JP2012100153A - Radio wave propagation characteristic estimation system, radio wave propagation characteristic estimation method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave propagation characteristic estimation system, a radio wave propagation characteristic estimation method, and a computer program, capable of improving accuracy of an actual measurement correction.SOLUTION: The radio wave propagation characteristic estimation system, which is a system to perform an actual measurement correction of a reception level estimated value of a radio wave transmitted from a transmission point having a transmitter station at an arbitrary evaluation point within an evaluation area to estimate a radio wave propagation characteristic using a reception level actual measurement value measured at a measuring point, comprises: a propagation estimation part to calculate a reception level estimated value using a predetermined propagation estimation formula at the evaluation point; an actual measurement correction part to perform an actual measurement correction of the reception level estimated value based on a reliability to show a relationship between a propagation loss at the evaluation point and a propagation loss at the measuring point of a radio wave transmitted from the transmission point; and an angle based reliability calculation part to calculate the reliability based on an angle subtended by a line segment connecting the transmission point and the evaluation point and a line segment connecting the transmission point and the measuring point.

Description

  The present invention relates to a radio wave propagation characteristic estimation system, a radio wave propagation characteristic estimation method, and a computer program.

  The estimation of radio wave propagation characteristics is important when performing area design and interference estimation of a wireless communication system.

  For example, in a mobile communication system, radio base stations are arranged so that a communication service can be maintained even when a mobile station moves, and a radio service area is continuously formed. At this time, by estimating the radio wave propagation characteristics, areas where radio waves cannot be received due to the influence of topography, features, etc. are identified, and radio parameters (transmission power, antennas) of the radio base station are set so that such areas do not exist. Tuning of directivity, antenna tilt angle, etc. is performed.

  Another example of estimating the radio wave propagation characteristics is a wireless system that performs communication by sharing that frequency when the existing wireless system does not use its assigned frequency spatially and temporally. There is a cognitive radio system. In a cognitive radio system, communication is performed by sharing a frequency within a range in which interference with an existing radio system due to own transmission does not affect an existing service. At this time, the radio wave propagation characteristic is estimated in order to estimate how much interference is caused to the existing wireless system by the transmission of the cognitive wireless system.

  The radio wave propagation characteristic is generally estimated by using a propagation estimation formula. Examples of the propagation estimation formula include Okumura and Kashiwa formulas, ITU-R (International Telecommunication Union Radiocommunications Sector), p. Various propagation estimation formulas such as the 1546 model (see Non-Patent Document 1) are known. However, no matter what type of propagation estimation formula is used, there are not a few errors due to the effects of topography and features in the area where the radio wave propagation characteristics are actually estimated, modeling errors in the propagation estimation formula, and the like.

  Measurement correction is known as a method for reducing such an estimation error (propagation estimation error) of the propagation estimation formula. For example, in the technique described in Patent Document 1, first, a running test is performed in an area where radio wave propagation characteristics are estimated, and a radio wave reception level is measured to obtain an actual measurement value. Next, parameters of the propagation estimation formula (surrounding feature height, distance attenuation coefficient, constant term) are set so that the error between the measured value of the reception level obtained in the running test and the reception level calculated using the propagation estimation formula becomes small. Etc.) is corrected. The actual measurement value used at this time is limited to measurement data within a predetermined distance from the transmission point (wireless base station). As a result, the distance from the transmission point is so far away that the influence of the actual measurement value obtained at the measurement point with a different propagation environment is excluded from the position where the propagation loss is estimated (evaluated) (hereinafter referred to as the evaluation point). Thus, the propagation estimation formula is actually corrected.

  Further, Patent Document 2 describes that an evaluation area is divided at a predetermined angle with a transmission point as a center, and actual measurement correction is performed using only measurement data in the divided evaluation area including the evaluation point. To do.

JP 2005-229453 A JP 2005-223732 A

ITU-R, Method for Point to area prediction for terrestrial services in the frequency range, 30 MHz to 3000 MHz, ITU-R P. 1546-3, 2007.

  However, in the case of the actual measurement correction technique described in Patent Document 1, there are concerns about the following problems. Even when the measurement point is within a predetermined distance from the transmission point, the distance between the measurement point and the evaluation point is not necessarily close (for example, in an extreme case, the measurement point has an evaluation point across the transmission point). Etc.). When the evaluation point and the measurement point are separated from each other, the similarity of the propagation environment (propagation loss) is reduced, so that the accuracy of the actual measurement correction may be lowered.

