Base station device and communication method thereof

Abstract

To enable control of a desired radio signal at desired timing at a remote station side of a base station communicating on analog RoF (Radio over Fiber) system.SOLUTION: A central station includes: a synchronization signal generation function part for generating a synchronization signal; an analog radio signal conversion function part for converting an upper-layer signal to an analog radio signal in an analog waveform based on the synchronization signal; a timing signal generation function part for generating a timing signal switched at timing synchronized with the analog radio signal; and a control signal conversion function part for extracting a remote station control signal for controlling the analog radio signal. The remote station includes: a storage part for accumulating the acquired remote station control signal; a trigger signal generation function part for generating a trigger signal for reading the control signal at timing at which the timing signal is switched; and a control function part for controlling the analog radio signal by reading the remote station control signal accumulated in the storage part based on the trigger signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication method for a base station device including a central station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, and to the communication method. [Background technology]

[0002] In recent years, mobile fronthaul (MFH) has become the standard for connecting base station aggregate stations and base stations. MFH not only transmits waveform data for radio signals emitted from antennas, but also transmits control signals, such as beamforming information, used to control radio signals at the base station. For this reason, proper wireless communication requires linking radio signals and control signals at the appropriate time.

[0003] In Non-Patent Document 1, both the radio signal (U-Plane: User-Plane) and the control signal (C-Plane: Control-Plane) are transmitted digitally. Both signals contain headers for identifying the transmission timing of the signals, in addition to data related to the radio signal and the control signal. Therefore, regardless of the timing at which the U-Plane and C-Plane signals arrive, the base station that receives both signals can appropriately link the two signals by referring to the headers of both signals, and as a result, control can be applied to the desired radio signal at the desired timing. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] ETSI TS 103 859 V7.0.2: “Publicly Available Specification (PAS); O-RAN Fronthaul Control, User and Synchronization Plane Specification v07.02,” Sept. 2022. Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of non-patent documents, both the radio signal and the control signal are transmitted digitally, so that headers and identification numbers can be easily added.

[0006] On the other hand, analog Radio over Fiber (RoF)-based MFH uses a method (analog method) of directly optically transmitting waveform data that is correlated with the analog waveform of the radio signal. Since the waveform changes continuously, it is impossible to determine the origin of the radio signal, making it impossible to properly link control signals. In other words, it is not possible to digitally add a header or identification number to the radio signal, as in Non-Patent Document 1. Therefore, a new control method is needed to control the desired radio signal at the desired timing at the base station.

[0007] The present invention has been made in consideration of these circumstances, and adjusts the transmission timing of the radio signal and control signal supplied from the central station to the base station, and also supplies a timing signal whose timing is synchronized with that of the radio signal.In addition, the base station determines the timing at which to reflect the previous control signal based on the timing signal, thereby enabling the base station to control the desired radio signal at the desired timing. [Means for solving the problem]

[0008] (1) In order to achieve the above object, the present invention provides the following means: That is, a base station device of the present invention is a base station device including an aggregate station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, wherein the aggregate station includes: a synchronization signal generation function unit that generates a synchronization signal for adjusting synchronization timing between signals; an analog radio signal conversion function unit that converts, based on the synchronization signal, upper layer signals including radio signals transmitted from an upper layer and control signals for controlling the radio signals, into analog radio signals having analog waveforms; a timing signal generation function unit that generates a timing signal that switches at a timing synchronized with the analog radio signals; and a control signal conversion function unit that extracts, from the control signal, an aggregate control signal for controlling the analog radio signals at the base station side; and the base station includes: a storage unit that accumulates the acquired aggregate control signal; a trigger signal generation function unit that generates a trigger signal that reads out the control signal at the timing when the timing signal switches; and a control function unit that reads out the aggregate control signal accumulated in the storage unit based on the trigger signal and controls the analog radio signal.

[0009] (2) Furthermore, in the base station device of the present invention, the base station further comprises a forwarding function unit having a forwarding function, the central station further comprises a difference calculation function unit that calculates a correction time for the transmission timing from the reception time of each signal, the memory unit generates first flag information which is a signal that indicates completion of reception of the extension control signal after completion of reception of the control signal, the trigger signal generation function unit generates second flag information at the timing of receiving the timing signal, the forwarding function unit transfers the first flag information and the second flag information to the difference calculation function unit, the difference calculation function unit uses the first flag information and the second flag information to output delay correction information calculated from the difference in reception time between the control signal and the analog radio signal at the base station, and the control signal conversion function unit adjusts the transmission timing of the extension control signal using the output delay correction information.

[0010] (3) Furthermore, in the base station device of the present invention, the base station further comprises a forwarding function unit having a forwarding function, the central station further comprises a difference calculation function unit that calculates a correction time for transmission timing from the reception time of each signal, the memory unit generates first flag information which is a signal that indicates completion of reception of the extension control signal after completion of reception of the control signal, the trigger signal generation function unit generates second flag information at the timing of receiving the timing signal, the forwarding function unit transfers the first flag information and the second flag information to the difference calculation function unit, the difference calculation function unit calculates a difference in reception time between the control signal and the analog radio signal at the base station using the first flag information and the second flag information, and the control signal conversion function unit receives the difference in reception time from the difference calculation function unit and adjusts the transmission timing of the extension control signal using the difference in reception time received as delay correction information.

[0011] (4) Furthermore, in the base station device of the present invention, the base station further comprises a forwarding function unit having a forwarding function, the central station further comprises a difference calculation function unit that calculates a correction time for the transmission timing from the reception time of each signal, the control signal conversion function unit generates an integer multiple reference signal at intervals that are an integer multiple of the timing signal, the memory unit generates first flag information that is a signal that notifies completion of reception of the extension control signal after completion of reception of the integer multiple reference signal, the trigger signal generation function unit generates second flag information at a timing that is the same number of times as the magnification of the integer multiple reference signal, the forwarding function unit transfers the first flag information and the second flag information to the difference calculation function unit, the difference calculation function unit calculates a difference in reception time between the control signal and the analog radio signal at the base station using the first flag information and the second flag information, and the control signal conversion function unit receives the difference in reception time from the difference calculation function unit and adjusts the transmission timing of the extension control signal using the difference in reception time that it has received as delay correction information.

