Short-wave communication frequency selection method based on historical communication record data

Abstract

The invention discloses a short-wave communication frequency selection method based on historical communication record data, which processes the historical data accumulated in the short-wave communication process, predicts and selects the optimal communication frequency, and the frequency selection result has great correlation and accuracy and better conforms to the actual communication condition. The defects of the medium-and-long-term frequency prediction system in the aspects of real-time performance and accuracy are overcome, a special additional frequency prediction system is not needed, and the method is simple, efficient and high in practicability.

Description

Technical Field

[0001] The invention belongs to the field of shortwave communication, and in particular relates to a shortwave communication frequency selection method based on shortwave communication historical record data. Background Art

[0002] Traditional shortwave communication frequency prediction methods include Chirp detection and medium- and long-term frequency prediction systems.

[0003] Chirp detection: The use of chirp detection method for frequency prediction and selection requires an independent shortwave chirp detection system. The data obtained from each real-time detection is statistically analyzed to determine the best communication frequency. It has high real-time and reliability. It is expensive and is often used by professional groups for ionospheric research, but not suitable for shortwave communication units.

[0004] Medium- and long-term frequency prediction system: The ionosphere is monitored for a long time through the ionosphere detection system, the ionosphere characteristics are recorded, the laws of solar activity and the earth's magnetic field are summarized, and the relevant characteristics of the ionosphere are discovered. The medium- and long-term frequency prediction software predicts the highest available frequency, the lowest available frequency, and the best available frequency of the current communication link based on the communication time, communication location (latitude and longitude), weather, number of sunspots, type of transceiver antenna, transmission power and other parameters of the transceiver station. Long-term forecasts are usually based on months or years, and the long-term change trend of the shortwave channel is considered, while the real-time situation of the shortwave channel is less considered. Therefore, it is generally used for rough selection of frequencies or to determine the passable frequency bands. Summary of the invention

[0005] In view of the problems existing in the existing frequency selection technology, the purpose of the present invention is to provide a shortwave communication frequency selection method based on historical communication record data. By processing the historical data accumulated in the shortwave communication process, the optimal communication frequency is selected to provide effective guarantee for the establishment of the shortwave communication link, and the success rate of shortwave communication link establishment is further improved.

[0006] In order to achieve the above object, the technical solution of the present invention is a shortwave communication frequency selection method based on historical communication record data, comprising the following steps: Step 1: Create a historical communication log: In the shortwave communication system, a historical communication log file is established, which records in detail the communication information of the shortwave communication system during the entire working process; the shortwave communication control system will save all historical communication logs, and the "frequency-score" information in the log is determined during the link quality analysis. The historical communication log file is stored in the form of a text file, and the daily communication record generates an independent historical communication log file; Step 2: Get the geographic location and time information of both communicating sites: The shortwave communication control system obtains the geographical location information and time information of both communication sites through Beidou or GPS; Step 3: Read historical communication records: Read the historical communication records in the historical communication log file in sequence; Step 4: Filter historical communication records based on geographic location and time range: The shortwave communication control system analyzes the historical communication logs according to the geographical locations of the communicating parties and the communication time, selects the "frequency-score" pairs that meet the geographical location range and time range, screens out the valid communication records, and predicts the communication frequency based on these communication records; Step 5: Determine whether the number of extracted historical communication records is sufficient, and use different methods to perform frequency prediction and selection according to the number of extracted historical communication records; Step 6: Process the historical communication records and sort them by scores; Step 4: After filtering out the valid historical communication records, it is necessary to score the acquired historical communication record data in the form of "frequency-score", where the highest score is 100 and the lowest is "×". "×" means that the communication at this frequency has failed. Since the same frequency may be used multiple times and the score for each use may not be the same, the filtered original "frequency-score" data must be processed; Step 7: Curve fitting to obtain the "frequency-score" curve: Step 6 extracts a large amount of "frequency-score" data that conforms to both the geographic location range and the time range from the historical communication records; adopts the least squares curve fitting method to fit the discrete "frequency-score" historical data into a smooth and continuous "frequency-score" curve, with the horizontal axis being the frequency and the vertical axis being the score. The scores of other frequencies can be easily predicted on this curve, and the frequencies are sorted from large to small according to the scores, thus obtaining the ranking result of the given frequencies; Step 8: Determine the best frequency based on the frequency selection conditions: (1) Unconditionally select the best frequency in the entire frequency band; (2) Select the best frequency in a given frequency band; (3) Select the best frequency among the given frequency points; (4) Select the best frequency band in the entire frequency band; (5) Select one or more optimal frequency bands from a given frequency band.

