore, in the IFoF transmission system described in (3) above, the IFoF transmission system further comprises a relay station, and the accommodating station further comprises: a first MUX that multiplexes the IF channel assignment signal and an IF signal transmitted from the base station; and a first DEMUX that separates frequency components corresponding to each of the IF channels from the uplink IF multiplexed signal transmitted from the relay station, and the relay station further comprises: a pilot signal relay station that evaluates transmission quality from the antenna devices to the relay station using first pilot signals placed in uplink IF signal sequences input from each of the antenna devices, and places, in each of the uplink IF signal sequences, a second pilot signal that is used for evaluating the evaluation results of each of the first pilot signals and the transmission quality from the relay station to the accommodating station, instead of the first pilot signals; a second MUX that multiplexes the IF signals input from the pilot signal relay station as a signal sequence on a frequency axis; and a second DEMUX that separates frequency components corresponding to each of the IF channels from the downlink IF multiplexed signal transmitted from the accommodating station.

[0015] The transmission quality between the antenna device and the relay station is evaluated using a first pilot signal, and the transmission quality between the relay station and the accommodating station is evaluated using a second pilot signal, so that the transmission quality of the IF channel can be grasped more accurately.

[0016] (5) In the IFoF transmission system described in (3) above, the IFoF transmission system further comprises a relay station, and the accommodation station further comprises an optical multiplexing unit that wavelength-multiplexes downstream signal light transmitted from the base station, and an optical demultiplexing unit that demultiplexes frequency components corresponding to each IF channel from the input upstream multiplexed signal light, and the relay station comprises an optical multiplexing unit that wavelength-multiplexes upstream signal light from each antenna device, an optical demultiplexing unit that demultiplexes frequency components corresponding to each IF channel from the input downstream multiplexed signal light, a first optical amplifier that amplifies the downstream multiplexed signal light, and a second optical amplifier that amplifies the upstream multiplexed signal light.

[0017] In the relay station, the multiplexed signal light transmitted from the accommodation station or antenna device is amplified before being transmitted, which prevents the relay station configuration from becoming too complex compared to when the signal is converted into an electrical signal at the relay station.

[0018] (6) In the IFoF transmission system described in any one of (3) to (5) above, the antenna device is characterized by further comprising: a first filter that filters out frequency components corresponding to the IF channels assigned to each antenna from the input downstream IF signal; and a second filter that filters out frequency components corresponding to the IF channels assigned to each antenna from the input upstream IF signal.

[0019] This makes it possible to filter out only the desired signal from the downstream IF signal or the upstream IF signal.

[0020] (7) Furthermore, an IF channel allocation method of the present invention is an IF channel allocation method applied to an IFoF (IF-over-Fiber) transmission system in which radio waves emitted from an antenna are transmitted over optical fiber as IF (Intermediate Frequency) signals, and comprises the steps of: calculating IF channel allocation information indicating IF channels to be allocated to one or more antenna devices; generating IF channel allocation signals based on the IF channel allocation information; and allocating the IF channel allocation signals for each of the antenna devices in a downstream IF signal sequence transmitted from a base station to one or more of the antenna devices; and wherein the step of calculating the IF channel allocation information calculates a bit rate for an IF channel with degraded transmission quality according to the transmission quality.

[0021] This allows IF channels to be dynamically allocated according to transmission quality, and IF channels with degraded transmission quality can be effectively utilized.

[0022] (8) Furthermore, the IF channel allocation method described in (7) above further comprises the steps of receiving, at a relay station or the antenna device that relays optical fiber transmission between the base station and the antenna device, a pilot signal placed in an uplink IF signal sequence transmitted from the relay station or the antenna device to the base station, and evaluating the transmission quality of each of the IF channels using the received pilot signal, wherein the step of calculating the IF channel allocation information calculates the IF channel allocation information based on the evaluation.

[0023] This allows the transmission quality of each IF channel to be grasped by evaluating the pilot signal, making it possible to dynamically allocate IF channels more appropriately. [Effects of the Invention]

[0024] According to the present invention, it is possible to dynamically allocate IF channels to one or more antenna devices in accordance with the transmission quality of the IF channels. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a configuration diagram showing a configuration of an IFoF transmission system according to a first embodiment. [Figure 2] FIG. 2 is a configuration diagram showing the configuration of an access station according to the first embodiment. [Figure 3] 1 is a configuration diagram showing a configuration of an antenna device according to a first embodiment and a second embodiment. [Figure 4] 3A and 3B are conceptual diagrams showing examples of downstream IF signal trains and upstream IF signal trains according to the first embodiment. [Figure 5] FIG. 2 is a flowchart showing the flow of an IF channel allocation method according to the first embodiment. [Figure 6] FIG. 1 is an explanatory diagram showing an overview of an IF channel allocation method according to a first embodiment. [Figure 7] FIG. 10 is a configuration diagram showing the configuration of an IFoF transmission system according to a second embodiment. [Figure 8] FIG. 10 is a configuration diagram showing the configuration of an access station according to a second embodiment. [Figure 9] 10A and 10B are conceptual diagrams showing examples of downstream IF signal trains and upstream IF signal trains according to the second embodiment. [Figure 10] FIG. 10 is a flowchart showing the flow of an IF channel allocation method according to the second embodiment. [Figure 11] FIG. 10 is a configuration diagram showing the configuration of an IFoF transmission system according to a third embodiment. [Figure 12] FIG. 11 is a configuration diagram showing the configuration of an exchange station according to a third embodiment. [Figure 13] FIG. 10 is a configuration diagram showing the configuration of a relay station according to a third embodiment. [Figure 14] FIG. 10 is a configuration diagram showing the configuration of an antenna device according to a third embodiment and a fourth embodiment. [Figure 15] 10A and 10B are conceptual diagrams showing examples of downstream IF signal trains and upstream IF signal trains according to the third and fourth embodiments. [Figure 16]FIG. 11 is a flowchart showing a flow for a downstream IF signal in an IF channel allocation method according to the third embodiment. [Figure 17] FIG. 11 is a flowchart showing a flow of an IF channel allocation method according to the third embodiment for an uplink IF signal. [Figure 18] FIG. 10 is a configuration diagram showing the configuration of an IFoF transmission system according to a fourth embodiment. [Figure 19] FIG. 10 is a configuration diagram showing the configuration of a receiving station according to a fourth embodiment. [Figure 20] FIG. 10 is a configuration diagram showing the configuration of a relay station according to the fourth embodiment. [Figure 21] FIG. 11 is a flowchart showing a flow for a downlink IF signal in an IF channel allocation method according to a fourth embodiment. [Figure 22] FIG. 10 is a flowchart showing a flow of an IF channel allocation method according to a fourth embodiment for an uplink IF signal. DETAILED DESCRIPTION OF THE INVENTION

[0026] In conventional IF channel allocation, IF channels that have deteriorated due to factors such as reflections and nonlinear effects in the optical transmission path or the effects of frequency characteristics in the RF circuit are not used, and instead, other IF channels capable of high-speed communication are allocated. As a result, the number of IF channels available for allocation gradually decreases, and there is a risk of a shortage of IF channel resources. On the other hand, high-speed communication is not necessarily required for all IF channels; for example, low-speed communication is acceptable for IoT communications.