[0012] (5) Furthermore, in the base station device of the present invention, the difference calculation function unit is characterized in that, when the difference in the reception time exceeds a first allowable value, it transmits the delay correction information to the control signal conversion function unit to correct the transmission time.

[0013] (6) The base station device of the present invention is also an analog RoF (Radio over Fibre) a control signal conversion function unit that extracts, from the control signal, a base station control signal for controlling the analog radio signal at the base station side; and a storage unit that stores the acquired base station control signal. The base station device is characterized in that it includes an aggregate station and a base station connected by a fronthaul that employs a fiber optics system, wherein the aggregate station comprises: a synchronization signal generation function unit that generates a synchronization signal for adjusting synchronization timing between signals; an analog radio signal conversion function unit that converts, based on the synchronization signal, upper layer signals including radio signals transmitted from an upper layer and control signals that control the radio signals, into analog radio signals having an analog waveform; a timing signal generation function unit that generates a timing signal synchronized with the analog radio signals; and a control signal conversion function unit that extracts, from the control signal, a base station control signal for controlling the analog radio signal at the base station side. The base station device is characterized in that it includes: a storage unit that stores the acquired base station control signal; a timing signal conversion function unit that generates a second timing signal obtained by converting the timing signal at a preset magnification; a trigger signal generation function unit that generates a trigger signal that reads out the control signal when the second timing signal switches at the same timing as the minimum interval for changing control; and a control function unit that reads out the base station control signal stored in the storage unit based on the trigger signal and controls the analog radio signal.

[0014] (7) Furthermore, the communication control method for a base station device of the present invention is a communication control method for a base station device including an aggregate station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, and is characterized by including at least the steps of: generating, in the aggregate station, a synchronization signal for adjusting synchronization timing between signals; converting, based on the synchronization signal, upper layer signals including radio signals transmitted from an upper layer and control signals for controlling the radio signals, into analog radio signals having analog waveforms; generating a timing signal that switches at a timing synchronized with the analog radio signals; extracting, from the control signal, a radio extension control signal for controlling the analog radio signals at the base station side; storing, in a memory unit, the radio extension control signal acquired from the aggregate station; generating, in the base station, a trigger signal for reading out the control signal at the timing when the timing signal switches; and reading out the radio extension control signal stored in the memory unit based on the trigger signal and controlling the analog radio signal. [Effects of the Invention]

[0015] According to the present invention, the transmission timing of the radio signal and control signal supplied from the central station to the base station is adjusted, and a timing signal whose timing is synchronized with that of the radio signal is also supplied. In addition, the base station determines the timing to reflect the previous control signal based on the timing signal, thereby enabling the base station to control the desired radio signal at the desired timing. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram illustrating a schematic configuration of a base station according to the first embodiment. [Figure 2] FIG. 10 is a diagram illustrating a first modification of signal supply according to the first embodiment. [Figure 3] FIG. 10 is a diagram illustrating a second modification of signal supply according to the first embodiment. [Figure 4] FIG. 3 is a conceptual diagram showing synchronization of signals on the base station side in the first embodiment. [Figure 5] FIG. 10 is a block diagram showing functions of a base station according to a modified example of the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating a schematic configuration of a base station according to a second embodiment. [Figure 7] FIG. 10 is an image diagram showing the arrival timing of each signal on the base station side according to the second embodiment. [Figure 8] FIG. 10 is a diagram illustrating a schematic configuration of a base station according to a third embodiment. [Figure 9] FIG. 11 is an image diagram showing the arrival timing of each signal on the base station side according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The inventors noticed that radio signal transmission methods using analog waveforms are unable to properly link radio signals with control signals that control the radio signals, and discovered that by transmitting a timing signal that switches at the same time as the radio signal, the radio signals and control signals can be properly linked, leading to the present invention.

[0018] That is, the present invention provides a base station device including an aggregate station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, wherein the aggregate station includes: a synchronization signal generation function unit that generates a synchronization signal for adjusting synchronization timing between signals; an analog radio signal conversion function unit that converts, based on the synchronization signal, upper layer signals including radio signals transmitted from an upper layer and control signals for controlling the radio signals, into analog radio signals having an analog waveform; a timing signal generation function unit that generates a timing signal that switches at a timing synchronized with the analog signal; and a control signal conversion function unit that extracts, from the control signal, an extension control signal for controlling the analog radio signal at the base station side; and the base station includes: a memory unit that accumulates the acquired extension control signal; a trigger signal generation function unit that generates a trigger signal that reads out the control signal at the timing when the timing signal switches; and a control function unit that reads out the extension control signal accumulated in the memory unit based on the trigger signal and controls the analog radio signal.

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. To facilitate understanding of the description, the same reference numerals will be used to designate the same components in the drawings of the respective embodiments, and duplicated descriptions will be omitted.

[0020] [First embodiment] 1 is a diagram showing a schematic configuration of a base station according to the first embodiment. The base station 1 according to the first embodiment is composed of an aggregate station 11 and a base station 21. The aggregate station 11 has at least a synchronization function for adjusting the timing of each function described below, a function for interpreting signals from an upper layer, including radio signals and control signals for controlling the radio signals, and converting them so that they can be used in a downstream base station, and a function for generating timing information to be supplied to a downstream base station. That is, the aggregate station 11 has a synchronization signal generation function unit 111, an analog radio signal conversion function unit 112, a control signal conversion function unit 113, and a timing signal generation function unit 114.

[0021] The details of each function constituting the central station 11 will be described below. The synchronization signal generation function unit 111 has a function of generating a signal (hereinafter referred to as a synchronization signal) for synchronizing the timing between each signal output from an analog radio signal conversion function unit 112, a control signal conversion function unit 113, and a timing signal generation function unit 114 (described later) based on information such as a Global Navigation Satellite System (GNSS) (not shown) or a Precision Time Protocol (PTP) (not shown), and supplying the signal to each function unit. The format of the synchronization signal output from the synchronization signal generation function unit 111 may be, for example, time information such as UNIX time or Coordinated Universal Time, or timing information correlated with one or more of a frame, a subframe, a slot, a symbol, or a TDD (Time Division Duplex) switching timing, or information combining these, but is not limited thereto.