[0007] Step 9: Eliminate interference frequencies and disabled frequencies to obtain the final frequency.

[0008] Furthermore, step 4 screening includes two processes: screening historical communication records based on geographical location range, and screening historical communication records based on time range: (1) Filter historical communication records based on geographic location range Taking the geographical location of the communicating parties as the center, a certain grid distance radius area is reasonably selected based on the actual situation. All the sites in this area are regarded as the same site. The longitude and latitude of the communication location in the historical communication records are all valid in this geographical area and can be used as the basis for selecting the communication frequency this time. (2) Filter historical communication records based on time range Select the records with communication time T from the historical communication records that meet the geographic location range selection conditions; the historical communication records at the same time T and one hour before and after time T within a month are all records that meet the time range; if there are too few communication records that meet the requirements, consider taking the historical communication records at the same time T and one hour before and after time T within a year as the basis for this communication frequency prediction.

[0009] Furthermore, step 5 adopts different methods to perform frequency prediction and selection according to the number of historical communication records extracted. The specific methods are as follows: (1) When there is no historical record that meets the requirements or the number is too small After screening according to the geographical location range and time range, the qualified historical communication records are obtained. If the qualified historical communication records do not exist or the number is too small, the program flow adopts the frequency selection based on the medium- and long-term prediction software; (2) When the number of historical communication records that meet the requirements is sufficient After filtering based on the geographic location range and time range, if sufficient historical communication records are obtained for reference, proceed to step 6.

[0010] Furthermore, the method for processing the filtered original "frequency-score" data in step 6 is: For the case where the frequency is the same but the scores are different, weighted processing should be performed according to the different usage time to obtain a weighted score as the final score corresponding to this frequency. In principle, the weight of the frequency closer to the communication time is set higher, and the weight of the frequency farther from the communication time is set lower. For the sake of simplicity of calculation, the average score is taken as the final score of the frequency; For the frequency with a score of "×", make full use of all frequency information, assign it a score and participate in the subsequent prediction. The assigned score is selected from -10 to 10 points.

[0011] Furthermore, the specific method of unconditionally selecting the best frequency in the entire frequency band in step 8 (1) is: First, in the entire frequency band of 1.0~30MHz, frequency points are evenly selected according to a certain frequency interval. The score of each frequency point is scored with reference to the "frequency-score" fitting curve result, and the frequencies are sorted from large to small according to the score. The required N frequencies with high scores are selected as the full-band frequency selection results.

[0012] Furthermore, the specific method of selecting the best frequency in a given frequency band in step 8 (2) is: In a given frequency band, frequency points are selected at a certain frequency interval, and the scores of the selected frequency points are predicted by referring to the results of the "frequency-score" fitting curve. The frequencies are sorted from large to small according to the scores, and the first N frequencies with high scores are taken as the frequency selection results.

[0013] Furthermore, the specific method of selecting the best frequency among the given frequency points in step 8 (3) is: Refer to the "frequency-score" fitting curve result for all frequencies in a given frequency point, score each frequency point, sort the frequencies from large to small according to the score, and take the first N frequencies with high scores as the frequency selection results.

[0014] Furthermore, the specific method of selecting the best frequency band in the whole frequency band in step 8 (4) is: In the entire frequency band of 1.0~30MHz, refer to the "frequency-score" fitting curve results and set a threshold score according to actual needs. Frequencies with frequency scores higher than the threshold score constitute one or more frequency bands, which are used as the frequency selection result. If all frequency scores are not higher than the threshold score, lower the threshold score to obtain a frequency band of suitable width as the frequency selection result.