[0027] The inventors discovered that among IF channels with degraded transmission quality, there are IF channels that are not capable of high-speed communication but are capable of low-speed communication with a lower bit rate, and this led to the invention.

[0028] That is, the IF channel allocation device of the present invention is an IF channel allocation device applicable to an IFoF (IF-over-Fiber) transmission system in which radio waves emitted from antennas are transmitted over optical fiber as IF (Intermediate Frequency) signals, and comprises: an IF channel allocation information calculation unit that calculates IF channel allocation information indicating IF channels to be allocated to one or more antenna devices; and an IF channel signal generation unit that generates IF channel allocation signals based on the IF channel allocation information, transmits the IF channel allocation signals to a base station, and allocates the IF channel allocation signals for each of the antenna devices in a downstream IF signal sequence transmitted from the base station to one or more of the antenna devices, wherein the IF channel allocation information calculation unit calculates the IF channel allocation information so that an IF channel with degraded transmission quality has a bit rate corresponding to the transmission quality.

[0029] As a result, the inventors have made it possible to dynamically allocate IF channels according to transmission quality, and to effectively utilize IF channels with degraded transmission quality. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0030] [First embodiment] [Configuration of IFoF transmission system] Fig. 1 is a diagram showing an example of a schematic configuration of an IFoF transmission system according to a first embodiment. Fig. 2 is a diagram showing an example of a schematic configuration of an accommodation station according to the first embodiment. Fig. 3 is a diagram showing an example of a schematic configuration of an antenna device according to the first embodiment. As shown in Fig. 1, the IFoF transmission system 1 is made up of an accommodation station 100, an antenna device 200, and an optical transmission line 10.

[0031] 4 is a diagram showing an example of a downstream IF signal sequence and an upstream IF signal sequence according to the first embodiment. In this specification, the direction from the base station 110 to the antenna device 200 is referred to as the downstream direction, and the direction from the antenna device 200 to the base station 110 is referred to as the upstream direction. As shown in FIG. 4, an IF channel assignment signal is allocated to the downstream IF signal sequence transmitted through the optical transmission line 10, and a pilot signal is allocated to the upstream IF signal sequence transmitted through the optical transmission line 10.

[0032] 2, the accommodating station 100 includes a base station 110, an IF channel allocation device 150, a BB-to-IF conversion unit 171, an IF-to-BB conversion unit 172, an E / O 191, and an O / E 192. Note that the base station 110 and the IF channel allocation device 150 may be integrated into one unit.

[0033] The base station 110 modulates the radio signal based on the IF channel allocation signal received from the IF channel allocation device 150 to generate a BB (BaseBand) signal. Radio signal modulation methods include, for example, BPSK, QPSK, 16QAM, 64QAM, and 256QAM. As a specific example of radio signal modulation, the base station 110 performs high-level modulation such as 256QAM on IF channels with no problems in transmission quality, and performs low-level modulation such as QPSK on IF channels with degraded transmission quality.

[0034] IF channel allocation device 150 includes pilot signal receiving section 151 , quality evaluation section 153 , IF channel allocation information calculation section 155 , and IF channel allocation signal generation section 157 . The pilot signal receiving unit 151 receives a pilot signal that is placed in an uplink IF signal.

[0035] The quality evaluation unit 153 uses the received pilot signal to evaluate the transmission quality of the IF channel in the optical transmission line 10. Examples of evaluation items for evaluating the transmission quality include EVM (Error Vector Magnitude) and SNR (Signal to Noise Ratio).

[0036] The IF channel allocation information calculation unit 155 determines how to allocate IF channels based on the evaluation result in the quality evaluation unit 153, and transmits the IF channel allocation information to the IF channel allocation signal generation unit 157. The IF channel allocation information calculation unit 155 determines how to allocate IF channels so that an IF channel with degraded transmission quality will have a bit rate appropriate to the transmission quality. Note that the IF channel allocation information calculation unit 155 may determine how to allocate IF channels based on information related to the transmission quality of the IF channels input by the user, rather than the evaluation result in the quality evaluation unit 153.

[0037] Furthermore, the IF channel allocation information calculation unit 155 determines how to allocate IF channels so as to leave a band in part of the IF signal sequence for allocating an IF channel allocation signal or a pilot signal. The IF channel allocation signal may be in a band on the low frequency side of the IF signal sequence, between IF signals in the IF signal sequence, or on the high frequency side of the IF signal sequence, but it is preferable to allocate the IF channel allocation signal on the low frequency side because low frequency bands may be difficult to use for data transmission.

[0038] When the IF channel allocation signal is provided on the low frequency side of the IF signal sequence, the IF channel allocation signal may also be provided on the high frequency side for the maximum frequency band. This makes it possible to monitor the quality of the maximum frequency even in the case of a transmission system with poor frequency characteristics on the high frequency side.

[0039] The IF channel allocation signal generator 157 generates an IF channel allocation signal based on the IF channel allocation information determined by the IF channel allocation information calculator 155. The IF channel allocation signal generator 157 transmits the IF channel allocation signal to the base station 110, and places the IF channel allocation signal in the downlink IF signal sequence transmitted from the BB-to-IF converter 171.

[0040] The antenna device 200 includes an antenna 210, filters 230-1 and 230-2, an IF channel monitoring device 250, an IF-to-RF conversion unit 271, an RF-to-IF conversion unit 272, an E / O 291, and an O / E 292.

[0041] The filters 230-1 and 230-2 filter out frequency components corresponding to the IF channels assigned to the respective antennas 210 from the input IF signals.

[0042] The IF channel monitoring device 250 includes an IF channel assignment signal receiving unit 251 and a pilot signal generating unit 253.

[0043] The IF channel assignment signal receiving unit 251 receives an IF channel assignment signal from the downlink IF signal series transmitted from the E / O 291 to the filter 230-1. The IF channel assignment signal receiving unit 251 transmits the received IF channel assignment signal to the filters 230-1, 230-2, the IF→RF conversion unit 271, and the RF→IF conversion unit 272.

[0044] The pilot signal generating unit 253 arranges pilot signals in the uplink IF signal series transmitted from the filter 230-2 to the E / O 291.

