Method for evaluating path loss fluctuation and waveguide environment correlation based on measured data

Abstract

The disclosure is a method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data, comprising: collecting propagation path loss measured data; detecting and eliminating abnormal points in the path loss measured data by using the quartile range algorithm; obtaining the evaporation waveguide height corresponding to the path loss measured data according to meteorological data, a PJ model, the antenna height of the transmitting end and the receiving end, the radio frequency, and an APM model; calculating the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height; calculating the correlation coefficient of the two vectors; performing statistical significance test on the correlation coefficient, and adjusting the modulation mode and the working bandwidth according to the result. The embodiment can guide the modulation mode selection and working bandwidth adjustment of the over-the-horizon communication system at sea, so as to adapt to a good evaporation waveguide channel and a smaller path loss fluctuation, and realize high-speed and reliable over-the-horizon communication by fully utilizing the evaporation waveguide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, and in particular to a method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data. BACKGROUND

[0002] Compared with the standard atmosphere, the atmospheric waveguide is a special atmospheric layer structure with certain horizontal extension and vertical distribution generated by certain tropospheric meteorological or weather conditions, and the radio waves of certain frequency can achieve over-the-horizon propagation in the atmospheric waveguide environment through refraction and reflection. The atmospheric waveguide is composed of evaporation waveguide, surface waveguide and suspended waveguide. Since the evaporation waveguide has the highest probability of occurrence on the sea surface, and the height of the evaporation waveguide is basically the same as the height of the antenna of the sea communication and radar system, the evaporation waveguide environment has a very important influence on the over-the-horizon propagation of the radio waves on the sea, which makes the evaporation waveguide the most concerned and the most widely used atmospheric waveguide.

[0003] The formation mechanism of the evaporation waveguide is that with the evaporation and diffusion of the sea surface water vapor, the atmospheric humidity in the range of tens of meters above the sea surface decreases sharply with the increase of the height, which makes the atmospheric refractive index decrease, and then presents a negative gradient change, resulting in the downward refraction of the radio waves of certain frequency; when the refraction curvature is greater than the curvature of the sea surface, the radio waves can be trapped in the evaporation waveguide layer, so that the propagation path loss is significantly reduced, and finally the over-the-horizon propagation is realized, and the longest propagation distance can reach hundreds of kilometers. Therefore, the over-the-horizon communication using the sea evaporation waveguide channel has the advantages of small path loss, high communication rate (up to tens of Mbps), high reliability and strong anti-interception.

[0004] Affected by parameters such as sea surface temperature, relative humidity, sea surface air pressure, air temperature above the sea surface and wind speed above the sea surface, the change rule of the sea evaporation waveguide is very complex. At present, the existing researches on the influence of the evaporation waveguide environment on the radio wave propagation only focus on the correlation between the evaporation waveguide height and the path loss itself, and do not further fully evaluate the correlation between the evaporation waveguide height and the path loss fluctuation, so as to give the relationship between the path loss fluctuation and the change of the evaporation waveguide height. At the same time, the existing researches on the influence of the evaporation waveguide environment on the radio wave propagation lack measured path loss data under different evaporation waveguide environments and different frequency points, and do not effectively identify and eliminate the outliers of the measured path loss data, so as to accurately evaluate the correlation between the path loss fluctuation and the evaporation waveguide height. In addition, the existing research results cannot guide the selection of modulation mode and working bandwidth of the over-the-horizon communication system on the sea according to the change of the waveguide environment, so as to guide the reliable over-the-horizon communication of the over-the-horizon communication system under the complex change of the sea evaporation waveguide environment.

[0005] Therefore, it is necessary to improve one or more problems in the above related technical solutions.

[0006] It should be noted that this section aims to provide a background or context for the technical solutions of the present disclosure stated in the claims. The description herein is not admitted to be prior art merely because it is included in this section. SUMMARY

[0007] The purpose of the present application is to provide a method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data, thereby at least partially overcoming one or more problems caused by the limitations and defects of the related art.

[0008] The present application provides a method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data, comprising:

[0009] S1, using a sea evaporation duct channel monitoring system to build a cross-sea over-the-horizon radio wave propagation link in a designated sea area, and collecting propagation path loss measured data of the propagation link in C and X frequency bands;

[0010] S2, detecting and removing abnormal points in the path loss measured data using the interquartile range algorithm;

[0011] S3, obtaining the evaporation duct height corresponding to the path loss measured data according to the meteorological data on the propagation link, the PJ model, the antenna height of the transmitting end and the receiving end, the radio wave frequency, and the APM model;

[0012] S31, inputting the meteorological data on the propagation link into the PJ model to calculate the initial modified refractive index profile and the evaporation duct height, and then obtaining the evaporation duct modified refractive index profile according to the PJ model, the initial modified refractive index profile, and the evaporation duct height;

[0013] S32, substituting the antenna height of the transmitting end and the receiving end of the sea evaporation duct channel monitoring system, the radio wave frequency, and the evaporation duct modified refractive index profile into the APM model to calculate the radio wave over-the-horizon propagation path loss simulation value under different evaporation duct heights;

[0014] S33, constructing a target function for evaluating the degree of conformity between the path loss measured data and the path loss simulation value;

[0015] S34, using exhaustive search to find the solution that makes the target function take the minimum value, obtaining the optimal evaporation duct profile on the propagation link, and thereby inversely obtaining the evaporation duct height corresponding to the path loss measured data;

[0016] S4, calculate the standard deviation of the path loss measured data and the average value of the evaporation waveguide height, and obtain the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height;

[0017] S5, calculate the correlation coefficient of the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height;

[0018] S6, perform a statistical significance test on the correlation coefficient, and adjust the modulation mode and working bandwidth of the sea over-the-horizon communication system according to the significance test result.