[0015] Furthermore, the specific method of selecting one or more optimal frequency bands from the given frequency bands in step 8 (5) is: In a given frequency band, a threshold score is set with reference to the "frequency-score" fitting curve result. Frequencies with frequency scores higher than the threshold constitute one or more frequency bands, which are used as the frequency selection result. If all frequency scores are not higher than the threshold score, the threshold score is lowered to obtain a frequency band of suitable width as the frequency selection result.

[0016] The present invention has the following beneficial effects: 1. The shortwave communication frequency selection method based on historical communication record data of the present invention is based on previous actual communication records. Compared with the medium- and long-term frequency prediction software that relies on past experience accumulation to obtain statistical formulas, it has unique innovation. It uses mathematical analysis methods to screen and process historical data, and the prediction results are more in line with the actual channel conditions, which makes up for the shortcomings of the medium- and long-term frequency prediction system in terms of real-time and accuracy. It has higher prediction accuracy and is more meaningful for practical applications.

[0017] 2. The shortwave communication frequency selection method of the present invention is based on historical communication record data. According to the historical data accumulated in the actual communication process and with reference to the previous actual communication records, the historical communication frequency that meets certain requirements (geographic location range, time range, frequency-score) is selected as the communication frequency of the current link, and frequency prediction and optimization are performed. It has great relevance and accuracy, does not require a special additional frequency prediction system, is simple and efficient, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the frequency selection flow chart of the present invention; Figure 2 It is a schematic diagram of historical communication log; Figure 3 is the least squares frequency prediction result. DETAILED DESCRIPTION

[0019] like Figure 1 As shown, a shortwave communication frequency selection method based on historical record data comprises the following steps: 1. Create a historical communication log Historical record data is the basis of this method. The richer the historical data, the higher the reliability of successful frequency selection. The present invention uses shortwave communication historical record data to select frequency, that is, in the shortwave communication control system software, a communication log file is designed, and the communication log file records in detail the communication information during the entire working process of shortwave communication, including communication contact time, geographical information of the shortwave radio station (latitude and longitude of the communication sites of both parties), call occurrence time, link establishment time, link establishment frequency, and link quality analysis detection score (frequency-score) when the corresponding communication link is established, what state is transferred to after successful link establishment, and the current system state, etc.

[0020] In each operation, the existing shortwave communication control system will save all communication logs. The "frequency-score" information in the logs is determined during the link quality analysis, so these logs have important reference value and are more specific and reliable than the current medium- and long-term prediction software. At present, log files are stored in the form of text files, and a separate file is generated for each day.

[0021] 2. Obtain the geographic location information and time information of the communicating parties The shortwave communication control equipment obtains the geographic location information and time information of the communicating parties through Beidou or GPS, mainly the longitude and latitude coordinates and system time, which are important bases for frequency selection and link establishment.

[0022] 3. Read historical communication records The first step of the frequency selection based on historical communication records of the present invention is to read these log files in sequence and then filter out effective information from them. The most important basis for data screening is the geographical location range and time range, and the size of their values ​​directly determines the accuracy of the prediction results.

[0023] 4. Filter historical communication records based on geographic location and time range The two key factors for frequency selection based on historical records are: geographic information (latitude and longitude) of both parties and communication time. At the same time, the communication conditions at different communication locations are very different. At the same communication location, the communication conditions at different communication times vary greatly due to the change of the ionosphere over time. The validity of the recorded information directly affects the reliability of frequency selection based on historical communication records. Rich historical communication information provides a good guarantee for improving the quality of shortwave communication.

[0024] like Figure 2 As shown, the shortwave communication control system analyzes the historical communication logs based on the geographic location information (latitude and longitude) of the communicating parties and the communication time, and selects the "frequency-score pairs" that meet the geographic location range and time range. It selects valid communication records and predicts the communication frequency based on these communication records.

[0025] It mainly includes two processes: filtering historical records based on geographical location range and filtering historical records based on time range.

[0026] (1) Filter historical communication records based on geographic location range Taking the geographic location (longitude and latitude) of the communicating parties as the center, a certain grid distance radius is reasonably selected based on the actual situation. All sites within this area are regarded as the same site. The longitude and latitude of the communication location in the historical communication records and all communication records within this geographical area are valid and can be used as the basis for selecting the communication frequency this time.

