Control device, wireless base station, program, and control method

Abstract

Provided is a control device mounted on a wireless base station that is a control target of a RAN control function for controlling a RAN function by executing AI processing (RAN Intelligent Controller (RIC)) or the like, the control device comprising: a control unit that stops frequency control of an oscillator for generating a clock signal that is frequency-controlled with reference to a reference signal provided from the outside; a clock signal acquiring unit that acquires the clock signal generated by the oscillator while the frequency control of the oscillator is stopped; and an identifying unit that identifies a drift characteristic of the clock signal generated by the non-frequency-controlled oscillator, on the basis of the clock signal generated by the oscillator while the frequency control of the oscillator is stopped.

Description

Control Device, Radio Base Station, Program, and Control Method 【0001】 The present invention relates to an information processing device, a radio base station, a program, and an information processing method. 【0002】 Patent Document 1 describes a circuit device that can be applied to various uses such as a configuration method of a PLL (Phase Locked Loop) and a method of generating a holdover signal. Patent Document 2 describes a PLL device with a holdover circuit that can prevent fluctuations in an output clock signal with respect to fluctuations in an input clock signal while detecting a failure of the input clock signal. Patent Document 3 describes a clock holdover circuit with improved frequency holding accuracy. Patent Document 4 describes a technique for solving at least part of the problem that the accuracy of temperature compensation processing cannot be improved. Patent Document 5 describes a circuit device that can achieve more accurate aging correction. Patent Document 6 describes a technique for solving the problem of cumulative quantization error during holdover control in a reference signal generation device equipped with a synchronization circuit that converts a digital signal into an analog signal and supplies it to a voltage-controlled oscillator for control in order to obtain a signal synchronized with a reference signal and is unable to acquire the reference signal. Patent Document 7 describes a PLL circuit device that can hold correct input clock phase information before degradation even in the case of long-term degradation of an input clock. Patent Document 8 describes a circuit device that can shorten the time until a PLL circuit converges to a locked state when holdover is released. Patent Document 9 describes a synchronization clock generation circuit that can suppress fluctuations in the phase between output clocks of a plurality of cascaded PLL circuits even when a reference clock is switched. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2017-123632 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 5-235756 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 5-243980 [Patent Document 4] Japanese Unexamined Patent Application Publication No. 2019-129487 [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2017-123628 [Patent Document 6] International Publication No. 2016 / 093004 [Patent Document 7] Japanese Unexamined Patent Application Publication No. 8-8738 [Patent Document 8] Japanese Unexamined Patent Application Publication No. 2017-199946 [Patent Document 9] Japanese Unexamined Patent Application Publication No. 9-64732 【0003】 In recent years, the efficiency of frequency resource utilization in mobile communications has increased, partly due to the active research and development of digital modulation schemes such as OFDM (Orthogonal Frequency Division Multiplexing) and OFDMA (Orthogonal Frequency Division Multiple Access). On the other hand, as the efficiency of frequency resource utilization increases, the communication environment becomes more susceptible to radio interference. In order to prevent the occurrence of radio interference in such a communication environment, it is important to improve the accuracy of the clock signal of wireless base stations. 【0004】 Currently, the accuracy of the clock signal is improved by controlling the frequency of the oscillator installed in the wireless base station, thereby phase-synchronizing the clock signal generated by the oscillator with a master clock signal (sometimes referred to as a reference signal) provided by GPS (Global Positioning System) satellites equipped with atomic clocks that keep extremely accurate time. However, in the event of an accident or disaster, it may become impossible to perform frequency control of the oscillator. In such cases, as time passes, the accuracy of the clock signal gradually decreases due to frequency drift, and eventually, the accuracy of the clock signal deteriorates to the point where it exceeds the operating range of the wireless base station. The function that maintains the accuracy of the clock signal within the operating range of the wireless base station while the oscillator's frequency control cannot be performed is sometimes referred to as the holdover function (HO), and the time during which the accuracy of the clock signal is maintained within the operating range of the wireless base station while the oscillator's frequency control cannot be performed is sometimes referred to as the holdover time. 【0005】If a situation arises where the oscillator's frequency control cannot be performed, a longer holdover time allows more time to be allocated for recovery work to restore operation. This increases the likelihood of recovering from the situation without shutting down the wireless base station, thus realizing a wireless base station that is less susceptible to adverse effects such as accidents and disasters. Therefore, improving the holdover function and extending the holdover time is important in order to realize a wireless base station that is less susceptible to adverse effects such as accidents and disasters. In particular, when a wireless base station uses the TDD (Time Division Duplex) method for wireless communication, the accuracy requirements for the clock signal are stricter compared to when the wireless base station uses the FDD (Frequency Division Duplex) method for wireless communication. Therefore, improving the holdover function and extending the holdover time is even more important in order to realize a wireless base station that is less susceptible to adverse effects such as accidents and disasters. 【0006】 In the system according to this embodiment, for example, the functions of RAN (Radio Access Network) can be run on a high-performance GPU (Graphics Processing Unit) server instead of a general-purpose server, thereby allowing the surplus computing resources to be utilized for AI (Artificial Intelligence) processing. Examples of AI processing include AI processing related to RAN control (sometimes referred to as RAN control AI processing) and AI processing unrelated to RAN control (sometimes referred to as non-RAN control AI processing). 【0007】An example of AI-based RAN control processing is the RIC (RAN Intelligent Controller). The RIC is a technology that uses AI to optimize RAN wireless resources and automate RAN operations. The RIC includes Non-RT RIC and Near-RT RIC (Near-Real Time RIC). The Non-RT RIC is sometimes called Centralized RIC. The Non-RT RIC is located within the SMO (Service Management and Orchestration), which manages and orchestrates the RAN. The Non-RT RIC generates and notifies policies related to RAN control and transmits information to the Near-RT RIC. For example, a Non-RT RIC generates a trained model for RAN control by performing machine learning using data collected from the RAN, and sends it to a Near-RT RIC. A Near-RT RIC is sometimes called a Distributed RIC. Compared to a Non-RT RIC, a Near-RT RIC is located closer to the RAN nodes (RU (Radio Unit), DU (Distributed Unit), CU (Central Unit)) and performs control of the RAN nodes and resources. Compared to a Non-RT RIC, a Near-RT RIC performs processing with higher real-time capabilities. For example, a Near-RT RIC performs inference processing related to RAN control using the trained model obtained from a Non-RT RIC. RAN control AI processing is not limited to RICs. 【0008】 Non-RAN-controlled AI processing may correspond to so-called MEC (Multi-access Edge Computing) applications. Examples of non-RAN-controlled AI processing include, but are not limited to, monitoring AI execution processing that determines the situation within the imaging range of an input image, and response AI execution processing that outputs a response to an inquiry made by a user. 【0009】In the system according to this embodiment, for example, in case a situation occurs where frequency control of an oscillator mounted on a wireless base station cannot be performed, the drift characteristics of the clock signal generated by the oscillator are learned by machine learning using training data collected by intentionally stopping the oscillator's frequency control, and when a situation occurs where the oscillator's frequency control cannot be performed, the inverse characteristics of the drift characteristics are added to the clock signal generated by the oscillator. This reduces the frequency drift of the clock signal generated by an oscillator that is not frequency controlled, thereby improving the holdover function and enabling a longer holdover time. 【0010】 According to one embodiment of the present invention, a control device is provided. The control device may include a control unit that stops the frequency control of an oscillator that generates a frequency-controlled clock signal with reference to an externally provided reference signal. The control device may include a clock signal acquisition unit that acquires the clock signal generated by the oscillator while the frequency control of the oscillator is stopped. The control device may include a identification unit that identifies the drift characteristics of the clock signal generated by the oscillator that is not frequency-controlled, based on the clock signal generated by the oscillator while the frequency control of the oscillator is stopped. 【0011】 The control device may further include a correction unit that corrects the clock signal generated by the oscillator based on the drift characteristics, so as to extend the period during which the frequency deviation of the clock signal generated by the oscillator with respect to the reference signal is smaller than a predetermined allowable frequency deviation, when frequency control of the oscillator cannot be performed. 【0012】 In any of the control devices described above, the correction unit may correct the clock signal generated by the oscillator by adding a correction signal having the inverse characteristics of the drift characteristics to the clock signal generated by the oscillator. 【0013】In any of the above-mentioned control devices, the control unit may stop frequency control of the oscillator when the connection status of a communication terminal to a wireless base station equipped with the oscillator satisfies predetermined connection status conditions. 