[0022] The analog radio signal conversion function unit 112 has a function of interpreting the synchronization signal supplied from the synchronization signal generation function unit 111 and the signal of the upper layer (also called the upper layer signal), converting them into an analog waveform of a radio signal, and outputting it at an appropriate timing (hereinafter called the analog radio signal). Note that the center frequency of the analog radio signal does not necessarily have to match the frequency that is ultimately output from the antenna, and an intermediate frequency or a baseband frequency may also be used.

[0023] The control signal conversion function unit 113 has a function of extracting only the control information used by the base station 21 (described later) based on the synchronization signal supplied from the synchronization signal generation function unit 111 and control signals such as the C-Plane and M-Plane (Management Plane) supplied from an upper layer, converting the information into a format that can be handled by the base station 21, and outputting the signal (hereinafter referred to as a base control signal). When outputting the base control signal, the timing is adjusted so that the least significant bit of the base control signal reaches the base station before the start of the analog wireless signal to be controlled. Furthermore, if the storage unit 211 (described later) has a function of writing commands to a holding register, the timing is adjusted so that the command writing is completed before the start of the analog wireless signal to be controlled.

[0024] The timing signal generation function unit 114 has a function of generating a signal (hereinafter referred to as a timing signal) that is synchronized with the analog signal based on the synchronization signal supplied from the synchronization signal generation function unit 111, or the synchronization signal and a higher layer signal, or the analog radio signal, or the synchronization signal and the analog radio signal, and that switches at a timing that coincides with the minimum interval at which the control function unit 213 (described later) changes control. Examples of timing signal switching intervals include intervals generally defined in radio systems, such as the same frame, subframe, slot, symbol, or TDD switching timing as the analog radio signal. Furthermore, considering that the timing signal must be precisely matched with the analog radio signal (for example, in the case of TD-LTE, the difference between the two must be within ±1.5 μs), it is desirable to generate the timing signal in analog format. Therefore, it is preferable to directly generate a rectangular wave used in transmission line coding such as RZ (Return to Zero), NRZ (Non RZ), or NRZI (NRZ Inversion), or to generate a signal modulated by amplitude phase modulation, frequency shift keying, or phase shift keying using these rectangular waves. However, if the timing can be precisely matched with the analog radio signal, the timing signal may be transmitted digitally.

[0025] The base station 21 has at least the functions of storing a base station control signal, generating a trigger from a timing signal, and controlling an analog radio signal at the timing when the trigger is input based on the content of the base station control signal. That is, the base station 21 includes a storage unit 211, a trigger signal generation function unit 212, and a control function unit 213.

[0026] Next, the details of each function constituting the base station will be explained. The memory unit 211 has a function of accumulating (storing) the extension control signal received from the central station 11. It also has a function of converting the format of the extension control signal when writing it to the control function unit 213 (described later) as necessary. Note that the extension control signal is sequentially sent from the central station 11, and the control content must be sequentially reflected in the control function unit 213 (described later). If the write destination of the extension control signal and the read destination of the control function unit 213 (for example, the write destination and read destination of the memory unit address) interfere with each other, the control content may not be read correctly, resulting in unintended control. Therefore, the memory unit must use a FIFO (First In First Out) storage method. Furthermore, the capacity of the memory unit 211 must be at least large enough to store the extension control signal used by the control function unit 213 for one control. If it is desired to absorb the relative delay of the extension control signal relative to the analog radio signal (hereinafter simply referred to as delay) or fluctuations in the arrival time of the extension control signal (hereinafter referred to as fluctuation), it is preferable to store two or more extension control signals so that the extension control signals can be buffered. In this case, it is necessary for the memory unit 211 to notify or set in advance the starting point for reading the extension control signal to the control function unit 213, that is, the number of previous signals that should be read. Furthermore, if the memory unit 211 has a function for the control function unit 213 to hold commands that are currently being executed (hereinafter referred to as working register), the memory unit 211 may further have a function for appropriately writing the extension control signal from the memory unit 211 to a holding register of the control function unit 213.

[0027] The trigger signal generating function unit 212 has a function of generating, at the timing when the received timing signal is switched, a control signal (hereinafter referred to as a trigger signal) that serves as a starting point for starting the operation of the control function unit 213, which will be described later. Note that if the timing signal coincides with the TDD switching timing, the timing signal may be branched before being supplied to the trigger signal generating function unit 212 and used as a reference signal for switching a switch (a switch for performing TDD communication) for switching between uplink and downlink (not shown).

[0028] The control function unit 213 has the function of adjusting the amplitude of a received analog radio signal, adjusting the phase of the analog radio signal, turning on or off devices on the circuit, or performing a combination of these controls based on control instructions stored in the working register, and then supplying the adjusted analog radio signal to a downstream device such as an antenna. The control function unit 213 also has the function of reading the amount of control information required for one control from the instructions stored in the memory unit 211 and writing it to the working register upon receiving a trigger signal. Alternatively, if a holding register is provided, the control function unit 213 has the function of writing the contents of the holding register to the working register upon receiving a trigger signal instead of the above function. The control function unit 213 can be realized, for example, by a front end or a beamformer.

[0029] Fig. 2 is a diagram showing a first modification of signal supply according to the first embodiment. Fig. 1 shows an example in which a synchronization signal and a signal of an upper layer are supplied to the timing signal generating function unit 114, but if only an analog radio signal is used to generate the timing signal, a path for branching and extracting the analog signal is provided, as shown in Fig. 2. When generating a timing signal from an analog radio signal, a PSS (Primary Synchronization Signal) and an SSS (Secondary Synchronization Signal) are extracted from the analog radio signal, and timing information is generated based on these.

[0030] Fig. 3 is a diagram showing a second modification of the signal supply according to the first embodiment. When timing information is generated from the PSS and SSS of the analog radio signal, the timing signal generation function unit 114 does not necessarily have to be provided on the central station side, and may be provided on the base station side instead of the central station side as shown in Fig. 3.

[0031] Fig. 4 is an image diagram showing synchronization of each signal on the base station side in the first embodiment. Fig. 4 illustrates an image of the timing at which the analog radio signal, timing signal, and extension control signal described above reach the control function unit 213, trigger signal generation function unit 212, and storage unit 211, which will be described later, respectively. Note that the waveforms of each signal shown in Fig. 4 are merely examples and are not limited to these. Fig. 4 also assumes a situation in which the control function unit 213 is controlled for each slot, and a situation in which the extension control signal is transmitted one slot earlier than the analog signal so that the signal reaches the base station at the appropriate timing, but these assumptions are merely examples and are not limited to these.