[0027] For example, the location of the shortwave communication master station is 120.04 degrees east longitude and 32.50 degrees north latitude, and the grid range is 5.0. Then the stations within the range of (E120.04±5.0, N32.50±5.0) can be regarded as being at the same location as the shortwave communication master station; the location of the communication slave station is 41.71 degrees east longitude and 18.33 degrees north latitude, and the grid range is 5.0. Then the stations within the range of (E41.71±5.0, N18.33±5.0) can be regarded as being at the same location as the communication slave station.

[0028] (2) Filter historical records based on time range Select the records with communication time T from the historical communication records that meet the geographic location range selection conditions. The historical records at the same time T and one hour before and after time T within a month are all records that meet the time range. If there are too few communication records that meet the requirements, you can consider using the historical records at the same time T and one hour before and after time T within a year as the basis for this communication frequency prediction.

[0029] 5. Determine whether the number of extracted historical communication records is sufficient, and use different methods to predict and select frequencies based on the number of extracted historical communication records: (1) The historical communication records that meet the requirements do not exist or are too few. After screening according to geographic location and time, historical communication records that meet the conditions are obtained. If historical communication records that meet the requirements do not exist or are too few, frequency selection based on medium- and long-term prediction software is adopted, which is not the content of the present invention.

[0030] (2) A sufficient number of historical communication records that meet the requirements After filtering based on geographic location and time, if sufficient historical communication records are available for reference (for example, the number of historical communication records available for reference is much greater than the number of frequencies required to be returned), the subsequent process is executed.

[0031] 6. Process historical records and sort them by scores In order to obtain enough historical data, it is necessary to read the logs of the previous few months or even years. The more historical data there is, the more accurate the prediction results will be and the closer they will be to the actual communication status. To read the log file, it is necessary to score the acquired data in the form of "frequency-score", where the highest score is 100 and the lowest is "×" (indicating that communication at this frequency failed). Since the same frequency may be used multiple times and the score for each use may not be the same, the filtered raw data must be preprocessed.

[0032] For the case where the frequency is the same but the scores are different, weighted processing should be performed according to the different usage time to obtain a weighted score as the final score corresponding to this frequency. In principle, the weight of the distance communication time is set higher, and the weight of the distance communication time is set lower. For the convenience of calculation, the average score can be taken as the final score of the frequency.

[0033] For frequencies with a score of "×", in order to make full use of all frequency information, you can assign a score to it and participate in the subsequent prediction. There are many reasons for communication failure, such as interference from other signal sources or noise during communication, temporary fluctuations in the ionosphere, or the frequency is indeed not suitable for communication in this time period. The assigned score can be selected from -10 to 10 points.

[0034] 7. Curve fitting to obtain the "frequency-score" curve like Figure 2 As shown, the frequency and score are not a simple linear relationship. After selecting the geographical range and time range, a large amount of "frequency-score" data that conforms to the geographical range and time range is extracted from the historical communication records. Curve fitting is to use a mathematical model to fit a series of discrete data into a smooth curve, which is convenient for discovering the internal connection between the data and analyzing the change trend between the predicted data. The present invention mainly uses the least squares curve fitting method to fit the discrete "frequency-score" historical data to obtain a smooth and continuous "frequency-score" curve, with the horizontal axis being the frequency and the vertical axis being the score. The scores of other frequencies can be easily predicted on this curve. In the subsequent steps, the frequencies are sorted from large to small according to the scores, and the superiority and inferiority ranking results of the given frequencies are obtained.

[0035] 8. Determine the best frequency based on the frequency selection conditions In the process of shortwave communication, frequency selection generally includes the following methods: (1) Unconditional selection of the best frequency in the entire frequency band First, in the entire frequency band of 1.0~30MHz, frequency points are evenly selected according to a certain frequency interval. The score of each frequency point is scored with reference to the "frequency-score" fitting curve result, and the frequencies are sorted from large to small according to the score. The required N frequencies with high scores are selected as the full-band frequency selection results.

[0036] (2) Select the best frequency in a given frequency band In a given frequency band, frequency points are selected at a certain frequency interval, and the scores of the selected frequency points are predicted by referring to the results of the "frequency-score" fitting curve. The frequencies are sorted from large to small according to the scores, and the first N frequencies with high scores are taken as the frequency selection results.