【0014】 In any of the above-mentioned control devices, the control unit may stop the frequency control of the oscillator if there is no communication terminal that has established a wireless communication connection with the wireless base station. 【0015】 Any of the above-mentioned control devices may further include a measuring unit for measuring the temperature of the oscillator, and the identifying unit may, when frequency control of the oscillator is being performed, further identify the temperature characteristics of the oscillator when the connection status of the communication terminal to the wireless base station does not satisfy the connection status conditions, based on the temperature of the oscillator measured by the measuring unit when the connection status of the communication terminal to the wireless base station does not satisfy the connection status conditions, and the control unit may control the temperature of the oscillator such that the temperature characteristics of the oscillator while frequency control of the oscillator is stopped better match the temperature characteristics of the oscillator when the connection status of the communication terminal to the wireless base station does not satisfy the connection status conditions. 【0016】 Any of the above-mentioned control devices may further include a measuring unit for measuring the temperature of the oscillator, and the identifying unit may identify the temperature characteristics of the oscillator during the period when the frequency control of the oscillator is stopped, based on the temperature of the oscillator measured by the measuring unit during the period when the frequency control of the oscillator is stopped, thereby identifying the drift characteristics of the clock signal generated by the oscillator that is not frequency controlled for each temperature characteristic of the oscillator. 【0017】Any of the above-mentioned control devices may further include: a learning data storage unit that stores learning data including operating time data indicating the operating time from when the oscillator starts operating until the frequency control of the oscillator is stopped, and drift characteristic data indicating the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator is stopped; and a model generation unit that uses a plurality of the learning data stored in the learning data storage unit as training data to generate a specific model by machine learning that identifies the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator cannot be performed, from input data including operating time data indicating the operating time from when the oscillator starts operating until the frequency control of the oscillator can no longer be performed, and the specific unit may use the specific model to identify the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator cannot be performed, from input data including operating time data indicating the operating time from when the oscillator starts operating until the frequency control of the oscillator can no longer be performed. 【0018】 Any of the above control devices may further include a measuring unit for measuring the temperature of the oscillator, the learning data storage unit may store the learning data which further includes temperature data indicating the temperature of the oscillator measured by the measuring unit when the frequency control of the oscillator is stopped, the model generation unit may generate the specific model which identifies the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator cannot be performed, from the input data which further includes temperature data indicating the temperature of the oscillator measured by the measuring unit when the frequency control of the oscillator can no longer be performed, and the identification unit may use the specific model to identify the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator cannot be performed, from the input data which further includes temperature data indicating the temperature of the oscillator measured by the measuring unit when the frequency control of the oscillator can no longer be performed. 【0019】According to one embodiment of the present invention, a wireless base station is provided. The wireless base station may include any of the control devices. The wireless base station may include the oscillator. 【0020】 According to one embodiment of the present invention, a program is provided that, when executed by a computer, causes the computer to function as one of the control devices. 【0021】 According to one embodiment of the present invention, a control method performed by a computer is provided. The control method may include a control step of stopping the frequency control of an oscillator that generates a frequency-controlled clock signal with reference to an externally provided reference signal. The control method may include a clock signal acquisition step of acquiring the clock signal generated by the oscillator while the frequency control of the oscillator is stopped. The control method may include a identification step of identifying the drift characteristics of the clock signal generated by the oscillator that is not frequency-controlled, based on the clock signal generated by the oscillator while the frequency control of the oscillator is stopped. 【0022】 It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. Furthermore, subcombinations of these features may also constitute an invention. 【0023】 An example of system 10 is schematically shown. This is an explanatory diagram illustrating an example of the operation of a conventional wireless base station. This is an explanatory diagram illustrating an example of the operation of a wireless base station 300. This is an explanatory diagram illustrating an example of a graph showing drift characteristics. An example of the functional configuration of the control device 350 is schematically shown. An example of the functional configuration of the distributed infrastructure 200 is schematically shown. This is an explanatory diagram illustrating an example of the processing flow of the control device 350. This is an explanatory diagram illustrating another example of the processing flow of the control device 350. An example of the hardware configuration of a computer 1200 that functions as the distributed infrastructure 200 or the control device 350 is schematically shown. 【0024】The present invention will be described below through embodiments, but these embodiments are not intended to limit the scope of the claimed invention. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. 【0025】 Figure 1 schematically shows an example of system 10. System 10 may include one or more wireless base stations 300 that constitute RAN 310. System 10 may include multiple distributed infrastructures 200. System 10 may include a management infrastructure 100 that manages the multiple distributed infrastructures 200. In system 10 according to this embodiment, for example, the management infrastructure 100 and the multiple distributed infrastructures 200 may cooperate to control RAN 310 and perform AI processing. 【0026】 RAN310 may be a virtualized vRAN (Virtual RAN), and system 10 may perform control of the vRAN. RAN310 may also be a physical RAN, and system 10 may perform control of the physical RAN. 【0027】 The AI ​​processing performed by system 10 may include RAN-controlled AI processing (sometimes referred to as RAN_AI). The AI ​​processing performed by system 10 may also include non-RAN-controlled AI processing (sometimes referred to as non-RAN_AI). 【0028】 The distributed infrastructure 200 may be data centers located in various locations. The distributed infrastructure 200 may be composed of multiple devices. The distributed infrastructure 200 may be implemented on a virtualization infrastructure consisting of multiple devices. The distributed infrastructure 200 may be implemented by a single device. In other words, the distributed infrastructure 200 may be a distributed device. 【0029】 The distributed infrastructure 200 includes, for example, an execution unit that includes a RAN control function for controlling the functions of RAN 310 and an application execution function for executing applications. The distributed infrastructure 200 may further include the functions of a wireless base station 300. 【0030】The RAN control function controls the functions of RAN310, for example, by executing RAN_AI. The RAN control function may also control the functions of RAN310 by executing any other arbitrary processing. 【0031】 The RAN control function controls, for example, the wireless base station 300. The RAN control function controls the wireless base station 300 so that, for example, it uses an antenna to form a wireless communication area and provides mobile communication services to communication terminals 30 within the wireless communication area. 【0032】 The communication terminal 30 is, for example, a mobile phone such as a smartphone. The communication terminal 30 may also be a tablet device or a PC (Personal Computer). The communication terminal 30 may also be a so-called IoT (Internet of Things) device. The communication terminal 30 may include anything that falls under the so-called IoE (Internet of Everything). 【0033】 The application execution function may, for example, have the ability to execute AI applications. The application execution function may also have the ability to execute non-RAN_AI applications. The application execution function may execute any other application. 【0034】 The execution unit may contain one or more CPUs (Central Processing Units). The execution unit may contain one or more GPUs. The execution unit may contain multiple superchips, each connected to a CPU and a GPU by an interconnect. This interconnect may be memory consistent and capable of achieving high bandwidth and low latency. Thus, the execution unit may have CPU resources and GPU resources as computing resources. 【0035】 The distributed infrastructure 200 is, for example, located on the core network. The term "on the core network" includes both the area inside and outside the core network. 【0036】The core network may conform to any mobile communication system. For example, the core network may conform to a 5G (5th Generation) communication system. The core network may conform to a 6G (6th Generation) communication system or later mobile communication systems. The core network may conform to a 3G (3rd Generation) communication system or an LTE communication system. 【0037】 The management infrastructure 100 may be a data center that manages multiple distributed infrastructures 200. The management infrastructure 100 may be composed of multiple devices. The management infrastructure 100 may be implemented on a virtualization infrastructure consisting of multiple devices. The management infrastructure 100 may be implemented by a single device. In other words, the management infrastructure 100 may be a management device. 