[0032] [Communication control method according to the first embodiment] Next, a communication control method according to the first embodiment will be described. For ease of explanation, this embodiment will show an example in which eCPRI is used as the upper layer signal. However, the upper layer signal is not limited to this, and any signal supplied from a layer higher than RF in Function Split defined by 3GPP (registered trademark) (3rd Generation Partnership Project) and O-RAN (Open Radio Access Network) may be used. For simplicity of explanation, it is assumed that the delay between the central station 11 and the base station 21 is always constant, and that a base control signal will arrive first if it is transmitted one slot before the radio signal. It is also assumed that the radiation pattern of the antenna provided in the base station can be controlled for each slot by analog beamforming. However, the above-mentioned conditions and the operation of each function are merely examples and do not impose any restrictions on the present invention.

[0033] The synchronization signal generation function unit 111 generates time information based on the information from the GNSS.

[0034] The analog radio signal conversion function unit 112 converts information such as U-Plane in-phase samples (iSamples) and quadrature samples (qSamples), and information related to digital beamforming and the like in the C-Plane (Control-Plane), into a signal in a format that can be interpreted by a digital to analog converter (DAC).The analog radio signal conversion function unit 112 then compares the time information supplied from the synchronization signal generation function unit 111 with the eCPRI header information to adjust the timing of output from the DAC, and outputs the analog radio signal at the desired timing.

[0035] The control signal conversion function unit 113 extracts information required to control the antenna of the base station from the C-Plane, i.e., control information related to analog beamforming, and converts it into a format that can be stored in the storage unit 211 of the base station. The control signal conversion function unit 113 then compares the time information supplied from the synchronization signal generation function unit 111 with the information in the eCPRI header, adjusts the timing so that the least significant bit of the extension control signal arrives at the base station before the analog radio signal to be controlled, and outputs the extension control signal. In this embodiment, as shown in the example of FIG. 4, the extension control signal is output one slot earlier than the analog radio signal. Note that in this embodiment, the delay is constant and the extension control signal is assumed to arrive within one slot, so it is transmitted one slot earlier; however, the extension control signal may be preset to be output at a timing that takes into account delays and fluctuations in the extension control signal.

[0036] Based on the time information supplied from the synchronization signal generating function unit 111, the timing signal generating function unit 114 outputs a rectangular wave whose amplitude changes in synchronization with the slot switching timing of the analog radio signal.

[0037] As described above, the analog radio signal generated by the analog radio signal conversion function unit 112, the extension control signal generated by the control signal conversion function unit 113, and the rectangular wave generated by the timing signal generation function unit 114 are multiplexed using a multiplexing method such as frequency multiplexing or wavelength multiplexing, and supplied to the base station 21.

[0038] The base station 21 separates the multiplexed signals sent from the aggregation station 11, and inputs the analog radio signal to the control function unit 213, the base station control signal to the memory unit 211, and the rectangular wave to the trigger signal generation function unit 212.

[0039] The storage unit 211 stores the extension control signals sequentially on a first-in, first-out basis. Also, when the control information required for one control is accumulated in the storage unit and the control information for the previous step has been transferred from the holding register to the working register, the extension control signal in the storage unit 211 is written to the holding register of the control function unit 213.

[0040] The trigger signal generation function unit 212 outputs a trigger signal required for the control function unit 213 to transfer the contents of the holding register to the working register at the timing when the amplitude of the rectangular wave sent from the trigger signal generation function unit 212 changes.

[0041] The control function unit 213 writes the contents of the holding register to the working register when it receives a trigger signal. The control function unit 213 also controls the phase of the analog radio signal based on the contents of the working register, and performs analog beamforming. This allows the direction in which the analog radio signal is emitted to be changed for each slot.

[0042] As described above, by sending the control signal before the radio signal and sequentially reflecting it using timing information that switches at the same timing as the analog radio signal, the base station can control the desired radio signal at the desired timing.

[0043] [Modification of the first embodiment] 5 is a block diagram showing the functions of a base station according to a modification of the first embodiment. In this modification of the first embodiment, a method is shown in which a timing signal is generated without matching it with the minimum control interval. Note that components that perform the same or similar operations as those in the first embodiment are denoted by the same or similar reference numerals, and their description will be omitted.

[0044] A base station 1a according to a modification of the first embodiment is configured with an aggregate station 11a and a base station 21a. The aggregate station 11a has at least a synchronization function for adjusting the timing of each function described below, a function for interpreting signals from higher layers and converting them so that they can be used in a downstream base station, and a function for generating timing information to be supplied to a downstream base station. Specifically, the aggregate station 11a includes a synchronization signal generation function unit 111, an analog radio signal conversion function unit 112, a control signal conversion function unit 113, and a timing signal generation function unit 114a. Next, the details of each function constituting the aggregate station will be described.

[0045] The timing signal generating function unit 114a has a function of generating a timing signal synchronized with the analog radio signal based on the synchronization signal supplied from the synchronization signal generating function unit 111, or the synchronization signal and a signal of an upper layer, or the analog radio signal, or the synchronization signal and the analog radio signal. Examples of the switching interval of the timing signal are specifically intervals generally defined in radio systems, such as the same frame, subframe, slot, symbol, and TDD switching timing as the analog radio signal, and intervals correlated thereto (for example, intervals obtained by dividing or multiplying the aforementioned intervals). Other formats and the like are the same as those of the timing signal generating function unit 114.

[0046] The base station 21a has at least the functions of storing the base control signal, converting the timing signal into a timing signal of a different format (second timing signal), generating a trigger from the timing signal, and controlling the analog radio signal at the timing when the trigger is input based on the content of the base control signal. That is, the base station 21a includes a timing signal conversion function unit 215, a storage unit 211, a trigger signal generation function unit 212, and a control function unit 213. Next, the details of each function constituting the base station will be described.