  On the other hand, in the actual measurement correction technique described in Patent Document 2, the evaluation area is divided at a predetermined angle around the transmission point, and is used by limiting to the actual measurement values obtained at the measurement points in the same division area as the evaluation point. Therefore, unlike Patent Document 1, it is possible to perform actual measurement correction that ensures a certain degree of similarity in the propagation environment. However, even in the case of Patent Document 2, for example, when evaluation points and measurement points are located at both ends of a divided area, the similarity of the propagation environment may be reduced. Therefore, even when the actual measurement correction of Patent Document 2 is used, the accuracy of the actual measurement correction may be reduced depending on the positional relationship between the evaluation point and the measurement point.

  The present invention has been made to solve the above-described problem, and an object thereof is to provide a radio wave propagation characteristic estimation system, a radio wave propagation characteristic estimation method, and a computer program capable of improving the accuracy of measurement correction. To do.

  The radio wave propagation characteristic estimation system according to the present invention includes a reception level estimation value of a radio wave transmitted from a transmission point of a transmission station at an arbitrary evaluation point within an evaluation area for estimating the radio wave propagation characteristic. A system that performs actual measurement correction using an actual level measurement value, the propagation estimation unit calculating a reception level estimation value at the evaluation point using a predetermined propagation estimation formula, and the evaluation of radio waves transmitted from the transmission point An actual measurement correction unit that actually corrects the reception level estimation value based on the reliability indicating the relationship between the propagation loss at the point and the propagation loss at the measurement point, the line segment that connects the transmission point and the evaluation point, and the transmission An angle-specific reliability calculation unit that calculates the reliability based on an angle formed by a point and a line segment connecting the measurement points.

  The radio wave propagation characteristic estimation method of the present invention is a reception in which an estimated reception level of a radio wave transmitted from a transmission point of a transmission station is measured at a measurement point at an arbitrary evaluation point within an evaluation area for estimating the radio wave propagation characteristic. A method of performing actual measurement correction using an actual level measurement value, wherein a reception level estimation value at the evaluation point is calculated using a predetermined propagation estimation formula, and a propagation loss at the evaluation point of a radio wave transmitted from the transmission point And the reliability indicating the relationship between the propagation loss at the measurement point, the received level estimation value is actually corrected, the reliability is a line segment connecting the transmission point and the evaluation point, the transmission point and the Calculation is based on the angle formed by the line connecting the measurement points.

  The computer program of the present invention is an actual reception level measurement value obtained by measuring an estimated reception level of a radio wave transmitted from a transmission point of a transmission station at an arbitrary evaluation point within an evaluation area for estimating a radio wave propagation characteristic. Is a computer program that performs actual measurement correction using a calculation process for calculating a reception level estimation value at the evaluation point using a predetermined propagation estimation formula, and a propagation loss at the evaluation point of radio waves transmitted from the transmission point. On the basis of the reliability indicating the relationship between the propagation loss at the measurement point and the process for correcting the measurement of the reception level estimated value, the reliability, a line segment connecting the transmission point and the evaluation point, and the transmission point And a process of calculating based on an angle formed by a line segment connecting the measurement points.

  According to the present invention, it is possible to improve the accuracy of actual measurement correction.

It is a figure explaining the evaluation area in the 1st Embodiment of this invention, and is a figure explaining the angle between measurement-evaluation in an evaluation area especially. It is a block diagram which shows the structural example of the electromagnetic wave propagation characteristic estimation system which concerns on 1st Embodiment. 3 is a graph of a function of path loss error correlation in the present embodiment. It is a flowchart which shows the operation example of the electromagnetic wave propagation characteristic estimation system shown in FIG. It is a figure explaining the evaluation area in the 2nd Embodiment of this invention, and is a figure which shows an evaluation area when there exists a feature especially. It is a block diagram which shows the structural example of the electromagnetic wave propagation characteristic estimation system which concerns on 2nd Embodiment. It is a figure which shows the relationship between the propagation path from a transmission point to an evaluation point, and a feature regarding 2nd Embodiment. It is a figure of another evaluation area in a 2nd embodiment, and is a figure showing an evaluation area in the case of considering a plurality of features especially. It is a block diagram of the radio | wireless communications system which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the structural example of the secondary system shown in FIG. FIG. 11 is a flowchart for explaining an operation example (mainly an operation example related to an interference level calculation) of the spectrum manager shown in FIG. 10.