【0038】 The management infrastructure 100 may be called the Core Brain, and the distributed infrastructure 200 may be called the Regional Brain. Note that Figure 1 illustrates a case where a single-layer distributed infrastructure 200 is located below the management infrastructure 100, but it is not limited to this. The distributed infrastructure 200 may have multiple layers. For example, if two layers of distributed infrastructure 200 are located below the management infrastructure 100, the management infrastructure 100 may be called the Core Brain, the distributed infrastructure 200 at the lower layer may be called the Regional Brain, and the distributed infrastructure 200 at the lower layer may be called the Sub-Regional Brain. 【0039】 Figure 2 is an explanatory diagram illustrating an example of the operation of a conventional wireless base station. Here, we will mainly explain an example of the operation in which a wireless base station generates a clock signal. 【0040】 A wireless base station comprises an oscillator, a frequency divider (FD), a phase frequency detector (PFD), and a filter. The oscillator, frequency divider, phase frequency detector, and filter may constitute a PLL circuit. 【0041】The oscillator has a function of generating a clock signal which is an electrical signal of a specific frequency. Note that the frequency of the clock signal may be described as the clock frequency (f Ｃｌｏ ). 【0042】 The oscillator has, for example, a crystal oscillator and an oscillation circuit. The oscillator further has, for example, a temperature compensation circuit for compensating the temperature of the crystal oscillator. Here, a voltage controlled oscillator (VCO) is exemplified as an example of the oscillator. 【0043】 The frequency divider has a function of dividing the frequency of an electrical signal. Frequency division may be to make the frequency of the electrical signal 1 / N. Note that N which is a positive integer is the division ratio. 【0044】 The phase frequency detector has a function of outputting an error signal indicating the error between two electrical signals by comparing the two electrical signals. The error signal includes, for example, a frequency error indicating the frequency error between the two electrical signals. The error signal includes, for example, a phase error signal indicating the phase error between the two electrical signals. 【0045】 The filter has a function of removing noise from an electrical signal. The filter removes the noise of the electrical signal by removing, for example, signal components having a frequency higher than the cut-off frequency of the electrical signal. Here, a low-pass filter is exemplified as an example of the filter. 【0046】 The upper diagram in FIG. 2 is an explanatory diagram for explaining an example of the operation of a conventional radio base station when the oscillator mounted on the conventional radio base station is frequency-controlled. Here, that the oscillator is frequency-controlled may mean that the clock signal generated by the oscillator is frequency-controlled. Note that the state in which the oscillator is frequency-controlled may be described as the control state. 【0047】 The oscillator generates a clock signal having a frequency of f Ｃｌｏ and inputs the generated clock signal to the frequency divider. The frequency divider divides the clock signal input from the oscillator and outputs a clock signal having a frequency of 1 / N × f Ｃｌｏ to the phase frequency detector. 【0048】 The phase frequency detector compares a reference signal input via an antenna from a GSNN (Global Navigation Satellite System) satellite equipped with an atomic clock with a clock signal input from a frequency divider, and outputs an error signal indicating the error between the reference signal and the clock signal to a filter. The frequency of the reference signal is set to the reference frequency (f Ｒｅｆ ) is sometimes written as such. Here, GPS satellites are used as an example of GSNN satellites. 【0049】 An antenna capable of receiving a reference signal may be installed in a location with good radio wave reception conditions, such as the rooftop of a building. Figure 2 shows an example where the antenna and the radio base station are separate devices. The antenna and the radio base station may also be an integrated device. 【0050】 The filter removes noise from the error signal input from the phase frequency detector. The error signal from which the noise has been removed by the filter is sometimes referred to as the oscillator control signal. 【0051】 Oscillator control signals include, for example, frequency control signals that control the clock frequency of the clock signal generated by the oscillator. Oscillator control signals also include, for example, phase control signals that control the phase of the clock signal generated by the oscillator. 【0052】 The oscillator generates a frequency-controlled clock signal based on an oscillator control signal input through a filter. A frequency-controlled clock signal includes, for example, a frequency-controlled clock signal. A frequency-controlled clock signal includes, for example, a phase-controlled clock signal. A frequency-controlled clock signal includes, for example, a clock signal phase-locked to a reference signal. 【0053】 Subsequently, the oscillator inputs the frequency-controlled clock signal to the frequency divider. By repeatedly performing the aforementioned process, the oscillator controls the clock frequency to f. Ｃｌｏ = N × f Ｒｅｆ It can generate highly accurate clock signals. 【0054】The lower diagram in Figure 2 illustrates an example of the operation of a conventional wireless base station when frequency control of the oscillator mounted on the conventional wireless base station cannot be performed. Here, "inability to perform frequency control of the oscillator" means that frequency control of the oscillator is impossible due to damage to the antenna or the coaxial cable connecting the antenna and the phase frequency detector, etc., caused by an accident or disaster. Note that the state in which frequency control of the oscillator cannot be performed may be described as an uncontrollable state. The lower diagram in Figure 2 shows an example where the antenna is damaged. 【0055】 The wireless base station cannot acquire a reference signal due to antenna damage. Therefore, the reference signal is not input to the phase-frequency detector. As a result, no oscillator control signal is generated, and the oscillator generates an uncontrolled clock signal. The accuracy of the uncontrolled clock signal gradually decreases due to frequency drift in the clock signal, and beyond the holdover time, it degrades to an accuracy that exceeds the operating range of the wireless base station. 【0056】 Figure 3 is an explanatory diagram illustrating an example of the operation of the wireless base station 300. First, we will explain the main configuration of the wireless base station 300, which differs from the configuration of conventional wireless base stations. 【0057】 The wireless base station 300 may be equipped with a control device 350. The control device 350 has functions for controlling various control targets. Details of the functions of the control device 350 will be described later. 【0058】 The wireless base station 300 may be equipped with a switch 370. The switch 370 has the function of switching whether or not to input a reference signal provided from a GSNN satellite to the phase frequency detector. The switch 370 receives a switch control signal from the control device 350, for example, and switches whether or not to input the reference signal to the phase frequency detector based on the received switch control signal. The switch 370 may be an example of an object controlled by the control device 350. 【0059】 The wireless base station 300 may be equipped with an adder 380. The adder 380 has the function of adding two or more electrical signals. 【0060】The upper diagram in Figure 3 is an explanatory diagram illustrating an example of the operation of a wireless base station 300 when the oscillator 360 mounted on the wireless base station 300 is frequency controlled. Here, we will mainly explain the parts that differ from the operation of conventional wireless base stations. 【0061】 The control device 350 controls the switch 370, for example, to input a reference signal to the phase frequency detector. The switch 370 may be switched to an input state that inputs the reference signal to the phase frequency detector according to the control by the control device 350. As a result, the reference signal is input to the phase frequency detector. Consequently, an oscillator control signal is generated, and the oscillator 360 generates a frequency-controlled clock signal. 【0062】 The middle diagram in Figure 3 is an explanatory diagram illustrating an example of the operation of the wireless base station 300 when the frequency control of the oscillator 360 is stopped. Here, stopping the oscillator's frequency control means that the oscillator's frequency control is not performed even when it is possible to perform it. Note that the state in which the oscillator's frequency control is stopped may be described as the control stopped state. 【0063】 The control device 350 controls the switch 370, for example, so that the reference signal is not input to the phase frequency detector. The switch 370 may be switched to a disconnected state in accordance with the control by the control device 350, so that the reference signal is not input to the phase frequency detector. As a result, the reference signal is not input to the phase frequency detector. Consequently, no oscillator control signal is generated, and the oscillator 360 generates a clock signal that is not frequency controlled. 【0064】 The control device 350 acquires, for example, the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped. Based on the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped, the control device 350 identifies the drift characteristics of the clock signal generated by the oscillator 360 that is not frequency controlled. 【0065】The drift characteristic of a clock signal may be an indicator of the frequency drift of the clock signal generated by an oscillator. When the oscillator is not frequency controlled, the frequency drift of the clock signal generated by the oscillator tends to increase in proportion to the time during which the oscillator is not frequency controlled. Therefore, the drift characteristic of a clock signal may be expressed as the amount of frequency drift of the clock signal generated by the oscillator per unit time. Here, 10 minutes, 30 minutes, 1 hour, etc., are given as examples of unit time. 【0066】 The lower diagram in Figure 3 is an explanatory diagram illustrating an example of the operation of the wireless base station 300 when frequency control of the oscillator 360 cannot be performed. Here, we will mainly explain the parts that differ from the operation of conventional wireless base stations. 