[0045] [IF Channel Assignment Method] <From Transmission of IF Channel Assignment Signal to Transmission of Downlink RF Signal to Antenna> FIG. 5 is a flowchart showing the flow of the IF channel assignment method according to the first embodiment. First, the IF channel assignment device 150 transmits an IF channel assignment signal generated by the IF channel assignment signal generation unit 157 based on the IF channel assignment information to the base station 110 (step S1-1). The base station 110 that has received the IF channel assignment signal generates a radio signal with a modulation degree corresponding to the channel number in each IF channel based on the IF channel assignment signal (step S1-2). The radio signal generated by the base station 110 is transmitted to the BB→IF conversion unit 171, and the BB→IF conversion unit 171 frequency-converts the frequency domain of the downlink radio signal from BB to IF (step S1-3).

[0046] Next, the base station 110 assigns an IF channel allocation signal to the downstream IF signal transmitted from the BB->IF converter 171 (step S1-4). The downstream IF signal to which the IF channel allocation signal is assigned is converted from an electrical signal to an optical signal by the E / O 191, and is transmitted to the antenna device 200 via the optical transmission path 10 (step S1-5).

[0047] Next, the antenna device 200 converts the downstream IF signal received from the accommodating station 100 from an optical signal to an electrical signal in the O / E 292 (step S1-6). The IF channel assignment signal receiver 251 receives an IF channel assignment signal from the electrical downstream IF signal (step S1-7) and transmits the IF channel assignment signal to the filters 230-1 and 230-2, the IF-to-RF converter 271, and the RF-to-IF converter 272. The electrical downstream IF signal is transmitted to the filter 230-1. The filter 230-1 removes, from the downstream IF signal, all frequency components other than those corresponding to the IF channel assigned to the antenna 210 of the antenna device 200, based on the IF channel assignment signal (step S1-8). The filtered downstream IF signal is transmitted to the IF-to-RF converter 271, where it is frequency-converted from an IF signal to an RF signal (step S1-9). The frequency-converted downstream RF signal is transmitted to the antenna 210 (step S1-10).

[0048] <From receiving the uplink RF signal from the antenna to updating the IF channel assignment signal> Next, an upstream RF signal is received from the antenna 210 (step S1-11). The received upstream RF signal is frequency-converted from an RF signal to an IF signal in the RF-to-IF converter 272 (step S1-12). The frequency-converted upstream IF signal is transmitted to the filter 230-2. The filter 230-2 removes from the upstream IF signal, based on the IF channel assignment signal, all frequency components other than those corresponding to the IF channel assigned to the antenna 210 included in the antenna device 200 (step S1-13). The filtered upstream IF signal is assigned a pilot signal by the pilot signal generator 253 while being transmitted to the E / O 291 (step S1-14). The E / O 291, which has received the upstream IF signal with the pilot signal assigned to it, converts the upstream IF signal from an electrical signal to an optical signal and transmits it to the accommodation station 100 via the optical transmission path 10 (step S1-15).

[0049] Next, the O / E 192 of the exchange 100 converts the upstream IF signal received from the antenna device 200 from an optical signal to an electrical signal (step S1-16). The electrical upstream IF signal is transmitted to the IF-to-BB converter 172. The IF-to-BB converter 172 receives the electrical upstream IF signal, converts the frequency band of the upstream IF signal from IF to BB (step S1-17), and transmits the resulting signal to the base station 110. The pilot signal receiver 151 receives a pilot signal from the upstream IF signal transmitted to the IF-to-BB converter 172, and the quality evaluation unit 153 evaluates the transmission quality of the IF channel (step S1-18). The IF channel allocation information calculator 155 determines how to allocate IF channels based on the evaluation result of the quality evaluation unit 153, updates the IF channel allocation information (step S1-19), and transmits the updated information to the IF channel allocation signal generator 157. The IF channel allocation information calculation unit 155 determines how to allocate IF channels so that an IF channel with deteriorated transmission quality will have a bit rate that corresponds to the transmission quality.

[0050] Fig. 6 is an explanatory diagram showing an overview of an IF channel allocation method according to a first embodiment. As shown in Fig. 6, in the IF channel allocation method of the present invention, an IF channel allocation signal is allocated in a downlink IF signal, while a pilot signal is allocated in an uplink IF signal. This makes it possible to constantly grasp the transmission quality of IF channels and determine an allocation method suited to the transmission quality of the IF channels. Furthermore, IF channels can be dynamically allocated according to the transmission quality, making it possible to effectively utilize IF channels with degraded transmission quality.

[0051] [Second embodiment] Next, a second embodiment of the present invention will be described. The IFoF transmission system of the second embodiment differs from the first embodiment in that multiple antenna devices are provided for one accommodation station. The following description will focus on the differences from the first embodiment, and the same components as those in the first embodiment will be assigned the same reference numerals and their description will be omitted.

[0052] [Configuration of IFoF transmission system] Fig. 7 is a diagram showing an example of a schematic configuration of an IFoF transmission system according to the second embodiment. Fig. 8 is a diagram showing an example of a schematic configuration of an accommodation station according to the second embodiment. In this specification, as an example of a case where there are multiple antenna devices, a case where one accommodation station has n antenna devices will be described.

[0053] As shown in FIG. 7, the IFoF transmission system 2 is made up of an accommodation station 100, a plurality of antenna devices 200-1, 200-2, and 200-n, and optical transmission lines 10-1, 10-2, and 10-n.

[0054] 9 is a diagram showing an example of downstream IF signal trains and upstream IF signal trains according to the second embodiment, illustrating downstream IF signal trains and upstream IF signal trains transmitted through the respective optical transmission paths 10-1, 10-2, and 10-n. As shown in FIG. 9, an IF channel assignment signal is allocated to each of the downstream IF signal trains transmitted through the respective optical transmission paths 10-1, 10-2, and 10-n, and a pilot signal is allocated to each of the upstream IF signal trains. In this specification, the IF signal trains aggregated for each of the antenna devices 200-1, 200-2, and 200-n have different frequency bands on the frequency axis.

[0055] In addition to the base station 110 and the IF channel allocation device 150, the accommodating station 100 includes BB to IF conversion units 171-1, 171-2, 171-n, IF to BB conversion units 172-1, 172-2, 172-n, E / Os 191-1, 191-2, 191-n, and O / Es 192-1, 192-2, 192-n corresponding to the antenna devices 200-1, 200-2, 200-n, respectively.

[0056] Based on the IF channel allocation signal, the base station 110 modulates the radio signals to be transmitted to the antenna devices 200-1, 200-2, and 200-n, respectively, and transmits the modulated signals to the corresponding BB-to-IF converters 171-1, 171-2, and 171-n.

[0057] The IF channel allocation device 150 assigns an IF channel assignment signal to a downstream IF signal transmitted to each of the antenna devices 200-1, 200-2, and 200-n, while evaluating each IF channel using a pilot signal assigned to an upstream IF signal transmitted from each of the antenna devices 200-1, 200-2, and 200-n.