[0019] In the present application, S2 comprises the following steps:

[0020] S21, divide the path loss measured data into multiple groups according to a preset time interval and sort them;

[0021] S22, calculate the positions of the first quartile, the second quartile and the third quartile of the sorted path loss measured data in the path loss measured data;

[0022] S23, calculate the first quartile, the second quartile and the third quartile according to the positions, and calculate the interquartile range of the path loss measured data according to the first quartile, the second quartile and the third quartile;

[0023] S24, obtain the normal value range of the path loss measured data according to the first quartile, the third quartile and the interquartile range, and eliminate abnormal points in the path loss measured data according to the normal value range.

[0024] In the present application, in S31, the expression of the evaporation waveguide correction refractive index profile M is as follows:

[0025]

[0026] wherein, is an initial correction refractive index profile, z is a vertical height above sea level, h is an evaporation waveguide height.

[0027] In the present application, in S33, the expression of the target function is as follows:

[0028] ,

[0029] wherein, is path loss measured data, is a path loss simulation value, is a path loss simulation value vector.

[0030] In the present application, S5 comprises the following steps:

[0031] S51, according to the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height, calculating the average value of the standard deviation of the path loss measured data and the average value of the average value of the evaporation waveguide height of all groups;

[0032] S52, according to the average value of the standard deviation of the path loss measured data and the average value of the average value of the evaporation waveguide height, calculating the covariance and variance of the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height;

[0033] S53, calculating the correlation coefficient according to the covariance and variance.

[0034] In the present application, when the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height exist a correlation: if the correlation coefficient is greater than or equal to 0.75, it is considered that the two are highly correlated; if 0.5 is less than or equal to the correlation coefficient and less than 0.75, it is considered that the two are moderately correlated; if 0.3 is less than or equal to the correlation coefficient and less than 0.5, it is considered that the two are lowly correlated; if the correlation coefficient is less than 0.3, it is considered that the correlation between the two is extremely weak and can be considered as unrelated.

[0035] In the present application, when the significance test result shows that the standard deviation vector of the path loss measured data and the average value vector of the evaporation waveguide height are negatively correlated, S6 comprises:

[0036] When the evaporation waveguide height is low, the over-the-horizon communication is carried out by using a low-order modulation mode and a narrow working bandwidth mode;

[0037] When the evaporation waveguide height is high, the over-the-horizon communication is carried out by using a high-order modulation mode and a wide working bandwidth mode.

[0038] The technical scheme provided by the present application can include the following beneficial effects:

[0039] The path loss fluctuation and waveguide environment correlation evaluation method based on measured data in the present application calculates the correlation coefficient between the path loss standard deviation and the evaporation waveguide height through the steps of measured path loss outlier discrimination and elimination based on the interquartile range (IQR) algorithm, evaporation waveguide height inversion, etc., evaluates the correlation between the two, and finally performs a significance test, which more reliably judges the authenticity of the correlation between the path loss standard deviation and the evaporation waveguide height, and avoids false correlation caused by random factors. The method can guide the modulation mode selection and working bandwidth adjustment of the over-the-horizon communication system at sea, and finally enables the over-the-horizon communication system at sea to fully adapt to the complex changes of the evaporation waveguide environment at sea, and realizes reliable over-the-horizon communication. BRIEF DESCRIPTION OF DRAWINGS

[0040] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present disclosure and, together with the description, further serve to explain the principles of the present disclosure. It is to be understood that the drawings are only schematic, and that they do not purport to be to scale with respect to one another. The embodiments described herein are meant to be illustrative only and are not intended to limit the scope of the disclosure. Although the drawings represent embodiments of various forms or examples, the drawings are not necessarily to scale and certain features can be exaggerated to show details which could be present in one or more embodiments.

[0041] Figure 1 is a flow chart of the method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to the present application;

[0042] Figure 2 is an application effect diagram of the method according to the present application in the measured path loss data of 4.5 GHz band radio wave on December 25, 2023, on a 53.4 km link;

[0043] Figure 3 is an application effect diagram of the method according to the present application in the measured path loss data of 4.5 GHz band radio wave on December 27, 2023, on a 53.4 km link;

[0044] Figure 4 is an application effect diagram of the method according to the present application in the measured path loss data of 4.9 GHz band radio wave on December 28, 2023, on a 53.4 km link;

[0045] Figure 5 is an application effect diagram of the method according to the present application in the measured path loss data of 8.2 GHz band radio wave on August 23, 2022, on a 53.4 km link;

[0046] Figure 6 is an application effect diagram of the method according to the present application in the measured path loss data of 8.2 GHz band radio wave on October 12, 2022, on a 53.4 km link;

[0047] Figure 7 is an application effect diagram of the method according to the present application in the measured path loss data of 8.2 GHz band radio wave on October 14, 2022, on a 53.4 km link. DETAILED DESCRIPTION

[0048] Example implementations will now be described with reference to the drawings; however, example implementations can be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example implementations to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more implementations.