【0067】 The control device 350 corrects, for example, the clock signal generated by the oscillator 360, which is not frequency controlled. The clock signal generated by the oscillator 360 may be an example of what the control device 350 controls. 【0068】 The control device 350, for example, generates a correction signal to correct the clock signal generated by the oscillator 360, and corrects the clock signal generated by the oscillator 360, which is not frequency controlled, by adding the clock signal generated by the oscillator 360 and the correction signal. The control device 350, for example, uses an adder 380 to add the clock signal generated by the oscillator 360, which is not frequency controlled, and the correction signal. 【0069】 The control device 350 generates a correction signal based on the drift characteristics of the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped. The control device 350 generates a correction signal based on the inverse characteristics of the drift characteristics of the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped. 【0070】Figure 4 is an explanatory diagram illustrating an example of a graph showing drift characteristics. Here, the frequency drift of the clock signal generated by oscillator 360 is represented by the frequency deviation of the clock signal generated by oscillator 360 with respect to a reference signal. 【0071】 In the graph shown in Figure 4, the horizontal axis represents time [h]. The vertical axis represents the frequency deviation [ppm]. 【0072】 The upper part of Figure 4 shows an example of a graph illustrating the drift characteristics of a clock signal generated by an uncontrolled oscillator 360 when the oscillator 360 is in a controlled-off state. In the example shown in the upper part of Figure 4, the drift characteristic of the clock signal generated by an uncontrolled oscillator 360 while the frequency control of the oscillator 360 is stopped is 0.008 ppm / h. 【0073】 The lower part of Figure 4 shows an example of a graph illustrating the drift characteristics of a clock signal generated by an uncontrolled oscillator 360 when the oscillator 360 is in an uncontrollable state. Here, the allowable frequency deviation is defined as the lower limit of the accuracy of the clock signal within the operating range of the wireless base station. The lower part of Figure 4 shows an example where the allowable frequency deviation is 0.05 ppm. In this case, the holdover time is the time when the frequency deviation of the clock signal is less than 0.05 ppm. 【0074】 In the example shown in the lower part of Figure 4, if the control device 350 does not correct the clock signal generated by the uncontrolled oscillator 360, the drift characteristic of the clock signal generated by the uncontrolled oscillator 360 is 0.01 ppm / h. Therefore, if the control device 350 does not correct the clock signal generated by the uncontrolled oscillator 360, the holdover time is approximately 5 hours. 【0075】In contrast, in the example shown in the lower part of Figure 4, when the control device 350 adds a correction signal to the clock signal generated by the uncontrolled oscillator 360, which is the inverse characteristic (-0.008 ppm / h) of the drift characteristic (0.008 ppm / h) of the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped, the drift characteristic of the clock signal generated by the uncontrolled oscillator 360 is 0.01 ppm / h - 0.008 ppm / h = 0.002 ppm / h. Therefore, when the control device 350 corrects the clock signal generated by the uncontrolled oscillator 360, the holdover time is approximately 25 hours. Thus, when the oscillator 360 is in an uncontrollable state, the control device 350 can extend the holdover time by approximately 20 hours by correcting the clock signal generated by the uncontrolled oscillator 360. 【0076】 As mentioned above, extending the holdover time is crucial for realizing wireless base stations that are less susceptible to adverse effects such as accidents and disasters. However, the drift characteristics of the clock signal generated by the oscillator depend on the cutoff accuracy of the crystal oscillator and the compensation performance of the temperature compensation circuit. The cutoff accuracy of the crystal oscillator and the compensation performance of the temperature compensation circuit are parameters that vary due to individual differences. Therefore, conventionally, extending the holdover time required using oscillators equipped with high-performance and expensive crystal oscillators and temperature compensation circuits. 【0077】In contrast, according to the system 10 of this embodiment, the control device 350 deliberately transitions the state of the oscillator 360 from a controlled state to a controlled-off state to identify the drift characteristics of the clock signal generated by the oscillator 360, which is not frequency controlled. By transitioning the state of the oscillator to a controlled-off state and identifying the drift characteristics, the system 10 of this embodiment can identify the drift characteristics unique to the oscillator mounted on the wireless base station in preparation for a situation in which the oscillator state transitions to an uncontrollable state. Subsequently, if a situation occurs in which the state of the oscillator 360 transitions to an uncontrollable state, the control device 350 corrects the clock signal to further reduce the frequency drift of the clock signal generated by the oscillator 360, which is not frequency controlled, based on the drift characteristics unique to the oscillator 360 identified by transitioning the state of the oscillator 360 to a controlled-off state. As a result, when a situation occurs in which the state of the oscillator transitions to an uncontrollable state, the clock signal can be corrected based on the drift characteristics unique to the oscillator mounted on the wireless base station, and the system 10 of this embodiment can achieve a longer holdover time. In particular, by adding a correction signal with the inverse characteristics of the drift characteristics to the clock signal, the system 10 according to this embodiment can achieve an even longer holdover time. Furthermore, by correcting the clock signal based on the drift characteristics inherent to the oscillator installed in the wireless base station, the system 10 according to this embodiment can achieve a longer holdover time even with an oscillator that is lower performance and less expensive compared to oscillators installed in conventional wireless base stations. As a result, the system 10 according to this embodiment can contribute to the inexpensive realization of wireless base stations that are less susceptible to adverse effects such as accidents and disasters. 【0078】 Figure 5 schematically shows an example of the functional configuration of the control device 350. The control device 350 comprises a control unit 352, a clock signal acquisition unit 354, a identification unit 356, a characteristic storage unit 358, a correction unit 362, a measurement unit 364, a learning data acquisition unit 366, a learning data storage unit 368, a model generation unit 372, a model storage unit 374, a model acquisition unit 376, and a learning data transmission unit 378. However, it is not necessarily required that the control device 350 comprises all of these components. 【0079】 The control unit 352 controls various control targets. For example, the control unit 352 controls various control targets by generating various control signals and transmitting the generated control signals to the various control targets. 【0080】 The control unit 352 controls, for example, an oscillator 360 that generates a frequency-controlled clock signal based on a reference signal provided from an external source. The oscillator 360 may be an example of an object controlled by the control device 350. 【0081】 The control unit 352 controls the oscillator 360 so that its state transitions from a controlled state to a controlled state. The control unit 352 transitions the state of the oscillator 360 from a controlled state to a controlled state by, for example, transitioning the state of the switch 370 from an input state to an off state. The control unit 352 controls the oscillator 360 so that its state transitions from a controlled state to a controlled state. The control unit 352 transitions the state of the oscillator 360 from a controlled state to a controlled state by, for example, transitioning the state of the switch 370 from an off state to an input state. 【0082】 The clock signal acquisition unit 354 acquires the clock signal generated by the oscillator 360. For example, the clock signal acquisition unit 354 acquires the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped. 【0083】 The identification unit 356 identifies various characteristics. The identification unit 356 may store the identified characteristics in the characteristic storage unit 358. 【0084】 The identification unit 356 identifies, for example, the drift characteristics of the clock signal generated by the oscillator 360. The identification unit 356 identifies, for example, the amount of frequency drift per unit time of the clock signal generated by the oscillator 360 as the drift characteristics of the clock signal generated by the oscillator 360. The identification unit 356 may also identify other arbitrary parameters that can identify the drift characteristics of the clock signal generated by the oscillator 360 as the drift characteristics of the clock signal generated by the oscillator 360. 【0085】The identification unit 356 identifies, for example, the drift characteristics of the clock signal generated by the unfrequency-controlled oscillator 360. The identification unit 356 identifies, for example, the drift characteristics of the clock signal generated by the unfrequency-controlled oscillator 360 based on the clock signal acquired by the clock signal acquisition unit 354, which was generated by the oscillator 360 while the frequency control of the oscillator 360 was stopped. 【0086】 The control unit 352 transitions the state of the oscillator 360 from a controlled state to a controlled state when the connection status of the communication terminals 30 to the wireless base station 300 equipped with the oscillator 360 satisfies predetermined connection status conditions. One connection status condition is that the number of communication terminals 30 that have established a wireless communication connection with the wireless base station 300 is less than a predetermined threshold for the number of communication terminals. Another connection status condition is that there are no communication terminals 30 that have established a wireless communication connection with the wireless base station 300. 【0087】 The control device 350 can identify the drift characteristics of the clock signal generated by the uncontrolled oscillator 360 by transitioning the state of the oscillator 360 from a controlled state to a controlled state when the connection status of the communication terminal 30 to the wireless base station 300 equipped with the oscillator 360 satisfies the connection status conditions. In this way, the control device 350 can identify the drift characteristics of the clock signal generated by the uncontrolled oscillator while suppressing a deterioration in the service quality of the mobile communication service provided by the wireless base station. 