[0047] The timing signal conversion function unit 215 has a function of multiplying or dividing the received timing signal to generate a new timing signal (second timing signal) that switches at the same timing as the minimum control interval (the minimum interval for changing control) of the control function unit 213 and can be used by the trigger signal generation function unit 212. Note that the magnification required for multiplication or division needs to be notified or set to the timing signal conversion function unit 215 in advance.

[0048] If the timing signal coincides with the TDD switching timing, the timing signal may be branched before being supplied to the timing signal conversion function unit 215 and used as a reference signal for switching a TDD switch (not shown).

[0049] As described above, in the modification of the first embodiment, although the number of components on the base station side increases, it is not necessary to match the timing signal with the minimum control interval. This has the advantage that, for example, by transmitting a timing signal with a switching interval longer than the control interval, the bandwidth required to transmit the timing signal can be reduced, and by sharing the timing signal with other functions, the number of signals transmitted from the central station to the base station can be reduced.

[0050] [Second embodiment] 6 is a diagram showing a schematic configuration of a base station according to the second embodiment. The second embodiment shows a method for automatically adjusting the timing at which to transmit a radio control signal by detecting the difference in time between the arrival of the radio control signal and the arrival of an analog radio signal at the radio station. Note that components that perform the same or similar operations as those in the first embodiment are denoted by the same or similar reference numerals, and descriptions thereof will be omitted.

[0051] The base station 2 according to the second embodiment is composed of an aggregate station 12 and a base station 22. The aggregate station 12 has at least a synchronization function for adjusting the timing of each function described below, a function for interpreting signals from higher layers and converting them so that they can be used in a downstream base station, a function for generating timing information to be supplied to a downstream base station, and a function for calculating the difference in timing between the arrival of a base control signal and an analog control signal and issuing a command to correct the delay time. Specifically, the aggregate station 12 has a synchronization signal generation function unit 111, an analog radio signal conversion function unit 112, a control signal conversion function unit 123, a timing signal generation function unit 114, and a difference calculation function unit 125.

[0052] Next, the details of each function constituting the central station will be explained. The control signal conversion function unit 123 has a function of extracting only the control information to be used by the base station 22 (described later) from the synchronization signal supplied from the synchronization signal generation function unit 111, delay time correction command information given by the difference calculation function unit 125 (described later), and control signals such as C-Plane and M-Plane supplied from the upper layer, and outputting the base control signal at the appropriate timing.

[0053] The difference calculation function unit 125 has a function of calculating the difference in arrival time of each signal based on a signal (flag information, described later) that is correlated with the arrival time of the base control signal and timing signal transmitted via the forwarding function unit 224, described later, and instructing the control signal conversion function unit 123 to correct the delay time if the calculation result is not within the allowable value. Detailed operation of this function will be described later. The difference calculation function unit 125 is preferably provided on the central station side to eliminate the need for time synchronization between the central station and the base station and simplify the configuration on the base station side. On the other hand, if this function is provided on the base station side, it is necessary to strictly synchronize the time between the base station and the central station in order to accurately estimate the time difference. To achieve this operation, a time synchronization function must also be added to the base station side, which complicates the configuration on the base station side, but this function may be provided on the base station.

[0054] The base station 22 has at least the functions of storing the extension control signal, generating a trigger from the timing signal, controlling the analog radio signal at the timing when the trigger is input based on the content of the extension control signal, and notifying the central station 12 of the timing at which the extension control signal and the analog control signal arrive.

[0055] Next, the details of each function constituting the base station will be described. In addition to the functions of the memory unit 211 described in the first embodiment, the memory unit 221 has a function of notifying a forwarding function unit 224 (described later) of the completion of reception when the reception of the least significant bit of the base station control signal is completed (a function of notifying flag information). Alternatively, when the memory unit 221 writes to a holding register of the control function unit 213, instead of the above-mentioned function, the memory unit 221 has a function of notifying flag information (first flag information) when the writing of the least significant bit is completed. Note that the notification of flag information to the forwarding function unit 224 may be performed repeatedly, or the flag information may be notified only when instructed by a control device (not shown).

[0056] The trigger signal generation function unit 222 has the function of the trigger signal generation function unit 212 described in the first embodiment, as well as the function of notifying flag information (second flag information) to a forwarding function unit 224, which will be described later, at the timing of generating a trigger signal. Note that the forwarding function unit 224 may be notified of the flag information repeatedly, or may be configured to notify the flag information only when instructed by a control device (not shown).

[0057] The forwarding function unit 224 has a function of forwarding the flag information (first flag information) received from the storage unit 221 and the flag information (second flag information) received from the trigger signal generation function unit 222 to the difference calculation function unit 125. At this time, in order to prevent unnecessary errors from being introduced when calculating a correction value later, the difference |D2-D1| between the transmission delay D1 between the difference calculation function unit 125 and the forwarding function unit 224 when forwarding the flag information received from the trigger signal generation function unit 222 and the transmission delay D2 between the difference calculation function unit 125 and the forwarding function unit 224 when forwarding the flag information received from the storage unit 221 must be transmitted so as not to affect (to be as small as possible to approximate) the difference |T2-T1| between the timing T1 at which the trigger signal generation function unit 222 generates the flag information. Therefore, it is desirable that the forwarder function unit 224 also transmits in an analog manner, and it is possible to transmit each flag information by frequency multiplexing or wavelength multiplexing, or by using a method of changing the amplitude, phase, frequency, etc. of the signal between the difference calculation function unit 125 and the forwarder function unit 224 depending on the state of the flag information. However, the format of the signal between the difference calculation function unit 125 and the forwarder function unit 224 is not limited to this. For example, if the above-mentioned condition (|D2-D1|<<|T2-T1|) is satisfied, the signal may be transmitted in a digital manner.

[0058] [Communication control method according to the second embodiment] FIG. 7 is an image diagram showing the arrival timing of each signal at the base station according to the second embodiment. In the communication control method according to this embodiment, a delay correction method, which is an additional operation to the communication control method according to the first embodiment, will be described with reference to FIG. 7. In this embodiment, a case will be described in which flag information (first flag information) is notified from the storage unit 221 upon completion of reception of the least significant bit of the base station control signal. However, the conditions handled in the communication control method according to this embodiment are merely an example and do not restrict the present invention. Furthermore, the transmission interval of the flag information (second flag information) output by the trigger signal generation function unit 222 is set to T3, the minimum allowable delay value of T2 relative to T1 is set to |Tmin|, and the maximum allowable delay value is set to |Tmax| (0≦|Tmin|≦|Tmax|). Since |D2−D1| is assumed to be sufficiently small, the difference in delay time between the difference calculation function unit 125 and the forwarding function unit 224 will be ignored for simplicity.