[First Embodiment]
FIG. 1 is a diagram for explaining an evaluation area 10 in the first embodiment of the present invention. In the evaluation area 10, a transmission point 12 that is a position of a transmission station 11 that transmits a radio wave that is an object of estimation of radio wave propagation characteristics, an evaluation point 13 that is an object point of which a reception level is estimated, and reception used in actual measurement correction. There is a measurement point 14 that is a point at which the actual level measurement value is measured. Here, the angle formed by the line segment connecting the transmission point 12 and the evaluation point 13 and the line segment connecting the transmission point 12 and the measurement point 14 is defined as a measurement-evaluation angle θ.

  In the present embodiment, for the purpose of estimating the reception level at the evaluation point 13, the reception level estimation value calculated at the measurement point 14 is used as the reception level estimation value calculated at the measurement point 14 as the means. A radio wave propagation characteristic estimation system that uses actual measurement correction will be described.

  FIG. 2 is a block diagram illustrating a configuration example of the radio wave propagation characteristic estimation system 200 according to the present embodiment. The radio wave propagation characteristic estimation system 200 includes a propagation estimation unit 202, a measurement data determination unit 203, a measurement data storage unit 204, an angle-specific reliability calculation unit 205, and an actual measurement correction unit 207.

  The radio wave propagation characteristic estimation system 200 includes evaluation point information (position information, assumed reception antenna height, assumed reception antenna) regarding an evaluation point that is an arbitrary point in the evaluation area 10 and is a target point whose reception level is estimated. Gain). This evaluation point information is input to the propagation estimation unit 202, the measurement data determination unit 203, and the angle-specific reliability calculation unit 205. Here, the position information can be, for example, latitude / longitude coordinate information. In the present embodiment, the evaluation score is the evaluation score 13 in FIG.

  The measurement data determination unit 203 determines measurement data used for actual measurement correction based on the input evaluation point information. This measurement data is data acquired by a running test or the like, and is composed of an actual value of reception level and measurement point information (measurement position, measurement antenna height, measurement antenna gain, etc.). Measurement data is held in the measurement data storage unit 204. The measurement data determination unit 203 acquires measurement data from the measurement data storage unit 204. For example, when there are a plurality of measurement data, it is possible to select a measurement point having the closest distance from the input evaluation point. In the present embodiment, the measurement data at the measurement point 14 is used as the measurement data. The measurement data determination unit 203 outputs the acquired measurement data to the propagation estimation unit 202, the angle-specific reliability calculation unit 205, and the actual measurement correction unit 207.

  Normally, information on radio wave-specific identification codes (for example, scrambling codes assigned to each transmitting station (base station)) can be obtained by measuring radio waves. Furthermore, it is necessary to grasp from which transmitting station the identification code is transmitted. For example, if transmitting station data representing an identification code to be used is held as transmitting station information, it becomes possible to specify which transmitting station's signal reception level the measurement data represents. In the present invention, for the sake of clarity, as described above, the transmission station that is the target of the radio wave propagation characteristic estimation and the measurement data are already associated using the identification code and the transmission station data. The measurement data is used for the actual measurement correction.

  The propagation estimation unit 202 inputs the evaluation point information regarding the evaluation point 13 and the measurement data at the measurement point 14 output from the measurement data determination unit 203. The propagation estimation unit 202 calculates reception level estimation values at each of the evaluation points 13 and the measurement points 14.

  Specifically, the propagation estimator 202 calculates the distance between the evaluation point 13 and the transmission point 12, and the propagation loss at this distance is calculated using a predetermined propagation estimation equation (for example, Okumura-Hagi equation or ITU-RP. (Propagation estimation formula such as 1546 model). The propagation estimation unit 202 evaluates using the propagation loss, the transmission power of the transmission station 11, the antenna gain including the directivity of the transmission antenna, and the reception antenna gain assumed to receive the radio wave at the evaluation point 13. A reception level estimation value at point 13 is calculated. In addition, the propagation estimation unit 202 calculates the distance between the measurement point 14 and the transmission point 12, and calculates the propagation loss at this distance using the above propagation estimation formula. The propagation estimation unit 202 uses the propagation loss, the transmission power of the transmission station 11, the antenna gain including the directivity of the transmission antenna, and the reception antenna gain at the time of actual measurement at the measurement point 14. A reception level estimation value is calculated.