[0058] The pilot signal receiving unit 151 receives pilot signals that are placed in the upstream IF signals transmitted from each of the O / Es 192-1, 192-2, and 192-n. The quality evaluation unit 153 evaluates each IF channel using the received pilot signal.

[0059] The IF channel allocation information calculation unit 155 determines the allocation method for each IF channel based on the evaluation result in the quality evaluation unit 153.

[0060] The IF channel allocation signal generation unit 157 transmits an IF channel allocation signal to the base station 110 and arranges the IF channel allocation signal in the downlink IF signal sequence transmitted from each of the BB→IF conversion units 171-1, 171-2, 171-n.

[0061] Each antenna device 200-1, 200-2, 200-n arranges a pilot signal in the uplink IF signal sequence transmitted from the filter 230-2 to the E / O 291 in the pilot signal generation unit 253. Note that each of the antenna devices 200-1, 200-2, 200-n itself has the same configuration as that in the first embodiment shown in FIG. 3.

[0062] [IF Channel Allocation Method] FIG. 10 is a flowchart showing the flow of the IF channel allocation method according to the second embodiment. As described above, the IFoF transmission system of the second embodiment is different from the first embodiment in that there are multiple antenna devices for one accommodation station. In the IF channel allocation method, only the operation in the accommodation station is different. Therefore, the description of the operation in the antenna device (S2-6 to S2-15) is omitted, and only the operation in the accommodation station (S2-1 to S2-5, S2-16 to S2-19) will be described.

[0063] [From Transmission of IF Channel Allocation Signal to Transmission of Downlink IF Signal to Antenna Device] First, the IF channel allocation device 150 transmits to the base station 110 an IF channel allocation signal generated by the IF channel allocation signal generator 157 based on the IF channel allocation information (step S2-1). The base station 110 receives the IF channel allocation signal and generates a radio signal in each IF channel with a modulation factor corresponding to the channel number based on the IF channel allocation signal (step S2-2). The radio signals generated by the base station 110 are transmitted to the BB-to-IF converters 171-1, 171-2, and 171-n, respectively. The BB-to-IF converters 171-1, 171-2, and 171-n frequency-convert the frequency band of the received downlink radio signal from BB to IF (step S2-3).

[0064] Next, the base station 110 assigns an IF channel assignment signal to each of the downstream IF signals transmitted from the BB-to-IF converters 171-1, 171-2, and 171-n (step S2-4). The downstream IF signals to which the IF channel assignment signals have been assigned are converted from electrical signals to optical signals by the E / Os 191-1, 191-2, and 191-n opposite the respective antenna devices 200-1, 200-2, and 200-n, and are transmitted to the antenna device 200 via the optical transmission paths 10-1, 10-2, and 10-n (step S2-5).

[0065] <From receiving the uplink IF signal from the antenna device to updating the IF channel assignment signal> In the exchange 100, the O / Es 192-1, 192-2, and 192-n corresponding to the antenna devices 200-1, 200-2, and 200-n convert the upstream IF signals from optical signals to electrical signals (step S2-16). The upstream IF signals converted into electrical signals are transmitted to the IF-to-BB converters 172-1, 172-2, and 172-n, respectively. The IF-to-BB converters 172-1, 172-2, and 172-n that receive the upstream IF signals converted into electrical signals frequency-convert the frequency band of the upstream IF signals from IF to BB (step S2-17) and transmit the signals to the base station 110. The pilot signal receiving unit 151 receives a pilot signal from each upstream IF signal transmitted to the IF → BB conversion units 172-1, 172-2, 172-n, and evaluates the transmission quality of each IF channel in the quality evaluation unit 153 (step S2-18). The IF channel allocation information calculation unit 155 determines how to allocate each IF channel based on the evaluation result in the quality evaluation unit 153, updates the IF channel allocation information, and transmits it to the IF channel allocation signal generation unit 157 (step S2-19).

[0066] [Third embodiment] [Configuration of IFoF transmission system] Next, a third embodiment of the present invention will be described. The IFoF transmission system of the third embodiment differs from the second embodiment in that it includes a relay station between the access station and the antenna device, and the relay station evaluates the transmission quality of each IF channel and allocates new pilot signals. In other respects, the configuration is similar to that of the second embodiment.

[0067] Fig. 11 is a diagram showing an example of a schematic configuration of an IFoF transmission system according to a third embodiment. Fig. 12 is a diagram showing an example of a schematic configuration of a receiving station according to the third embodiment. Fig. 13 is a diagram showing an example of a schematic configuration of a relay station according to the third embodiment. Fig. 14 is a diagram showing an example of a schematic configuration of an antenna device according to the third embodiment.

[0068] As shown in FIG. 11, the IFoF transmission system 3 is composed of an accommodation station 100, a plurality of antenna devices 200-1, 200-2, and 200-n, a repeater station 300, a first optical transmission line 10, and second optical transmission lines 20-1, 20-2, and 20-n.

[0069] The IFoF transmission system 3 according to the third embodiment uses a first pilot signal to evaluate the transmission quality from each antenna device to the relay station, and a second pilot signal to evaluate the transmission quality from the relay station to the accommodating station, and determines how to allocate IF channels based on the evaluation results. The first pilot signal is placed in the uplink IF signal at each antenna device and is used at relay station 300 to evaluate the transmission quality from each antenna device to the relay station. The second pilot signal is placed in the uplink IF signal at relay station 300 and is used at accommodating station 100 to evaluate the transmission quality from the relay station to the accommodating station.

[0070] 15 is a diagram showing an example of a downstream IF signal sequence and an upstream IF signal sequence according to the third embodiment. As shown in FIG. 15, an IF channel assignment signal is allocated to each of the downstream IF multiplexed signal transmitted through the first optical transmission path 10 and the downstream IF signals transmitted through the second optical transmission paths 20-1, 20-2, and 20-n. Furthermore, a second pilot signal used for evaluating each IF channel is allocated to the upstream IF multiplexed signal transmitted through the first optical transmission path 10, and a first pilot signal is allocated to each of the upstream IF signals transmitted through the second optical transmission paths 20-1, 20-2, and 20-n.

[0071] The accommodating station 100 includes a base station 110, an IF channel allocation device 150, BB to IF conversion units 171-1, 171-2, and 171-n, IF to BB conversion units 172-1, 172-2, and 172-n, E / Os 191-1, 191-2, and 191-n, and O / Es 192-1, 192-2, and 192-n, as well as a MUX 131 and a DEMUX 132.