【0088】 The correction unit 362 corrects the clock signal generated by the oscillator 360. The correction unit 362 corrects the clock signal generated by the oscillator 360 based on various characteristics stored in the characteristic storage unit 358, for example. 【0089】The correction unit 362 corrects the clock signal generated by the uncontrolled oscillator 360 when the oscillator 360 is in an uncontrollable state. The correction unit 362 corrects the clock signal generated by the uncontrolled oscillator 360 based on the drift characteristics of the clock signal generated by the uncontrolled oscillator 360, which are stored in the characteristic storage unit 358. 【0090】 The correction unit 362 corrects the clock signal generated by the uncontrolled oscillator 360, for example, to make the holdover time longer. The correction unit 362 corrects the clock signal generated by the uncontrolled oscillator 360, for example, to make the period during which the frequency deviation of the clock signal generated by the uncontrolled oscillator 360 with respect to a reference signal is smaller than a predetermined allowable frequency deviation longer. The correction unit 362 corrects the clock signal generated by the uncontrolled oscillator 360, for example, by adding a correction signal with the inverse characteristics of the drift characteristics to the clock signal generated by the uncontrolled oscillator 360. The correction unit 362 may use an adder 380 to add the correction signal to the clock signal generated by the uncontrolled oscillator 360. 【0091】 The measuring unit 364 measures the temperature of the oscillator 360. The measuring unit 364 can be any temperature sensor that is capable of measuring the temperature of the oscillator 360. Here, a thermistor is given as an example of a temperature sensor for measuring the temperature of the oscillator 360. 【0092】 The measuring unit 364 measures the temperature of the oscillator 360, for example, while the frequency control of the oscillator 360 is stopped. The measuring unit 364 also measures the temperature of the oscillator 360, for example, while the connection status of the communication terminal 30 to the wireless base station 300 equipped with the oscillator 360 satisfies the connection status conditions. 【0093】The identification unit 356 identifies, for example, the temperature characteristics of the oscillator 360. The temperature characteristics of the oscillator 360 may be an indicator showing the change in the temperature of the oscillator 360 in response to changes in the operating status of the oscillator 360 or the ambient temperature around the oscillator 360. 【0094】 The identification unit 356 identifies, for example, the temperature characteristics of the oscillator 360 while the frequency control of the oscillator 360 is stopped. The identification unit 356 identifies, for example, the temperature characteristics of the oscillator 360 while the frequency control of the oscillator 360 is stopped, based on the temperature of the oscillator 360 measured by the measurement unit 364 while the frequency control of the oscillator 360 is stopped. 【0095】 The identification unit 356 further identifies the drift characteristics of the clock signal generated by the unwavenumber-controlled oscillator 360, for example, based on the temperature characteristics of the oscillator 360 stored in the characteristic storage unit 358. The identification unit 356 identifies the drift characteristics of the clock signal generated by the unwavenumber-controlled oscillator 360 for each temperature characteristic of the oscillator 360 while the frequency control of the oscillator 360 is stopped. 【0096】 The drift characteristics of a clock signal generated by an oscillator that is not frequency-controlled vary depending on the temperature characteristics of the oscillator. Therefore, by specifying the drift characteristics of the clock signal for each temperature characteristic of the oscillator, the control device 350 can correct the clock signal using an index that allows for an even longer holdover time. 【0097】 The measuring unit 364 measures the temperature of the oscillator 360, for example, while frequency control of the oscillator 360 is being performed. The measuring unit 364 also measures the temperature of the wireless base station 300, for example, when frequency control of the oscillator 360 is being performed and the connection status of the communication terminal 30 to the wireless base station 300 does not meet the connection status conditions. The measuring unit 364 may also measure the temperature of the oscillator 360 when frequency control of the oscillator 360 cannot be performed. 【0098】The identification unit 356 identifies the temperature characteristics of the oscillator 360 when, for example, frequency control of the oscillator 360 is being performed, and the connection status of the wireless base station 300 to the wireless base station 300 does not meet the connection status conditions. The identification unit 356 identifies the temperature characteristics of the oscillator 360 when the connection status of the wireless base station 300 to the wireless base station 300 does not meet the connection status conditions, based on the temperature of the oscillator 360 measured by the measurement unit 364 when the connection status of the communication terminal 30 to the wireless base station 300 does not meet the connection status conditions. 【0099】 The control unit 352 controls the temperature of the oscillator 360, for example. The control unit 352 controls the temperature of the oscillator 360 based on the temperature of the oscillator 360 measured by the measuring unit 364, for example. 【0100】 The control unit 352 controls the temperature of the oscillator 360, for example, by controlling a temperature compensation circuit mounted on the oscillator 360. The control unit 352 may also control the temperature of the oscillator 360 by controlling the operating rate of the wireless base station 300. The temperature of the wireless base station 300 tends to increase as the operating rate of the wireless base station 300 increases. 【0101】 The control unit 352 controls the temperature of the oscillator 360, for example, while the frequency control of the oscillator 360 is stopped. The control unit 352 controls the temperature of the oscillator 360 so that the temperature characteristics of the oscillator 360 while the frequency control of the oscillator 360 is stopped better match the temperature characteristics of the oscillator 360 when the connection status of the communication terminal 30 to the wireless base station 300 does not meet the connection status conditions. 【0102】As described above, by controlling the temperature of the oscillator 360, the control device 350 can create a connection situation similar to a connection situation with a large number of communication terminals 30 that have established wireless communication connections with the wireless base station 300, even when the number of communication terminals 30 that have established wireless communication connections with the wireless base station 300 is small. This allows the control device 350 to identify the drift characteristics of the clock signal generated by the uncontrolled oscillator in a connection situation with a large number of communication terminals that have established wireless communication connections with the wireless base station, while suppressing a deterioration in the service quality of the mobile communication service provided by the wireless base station. 【0103】 The learning data acquisition unit 366 acquires learning data. The learning data includes, for example, operating time data showing the operating time from when the oscillator 360 starts operating until the frequency control of the oscillator 360 is stopped, and drift characteristic data showing the drift characteristics of the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped. The learning data further includes, for example, temperature data showing the temperature of the oscillator 360 measured by the measurement unit 364 when the frequency control of the oscillator 360 is stopped. The learning data further includes, for example, temperature characteristic data showing the temperature characteristics of the oscillator 360 while the frequency control of the oscillator 360 is stopped. The learning data acquisition unit 366 may store the acquired learning data in the learning data storage unit 368. 【0104】 The model generation unit 372 generates a specific model that identifies the drift characteristics of the clock signal generated by the oscillator 360. For example, the model generation unit 372 uses multiple training data stored in the training data storage unit 368 as training data to generate a specific model that identifies the drift characteristics of the clock signal generated by the oscillator 360 using machine learning. The model generation unit 372 may store the generated specific model in the model storage unit 374. 【0105】The model generation unit 372 generates a specific model that identifies the drift characteristics of the clock signal generated by the oscillator 360 while the oscillator 360 is unable to perform frequency control, from input data that includes, for example, operating time data indicating the operating time from when the oscillator 360 starts operating until when it becomes impossible to perform frequency control of the oscillator 360. The model generation unit 372 also generates a specific model that identifies the drift characteristics of the clock signal generated by the oscillator 360 while the oscillator 360 is unable to perform frequency control, from input data that further includes, for example, temperature data indicating the temperature of the oscillator 360 measured by the measurement unit 364 when it becomes impossible to perform frequency control of the oscillator 360. 【0106】 The model acquisition unit 376 acquires a specific model that identifies the drift characteristics of the clock signal generated by the oscillator 360. The model acquisition unit 376 acquires the specific model by receiving it, for example, via a network that includes at least one of the core network and the internet. The specific model acquired by the model acquisition unit 376 may be a characteristic model similar to the specific model that the model generation unit 372 can generate. The model acquisition unit 376 may store the acquired specific model in the model storage unit 374. 【0107】 The model acquisition unit 376 acquires a specific model from, for example, a distributed infrastructure 200 that controls the functions of a RAN 310 composed of wireless base stations 300. The model acquisition unit 376 may also acquire a specific model from any other model generation device. 