  The reception level estimation values obtained at the evaluation points 13 and the measurement points 14 are input to the actual measurement correction unit 207.

  In this embodiment, information (position information, transmission power, transmission antenna gain, transmission antenna height, etc.) about the transmission station that is the target of radio wave propagation characteristic estimation is given to the radio wave propagation characteristic estimation system 200 and used. It shall be possible.

  The angle-specific reliability calculation unit 205 is used when the reception level estimation value at the evaluation point 13 calculated by the propagation estimation unit 202 is actually measured and corrected using the reception level actual value acquired by a running test or the like. The reliability of the actual measurement value (hereinafter referred to as “measurement reliability”) is calculated. The measurement reliability essentially represents the relationship between the propagation loss at the evaluation point 13 and the propagation loss at the measurement point 14 of the transmission wave from the transmission point 12 (transmission station 11) (for example, correlation of path loss error, etc.). Is. And this measurement reliability becomes weight information which shows the effectiveness with respect to the evaluation point 13 of a reception level actual value. Regarding the calculation of the measurement reliability, the angle-specific reliability calculation unit 205 inputs the evaluation point information regarding the evaluation point 13 and the measurement data at the measurement point 14 output from the measurement data determination unit 203. The angle-specific reliability calculation unit 205 includes a line segment connecting the transmission point 12 and the evaluation point 13 and a line segment connecting the transmission point 12 and the measurement point 14 based on the position information of the evaluation point information and the position information of the measurement data. An angle θ between measurement and evaluation, which is an angle formed by The angle-specific reliability calculation unit 205 calculates the measurement reliability based on the measurement-evaluation angle θ.

  The measurement reliability used in the present embodiment is the path loss error, which is the difference between the actual reception level (reception level true value) at the evaluation point 13 and the reception level estimation value calculated using the propagation estimation formula, and the measurement point 14. A path loss error correlation which is a correlation value between a path loss error which is a difference between a reception level true value (corresponding to an actual measurement value at the measurement point 14) and a reception level estimation value calculated using the propagation estimation formula is used. As a property of the path loss error correlation, for example, when the path loss error correlation is high (close to 1), if the path loss error at the measurement point 14 is +2 dB, for example, the path loss error at the evaluation point may be about +2 dB. Increases nature. On the contrary, when the path loss error correlation is low (close to 0), just because the path loss error at the measurement point 14 is +2 dB, the path loss error at the evaluation point is not always +2 dB.

  This path loss error correlation is a value that depends on the measurement-evaluation angle θ. In this embodiment, this path loss error correlation is expressed as ρ (θ) with the measurement-evaluation angle θ as a variable. Hereinafter, this ρ (θ) will be referred to as a path loss error correlation for the sake of convenience, but this ρ (θ) may also be referred to as a path loss error angle correlation.

  FIG. 3 is a graph of the path loss error correlation function ρ (θ) (in other words, the function ρ (θ) can be said to be a function of the characteristics shown in FIG. 3). As can be seen from FIG. 3, when the measurement-evaluation angle θ is small, the degree of similarity between the surrounding environment of the measurement point 14 and the surrounding environment of the evaluation point 13 is high, so that the path loss error correlation is high and the opposite. When the measurement-evaluation angle θ is large, the path loss error correlation becomes low. The characteristic shown in FIG. 3 is merely an example, and the function ρ (θ) of the path loss error correlation is any method that can identify the relationship between the measurement-evaluation angle θ and the path loss error correlation (angle correlation). It may be determined by the method. For example, a characteristic obtained from an experimental result or the like can be converted into a function, or can be a predetermined calculation formula.

  The angle-specific reliability calculation unit 205 calculates the path loss error correlation ρ (θ) by using the measurement-evaluation angle θ, and sets this as the measurement reliability. The measurement reliability obtained in this way is output to the actual measurement correction unit 207.