[0072] MUX 131 has a plurality of input ports, including an input port for receiving the downlink IF signals transmitted from base station 110, an input port for receiving the IF channel assignment signal, and an input port for receiving the MUX input port control signal, and an output port for outputting the downlink IF multiplexed signal. MUX 131 assigns an IF channel assignment signal to each of the input downlink IF signals based on the MUX input port control signal received from IF channel assignment device 150, multiplexes the signals as a signal sequence on the frequency axis, and outputs the downlink IF multiplexed signal. Specifically, input ports are assigned based on the MUX input port control signal, and the downlink IF signals input to each input port are multiplexed.

[0073] The DEMUX 132 separates frequency components corresponding to each IF channel from the input upstream IF multiplexed signal based on the DEMUX output port control signal received from the IF channel allocation device 150, and outputs each of them as an upstream IF signal. Specifically, the DEMUX 132 identifies the frequency of each IF signal channel based on the DEMUX output port control signal, and separates the frequency components corresponding to each IF channel from the input upstream IF multiplexed signal. The DEMUX 132 has an input port to which the upstream IF multiplexed signal transmitted from the relay station and the DEMUX output port control signal are input, and output ports to which the separated downstream IF signals are output.

[0074] IF channel allocation device 150 includes pilot signal receiver 151, quality evaluation unit 153, IF channel allocation information calculator 155, and IF channel allocation signal generator 157, as well as MUX input port control signal generator 158 and DEMUX output port control signal generator 159.

[0075] Pilot signal receiving section 151 receives the evaluation results of the transmission quality of each IF channel allocation signal from each antenna device in relay station 300 to the relay station, and the second pilot signal.

[0076] The quality evaluation unit 153 uses the second pilot signal to evaluate the transmission quality of the IF channel from the relay station to the accommodation station.

[0077] The IF channel allocation information calculation unit 155 determines how to allocate IF channels based on the evaluation results from each antenna device to the relay station and the evaluation results from the relay station to the accommodation station.

[0078] The MUX input port control signal generator 158 generates a MUX input port control signal based on the IF channel allocation information received from the IF channel allocation information calculator 155, and transmits the signal to the MUX 131. The MUX input port control signal is a signal that controls the allocation of input ports in the MUX, and is generated in response to updates of the IF channel allocation information.

[0079] The DEMUX output port control signal generator 159 generates a DEMUX output port control signal based on the IF channel allocation information received from the IF channel allocation information calculator 155, and transmits the signal to the DEMUX 132. The DEMUX output port control signal is a signal that controls the identification of the frequency for each IF channel in the DEMUX and the separation of frequency components according to each IF channel, and is generated in response to updates of the IF channel allocation information.

[0080] Relay station 300 includes DEMUX 311, MUX 312, allocation signal relay station 350, pilot signal relay station 370, E / O 381 and O / E 382 that transmit and receive with accommodation station 100, and E / O 391 and O / E 392 that transmit and receive with antenna device 200.

[0081] The DEMUX 311 separates the frequency components corresponding to the IF channels from the downstream IF multiplexed signal transmitted from the accommodating station 100, and outputs each of them as a downstream IF signal.

[0082] The MUX 312 assigns an IF channel allocation signal to each of the upstream IF signals transmitted from the antenna devices 200-1, 200-2, and 200-n, multiplexes the signals as a signal sequence on the frequency axis, and outputs an upstream IF multiplexed signal.

[0083] Allocation signal relay station 350 transmits the IF signals separated from the IF multiplexed signal to each antenna device based on the IF channel allocation signal. Allocation signal relay station 350 includes IF channel allocation signal receiver 351 and DEMUX output port control signal generator 353.

[0084] The IF channel assignment signal receiver 351 receives an IF channel assignment signal from the downstream IF multiplexed signal transmitted from the accommodating station 100, and transmits the received IF channel assignment signal to the DEMUX output port control signal generator 353 and the MUX input port control signal generator 373.

[0085] The DEMUX output port control signal generator 353 receives the IF channel allocation information from the IF channel allocation signal receiver 351 , generates a DEMUX output port control signal, and transmits it to the DEMUX 311 .

[0086] Pilot signal relay station 370 transmits uplink IF signals received from each antenna device to MUX, evaluates the transmission quality from each antenna device to the relay station using a first pilot signal, and allocates the transmission quality evaluation result and a second pilot signal. Pilot signal relay station 370 includes MUX input port control signal generator 373, pilot signal receiver 375, quality evaluator 377, and pilot signal generator 379.

[0087] The MUX input port control signal generator 373 receives the IF channel allocation information from the IF channel allocation signal receiver 351 , generates a MUX input port control signal, and transmits it to the MUX 312 .

[0088] The pilot signal receiving unit 375 transmits the upstream IF signals received from each O / E 392 and extracts the first pilot signals allocated to the upstream IF signals.

[0089] The quality evaluation unit 377 transmits the upstream IF signal received from the pilot signal reception unit 375, and evaluates the transmission quality of the IF channels in each of the second optical transmission paths 20-1, 20-2, 20-n using the extracted first pilot signal.

[0090] The pilot signal generation unit 379 arranges a second pilot signal in the upstream IF signal received from the quality evaluation unit 377 and transmits it toward the MUX 312.

[0091] Each antenna device 200-1, 200-2, 200-n receives the downstream IF signal from the relay station 300 at the E / O 291 and transmits the upstream IF signal to the relay station 300 at the O / E 292. Other points are the same as in the second embodiment.

[0092] [IF Channel Allocation Method] <From the transmission of the IF channel allocation signal to the transmission of the downstream RF signal to the antenna> FIG. 16 is a flowchart showing the flow in the downstream IF signal of the IF channel allocation method according to the third embodiment. First, the IF channel allocation device 150 transmits the IF channel allocation signal generated by the IF channel allocation signal generation unit 157 based on the IF channel allocation information to the base station 110 and the MUX 131 (step U1). Also, the IF channel allocation device 150 transmits the MUX input port control signal generated by the MUX input port control signal generation unit 158 to the MUX 131 (step U2), and transmits the DEMUX output port control signal generated by the DEMUX output port control signal generation unit 159 to the DEMUX 132 (step U3).

[0093] Next, the base station 110, having received the IF channel assignment signal, generates a radio signal in each IF channel with a modulation factor corresponding to the channel number based on the IF channel assignment signal (step U4). The radio signals generated by the base station 110 are transmitted to the BB-to-IF converters 171-1, 171-2, and 171-n, respectively. The BB-to-IF converters 171-1, 171-2, and 171-n frequency-convert the frequency band of the received downstream radio signals from BB to IF (step U5). The MUX 131 assigns an input port based on the received MUX input port control signal (step U6). The MUX 131 assigns an IF channel assignment signal to each IF downstream signal input from each input port (step U7), and then multiplexes the downstream IF signals (step U8). The downstream IF multiplexed signal multiplexed by the MUX 131 is transmitted to the E / O 191, where it is converted from an electrical signal to an optical signal and then transmitted to the repeater station 300 via the first optical transmission path 10 (step U9).