[0059] Furthermore, when the difference calculation function unit 125 evaluates whether or not correction is necessary, the timing at which the difference calculation function unit 125 receives flag information that was originally transferred via the forwarding function unit 224 is used. That is, the times that the difference calculation function unit 125 originally handles are T1+D1 and T2+D2. However, as will be described later, when correcting delay time, the difference between the two is taken, so that T2+D2-(T1+D1)=T2-T1+D2-D1≈T2-T1, and the same result as when T1 and T2 are handled directly, ignoring the delay, is obtained. Therefore, in this embodiment, in order to avoid confusion about the content of the present invention, the explanation will be continued ignoring the difference in delay time between the difference calculation function unit 125 and the forwarding function unit 224.

[0060] First, the difference T2 - T1 between T2 generated within ±T3 / 2 with respect to T1 is calculated by the difference calculation functional unit 125. In order to relax the conditions when applying the integer multiple reference signal described later, when it is clear that the extension control signal reaches the extension board earlier than the analog radio signal, that is, when T1 < T2 does not hold, the difference between T2 generated within -T3 to 0 with respect to T1 may be calculated. To avoid confusion, the operation when calculating the difference between T2 generated within -T3 to 0 with respect to T1 will be described in [Modification Example of the Second Embodiment] described later, and only the case of calculating the difference between T2 generated within ±T3 / 2 from T1 in the communication control method according to this embodiment will be described. When -Tmax < T2 - T1 < -Tmin, since the transmission timing of the extension control signal is within the allowable value (allowable range), no instruction is given from the difference calculation functional unit 125 to the control signal conversion functional unit 123.

[0061] On the other hand, when the extension control signal arrives later than expected (-Tmin ≦ T2 - T1) or arrives earlier than expected (T2 - T1 ≦ -Tmax), the time to be corrected (delay correction information) is notified from the difference calculation functional unit 125 to the control signal conversion functional unit 123. The control signal conversion functional unit 123 adjusts the transmission timing of the extension control signal based on the received time (delay correction information) so that T2 - T1 = -|Tmin + Tmax| / 2 is satisfied. Regarding this delay correction, if it is obvious that the delay and fluctuation of the extension control signal after correction always satisfy -Tmax < T2 - T1 < -Tmin, it may be corrected only once. However, in other cases, etc., it is desirable to repeatedly calculate T2 - T1 at regular intervals and always confirm and correct whether it is within the allowable value (allowable range). The difference (T2 - T1) of the received signal may be notified from the difference calculation functional unit 125 to the control signal conversion functional unit 123, and the control signal conversion functional unit 123 may adjust the transmission timing of the extension control signal using the difference in reception time as delay correction information.

[0062] Note that the method described in the second embodiment is effective only when the delay time satisfies -T3 / 2 < T2 - T1 < T3 / 2. When the delay time exceeds the above range, it is necessary to correct the delay by combining a modified example of the second embodiment or the third embodiment described below.

[0063] As described above, the convergence station side can detect the difference in arrival times between the outreach control signal and the analog radio signal, and automatically correct the timing at which the outreach control signal should be transmitted. As a result, compared with the first embodiment, the interval between the outreach control signal and the analog radio signal can be narrowed, so that the real-time performance of the control can be improved. Since the fluctuation of the outreach control signal can always be corrected, the capacity of the storage unit required to absorb the fluctuation can be suppressed.

[0064] [Modified Example of the Second Embodiment] As a modified example of the second embodiment, instead of the method of calculating and correcting the difference between T2 generated within ±T3 / 2 with respect to T1 by the difference calculation function unit 125, a method of calculating and correcting the difference between T2 generated within -T3 to 0 with respect to T1 will be described. For components that perform the same or similar operations as those in the first embodiment and the second embodiment, the same or similar reference numerals will be used and the description will be omitted.

[0065] [Communication Control Method According to the Modified Example of the Second Embodiment] First, the difference between T2 generated within -T3 to 0 with respect to T1 and T1, i.e., T2 - T1, is calculated by the difference calculation functional unit 125. When -Tmax < T2 - T1 < -Tmin, since the transmission timing of the overhang control signal is within the allowable value, no instruction is given from the difference calculation functional unit 125 to the control signal conversion functional unit 123. On the other hand, when the overhang control signal arrives later than expected (-Tmin ≤ T2 - T1) or arrives earlier than expected (T2 - T1 ≤ -Tmax), the time to be corrected is notified from the difference calculation functional unit 125 to the control signal conversion functional unit 123. The control signal conversion functional unit 123 adjusts the timing for transmitting the overhang control signal based on the received time so that T2 - T1 = -|Tmin + Tmax| / 2 is satisfied. Regarding this delay correction, if it is obvious that the delay and fluctuation of the overhang control signal after correction always satisfy -Tmax < T2 - T1 < -Tmin, it may be corrected only once. However, in other cases, etc., it is desirable to repeatedly calculate T2 - T1 at regular intervals and always check and correct whether it is within the allowable value (allowable range). [[ID=I]]

[0066] From the above, compared with the second embodiment, the conditions for applying the integer multiple reference signal are relaxed forward (changing from -T3 / 2 < T2 - T1 < T3 / 2 to -T3 < T2 - T1 < 0). As a result, using the same structure as the second embodiment, it becomes possible to handle a larger delay than the second embodiment.

[0067] [Third Embodiment] Figure 8 is a diagram showing a schematic configuration of a base station according to the third embodiment. The third embodiment shows a method of expanding the allowable delay range compared to the second embodiment. Regarding configurations that perform the same or similar operations as those in the first and second embodiments, the same or similar reference numerals are given and the description is omitted.

[0068] The base station 3 according to the third embodiment is composed of an aggregation station 13 and an outstation 23.