[0049] Further, the accompanying drawings are included to provide a thorough understanding of embodiments of the present disclosure and are not intended to be exhaustive or to limit the present disclosure to particular embodiments. The same or similar reference numerals in different drawings represent the same or similar elements, and redundant description thereof will be omitted. Some of the block diagrams in the drawings are functional entities, and do not necessarily correspond to physical or logical independent entities.

[0050] In the present example embodiment, a method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data is first provided, please refer to Figure 1 The method can include S1-S6, which are specifically as follows:

[0051] S1, a cross-sea over-the-horizon radio propagation link is built in a specified sea area by using a sea evaporation duct channel monitoring system, and propagation path loss measured data of the propagation link in C band and X band are collected;

[0052] S2, outliers in the path loss measured data are detected and removed by using a quartile range algorithm;

[0053] S3, according to meteorological data on the propagation link, a PJ model, antenna heights of a transmitting end and a receiving end, a radio frequency, and an APM model, an evaporation duct height corresponding to the path loss measured data is obtained;

[0054] S31, the meteorological data on the propagation link is input into the PJ model, and an initial modified refractive index profile and an evaporation duct height are calculated, and then an evaporation duct modified refractive index profile is obtained according to the PJ model, the initial modified refractive index profile, and the evaporation duct height;

[0055] S32, the antenna heights of the transmitting end and the receiving end of the sea evaporation duct channel monitoring system, the radio frequency, and the evaporation duct modified refractive index profile are substituted into the APM model, and radio over-the-horizon propagation path loss simulation values under different evaporation duct heights are calculated;

[0056] S33, a target function for evaluating the degree of conformity between the path loss measured data and the path loss simulation values is constructed;

[0057] S34, an exhaustive search is used to find a solution that makes the value of the target function minimum, and an optimal evaporation duct profile on the propagation link is obtained, so that the evaporation duct height corresponding to the path loss measured data is inversely obtained;

[0058] S4, the standard deviation of the path loss measured data and the average value of the evaporation duct height are calculated, and a standard deviation vector of the path loss measured data and an average value vector of the evaporation duct height are obtained;

[0059] S5, the correlation coefficient of the standard deviation vector of the path loss measured data and the average value vector of the evaporation duct height is calculated;

[0060] S6, performing a statistical significance test on the correlation coefficient, and adjusting the modulation mode and working bandwidth of the sea over-the-horizon communication system according to the result of the significance test.

[0061] Wherein, the PJ model (Paulus-Jeske Model) and the APM model (Advanced Propagation Model) are both prior art.

[0062] In the embodiment, through the steps of measured path loss abnormal value discrimination and elimination based on the Interquartile Range (IQR) algorithm, evaporation duct height inversion, calculation of the correlation coefficient between the path loss standard deviation and the evaporation duct height, evaluation of the correlation between the two, and finally the significance test, the authenticity of the correlation between the path loss standard deviation and the evaporation duct height is more reliably judged, and false correlation caused by random factors is avoided. Therefore, the method can guide the modulation mode selection and working bandwidth adjustment of the sea over-the-horizon communication system, so that the sea over-the-horizon communication system can fully adapt to the complex changes of the sea evaporation duct environment, and reliable over-the-horizon communication is realized.

[0063] The specific process of each step in the above embodiment will be described below.

[0064] S1, according to the transmission power of the sea evaporation duct channel monitoring system, the transmission and reception antenna gain, the received signal strength and the system loss, the measured value of the path loss on the sea over-the-horizon radio propagation link is obtained by formula (1) (unit: dB):

[0065] (1)

[0066] Wherein, represents the transmission power of the evaporation duct channel monitoring system, and the unit is dBm; and respectively represent the gain of the directional transmission and directional reception antennas, and the unit is dBi; RSSI represents the received signal strength, and the unit is dBm; represents the evaporation duct channel monitoring system loss, and the unit is dB.

[0067] In formula (1), dBi represents the gain of the directional antenna in a specific direction relative to the "ideal isotropic antenna" (uniformly radiated to all directions), for example, a directional antenna of 20dBi is 20dB stronger than an isotropic antenna in that direction. Therefore, dBi can be added or subtracted with dB.

[0068] Since The units of RSSI are both dBm, and the difference between them is dB, The units of the left and right ends of formula (1) are both dB.

[0069] S2, using the interquartile range (IQR) algorithm to detect and remove outliers in the path loss measured data obtained by S1, the specific steps are as follows:

[0070] S21, the path loss measured data is divided into multiple groups according to the preset time interval and sorted.