【0108】The identification unit 356, for example, uses a specific model stored in the model storage unit 374 to identify the drift characteristics of the clock signal generated by the oscillator 360 during the period when frequency control of the oscillator 360 cannot be performed, from input data including operating time data indicating the operating time from when the oscillator 360 starts operating until when frequency control of the oscillator 360 becomes impossible. The identification unit 356, for example, uses a specific model to identify the drift characteristics of the clock signal generated by the oscillator 360 during the period when frequency control of the oscillator 360 cannot be performed, from input data including temperature data indicating the temperature of the oscillator 360 measured by the measurement unit 364 when frequency control of the oscillator 360 becomes impossible. 【0109】 The learning data transmission unit 378 transmits the learning data stored in the learning data storage unit 368. The learning data transmission unit 378 transmits the learning data, for example, via a network. 【0110】 The learning data transmission unit 378 transmits the learning data to a distributed infrastructure 200 that controls the functions of the RAN 310, which is composed of, for example, a wireless base station 300. The learning data transmission unit 378 may also transmit the learning data to any other model generation device. 【0111】 Figure 6 schematically shows an example of the functional configuration of the distributed infrastructure 200. The distributed infrastructure 200 includes a training data acquisition unit 202, a training data storage unit 204, an execution unit 206, a model storage unit 212, and a model transmission unit 214. However, it is not necessarily required that the distributed infrastructure 200 have all of these components. 【0112】 The learning data acquisition unit 202 acquires learning data. The learning data acquisition unit 202 may store the acquired learning data in the learning data storage unit 204. 【0113】 The learning data acquisition unit 202 acquires learning data, for example, from a wireless base station 300 that constitutes the RAN 310. The learning data acquisition unit 202 acquires learning data from the wireless base station 300, for example, by receiving the learning data from the wireless base station 300 via a network. 【0114】The execution unit 206 performs various processes. The execution unit 206 includes, for example, a RAN control function 207 and a model generation function 209. The RAN control function 207 and the model generation function 209 may use the same computing resources. 【0115】 The RAN control function 207 controls the functions of the RAN 310. The RAN control function 207 controls the functions of the RAN 310, for example, by executing RAN_AI. The RAN control function 207 may also control the functions of the RAN 310 by executing any other processing. 【0116】 The model generation function 209 generates a specific model that identifies the drift characteristics of the clock signal generated by the oscillator 360 mounted on the wireless base station 300 that constitutes the RAN 310. The model generation function 209 generates a specific model similar to, for example, a specific model that can be generated by the control device 350 mounted on the wireless base station 300. The model generation function 209 may store the generated specific model in the model storage unit 212. 【0117】 The model generation function 209 generates a specific model using machine learning, for example, by using multiple training data stored in the training data storage unit 204 as training data. The application execution function may be an example of the model generation function 209. 【0118】The model generation function 209 generates a specific model by machine learning when, for example, the computing resources of the execution unit 206 meet predetermined resource conditions. The model generation function 209 generates a specific model by machine learning when, for example, the amount of available resources in the computing resources of the execution unit 206 is greater than a predetermined threshold for available resources. The model generation function 209 generates a specific model by machine learning when, for example, the amount of available resources of the GPU resources included in the computing resources of the execution unit 206 is greater than a threshold for available resources. The model generation function 209 generates a specific model by machine learning when, for example, the amount of available resources of the CPU resources included in the computing resources of the execution unit 206 is greater than a threshold for available resources. The model generation function 209 generates a specific model by machine learning when, for example, the sum of the available resources of the GPU resources and CPU resources included in the computing resources of the execution unit 206 is greater than a threshold for available resources. 【0119】 The model transmission unit 214 transmits a specific model stored in the model storage unit 212. The model transmission unit 214 transmits the specific model to, for example, a wireless base station 300 that constitutes the RAN 310. The model transmission unit 214 transmits the specific model to the wireless base station 300, for example, via the network. 【0120】 Figure 7 is an explanatory diagram illustrating an example of the processing flow of the control device 350. Here, an example of the processing flow of the control device 350 when identifying the drift characteristics of a clock signal generated by an oscillator 360 that is not frequency controlled is described. The state of the oscillator 360 being in a controlled state is considered the starting state. 【0121】In step 102 (steps may be abbreviated as S), the control unit 352 determines whether the connection status of the communication terminal 30 to the wireless base station 300 equipped with the oscillator 360 satisfies the connection status conditions. If the control unit 352 determines that the connection status of the communication terminal 30 to the wireless base station 300 equipped with the oscillator 360 satisfies the connection status conditions, the process proceeds to S104. If the control unit 352 determines that the connection status of the communication terminal 30 to the wireless base station 300 equipped with the oscillator 360 does not satisfy the connection status conditions, the processing of the control device 350 ends without specifying the drift characteristics of the clock signal generated by the oscillator 360, which is not frequency controlled. 【0122】 In S104, the control unit 352 controls the switch 370 to transition the state of the oscillator 360 from the controlled state to the controlled state. In S106, the clock signal acquisition unit 354 acquires the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped, in response to the control unit 352 transitioning the state of the oscillator 360 from the controlled state to the controlled state in S104. In S108, the control unit 352 controls the switch 370 to transition the state of the oscillator 360 from the controlled state to the controlled state, in response to the clock signal acquisition unit 354 acquiring the data necessary for the identification unit 356 to identify the drift characteristics of the clock signal generated by the oscillator 360, which is not frequency controlled, in S106. 【0123】 In S110, the identification unit 356 identifies the drift characteristics of the clock signal generated by the oscillator 360 while the frequency control of the oscillator 360 is stopped, based on the clock signal acquired by the clock signal acquisition unit 354 in S106. After that, the processing of the control device 350 is completed. 【0124】 Figure 8 is an explanatory diagram illustrating another example of the processing flow of the control device 350. Here, an example of the processing flow of the control device 350 when frequency controlling or correcting the clock signal generated by the oscillator 360 is described. The state of the oscillator 360 being in the control state is defined as the starting state. 【0125】 In S202, the control unit 352 determines whether the oscillator 360 is in an uncontrollable state. For example, if the reference signal is not input to the switch 370, the control unit 352 determines that the oscillator 360 is in an uncontrollable state. On the other hand, if the reference signal is input to the switch 370, the control unit 352 determines that the oscillator 360 is not in an uncontrollable state. If the control unit 352 determines that the oscillator 360 is not in an uncontrollable state, the process proceeds to S204. If the control unit 352 determines that the oscillator 360 is in an uncontrollable state, the process proceeds to S206. 【0126】 In S204, the control unit 352 performs frequency control of the oscillator 360. In S206, the correction unit 362 corrects the clock signal generated by the uncontrolled oscillator 360 based on the drift characteristics of the clock signal generated by the uncontrolled oscillator 360, which are stored in the characteristic storage unit 358. 【0127】 In S208, the control unit 352 determines whether the holdover time has elapsed. If the control unit 352 determines that the holdover time has not elapsed, the process proceeds to S210. If the control unit 352 determines that the holdover time has elapsed, the process proceeds to S212. 【0128】 In S210, the control unit 352 instructs the radio base station 300 to continue operation until the holdover time has elapsed. The radio base station 300 may be an example of an object controlled by the control device 350. 【0129】 In S212, the control unit 352 instructs the wireless base station 300 to stop operation because the holdover time has elapsed. After that, the control device 350 finishes processing. 【0130】 In S214, the control unit 352 determines whether or not it has received an operation termination instruction to terminate the operation of the wireless base station 300. If the control unit 352 determines that it has received an operation termination instruction, it proceeds to S216. If the control unit 352 determines that it has not received an operation termination instruction, it returns to S202. 【0131】In S216, the control unit 352 instructs the wireless base station 300 to terminate its operation. After that, the control device 350 finishes processing. 【0132】 Figure 9 schematically shows an example of the hardware configuration of a computer 1200 that functions as a distributed infrastructure 200 or a control device 350. A program installed on the computer 1200 can cause the computer 1200 to function as one or more "parts" of the apparatus according to this embodiment, or to cause the computer 1200 to execute operations associated with the apparatus according to this embodiment or such one or more "parts", and / or to cause the computer 1200 to execute a process or a stage of such process according to this embodiment. Such a program may be executed by the CPU 1212 to cause the computer 1200 to execute specific operations associated with some or all of the blocks in the flowcharts and block diagrams described herein. 