[0094] Next, the relay station 300 converts the downstream IF multiplexed signal received from the accommodation station 100 from an optical signal to an electrical signal in the O / E 382 (step U10). The converted electrical downstream IF multiplexed signal is transmitted to the DEMUX 311. The IF channel assignment signal receiver 351 receives an IF channel assignment signal from the downstream IF multiplexed signal to be transmitted to the DEMUX 311 (step U11). The assignment signal relay station 350 generates a DEMUX output port control signal in the DEMUX output port control signal generator 232 based on the received IF channel assignment signal and transmits the signal to the DEMUX 311 (step U12). The DEMUX 311 separates the received downstream IF multiplexed signal into frequency components corresponding to each IF channel based on the DEMUX output port control signal (step U13). The DEMUX 311 transmits each separated IF downstream signal to each E / O 391. Each E / O 391-1, 391-2, 391-n converts the input IF downstream signal from an electrical signal to an optical signal and transmits it to the antenna devices 200-1, 200-2, 200-n via the second optical transmission paths 20-1, 20-2, 20-n (step U14).

[0095] Next, in each of the antenna devices 200-1, 200-2, and 200-n and the optical transmission paths 10-1, 10-2, and 10-n, the O / E 292 converts the downstream IF signal received from the accommodation station 100 from an optical signal to an electrical signal (step U15). The IF channel assignment signal receiver 251 receives an IF channel assignment signal from the electrical downstream IF signal (step U16) and transmits the IF channel assignment signal to the filters 230-1 and 230-2, the IF-to-RF converter 271, and the RF-to-IF converter 272. The electrical downstream IF signal is transmitted to the filter 230-1. Based on the IF channel assignment signal, the filter 230-1 removes from the downstream IF signal all frequency components other than those corresponding to the IF channel assigned to the antenna 210 of the antenna device 200 (step U17). The filtered downstream IF signal is transmitted to the IF-to-RF converter 271, where it is frequency-converted from an IF signal to an RF signal (step U18). The frequency-converted downstream RF signal is transmitted to the antenna 210 (step U19).

[0096] <From receiving the uplink RF signal from the antenna to updating the IF channel assignment signal> FIG. 17 is a flowchart showing a flow of an IF channel allocation method according to the third embodiment for an uplink IF signal.

[0097] First, each of the antenna devices 200-1, 200-2, and 200-n receives an upstream RF signal from the antenna 210 (step U20). The received upstream RF signal is frequency-converted from an RF signal to an IF signal in the RF-to-IF converter 272 (step U21). The frequency-converted upstream IF signal is transmitted to the filter 230-2. The filter 230-2 removes from the upstream IF signal all frequency components other than those corresponding to the IF channel assigned to the antenna 210 of the antenna device 200 based on the IF channel assignment signal (step U22). The filtered upstream IF signal is assigned a first pilot signal by the pilot signal generator 253 while being transmitted to the E / O 291 (step U23). The E / O 291, which has received the upstream IF signal with the assigned first pilot signal, converts the upstream IF signal from an electrical signal to an optical signal and transmits the converted signal to the accommodation station 100 via the optical transmission path 10 (step U24).

[0098] Next, in the relay station 300, the O / Es 392-1, 392-2, and 392-n convert the upstream IF signals received from the antenna devices 200-1, 200-2, and 200-n from optical signals to electrical signals (step U25). The converted upstream IF signals are transmitted to the pilot signal receiving units 375, respectively.

[0099] The pilot signal receiving unit 375 extracts the first pilot signal to be assigned to the upstream IF signal and transmits the extracted first pilot signal together with each upstream IF signal to the quality evaluation unit 377. The quality evaluation unit 377 uses the extracted first pilot signal to evaluate the transmission quality of the IF channel in each of the optical transmission paths 20-1, 20-2, and 20-n (step U26). The quality evaluation unit 377 then transmits the evaluation result of the first pilot signal together with each upstream IF signal to the pilot signal generating unit 379. The pilot signal generating unit 379 assigns the evaluation result of the second pilot signal and the first pilot signal to each upstream IF signal (step U27), and transmits the result to the MUX 312.

[0100] The MUX input port control signal generator 373 acquires the IF channel assignment signal from the IF channel assignment signal receiver 351, generates a MUX input port control signal based on the latest IF channel assignment signal, and transmits it to the MUX 312 (step U28). The MUX 312 assigns an input port based on the MUX input port control signal, and the MUX 131 multiplexes the IF upstream signals input from each input port (step U29). The IF upstream multiplexed signal multiplexed by the MUX 312 is transmitted to the E / O 381, where it is converted from an electrical signal to an optical signal and then transmitted toward the exchange 100 (step U30).

[0101] Next, the O / E 192 of the exchange station 100 receives the upstream IF multiplexed signal from the relay station 300 (step U31) and converts the received upstream IF multiplexed signal from an optical signal to an electrical signal. The converted electrical upstream IF multiplexed signal is transmitted to the DEMUX 132. The DEMUX 132 acquires a DEMUX output port control signal from the DEMUX output port control signal generator 159 and separates frequency components corresponding to each IF channel from the upstream IF multiplexed signal based on the acquired DEMUX output port control signal. The DEMUX 132 transmits the separated upstream IF signals to the IF-to-BB converters 172-1, 172-2, and 172-n, respectively. The IF-to-BB converters 172-1, 172-2, and 172-n that have received the upstream IF signals frequency-convert the frequency band of the upstream IF signals from IF to BB and transmit the signals to the base station 110 (step U32).

[0102] Furthermore, the DEMUX 132 extracts the evaluation result of the first pilot signal and the second pilot signal from the uplink IF multiplexed signal and transmits them to the pilot signal receiver 151. The pilot signal receiver 151 transmits the evaluation result of the first pilot signal and the second pilot signal received from the DEMUX 132 to the quality evaluation unit 153, which then evaluates the transmission quality of each IF channel in the first optical transmission path 10 using the second pilot signal (step U33). The quality evaluation unit 153 transmits the evaluation results of the first pilot signal and the second pilot signal to the IF channel allocation information calculator 155. The IF channel allocation information calculator 155 determines how to allocate each IF channel using the evaluation results of the first pilot signal and the second pilot signal. The IF channel allocation information calculation unit 155 updates the IF channel allocation information (step U 34 ) and transmits the IF channel allocation information to the IF channel allocation signal generation unit 157 , the MUX input port control signal generation unit 158 ​​and the DEMUX output port control signal generation unit 159 .