[0071] First, the obtained measured path loss data is divided into groups according to the time interval. Then, the measured data G of the first j group is sorted in ascending order, and the sorted measured data set is obtained, where . N j The first j group of measured path loss data sample size) is sorted in ascending order, and the sorted measured data set is obtained, where .

[0072] S22, the positions of the first quartile, the second quartile and the third quartile of the sorted path loss measured data in the path loss measured data are calculated.

[0073] Specifically, the positions , and of the first quartile , the second quartile and the third quartile of the measured data set are calculated. If , and are all integers, the calculation formula is as follows:

[0074] (2)

[0075] (3)

[0076] (4)

[0077] Wherein, the first quartile is the path loss value at the 25% position in the sorted data set , that is, the path loss value at the first division; the second quartile is the path loss value at the 50% position in the data set The path loss value at the 50% mark, i.e., the path loss value in the middle position; the third quartile. For dataset The path loss value at the 75% position, that is, the path loss value in the third division.

[0078] S23, calculate the first quartile, second quartile, and third quartile based on the location, and calculate the interquartile range of the measured path loss data based on the first quartile, second quartile, and third quartile.

[0079] according to , and Determine the measured dataset First quartile Second quartile and the third and fourth quartiles .

[0080] It is important to note that when When the integer is not an integer, take the closest one. The integer values ​​at both ends are and and through and In the dataset Find two corresponding path loss values ​​and take the average of these two path loss values ​​as the mean. First quartile .when When the integer is not an integer, the same method can be used to obtain the result. The third quartile .

[0081] Calculate the measured dataset The interquartile range (IQR) is calculated using the following formula:

[0082] (5)

[0083] Among them, IQR reflects The degree of dispersion of the measured path loss data in the middle 50% (i.e., 25%-75%).

[0084] S24. Obtain the normal range of path loss measured data based on the first quartile, the third quartile, and the interquartile range. Remove outliers from the path loss measured data based on the normal range.

[0085] The measured path loss dataset is determined using formulas (6) and (7). The range of normal values:

[0086] (6)

[0087] (7)

[0088] wherein, m ( ) represents a variable that controls the width of the normal value range in the measured path loss data: m The larger it is, the wider the normal value range is, m The smaller it is, the narrower the normal value range is; And respectively represent the lower boundary and the upper boundary of the normal value in the measured path loss data, that is, if ( ), the measured path loss value is a normal value.

[0089] Discriminate and eliminate abnormal values in the measured path loss data set . Compare each sample in the measured path loss data set with the calculated and , if or , then is an abnormal value, which is eliminated from , and is updated.

[0090] Update : for the remaining G -1 groups, repeat the above steps to obtain the data set after eliminating the measured path loss abnormal values.

[0091] S3 includes the following steps:

[0092] S31, input the meteorological data on the propagation link into the PJ model, calculate the initial corrected refractive index profile and the evaporation duct height, and then obtain the evaporation duct corrected refractive index profile according to the PJ model, the initial corrected refractive index profile and the evaporation duct height.

[0093] The meteorological data (sea surface temperature, relative humidity, sea surface pressure, air temperature at 4m above the sea surface and wind speed at 4m above the sea surface, etc.) measured on the sea over-the-horizon radio propagation link are input into the PJ model, and the initial corrected refractive index profile and the evaporation duct height h are calculated, and the evaporation duct corrected refractive index profile M is calculated according to formula (8):

[0094] (8)

[0095] In this step, it is assumed that the height of the evaporation duct on the sea over-the-horizon radio propagation link is uniform, so only a single profile needs to be considered. In formula (8), the initial modified refractive index profile Generally, the value is 300, dimensionless; z is the vertical height above the sea surface, with a unit of m.

[0096] It should be noted that the PJ model refers to: JESKE H. State and limits of prediction methods of radar wave propagation conditions over sea. Modern Topics in Microwave Propagation and Air-Sea Interaction: Springer, 1973: 130-148. or PAULUS R A. Practical application of an evaporation duct model[J. Radio Science, 1985, 20(4):887-896.

[0097] S32, the transmitting end and receiving end antenna height of the sea evaporation duct channel monitoring system, the radio frequency and the evaporation duct modified refractive index profile are substituted into the APM model, and the radio over-the-horizon propagation path loss simulation value under different evaporation duct heights is obtained.

[0098] In this step, the modified refractive index profile M is substituted into the APM model, and the radio over-the-horizon propagation path loss simulation value vector under different evaporation duct heights is obtained. , wherein is the s-th element of , which satisfies , is the element number in .

[0099] It should be noted that the APM model please refer to: BARRIOS A E. Considerations in the development of the advanced propagation model (APM) for US Navy applications [C]. 2003 / 01 / 01. IEEE. P 77-82. Or [2] BARRIOS A E, ANDERSON K, LINDEM G. Low Altitude Propagation Effects - A Validation Study of the Advanced Propagation Model (APM) for Mobile Radio Applications [J]. Antennas and Propagation, IEEE Transactions on, 2006, 54(10): 2869-2877.