【0133】 The computer 1200 according to this embodiment includes a CPU 1212, RAM 1214, and a graphics controller 1216, which are interconnected by a host controller 1210. The computer 1200 also includes input / output units such as a communication interface 1222, a storage device 1224, a DVD drive 1226, and an IC card drive, which are connected to the host controller 1210 via an input / output controller 1220. The DVD drive 1226 may be a DVD-ROM drive and a DVD-RAM drive, etc. The storage device 1224 may be a hard disk drive and a solid-state drive, etc. The computer 1200 also includes legacy input / output units such as a ROM 1230 and a keyboard, which are connected to the input / output controller 1220 via an input / output chip 1240. 【0134】The CPU 1212 operates according to the programs stored in the ROM 1230 and RAM 1214, thereby controlling each unit. The graphics controller 1216 acquires the image data generated by the CPU 1212 and stores it in the frame buffer provided in the RAM 1214 or within itself, so that the image data is displayed on the display device 1218. 【0135】 The communication interface 1222 communicates with other electronic devices via a network. The storage device 1224 stores programs and data used by the CPU 1212 in the computer 1200. The DVD drive 1226 reads programs or data from the DVD-ROM 1227, etc., and provides them to the storage device 1224. The IC card drive reads programs and data from the IC card and / or writes programs and data to the IC card. 【0136】 The ROM 1230 stores boot programs and / or hardware-dependent programs of the computer 1200, which are executed by the computer 1200 when activated. The input / output chip 1240 may also connect various input / output units to the input / output controller 1220 via USB ports, parallel ports, serial ports, keyboard ports, mouse ports, etc. 【0137】 The program is provided on a computer-readable storage medium such as a DVD-ROM 1227 or an IC card. The program is read from the computer-readable storage medium and installed on a storage device 1224, RAM 1214, or ROM 1230, which are examples of computer-readable storage media, and executed by the CPU 1212. The information processing described within these programs is read by the computer 1200, resulting in coordination between the program and the various types of hardware resources described above. The apparatus or method may be configured to realize the operation or processing of information in accordance with the use of the computer 1200. 【0138】For example, when communication is performed between a computer 1200 and an external device, the CPU 1212 may execute a communication program loaded into the RAM 1214 and, based on the processing described in the communication program, instruct the communication interface 1222 to perform communication processing. Under the control of the CPU 1212, the communication interface 1222 reads transmission data stored in a transmission buffer area provided in a recording medium such as the RAM 1214, storage device 1224, DVD-ROM 1227, or IC card, transmits the read transmission data to the network, or writes received data received from the network to a reception buffer area or the like provided on the recording medium. 【0139】 Furthermore, the CPU 1212 may read all or necessary parts of a file or database stored on an external recording medium such as a storage device 1224, a DVD drive 1226 (DVD-ROM 1227), or an IC card into the RAM 1214, and perform various types of processing on the data in the RAM 1214. The CPU 1212 may then write the processed data back to the external recording medium. 【0140】 Various types of information, such as various types of programs, data, tables, and databases, may be stored on the recording medium and subjected to information processing. The CPU 1212 may perform various types of processing on the data read from the RAM 1214, including various types of operations, information processing, conditional judgments, conditional branching, unconditional branching, information retrieval / replacement, etc., as described throughout this disclosure and specified by the program instruction sequence, and write the results back to the RAM 1214. The CPU 1212 may also retrieve information in files, databases, etc., within the recording medium. For example, if a plurality of entries are stored in the recording medium, each having an attribute value of a first attribute associated with an attribute value of a second attribute, the CPU 1212 may search among the plurality of entries for an entry that matches the specified condition for the attribute value of the first attribute, read the attribute value of the second attribute stored in that entry, and thereby obtain the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition. 【0141】 The program or software module described above may be stored on or near the computer 1200 in a computer-readable storage medium. Alternatively, a recording medium such as a hard disk or RAM provided within a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, thereby providing the program to the computer 1200 via the network. 【0142】 In this embodiment, blocks in the flowchart and block diagram may represent a stage in a process in which an operation is performed or a "part" of a device that has the role of performing an operation. A particular stage and "part" may be implemented by a dedicated circuit, a programmable circuit supplied with computer-readable instructions stored on a computer-readable storage medium, and / or a processor supplied with computer-readable instructions stored on a computer-readable storage medium. The dedicated circuit may include digital and / or analog hardware circuits, and may include integrated circuits (ICs) and / or discrete circuits. The programmable circuit may include reconfigurable hardware circuits, such as field-programmable gate arrays (FPGAs) and programmable logic arrays (PLAs), which include logical AND, logical OR, exclusive OR, negated AND, negated OR, and other logical operations, flip-flops, registers, and memory elements. 【0143】Computer-readable media may include any tangible device capable of storing instructions to be executed by a suitable device, and as a result, computer-readable media having instructions stored therein will comprise a product that includes instructions that can be executed to create means for performing operations specified in a flowchart or block diagram. Examples of computer-readable media may include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, etc. More specific examples of computer-readable media may include floppy disks (registered trademark), diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), electrically erasable programmable read-only memory (EEPROM), static random access memory (SRAM), compact disk read-only memory (CD-ROM), digital multipurpose disc (DVD), Blu-ray (registered trademark) disc, memory stick, integrated circuit card, etc. 【0144】 Computer-readable instructions may include assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk®, Java®, C++, and conventional procedural programming languages ​​such as the C programming language or similar programming languages. 【0145】Computer-readable instructions are provided locally or via a wide area network (WAN) such as a local area network (LAN) or the internet to the processor or programmable circuit of a programmable data processing device such as a computer, and may be executed to create means for performing operations specified in a flowchart or block diagram. Here, the computer may be a PC (personal computer), tablet computer, smartphone, workstation, server computer, general-purpose computer, or special-purpose computer, and may also be a computer system in which multiple computers are connected. Such a computer system in which multiple computers are connected is also called a distributed computing system and is a computer in a broad sense. In a distributed computing system, multiple computers execute a program by having each computer execute a part of the program and by passing data during program execution between computers as needed. 【0146】 Examples of processors include computer processors, central processing units (CPUs), processing units, microprocessors, digital signal processors, controllers, and microcontrollers. A computer may have one or more processors. In a multiprocessor system with multiple processors, each processor executes a portion of the program, and the processors collectively execute the program by passing program execution data between them as needed. For example, in the execution of multitasks, each of the multiple processors may execute a portion of each task in small chunks by switching tasks at each time slice. In this case, which part of a program each processor executes changes dynamically. Which part of a program each of the multiple processors executes may also be statically determined by multiprocessor-aware programming. 【0147】This invention can contribute to the low-cost realization of wireless base stations that are less susceptible to adverse effects such as accidents and disasters, and can contribute to the low-cost realization of highly power-efficient mobile communications, thereby contributing to the achievement of Sustainable Development Goal (SDG) 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and Goal 11 "Make cities and human settlements inclusive, safe, resilient and sustainable." 【0148】 Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention. 【0149】 It should be noted that the execution order of operations, procedures, steps, and stages in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before" or "prior to," and that these can be performed in any order unless the output of a previous operation is used in a later operation. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," and "next," for convenience, this does not mean that it is mandatory to perform the operations in that order. 【0150】10 System, 30 Communication terminal, 100 Management infrastructure, 200 Distributed infrastructure, 202 Learning data acquisition unit, 204 Learning data storage unit, 206 Execution unit, 207 RAN control function, 209 Model generation function, 212 Model storage unit, 214 Model transmission unit, 300 Wireless base station, 350 Control device, 352 Control unit, 354 Clock signal acquisition unit, 356 Identification unit, 358 Characteristics storage unit, 360 Oscillator, 362 Correction unit, 364 Measurement unit, 366 Learning data acquisition unit, 368 Learning data storage unit, 370 Switch, 372 Model generation unit, 374 Model storage unit, 376 Model acquisition unit, 378 Learning data transmission unit, 380 Adder, 1200 Computer, 1210 Host controller, 1212 CPU, 1214 RAM, 1216 Graphics controller, 1218 Display device, 1220 Input / Output controller, 1222 Communication interface, 1224 Storage device, 1226 DVD drive, 1227 DVD-ROM, 1230 ROM, 1240 Input / Output chip