[0103] [Fourth embodiment] Next, a fourth embodiment of the present invention will be described. The IFoF transmission system of the fourth embodiment differs from the second embodiment in that it includes a relay station between the accommodation station and the antenna device, and the relay station amplifies and transmits the multiplexed signal light. In other respects, the IFoF transmission system has the same configuration as the second embodiment.

[0104] [Configuration of IFoF transmission system] Fig. 18 is a diagram showing an example of a schematic configuration of an IFoF transmission system according to the fourth embodiment. Fig. 19 is a diagram showing an example of a schematic configuration of a receiving station according to the fourth embodiment. Fig. 20 is a diagram showing an example of a schematic configuration of a relay station according to the fourth embodiment.

[0105] As shown in FIG. 18, the IFoF transmission system 4 is composed of an accommodation station 100, a plurality of antenna devices 200-1, 200-2, and 200-n, a repeater station 300, a first optical transmission line 10, and second optical transmission lines 20-1, 20-2, and 20-n.

[0106] In the IFoF transmission system 4 according to the fourth embodiment, wavelength-multiplexed multiplexed signal light is transmitted through the first optical transmission line 10 and the second optical transmission lines 20-1, 20-2, and 20-n. The multiplexed signal light is amplified and then relayed in the repeater station 300. Therefore, the IFoF transmission system 4 evaluates the transmission quality from the accommodation station to each antenna device using one type of pilot signal, and determines how to allocate IF channels based on the evaluation results. When converted into IF signals, the multiplexed signal light transmitted through the first optical transmission line 10 and the second optical transmission lines 20-1, 20-2, and 20-n has the same configuration as the downstream IF signal train and the upstream IF signal train according to the third embodiment shown in FIG. 15.

[0107] The exchange 100 includes a base station 110, an IF channel allocation device 150, BB to IF conversion units 171-1, 171-2, 171-n, IF to BB conversion units 172-1, 172-2, 172-n, E / Os 191-1, 191-2, 191-n, and O / Es 192-1, 192-2, 192-n, as well as an optical multiplexing unit 121 and an optical demultiplexing unit 122.

[0108] The repeater station 300 includes an optical multiplexer 331 , an optical demultiplexer 332 , a first optical amplifier 321 , and a second optical amplifier 322 .

[0109] The optical multiplexers 121 and 331 wavelength-multiplex the input signal light to generate multiplexed signal light. The optical multiplexers 121 and 331 acquire IF channel allocation signals from the respective signal lights and wavelength-multiplex based on the IF channel allocation signals.

[0110] The optical demultiplexing units 122 and 332 demultiplex the frequency components corresponding to each IF channel from the input multiplexed signal light. The optical demultiplexing units 122 and 332 acquire the IF channel assignment signal from the multiplexed signal light and demultiplex the frequency components corresponding to each IF channel based on the IF channel assignment signal.

[0111] The first optical amplifier unit 321 amplifies the downstream multiplexed signal light transmitted from the accommodation station 100 and transmits the amplified signal light to the optical demultiplexer unit 332 .

[0112] The second optical amplifier section 322 amplifies the upstream multiplexed signal light transmitted from the optical multiplexer section 331 and transmits it toward the accommodation station 100 via the optical transmission line 10.

[0113] Each of the antenna devices 200-1, 200-2, 200-n has the same configuration as that in the third embodiment shown in FIG. 14.

[0114] [IF Channel Assignment Method] As described above, the IFoF transmission system of the third embodiment is different from the second embodiment in that a relay station is provided between the accommodation station and the antenna device, and the multiplexed signal light is amplified and transmitted at the relay station, and the operation in the antenna device is the same as that in the third embodiment. Therefore, the description of the operations (W9 to W18) in the antenna device is omitted.

[0115] <From the transmission of the IF channel assignment signal to the transmission of the downstream multiplexed signal light to the antenna device> FIG. 21 is a flowchart showing the flow in the downstream IF signal of the IF channel assignment method according to the fourth embodiment. First, the IF channel assignment device 150 transmits the IF channel assignment signal generated by the IF channel assignment signal generation unit 157 based on the IF channel assignment information to the base station 110 (step W1). The base station 110 that has received the IF channel assignment signal generates a radio signal with a modulation degree corresponding to the channel number in each IF channel based on the IF channel assignment signal (step W2). The radio signals generated by the base station 110 are respectively transmitted to the BB→IF conversion units 171-1, 171-2, 171-n. The BB→IF conversion units 171-1, 171-2, 171-n frequency-convert the frequency domain of the received downstream radio signal from BB to IF (step W3).

[0116] Next, the base station 110 assigns an IF channel assignment signal to each of the downstream IF signals transmitted from the BB->IF conversion units 171-1, 171-2, and 171-n (step W4). The downstream IF signals to which the IF channel assignment signal has been assigned are converted from electrical signals to optical signals by the E / Os 191-1, 191-2, and 191-n (step W5). The downstream IF signals converted into optical signals are transmitted to the optical multiplexing units 121, where they are wavelength-multiplexed to generate downstream multiplexed signal light (step W6). The wavelength-multiplexed downstream multiplexed signal light is transmitted to the repeater station 300 via the optical transmission path 10.

[0117] Next, the repeater 300 amplifies the received downstream multiplexed signal light using the first optical amplifier (step W7) and transmits it to the optical demultiplexing unit 332. The optical demultiplexing unit 332 demultiplexes the downstream multiplexed signal light and outputs it to each of the antenna devices 200-1, 200-2, and 200-n.

[0118] <From receiving the upstream signal light from the antenna device to updating the IF channel assignment signal> 22 is a flow diagram showing a flow of an upstream IF signal in the IF channel allocation method according to the fourth embodiment. First, the optical multiplexing unit 331 of the relay station 300 receives the upstream signal light transmitted from each of the antenna devices 200-1, 200-2, and 200-n via the second optical transmission paths 20-1, 20-2, and 20-n. The optical multiplexing unit 331 wavelength-multiplexes the received upstream signal light (step W19) to generate upstream multiplexed signal light. The generated upstream multiplexed signal light is transmitted to the second optical amplifier unit 322. The second optical amplifier unit 322 amplifies the received upstream multiplexed signal light and outputs it toward the accommodation station 100 (step W20).