[0100] S33, construct a target function for evaluating the degree of conformity between the path loss measured data and the path loss simulation value.

[0101] Construct a target function for evaluating the degree of conformity between the path loss measured value in the first j group and the path loss simulation value . , the target function is defined as the absolute value of the difference between and , that is:

[0102] , (9)

[0103] S34, find the solution that makes the target function take the minimum value by using exhaustive search, get the optimal evaporation duct profile on the propagation link, and thus the evaporation duct height corresponding to the path loss measured data is obtained.

[0104] Specifically, find the solution that makes the target function take the minimum value by using exhaustive search, get the optimal evaporation duct profile on the sea over-the-horizon radio propagation link, and thus the evaporation duct height corresponding to the path loss measured data is obtained. .

[0105] For the remaining G -1 group, similarly, the evaporation duct height corresponding to the measured path loss is obtained.​​​​

[0106] S4, first, calculate the measured path loss standard deviation of the first j group, the formula is as follows:

[0107] (10)

[0108] wherein, N j represents the number of measured path loss data samples in the first j group, represents the first measured path loss data in the first j group, satisfies i , , ; is the measured path loss mean value of the first j group, the formula is as follows:

[0109] (11)

[0110] for the remaining G -1 group, the same method can be calculated to obtain the corresponding group of measured path loss standard deviation, ultimately get G the vector consisting of the measured path loss standard deviation in the first group.

[0111] secondly, calculate the average value of the first j group of evaporation duct height , the formula is as follows:

[0112] (12)

[0113] wherein, represents the first inversion of the first j group of evaporation duct height, ultimately get i the vector G consisting of the average value of evaporation duct height in the first group.

[0114] S5, according to the vector G consisting of the measured path loss standard deviation of the first group, and the vector G consisting of the average value of evaporation duct height in the first group, calculate the correlation coefficient between .

[0115] S5 includes the following steps:

[0116] ​S51. Based on the standard deviation vector of the measured path loss data and the average vector of the average evaporation waveguide height, calculate the average of the standard deviation of the measured path loss data and the average of the average evaporation waveguide height for all groups.

[0117] Calculate according to formulas (13) and (14) respectively G Standard deviation of measured path loss for each group average and the average height of the evaporation waveguide average :

[0118] (13)

[0119] (14)

[0120] S52, based on the average of the standard deviation of the path loss measured data and the average of the average evaporation waveguide height, calculate the covariance and variance of the standard deviation vector of the path loss measured data and the average vector of the average evaporation waveguide height.

[0121] calculate and covariance The formula is as follows:

[0122] (15)

[0123] calculate and variance and The formulas are as follows:

[0124] (16)

[0125] (17)

[0126] S53, calculate the correlation coefficient based on covariance and variance.

[0127] Calculate according to formulas (13)-(17). and Correlation coefficient between :

[0128] (18)

[0129] Correlation coefficient Reflects and The degree of correlation between them, satisfying .

[0130] S6, based on the calculation of S5 correlation between correlation coefficient between , the statistical significance test of the correlation relationship is as follows:

[0131] (1) Hypothesis setting.

[0132] Null hypothesis H0: There is no correlation between

[0133] Alternative hypothesis H1: There is a correlation between

[0134] (2) When the null hypothesis H0 is true, the test statistic t follows the t distribution with degrees of freedom d , and the calculation formula is as follows:

[0135] (19)

[0136] wherein represents the correlation coefficient between and

[0137] (3) In practical applications, in hypothesis testing, when the null hypothesis is true, the probability of the occurrence of a more extreme result than the sample observation result is called the p value, and when a two-tailed test is used, the calculation formula is as follows:

[0138] (20)

[0139] wherein is the absolute value of the test statistic, and T represents the cumulative distribution function of the t distribution with degrees of freedom d f .

[0140] (4) Compare the calculated p value with the significance level ( usually 0.01, 0.05 or 0.1), to determine the statistical significance of the correlation between and . If , the null hypothesis H0 is rejected, and it is considered that there is a correlation between and at the significance level, i.e. the correlation is unlikely to be caused by random factors; if , the null hypothesis H0 is accepted, and it is considered that there is no correlation between and , i.e. the correlation may be caused by random factors. ​​​​

[0141] (5) If and If a correlation exists, then through The value will be and The degree of correlation between them can be divided into the following four cases: if ,but and They are highly correlated; if ,but and There is a moderate correlation between them; if ,but and There is a low correlation between them; if ,but and The correlation between them is extremely weak and can be considered as no correlation.

[0142] The above are all theoretical steps. Subsequently, measured path loss data from a designated transoceanic beyond-line-of-sight test link will be selected according to these steps for specific evaluation and processing. The selected measured path loss data will be processed according to the above steps to finally obtain the correlation coefficient between the standard deviation vector of the measured path loss data and the average vector of the evaporation waveguide height.