[0037] (3) Select the best frequency among given frequency points Refer to the "frequency-score" fitting curve result for all frequencies in a given frequency point, score each frequency point, sort the frequencies from large to small according to the score, and take the first N frequencies with high scores as the frequency selection results.

[0038] (4) Select the best frequency band in the whole frequency band In the entire frequency band of 1.0~30MHz, refer to the "frequency-score" fitting curve results and set a threshold score according to actual needs. Frequencies with frequency scores higher than the threshold score constitute one or more frequency bands, which are used as the frequency selection result. If all frequency scores are not higher than the threshold score, lower the threshold score to obtain a frequency band of suitable width as the frequency selection result.

[0039] (5) Select one or more optimal frequency bands from a given frequency band In a given frequency band, a threshold score is set with reference to the result of the "frequency-score" fitting curve. Frequencies with frequency scores higher than the threshold constitute one or more frequency bands, which are used as the selected frequency. If all frequency scores are not higher than the threshold score, the threshold score is lowered to obtain a frequency band of suitable width as the frequency selection result.

[0040] 9. Eliminate interference frequencies and disabled frequencies to obtain the final frequency In actual communication, the shortwave communication system needs to consider the following when selecting the frequency: (1) Avoid co-channel interference and adjacent channel interference. The frequency interval cannot be too narrow. The current maximum shortwave communication bandwidth is 3KHz. Therefore, when selecting a frequency, the interval between two frequencies cannot be less than 3KHz.

[0041] (2) Avoid third-order intermodulation interference. The predicted frequencies cannot satisfy the conditions for third-order intermodulation interference, that is, any three frequencies cannot satisfy the conditions for third-order intermodulation interference, thereby avoiding third-order intermodulation interference.

[0042] (3) Avoid conflicts with prohibited frequencies or protection frequencies. During the frequency selection process, frequencies that are the same as national maritime frequencies, emergency frequencies, etc. need to be eliminated to avoid interference with public affairs frequencies.

[0043] The above is only a specific implementation of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other implementations obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. Any changes or substitutions that can be easily thought of by any technician familiar with the field within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A shortwave communication frequency selection method based on historical communication record data, characterized in that: The following steps are involved: Step 1: Create a historical communication log: In the shortwave communication control system, a historical communication log file is established, which records the information in the communication process in detail; the shortwave communication control system will save all historical communication logs, and the "frequency-score" information in the log is determined during the link quality analysis. The historical communication log file is stored in the form of a text file, and the daily communication records generate an independent historical communication log file; Step 2: Get the geographic location and time information of both communicating sites: The shortwave communication control system obtains the geographical location information and time information of both communication sites through Beidou or GPS; Step 3: Read historical communication records: Read the records in the historical communication log file in sequence; Step 4: Filter historical communication records based on geographic location and time range: The shortwave communication control system analyzes the historical communication logs according to the geographical locations of the two communication sites and the communication time, and selects the "frequency-score" pairs that meet the geographical location range and time range of the two communication sites, and screens out the valid historical communication records; Step 5: Determine whether the number of extracted historical communication records is sufficient, and use different methods to perform frequency prediction and selection according to the number of extracted historical communication records; Step 6: Process the historical communication records and sort them by scores; Step 4: After filtering out valid historical communication records, it is necessary to score the acquired historical communication record data in the form of "frequency-score", where the highest score is 100 and the lowest is "×", where "×" indicates that the communication at this frequency has failed. Since the same frequency may be used multiple times and the score for each use may not be the same, the filtered original "frequency-score" data must be processed; Step 7: Curve fitting to obtain the "frequency-score" curve; A large number of "frequency-score" data points that meet both the geographic location range and the time range were extracted from the historical communication records. The discrete "frequency-score" data were fitted by the least squares curve fitting method to obtain a smooth and continuous "frequency-score" curve, with the horizontal axis being the frequency and the vertical axis being the score. The scores of other frequencies can be predicted on this curve, and the frequencies can be sorted from large to small according to the scores, thus obtaining the ranking results of the given frequencies. Step 8: Determine the best frequency based on the frequency selection conditions: (1) Unconditionally select the best frequency in the entire frequency band; (2) Select the best frequency in a given frequency band; (3) Select the best frequency among the given frequency points; (4) Select the best frequency band in the entire frequency band; (5) Selecting one or more optimal frequency bands from a given frequency band; Step 9: Eliminate interference frequencies and disabled frequencies to obtain the final frequency.

2. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 4: Screening includes two processes: Screening historical communication records based on geographic location range and screening historical communication records based on time range: (1) Filter historical communication records based on geographic location range Taking the geographical location of the two communicating sites as the center, a certain grid distance radius area is reasonably selected based on the actual situation. All sites within this area are regarded as the same site. The longitude and latitude of the communication location in the historical communication records are all valid in this geographical area and can be used as the basis for the frequency selection of this communication. (2) Filter historical communication records based on time range Select the records with communication time T from the historical communication records that meet the geographic location range selection conditions; the historical communication records at the same time T and one hour before and after time T within a month are all records that meet the time range; if there are too few communication records that meet the requirements, consider taking the historical communication records at the same time T and one hour before and after time T within a year as the basis for frequency prediction of this communication.

3. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 5 uses different methods to predict and select frequencies according to the number of historical communication records extracted. The specific methods are as follows: (1) When there is no historical record that meets the requirements or the number is too small After screening according to the geographical location range and time range, the qualified historical communication records are obtained. If the qualified historical communication records do not exist or the number is too small, the frequency selection is based on the medium- and long-term prediction software; (2) When the number of historical communication records that meet the requirements is sufficient After filtering based on the geographic location range and time range, if sufficient historical communication records are obtained for reference, proceed to step 6.

4. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 6: The method for processing the filtered original "frequency-score" data is: For the case where the frequency is the same but the scores are different, weighted processing should be performed according to the different usage time to obtain a weighted score as the final score corresponding to this frequency. In principle, the weight of the frequency closer to the communication time is set higher, and the weight of the frequency farther from the communication time is set lower. For the sake of simplicity of calculation, the average score is taken as the final score of the frequency; For the frequency with a score of "×", make full use of all frequency information, assign it a score and participate in the subsequent prediction. The assigned score is selected from -10 to 10 points.

5. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 8 (1) The specific method of unconditionally selecting the best frequency in the entire frequency band is: First, in the entire frequency band of 1.0~30MHz, frequency points are evenly selected according to a certain frequency interval. The score of each frequency point is scored with reference to the "frequency-score" fitting curve result, and the frequencies are sorted from large to small according to the score. The required N frequencies with high scores are selected as the full-band frequency selection results.

6. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 8 (2) The specific method for selecting the best frequency in a given frequency band is: In a given frequency band, frequency points are selected at a certain frequency interval, and the scores of the selected frequency points are predicted by referring to the "frequency-score" fitting curve results. The frequencies are sorted from large to small according to the scores, and the first N frequencies with high scores are taken as the frequency selection results.

7. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 8 (3) The specific method of selecting the best frequency among the given frequency points is: Refer to the "frequency-score" fitting curve result for all frequencies in a given frequency point, score each frequency point, sort the frequencies from large to small according to the score, and take the first N frequencies with high scores as the frequency selection results.

8. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: Step 8 (4) The specific method of selecting the best frequency band in the whole frequency band is: In the entire frequency band of 1.0~30MHz, refer to the "frequency-score" fitting curve result and set a threshold score according to actual needs. Frequencies with frequency scores higher than the threshold score constitute one or more frequency segments, and finally one or more frequency segments are selected as the frequency selection result; if all frequency scores are not higher than the threshold score, lower the threshold score to obtain a frequency segment of suitable width as the frequency selection result.

9. The shortwave communication frequency selection method based on historical communication record data as claimed in claim 1, characterized in that: The specific method of step 8 (5) selecting one or more optimal frequency bands from the given frequency bands is: In a given frequency band, refer to the "frequency-score" fitting curve result and set a threshold score. Frequencies with frequency scores higher than the threshold constitute one or more frequency bands, which are used as the frequency selection result. If all frequency scores are not higher than the threshold score, lower the threshold score to obtain a frequency band of suitable width as the frequency selection result.

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