[0119] Next, the optical demultiplexing unit 122 of the exchange station 100 receives the upstream multiplexed signal light transmitted from the repeater station 300 via the first optical transmission line 10. The optical demultiplexing unit 122 demultiplexes the received upstream multiplexed signal light (step W21) and transmits the demultiplexed signal light to each of the O / Es 192-1, 192-2, and 192-n. Each of the O / Es 192-1, 192-2, and 192-n converts the received upstream signal light from an optical signal to an electrical signal (step W22). The converted electrical upstream signal light is transmitted to the IF-to-BB converters 172-1, 172-2, and 172-n, respectively. Each of the IF-to-BB converters 172-1, 172-2, and 172-n that receive the converted electrical upstream signal light frequency-converts the frequency band of the upstream signal light from IF to BB and transmits the converted electrical upstream signal light to the base station 110 (step W23). The pilot signal receiver 151 receives a pilot signal from each upstream optical signal transmitted to the IF-to-BB converters 172-1, 172-2, 172-n, and the quality evaluation unit 153 evaluates the transmission quality of each IF channel (step W24). The IF channel allocation information calculator 155 determines how to allocate each IF channel based on the evaluation results of the quality evaluation unit 153. The IF channel allocation information calculator 155 updates the IF channel allocation information (step W25), and transmits the IF channel allocation information to the IF channel allocation signal generator 157, the MUX input port control signal generator 158, and the DEMUX output port control signal generator 159.

[0120] As described above, the IF channel allocation device, IF channel allocation method, and IFoF transmission system of the present invention are characterized by calculating IF channel allocation information so that an IF channel with degraded transmission quality has a bit rate appropriate to the transmission quality, and are capable of dynamically allocating IF channels to one or more antenna devices according to the transmission quality of the IF channels, thereby enabling effective use of IF channels with degraded transmission quality. [Explanation of symbols]

[0121] 1, 2, 3, 4 IFoF transmission system, 100 accommodation station, 110 base station, 131 MUX, 132 DEMUX, 150 IF channel allocation device, 151 pilot signal receiver, 153 quality evaluation unit, 155 IF channel allocation information calculation unit, 157 IF channel allocation signal generator, 200, 200-1, 200-2, 200-n antenna device, 210 antenna, 230-1, 230-2 filter, 300 relay station, 311 DEMUX, 312 MUX, 321 first optical amplifier unit, 322 second optical amplifier unit, 331 optical multiplexer unit, 332 optical demultiplexer unit, 370 pilot signal relay station

Claims

1. An IF channel allocation device applied to an IFoF (IF-over Fiber) transmission system that transmits radio waves emitted from an antenna as IF (Intermediate Frequency) signals over optical fiber, comprising: an IF channel allocation information calculation unit that calculates IF channel allocation information indicating IF channels to be allocated to one or more antenna devices; an IF channel signal generation unit that generates an IF channel allocation signal based on the IF channel allocation information, transmits the IF channel allocation signal to a base station, and allocates the IF channel allocation signal for each of the antenna devices in a downstream IF signal sequence transmitted from the base station to one or more of the antenna devices, The IF channel allocation device is characterized in that the IF channel allocation information calculation unit calculates the IF channel allocation information based on information obtained from the antenna device so that an IF channel with degraded transmission quality has a bit rate that corresponds to the transmission quality.

2. The IF channel allocation device a pilot signal receiving unit that receives a pilot signal generated in a relay station or the antenna device that relays optical fiber transmission between the base station and the antenna device, and placed in an uplink IF signal sequence that is transmitted from the relay station or the antenna device to the base station; a quality evaluation unit that evaluates the transmission quality of each of the IF channels using the received pilot signal, 2. The IF channel allocation device according to claim 1, wherein the IF channel allocation information calculation unit calculates the IF channel allocation information based on the evaluation in the quality evaluation unit.

3. An IFoF (IF-over Fiber) transmission system that transmits radio waves emitted from an antenna as IF (Intermediate Frequency) signals over optical fiber, A radio communication system including at least a base station, an accommodating station including the IF channel allocation device according to claim 1, and one or more antenna devices, the base station modulates a radio signal based on the IF channel allocation signal received from the IF channel allocation device to generate a BB (BaseBand) signal; The IFoF transmission system is characterized in that the antenna device includes an IF channel monitoring device that places a pilot signal in an uplink IF signal sequence transmitted from the antenna device to the base station.

4. The IFoF transmission system further comprises a relay station; The receiving station comprises: a first MUX that multiplexes the IF channel assignment signal and an IF signal transmitted from the base station; a first DEMUX that separates frequency components corresponding to the respective IF channels from an upstream IF multiplexed signal transmitted from the relay station; The relay station a pilot signal relay station that evaluates transmission quality from the antenna devices to the relay station using first pilot signals placed in uplink IF signal strings input from the antenna devices, and places second pilot signals, instead of the first pilot signals, in the uplink IF signal strings to be used for evaluating the evaluation results of the first pilot signals and the transmission quality from the relay station to the accommodating station; a second MUX that multiplexes the IF signals input from the pilot signal relay station as a signal sequence on a frequency axis; 4. The IFoF transmission system according to claim 3, further comprising: a second DEMUX that separates frequency components corresponding to the respective IF channels from the downstream IF multiplexed signal transmitted from the accommodation station.

5. The IFoF transmission system further comprises a relay station; The receiving station comprises: an optical multiplexing unit that wavelength-multiplexes downstream signal light transmitted from the base station; an optical demultiplexing unit that demultiplexes frequency components corresponding to the respective IF channels from the input upstream multiplexed signal light, The relay station an optical multiplexing unit that wavelength-multiplexes upstream signal light from each antenna device; an optical demultiplexing unit that demultiplexes frequency components corresponding to the respective IF channels from the input downstream multiplexed signal light; a first optical amplifier for amplifying the downstream multiplexed signal light; 4. The IFoF transmission system according to claim 3, further comprising: a second optical amplifier for amplifying the upstream multiplexed signal light.

6. The antenna device includes: a first filter for filtering out frequency components corresponding to IF channels assigned to each antenna from the input downstream IF signal; The IFoF transmission system according to any one of claims 3 to 5, further comprising: a second filter that filters out frequency components corresponding to the IF channels assigned to each antenna from the input upstream IF signal.

7. An IF channel allocation method applied to an IFoF (IF-over-Fiber) transmission system in which radio waves emitted from an antenna are transmitted over an optical fiber as IF (Intermediate Frequency) signals, comprising: calculating IF channel allocation information indicating IF channels to be allocated to one or more antenna devices; generating an IF channel allocation signal based on the IF channel allocation information, and allocating the IF channel allocation signal for each of the antenna devices in a downstream IF signal sequence transmitted from a base station to one or more of the antenna devices; The IF channel allocation method, wherein the step of calculating IF channel allocation information includes calculating a bit rate according to the transmission quality for an IF channel whose transmission quality has deteriorated.

8. receiving, in a relay station or the antenna device that relays optical fiber transmission between the base station and the antenna device, a pilot signal placed in an uplink IF signal sequence transmitted from the relay station or the antenna device to the base station; and evaluating the transmission quality of each of the IF channels using the received pilot signals; 8. The IF channel allocation method according to claim 7, wherein the step of calculating IF channel allocation information calculates the IF channel allocation information based on the evaluation.

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