[0143] S6. Perform a statistical significance test on the correlation coefficients, and adjust the modulation scheme and operating bandwidth of the maritime over-the-horizon (FTTH) communication system based on the significance test results to ensure reliable FTTH communication. When the evaporation waveguide height is low, i.e., the channel conditions are poor, and the path loss fluctuation on the FTTH communication link is also large. Therefore, the maritime FTTH communication system uses a low-order modulation scheme and a narrow operating bandwidth for FTTH communication. When the evaporation waveguide height is high, i.e., the channel conditions are good, and the path loss fluctuation on the FTTH communication link is also small. Therefore, the maritime FTTH communication system uses a high-order modulation scheme and a wide operating bandwidth for FTTH communication, enabling the FTTH communication system to fully adapt to the complex changes in the maritime evaporation waveguide environment and achieve reliable FTTH communication. Specifically, when the maritime FTTH communication link length is 50-100km, a low evaporation waveguide height refers to less than or equal to 8m, and a high evaporation waveguide height refers to greater than 8m.

[0144] The following specific embodiments further illustrate the method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data in this application.

[0145] Measured path loss data from a 53.4km over-the-sea beyond-line-of-sight test link between Jizhao Bay and Donghai Island in Zhanjiang City, Guangdong Province, were selected to evaluate the correlation between the evaporation waveguide environment and path loss fluctuations. First, the measured path loss data from the selected over-the-sea link on a specified date were processed according to... = 30-minute time interval is divided into G = 10 groups, that is, the time span of the measured path loss data in each group is 30 minutes (the measured path loss data of the C frequency band on December 27, 2023 is divided into G = 7 groups), and outliers are removed by using the interquartile range (IQR) algorithm (where the IQR coefficient m is 1); then, the evaporation duct height is obtained by using the PJ model and the APM model, and the path loss standard deviation vector and the evaporation duct height average vector in the 10 groups are calculated respectively; Finally, the correlation coefficient between and is calculated, and the p value is calculated to perform a significance test at a significance level

[0146] When the evaporation duct height is low, that is, the channel condition is poor, a low-order modulation mode (such as BPSK, QPSK) and a narrow working bandwidth (such as 5MHz) are used for maritime over-the-horizon communication to adapt to the poor evaporation duct channel and large path loss fluctuation, and to realize low-speed reliable over-the-horizon communication using the evaporation duct; when the evaporation duct height is high, that is, the channel condition is good, a high-order modulation mode (such as 16-QAM, 64-QAM) and a wide working bandwidth (such as 20MHz) are used for maritime over-the-horizon communication to well adapt to the evaporation duct channel and small path loss fluctuation, and to realize high-speed reliable over-the-horizon communication using the evaporation duct.

[0147] Specific experiments

[0148] The measured path loss data of the 4.5G and 4.9GHz frequency bands (C frequency band) obtained on the 53.4km cross-sea test link from the Jizhaowan in Zhanjiang, Guangdong to the Dongdaishan in Zhanjiang, Guangdong on December 25, 2023, December 26, 2023 and December 28, 2023 are selected to verify the accuracy and applicability of the evaluation method proposed in the application. Figures 2-4 The application effect diagram of the method proposed in the application in the measured path loss data of the 4.5GHz and 4.9GHz frequency bands of the 53.4km cross-sea over-the-horizon link is given.

[0149] Figure 2The measured path loss data of 4.5 GHz band radio waves in the period of 9:00-14:00 on December 25, 2023, and the average path loss, average evaporation duct height and path loss standard deviation every 30 minutes are plotted. Among them, the sample size of the measured path loss data is 17217, and the sample size of the abnormal point data detected by the interquartile range (IQR) algorithm is 1542, so the effective path loss data sample size is 15675. The correlation coefficient and p value calculated are 0.666 and 0.035 respectively, which satisfy . Therefore, the path loss standard deviation and the evaporation duct height show a moderate negative correlation.

[0150] Figure 3 The measured path loss data of 4.5 GHz band radio waves in the period of 8:30-12:00 on December 27, 2023, and the average path loss, average evaporation duct height and path loss standard deviation every 30 minutes are plotted. Among them, the sample size of the measured path loss data is 11373, and the sample size of the path loss abnormal point data detected by the interquartile range (IQR) algorithm is 1078, so the effective path loss data sample size is 10295. The correlation coefficient and p value calculated are 0.776 and 0.040 respectively, which satisfy . Therefore, in the period of 8:30-12:00 on December 27, 2023, the path loss standard deviation and the evaporation duct height show a high negative correlation.

[0151] Figure 4 The measured path loss data of 4.9 GHz band radio waves in the period of 9:00-14:00 on December 28, 2023, and the average path loss, average evaporation duct height and path loss standard deviation every 30 minutes are plotted. Among them, the sample size of the measured path loss data is 16921, and the sample size of the path loss abnormal point data detected by the interquartile range (IQR) algorithm is 1219, so the effective path loss data sample size is 15702. The correlation coefficient and p value calculated are 0.788 and 0.007 respectively, which satisfy . Therefore, in the period of 9:00-14:00 on December 28, 2023, the path loss standard deviation and the evaporation duct height show a high negative correlation.