Claims

1. A control device comprising: a control unit that stops the frequency control of an oscillator that generates a frequency-controlled clock signal based on a reference signal provided from an external source; a clock signal acquisition unit that acquires the clock signal generated by the oscillator while the frequency control of the oscillator is stopped; and a specification unit that identifies the drift characteristics of the clock signal generated by the oscillator that is not frequency-controlled, based on the clock signal generated by the oscillator while the frequency control of the oscillator is stopped.

2. The control device according to claim 1, further comprising a correction unit that corrects the clock signal generated by the oscillator based on the drift characteristics, so as to extend the period during which the frequency deviation of the clock signal generated by the oscillator with respect to the reference signal is less than a predetermined allowable frequency deviation when frequency control of the oscillator cannot be performed.

3. The control device according to claim 2, wherein the correction unit corrects the clock signal generated by the oscillator by adding a correction signal having the inverse characteristics of the drift characteristics to the clock signal generated by the oscillator.

4. The control device according to any one of claims 1 to 3, wherein the control unit stops frequency control of the oscillator when the connection status of a communication terminal to a wireless base station equipped with the oscillator satisfies predetermined connection status conditions.

5. The control device according to claim 4, wherein the control unit stops the frequency control of the oscillator when there is no communication terminal that has established a wireless communication connection with the wireless base station.

6. The control device according to claim 4, further comprising a measuring unit for measuring the temperature of the oscillator, wherein the identifying unit further identifies the temperature characteristics of the oscillator when the connection status of the communication terminal to the wireless base station does not satisfy the connection status conditions, based on the temperature of the oscillator measured by the measuring unit when the connection status of the communication terminal to the wireless base station does not satisfy the connection status conditions, when frequency control of the oscillator is being performed, and the control unit controls the temperature of the oscillator such that the temperature characteristics of the oscillator while the frequency control of the oscillator is stopped better match the temperature characteristics of the oscillator when the connection status of the communication terminal to the wireless base station does not satisfy the connection status conditions.

7. The control device according to any one of claims 1 to 6, further comprising a measuring unit for measuring the temperature of the oscillator, wherein the identifying unit identifies the temperature characteristics of the oscillator during the period when the frequency control of the oscillator is stopped, based on the temperature of the oscillator measured by the measuring unit during the period when the frequency control of the oscillator is stopped, thereby identifying the drift characteristics of the clock signal generated by the oscillator that is not frequency controlled for each temperature characteristic of the oscillator.

8. A control device according to any one of claims 1 to 7, further comprising: a learning data storage unit that stores learning data including operating time data indicating the operating time from when the oscillator starts operating until the frequency control of the oscillator is stopped, and drift characteristic data indicating the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator is stopped; and a model generation unit that uses a plurality of the learning data stored in the learning data storage unit as training data to generate a specific model by machine learning that identifies the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator cannot be performed, from input data including operating time data indicating the operating time from when the oscillator starts operating until the frequency control of the oscillator can no longer be performed, wherein the specific unit uses the specific model to identify the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator cannot be performed.

9. The control device according to claim 8, further comprising a measurement unit for measuring the temperature of the oscillator, the learning data storage unit storing the learning data further including temperature data indicating the temperature of the oscillator measured by the measurement unit when the frequency control of the oscillator is stopped, the model generation unit generating a specific model from the input data further including temperature data indicating the temperature of the oscillator measured by the measurement unit when the frequency control of the oscillator becomes impossible to perform, the specific unit using the specific model to identify the drift characteristics of the clock signal generated by the oscillator while the frequency control of the oscillator becomes impossible to perform, from the input data further including temperature data indicating the temperature of the oscillator measured by the measurement unit when the frequency control of the oscillator becomes impossible to perform.

10. A wireless base station comprising a control device according to any one of claims 1 to 9 and the oscillator.

11. A program, when executed by a computer, that causes the computer to function as a control device according to any one of claims 1 to 9.

12. A control method performed by a computer, comprising: a control step of stopping the frequency control of an oscillator that generates a frequency-controlled clock signal with reference to an externally provided reference signal; a clock signal acquisition step of acquiring the clock signal generated by the oscillator while the frequency control of the oscillator is stopped; and a identification step of identifying the drift characteristics of the clock signal generated by the oscillator that is not frequency-controlled, based on the clock signal generated by the oscillator while the frequency control of the oscillator is stopped.

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