[0069] The central station 13 has at least a synchronization function for adjusting the timing of each function described below, a function for interpreting signals from higher layers and converting them so that they can be used in downstream base stations, a function for generating timing information to be supplied to downstream base stations, and a function for calculating the difference in timing between the arrival of a base control signal and an analog control signal and issuing a command to correct the delay time. Specifically, the central station 13 includes a synchronization signal generation function unit 111, an analog radio signal conversion function unit 112, a control signal conversion function unit 133, a timing signal generation function unit 114, and a difference calculation function unit 135. Next, the details of each function constituting the central station will be described.

[0070] In addition to the functions of the control signal conversion function unit 123, the control signal conversion function unit 133 has a function of generating a reference signal (hereinafter referred to as an integer multiple reference signal) immediately after the extension control signal at intervals that are an integer multiple of the timing information, if necessary for delay time correction processing, which will be described later. The criteria for determining whether to output an integer multiple reference signal will be described later.

[0071] The difference calculation function unit 135 has the same function as the difference calculation function unit 125. Furthermore, when the control signal conversion function unit 133 generates an integer multiple reference signal and when the storage unit 231, which will be described later, writes to a holding register, the difference between flag information is calculated by adding a write delay DH to the holding register to the timing described above, rather than directly using the timing at which the flag information generated by the storage unit 231 is received. However, if it is clear from the specifications of the control function unit 213 that DH<<|T2-T1|, the above-mentioned addition does not need to be performed.

[0072] The base station 23 has at least the function of storing the base control signal, the function of generating a trigger from a timing signal, the function of controlling an analog radio signal at the timing when the trigger is input based on the content of the base control signal, and the function of notifying the central station 13 of the timing at which the base control signal and the analog control signal arrive. That is, the base station 23 includes a storage unit 231, a trigger signal generation function unit 232, a control function unit 213, and a transfer function unit 224. Next, the details of each function constituting the base station will be described.

[0073] In addition to the functions of the memory unit 221, when the control signal conversion function unit 133 generates an integer multiple reference signal, the memory unit 231 has a function of notifying flag information (first flag information) at the timing when reception of the integer multiple reference signal is started instead of the above-mentioned function. Note that the same applies when the control signal conversion function unit 133 generates an integer multiple reference signal and writes to a holding register. Note that the flag information may be notified to the transfer function unit 224 repeatedly, or the flag information may be notified only when instructed by a control device (not shown).

[0074] The trigger signal generation function unit 232 has the same function as the trigger signal generation function unit 222. Furthermore, when the control signal conversion function unit 123 outputs an integer-multiplied reference signal, instead of the above-mentioned function, the trigger signal generation function unit 232 has a function of notifying flag information (second flag information) to the forwarding function unit 224 at the timing when the trigger signal has been generated the same number of times as the magnification of the integer-multiplied reference signal. Note that the flag information may be notified to the forwarding function unit 224 repeatedly, or the flag information may be notified only when instructed by a control device (not shown).

[0075] [Communication control method according to the third embodiment] Fig. 9 is an image diagram showing the arrival timing of each signal at the base station side according to the third embodiment. In the communication control method according to this embodiment, a delay correction method, which is an additional operation to the communication control method according to the first embodiment, will be described with reference to Fig. 9. Note that the conditions handled in this communication control method are merely examples and do not impose any restrictions on the present invention.

[0076] First, the difference T2 - T1 between T2 output within ±T3 / 2 with respect to T1 is calculated by the difference calculation functional unit 135. When -Tmax < T2 - T1 < +Tmax, since the transmission timing of the overhang control signal is within the allowable value (allowable range), no instruction is given from the difference calculation functional unit 135 to the control signal conversion functional unit 123. On the other hand, when the overhang control signal arrives later than expected (-Tmin ≤ T2 - T1) or arrives earlier than expected (T2 - T1 ≤ -Tmax), the time to be corrected is notified from the difference calculation functional unit 135 to the control signal conversion functional unit 123. The control signal conversion functional unit 123 adjusts the timing for transmitting the overhang control signal based on the received time so that T2 - T1 = -|Tmin + Tmax| / 2 is satisfied. Regarding this delay correction, if it is obvious that the delay and fluctuation of the overhang control signal after correction always satisfy -Tmax < T2 - T1 < -Tmin, it may be corrected only once. However, in other cases, it is desirable to repeatedly calculate T2 - T1 at regular intervals and always check and correct whether it is within the allowable value (allowable range).

[0077] Also, the condition for applying the integer multiple reference signal during delay correction is to apply it when there is a possibility that T3 / 2 ≤ |T2 - T1| under the conditions introduced in the (additional operations for the first embodiment) of the second embodiment, and it is good to judge not to apply it when it is clear that |T2 - T1| < T3 / 2. This is because when calculating the difference between T2 output within T3 / 2 before and after T1 when T3 / 2 ≤ |T2 - T1|, as shown in FIG. 9, the difference calculation functional unit 135 calculates the difference from an incorrect starting point and applies an incorrect correction. Therefore, when T3 / 2 ≤ |T2 - T1|, it is necessary to adjust the magnification of the integer multiple reference signal to widen the interval of T3 so that |T2 - T1| < T3 / 2 is satisfied, thereby enabling an accurate evaluation of the signal delay.

[0078] If the expected specific value of |T2 - T1| is unknown (for example, when the parameters are unknown immediately after the device has been started up), the magnification of the integer-multiplied reference signal can be adjusted so that it falls within a range that clearly defines |T2 - T1|. For example, if timing information is generated in frame units (T3 = 10 ms) and it is clear from the device specifications that the timing signal will be delayed by a maximum of 20 ms and the analog wireless signal will be delayed by a maximum of 1 ms, then the minimum required magnification is 2 × |20 - 1| / 10 = 3.8. Because the magnification of the integer-multiplied reference signal must be an integer, the magnification can be rounded up to 4 (T3 = 40 ms).

[0079] In the above example, if it is desired to repeatedly perform correction by the difference calculation function unit 135, the interval between corrections is 40 ms. Therefore, if it is desired to shorten the interval between corrections from the second time onwards, it is possible to perform control to change the magnification during operation, such as initially selecting a high magnification (in this case, a magnification of 4), gradually decreasing the magnification after one correction is performed by the difference calculation function unit 135, and finally not using the integer-multiplied reference signal (changing the magnification to 1).