The actual measurement correction unit 207 inputs the reception level estimation value at the evaluation point 13 (hereinafter referred to as E _T ) and the reception level estimation value at the measurement point 14 (hereinafter referred to as E _M ) from the propagation estimation unit 202. Further, the measured correction unit 207, measured data (hereinafter, the reception level measured value of this to R _M) from the measurement data determining unit 203 inputs the evaluation point of the measurement data from each angle reliability calculation unit 205 A measurement reliability for 13 (hereinafter referred to as w) is input. Using these inputs, the actual measurement correction unit 207 performs actual measurement correction on the reception level estimation value E _T of the evaluation point 13 obtained by the propagation estimation formula using the following (Formula 1).

In (Equation 1), _{C T} represents the reception level after the measured corrected at the evaluation point 13. (Equation 1) multiplies the path loss error (R _M −E _M ) at the measurement point 14 by the measurement reliability w as a weight to correct the reception level estimation value E _T. In the actual measurement correction method, when the measurement reliability is high, correction is performed to largely reflect the reception level actual measurement value with respect to the reception level estimation value, and when the measurement reliability is low, the reception level actual measurement value is decreased. Correction to reflect is performed. The reception level after actual measurement correction at the evaluation point 13 obtained in this way is output.

In the above description, the measurement reliability w in (Expression 1) is the path loss error correlation ρ (θ) (that is, w = ρ (θ)). For this measurement reliability w, it is also possible to take into account a measurement error when actually measuring the reception level at the measurement point 14. Here, the measurement error is a statistical error generated due to the influence of thermal noise or the like included in the measurement. In accordance with the magnitude of the measurement error, the deviation between the actual received level value and the true received level value increases, and the accuracy of the actual measurement correction deteriorates. In order to take into account the influence of the measurement error, if the variance of the measurement error of the reception level actual measurement value at the measurement point 14 is σ _M ² and the variance of the path loss error in the propagation estimation formula is σ _L ² , the measurement is performed. The reliability can be given by (Equation 2).

  In this (Equation 2), the measurement reliability is determined by taking into account the measurement error of the received level actual measurement value and the path loss error. The measurement reliability defined in (Equation 2) is sufficient for the measurement error compared to the path loss error. When it is low, it approaches the path loss error correlation, while when the measurement error is sufficiently higher than the path loss error, it becomes smaller than the path loss error correlation. The corrected reception level obtained in this way is output to the outside.

  FIG. 4 shows a flowchart showing an operation example of the radio wave propagation characteristic estimation system 200 shown in FIG. In the following description, FIGS. 1 to 3 are referred to as necessary.

  First, in the evaluation area 10 where the radio wave propagation characteristics are estimated, the position of the evaluation point 13 which is the target for estimating the reception level is input (step S10). Next, the measurement point 14 used for the actual correction of the reception level at the evaluation point 13 is determined (step S11). The propagation estimation unit 202 calculates each reception level estimation value at the evaluation point 13 and the measurement point 14 by using the above-described propagation estimation formula (step S12). Subsequently, the angle-specific reliability calculation unit 205 calculates the measurement-evaluation angle θ by using the position information of the evaluation point 13 and the measurement point 14, and the path loss error correlation based on the measurement-evaluation angle θ. ρ (θ) is calculated, and this path loss error correlation ρ (θ) is set as the measurement reliability of the measurement point 14 with respect to the evaluation point 13 (step S13). Next, the actual measurement correction unit 207 performs actual measurement correction using the measurement reliability (step S14). Specifically, the actual measurement correcting unit 207 adds the measurement reliability (in this case, the path loss error correlation ρ (in this case) to the path loss error (the error between the reception level actual measurement value and the reception level estimation value obtained by the propagation estimation formula) at the measurement point 14. The reception level estimation value at the evaluation point 13 is corrected using a value obtained by multiplying θ)) as a correction value.