[0152] The measured path loss data of 8.2 GHz band (X band) in the period of August 23, 2022, October 12, 2022 and October 14, 2022 on the 53.4 km cross-sea test link of East China Island-Jizha Bay is selected to verify the accuracy and applicability of the method. Figure 5 , Figure 6and Figure 7 The application effect diagram of the method in the application of 8.2 GHz band radio wave measured path loss data on a 53.4 km over-sea beyond line of sight link is given.

[0153] Figure 5 The curves of 8.2 GHz band radio wave measured path loss data, average path loss, average evaporation duct height and path loss standard deviation within each 30 minutes in the period from 15:00 to 20:00 on August 23, 2022 are drawn. Among them, the number of measured path loss samples is 1628, the number of path loss abnormal point samples detected by the interquartile range (IQR) algorithm is 193, and therefore the number of effective path loss data samples is 1435. The correlation coefficient and p value are 0.759 and 0.011 respectively, which satisfy Therefore, in the period from 15:00 to 20:00 on August 23, 2022, the path loss standard deviation and the evaporation duct height are highly negatively correlated.

[0154] Figure 6 The curves of 8.2 GHz band radio wave measured path loss data, average path loss, average evaporation duct height and path loss standard deviation within each 30 minutes in the period from 5:00 to 10:00 on October 12, 2022 are drawn. Among them, the number of measured path loss samples is 1629, the number of path loss abnormal point samples detected by the interquartile range (IQR) algorithm is 136, and therefore the number of effective path loss data samples is 1493. The correlation coefficient and p value are 0.865 and 0.001 respectively, which satisfy Therefore, in the period from 5:00 to 10:00 on October 12, 2022, the path loss standard deviation and the evaporation duct height are highly negatively correlated.

[0155] Figure 7 The curves of 8.2 GHz band radio wave measured path loss data, average path loss, average evaporation duct height and path loss standard deviation within each 30 minutes in the period from 3:00 to 8:00 on October 14, 2022 are drawn. Among them, the number of measured path loss samples is 1628, the number of path loss abnormal point samples detected by the interquartile range (IQR) algorithm is 178, and therefore the number of effective path loss data samples is 1450. The correlation coefficient and p value are 0.958 and 0.000 respectively, which satisfy Therefore, in the period from 3:00 to 8:00 on October 14, 2022, the path loss standard deviation and the evaporation duct height are highly negatively correlated.

[0156] By​​​Figures 2-7 It can be known that, on the 53.4km over-the-horizon test link between Jizha Bay in Zhanjiang City of Guangdong Province and Donghai Island in Zhanjiang City of Guangdong Province, the standard deviations of path loss under 4.5GHz, 4.9GHz and 8.2GHz frequency bands are all in high or moderate negative correlation with the evaporation duct heights. The evaporation duct heights The evaporation duct effect of the 8.2GHz frequency band is better than that of the 4.5GHz and 4.9GHz frequency bands, that is, the radio wave propagation path loss of the 8.2GHz frequency band on the 53.4km over-the-horizon test link is smaller, and the negative correlation between the path loss standard deviation of the 8.2GHz frequency band and the evaporation duct height is stronger than the negative correlation between the path loss standard deviation of the 4.5GHz and 4.9GHz frequency bands and the evaporation duct height. The present application can more reliably judge the authenticity of the correlation between the evaporation duct height and the path loss standard deviation through significance test, and avoid false correlation caused by random factors. The correlation between the evaporation duct height and the path loss standard deviation The correlation between the evaporation duct height and the path loss standard deviation

[0157] Finally, the average values of all the inversed evaporation duct heights in the corresponding period are calculated, and the results are 11.4m, 13.2m and 14.6m respectively. Figures 2-4 The average values of all the inversed evaporation duct heights in the corresponding period are calculated, and the results are 10.1m, 10.3m and 10.6m respectively. Figures 5-7 The correlation coefficient It can be seen that: under the 4.5GHz, 4.9GHz and 8.2GHz frequency bands, that is, under the C and X frequency bands, the higher the evaporation duct height, the larger the correlation coefficient .

[0158] In summary, the application proposes a path loss fluctuation and waveguide environment correlation evaluation method based on measured data. The method determines and eliminates abnormal values of measured path loss based on the interquartile range (IQR) algorithm, and performs evaporation waveguide height inversion. The correlation coefficient between the path loss standard deviation and the evaporation waveguide height is calculated, and the correlation between the two is evaluated. Finally, a significance test is performed to more reliably determine the authenticity of the correlation between the path loss standard deviation and the evaporation waveguide height, and to avoid false correlations caused by random factors. The method can guide the modulation mode selection and working bandwidth adjustment of the over-the-horizon communication system at sea, so that when the evaporation waveguide height is low, that is, the channel condition is poor, the path loss fluctuation on the over-the-horizon communication link is also large. Therefore, low-order modulation modes (such as BPSK and QPSK) and narrow working bandwidths (such as 5MHz) are used for over-the-horizon communication at sea to adapt to poor evaporation waveguide channels and large path loss fluctuations, and to realize low-speed reliable over-the-horizon communication using evaporation waveguides. When the evaporation waveguide height is high, that is, the channel condition is good, the path loss fluctuation on the over-the-horizon communication link is also small. Therefore, high-order modulation modes (such as 16-QAM and 64-QAM) and wide working bandwidths (such as 20MHz) are used for over-the-horizon communication at sea to adapt to good evaporation waveguide channels and small path loss fluctuations, and to realize high-speed reliable over-the-horizon communication using evaporation waveguides.