[0080] As a result, it is possible to accommodate larger delays than in the second embodiment, which has the advantage that it is no longer necessary to manually adjust the transmission timing of the control signal conversion function unit when the base station is first started up.

[0081] As described above, according to the above embodiment, the transmission timing of the radio signal and control signal supplied from the central station to the base station is adjusted, and a timing signal whose timing is synchronized with that of the radio signal is also supplied. In addition, the base station determines the timing to reflect the previous control signal based on the timing signal, thereby enabling the base station to control the desired radio signal at the desired timing. [Explanation of symbols]

[0082] 1, 1a, 2, 3 base station 11, 11a, 12, 13 Aggregation Station 21, 21a, 22, 23 Zhang station 111 Synchronization signal generation function unit 112 Analog wireless signal conversion function unit 113 Control signal conversion function unit 114, 114a Timing signal generation function unit 123, 133 control signal conversion function unit 125, 135 Difference calculation function section 211, 221, 231 Storage section 212, 222, 232 Trigger signal generation function unit 213 Control Function Unit 215 Timing signal conversion function unit 224 forwarding function unit

Claims

1. A base station device including an aggregation station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, The aggregation station a synchronization signal generating function unit that generates a synchronization signal for adjusting synchronization timing between the signals; an analog radio signal conversion function unit that converts, based on the synchronization signal, a radio signal transmitted from an upper layer and an upper layer signal including a control signal for controlling the radio signal, into an analog radio signal having an analog waveform; a timing signal generating function unit that generates a timing signal that switches at a timing synchronized with the analog radio signal; a control signal conversion function unit that extracts, from the control signal, a base control signal for controlling the analog radio signal at the base station side; The said base station a storage unit that stores the acquired extension control signal; a trigger signal generating function unit that generates a trigger signal for reading out the control signal at the timing when the timing signal is switched; a control function unit that reads out the extension control signal stored in the storage unit based on the trigger signal and controls the analog radio signal.

2. the base station further comprises a forwarding function unit having a forwarding function, the central station further comprises a difference calculation function unit that calculates a correction time of the transmission timing from the reception time of each signal, the storage unit generates first flag information that is a signal indicating completion of reception of the extension control signal after completion of reception of the control signal; the trigger signal generating function unit generates second flag information at the timing of receiving the timing signal; the transfer function unit transfers the first flag information and the second flag information to the difference calculation function unit; the difference calculation function unit uses the first flag information and the second flag information to output delay correction information calculated from a difference in reception time between the control signal and the analog radio signal at the base station; 2. The base station apparatus according to claim 1, wherein the control signal conversion function unit adjusts the transmission timing of the extension control signal using the output delay correction information.

3. the base station further comprises a forwarding function unit having a forwarding function, the central station further comprises a difference calculation function unit that calculates a correction time of the transmission timing from the reception time of each signal, the storage unit generates first flag information that is a signal indicating completion of reception of the extension control signal after completion of reception of the control signal; the trigger signal generating function unit generates second flag information at the timing of receiving the timing signal; the transfer function unit transfers the first flag information and the second flag information to the difference calculation function unit; the difference calculation function unit calculates a difference between the reception times of the control signal and the analog radio signal at the base station using the first flag information and the second flag information; 2. The base station device according to claim 1, wherein the control signal conversion function unit receives the difference in reception time from the difference calculation function unit, and adjusts the transmission timing of the extension control signal by using the received difference in reception time as delay correction information.

4. the base station further comprises a forwarding function unit having a forwarding function, the central station further comprises a difference calculation function unit that calculates a correction time of the transmission timing from the reception time of each signal, the control signal conversion function unit generates an integer multiple reference signal at intervals that are an integer multiple of the timing signal; the storage unit generates first flag information that is a signal indicating completion of reception of the extension control signal after completion of reception of the integer multiple reference signal; the trigger signal generating function unit generates second flag information at a timing when the integer-multiplied reference signal has been generated a number of times equal to a magnification of the integer-multiplied reference signal; the transfer function unit transfers the first flag information and the second flag information to the difference calculation function unit; the difference calculation function unit calculates a difference between the reception times of the control signal and the analog radio signal at the base station using the first flag information and the second flag information; 2. The base station device according to claim 1, wherein the control signal conversion function unit receives the difference in reception time from the difference calculation function unit, and adjusts the transmission timing of the extension control signal by using the received difference in reception time as delay correction information.

5. 5. The base station device according to claim 2, wherein the difference calculation function unit transmits the delay correction information for correcting the transmission time to the control signal conversion function unit when the difference in the reception time exceeds a first allowable value.

6. A base station device including an aggregation station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, The aggregation station a synchronization signal generating function unit that generates a synchronization signal for adjusting synchronization timing between the signals; an analog radio signal conversion function unit that converts, based on the synchronization signal, a radio signal transmitted from an upper layer and an upper layer signal including a control signal for controlling the radio signal, into an analog radio signal having an analog waveform; a timing signal generating function unit that generates a timing signal synchronized with the analog radio signal; a control signal conversion function unit that extracts, from the control signal, a base control signal for controlling the analog radio signal at the base station side; The said base station a storage unit that stores the acquired extension control signal; a timing signal conversion function unit that converts the timing signal at a preset magnification to generate a second timing signal; a trigger signal generating function unit that generates a trigger signal for reading out the control signal when the second timing signal is switched at the same timing as the minimum interval for changing the control; a control function unit that reads out the extension control signal stored in the storage unit based on the trigger signal and controls the analog radio signal; A base station device comprising:

7. A communication control method for a base station device including an aggregation station and a base station connected by a fronthaul to which an analog RoF (Radio over Fiber) system is applied, In the central station, generating a synchronization signal for adjusting synchronization timing between the signals; converting, based on the synchronization signal, a radio signal transmitted from an upper layer and an upper layer signal including a control signal for controlling the radio signal, into an analog radio signal having an analog waveform; generating a timing signal that switches in synchronization with the analog radio signal; extracting, from the control signal, a base station control signal for controlling the analog radio signal; At the said control station, storing the extension control signal acquired from the central station in a storage unit; generating a trigger signal for reading out the control signal at the timing when the timing signal is switched; and a step of reading out the extension control signal stored in the storage unit based on the trigger signal and controlling the analog radio signal.

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