  Here, as described above, when the evaluation area is divided at a predetermined angle with the transmission point as the center, the similarity of the propagation environment (propagation loss) may be different at both ends of the divided area. That is, the similarity of the propagation environment depends on the angle formed by the line segment connecting the transmission point and the evaluation point and the line segment connecting the transmission point and the measurement point. Correspondingly, in the first embodiment described above, the path loss error correlation, which is the correlation between the path loss error at the measurement point and the path loss error at the evaluation point, is measured using the line segment connecting the transmission point and the evaluation point, the transmission point, and the measurement. Calculation is made based on the measurement-evaluation angle, which is the angle formed by the line segment connecting the points, and this is taken as the measurement reliability. Then, using this measurement reliability, the reception level estimated value at the evaluation point is actually corrected. That is, effective measurement correction according to the similarity of the propagation environment between the measurement point and the evaluation point becomes possible.

  Furthermore, by taking into account not only the path loss error correlation but also the measurement error variance at the time of reception level measurement and the variance of the path loss error in the measurement reliability, measurement correction that reduces the influence of measurement error is possible. .

  In the present embodiment, the path loss error correlation is determined as a function using the measurement-evaluation angle as a variable, but in addition to this, the distance between the measurement point and the evaluation point can be made a variable. In this case, the angle-specific reliability calculation unit 205 calculates not only the measurement-evaluation angle but also the distance between the measurement point and the evaluation point from the position information between the measurement point and the evaluation point. A path loss error correlation corresponding to the distance and the measurement-evaluation angle is calculated, and actual measurement correction is performed with measurement reliability. Here, even if the measurement-evaluation angle is the same, the distance between the measurement point and the evaluation point may be different. By performing such actual measurement correction, for example, even if the same measurement-evaluation angle is used, if the distance between the measurement point and the evaluation point is short, the influence of measurement data having a similar propagation environment is increased. Since it can be reflected in the correction, the accuracy of the actual measurement correction can be further improved.

[Second Embodiment]
The feature of the second embodiment is that the measurement reliability is determined by using the feature data around the propagation path in addition to the measurement-evaluation angle in the first embodiment.

  FIG. 5 shows an evaluation area 10 illustrating the feature 30 whose influence is taken into account in the measurement reliability according to the second embodiment. In FIG. 5, the evaluation area 10, the transmission point 12, and the evaluation point 13 are the same as those in FIG.

  As shown in FIG. 5, the evaluation area 10 is not affected by the evaluation area (shown as A in FIG. 5) where the radio wave transmitted from the transmission point 12 is shielded by the feature 30 and the shielding by the feature 30. An evaluation area (shown as B in FIG. 5) is included. In addition, a feature shielding angle that is an angle shielded by the feature is θ1. Here, it is assumed that there are measurement points 17 in the evaluation area A and measurement points 16 in the evaluation area B. In the second embodiment, different measurement reliability is used for the measurement point 17 in the evaluation area A affected by the shielding by the feature 30 and the measurement point 16 in the evaluation area B not affected by the shielding. .

  FIG. 6 is a block diagram illustrating a configuration example of a radio wave propagation characteristic estimation system 300 according to the second embodiment. The propagation estimation unit 202, the measurement data determination unit 203, the measurement data storage unit 204, and the actual measurement correction unit 207 in FIG. 6 are shown in the radio wave propagation characteristic estimation system 200 (see FIG. 2) of the first embodiment. Is the same as The difference between the radio wave propagation characteristic estimation system 300 and the radio wave propagation characteristic estimation system 200 is that the angle-specific reliability calculation unit 205 is replaced with an angle-specific reliability calculation unit 301 and a feature data storage unit 302 is newly provided. It is in. From the above, for the sake of clarity, the same components as those of the radio wave propagation characteristic estimation system 200 will not be described below, and different configurations (that is, the reliability calculation unit 301 for each angle and the feature) will be omitted. Only the data storage unit 302) will be described.

  The feature data storage unit 302 holds data about features in the evaluation area 10 (hereinafter referred to as feature data. In addition, as an example, information on a building). Here, the feature data represents information such as the position, height, and size of the feature (for example, the width and depth when a building is approximated by a rectangular parallelepiped), the direction of the feature, and the like. By using this feature data, it is possible to perform mapping on the map like the feature 30 in FIG. Note that the number of floors of the building may be held instead of the height. This feature data is used in the angle-specific reliability calculation unit 301.