[0159] The embodiments of the application are described above in conjunction with the drawings, but the application is not limited to the specific embodiments described above, and the specific embodiments described above are only illustrative, not restrictive. Those skilled in the art can make many forms under the inspiration of the application without departing from the purpose of the application and the scope protected by the claims, and these are all within the protection of the application.

Claims

1. A method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data, characterized in that, include: S1. A cross-sea over-the-horizon radio wave propagation link is established in a designated sea area using a marine evaporation waveguide channel monitoring system, and the propagation path loss of the propagation link in the C-band and X-band is collected. S2, using the interquartile range algorithm to detect and remove outliers in the measured path loss data; S3. Based on the meteorological data, PJ model, antenna heights at the transmitting and receiving ends, radio frequency, and APM model along the propagation link, the evaporation waveguide height corresponding to the measured path loss data is obtained: S31. Input the meteorological data on the propagation link into the PJ model to calculate the initial corrected refractive index profile and the evaporation waveguide height. Then, based on the PJ model, the initial corrected refractive index profile, and the evaporation waveguide height, obtain the evaporation waveguide corrected refractive index profile. S32. Substitute the antenna height, radio frequency and modified refractive index profile of the evaporating waveguide channel monitoring system at the transmitting and receiving ends into the APM model to calculate the simulated values ​​of radio wave over-the-horizon propagation path loss at different evaporating waveguide heights. S33, Construct an objective function to evaluate the degree of agreement between measured path loss data and simulated path loss values; S34. By using exhaustive search, the solution that minimizes the objective function is found, and the optimal evaporation waveguide profile on the propagation link is obtained. Thus, the evaporation waveguide height corresponding to the measured path loss data is obtained by inversion. S4, calculate the standard deviation of the measured path loss data and the average height of the evaporating waveguide, and obtain the standard deviation vector and the average height vector of the measured path loss data. S5, calculate the correlation coefficient between the standard deviation vector of the measured path loss data and the average height vector of the evaporating waveguide; S6. Perform a statistical significance test on the correlation coefficient, and adjust the modulation method and operating bandwidth of the maritime over-the-horizon communication system based on the significance test results.

2. The method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to claim 1, characterized in that, S2 includes the following steps: S21, Divide the measured path loss data into multiple groups according to a preset time interval and sort them; S22, Calculate the positions of the first quartile, second quartile, and third quartile of the sorted path loss measured data in the path loss measured data; S23, calculate the first quartile, second quartile, and third quartile based on the location, and calculate the interquartile range of the measured path loss data based on the first quartile, second quartile, and third quartile; S24. Obtain the normal range of path loss measured data based on the first quartile, the third quartile, and the interquartile range. Remove outliers from the path loss measured data based on the normal range.

3. The method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to claim 1, characterized in that, In S31, the evaporation waveguide modified refractive index profile M The expression is as follows: in, For the initial corrected refractive index profile, z The vertical height above sea level. h The height is the evaporation waveguide height.

4. The method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to claim 1, characterized in that, In S33, the objective function The expression is as follows: ， in, These are measured path loss data. These are simulated values ​​for path loss. This is a vector of simulated path loss values.

5. The method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to claim 2, characterized in that, S5 includes the following steps: S51. Based on the standard deviation vector of the measured path loss data and the average vector of the average evaporation waveguide height, calculate the average of the standard deviation of the measured path loss data and the average of the average evaporation waveguide height for all groups. S52, based on the average of the standard deviation of the measured path loss data and the average of the average evaporation waveguide height, calculate the covariance and variance of the standard deviation vector of the measured path loss data and the average vector of the average evaporation waveguide height. S53, calculate the correlation coefficient based on covariance and variance.

6. The method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to claim 5, characterized in that, When there is a correlation between the standard deviation vector of the measured path loss data and the average vector of the evaporation waveguide height: if the correlation coefficient is ≥0.75, they are considered to be highly correlated; if 0.5≤correlation coefficient<0.75, they are considered to be moderately correlated; if 0.3≤correlation coefficient<0.5, they are considered to be poorly correlated; if the correlation coefficient<0.3, they are considered to be extremely weakly correlated and can be regarded as uncorrelated.

7. The method for evaluating the correlation between path loss fluctuation and waveguide environment based on measured data according to claim 5, characterized in that, When the significance test results show that the standard deviation vector of the measured path loss data is negatively correlated with the average vector of the evaporation waveguide height, S6 includes: When the evaporation waveguide height is low, over-line-of-sight communication is achieved by using low-order modulation and narrowing the operating bandwidth. When the evaporation waveguide is high, beyond-line-of-sight communication is achieved by using higher-order modulation methods and widening the operating bandwidth.

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