  As described above, the angle-specific reliability calculation unit 301 calculates the measurement reliability in consideration of the influence of shielding by the feature in addition to the measurement-evaluation angle. First, the angle-specific reliability calculation unit 301 inputs evaluation point information and measurement data output from the measurement data determination unit 203. Next, the angle-specific reliability calculation unit 301 obtains, from the angle-specific reliability calculation unit 301, feature data related to the feature 30 around the propagation path from the transmission point 12 to the evaluation point 13, as shown in FIG. To do. Here, the propagation path includes both a line segment connecting the antenna of the transmitting station 11 and the assumed antenna at the evaluation point 13 and a line segment obtained by projecting the line segment onto the ground. Next, the angle-specific reliability calculation unit 301 determines whether the measurement point belongs to the evaluation area A shielded by the feature 30 or is not affected by the shielding based on the position information of the input measurement data. To belong to.

  For example, when the measurement point belongs to the evaluation area A (for example, in the case of the measurement point 17), the angle-specific reliability calculation unit 301 calculates the measurement reliability using ρa (θ) as a function of the measurement reliability. calculate. On the other hand, when belonging to the evaluation area B (for example, in the case of the measurement point 16), the angle-specific reliability calculation unit 301 calculates the measurement reliability using ρb (θ) as a function of the measurement reliability. Here, θ is an angle between measurement and evaluation, and is calculated from the position information of the transmission point 12, the position information of the measurement points (16, 17), and the position information of the evaluation point 13. The calculated measurement reliability is output to the actual measurement correction unit 207.

  Since the measurement point 17 belonging to the evaluation area A is affected by the shielding of radio waves by the feature 30 similarly to the evaluation point 13, both points have high propagation environment similarity (that is, the reliability of the measurement point is high). ). On the other hand, since the measurement point 16 belonging to the evaluation area B is not affected by the shielding by the feature 30, the similarity with the propagation environment of the evaluation point 13 is low (that is, the reliability of the measurement point is low). . Therefore, the functions ρa (θ) and ρb (θ) are determined so that the measurement reliability in the evaluation area A is higher than the measurement reliability in the evaluation area B. Here, the functions ρa (θ) and ρb (θ) are satisfied by the above relationship (that is, at least the measurement reliability in the evaluation area A is higher than the measurement reliability in the evaluation area B). Any function may be used as long as it is. For example, similar to the function ρ (θ) shown in FIG. 3, the characteristics obtained from the experimental results and the like can be converted into functions, or can be a predetermined calculation formula. Further, for example, the functions ρa (θ) and ρb (θ) can be functions in which the measurement reliability decreases in the evaluation areas A and B as θ increases. Alternatively, the functions ρa (θ) and ρb (θ) may be functions that output a constant value in each of the evaluation areas A and B (of course, in this case, the measurement reliability in the evaluation area A is evaluated more. Higher than the measurement reliability in area B).

  As described above, it is possible to set an appropriate reliability even when there is a shield or the like, and as a result, effective actual measurement correction according to the similarity of the propagation environment between the measurement point and the evaluation point becomes possible.

  In the above description, it is assumed that the feature 30 exists around the propagation path from the transmission point 12 to the evaluation point 13. However, in reality, it is assumed that there are many features around the propagation path.

  FIG. 7 is a diagram showing the relationship between the propagation path from the transmission point 12 to the evaluation point 13 and the feature. In FIG. 7, the horizontal axis represents the propagation path from the transmission point 12 to the evaluation point 13, and the vertical axis represents the height. FIG. 7 illustrates an example in which a plurality of features (feature 31, feature 32, feature 33, feature 34) are located around the propagation path. Further, FIG. 7 shows a transmission station antenna 41 at the transmission point 12 and an assumed antenna 40 at the evaluation point 13, and a line segment connecting these antennas (that is, a propagation path of a line-of-sight direct wave). Is indicated by a broken line.

  When there are a plurality of features around the propagation path as shown in FIG. 7, it is possible to select a feature that considers the influence of radio wave shielding using the height of the feature as a selection criterion. For example, the feature 32 having the maximum height among the features around the propagation path can be selected. Further, as another method for selecting a feature considering the influence of radio wave shielding, it is also possible to select a feature having a predetermined height or more. Further, as another feature selection method, the relative height of the feature is determined based on the height of the propagation path of the line-of-sight direct wave that is a line segment connecting the transmitting station antenna 41 and the assumed antenna 40 of the evaluation point 13. The selection criterion can be used.

  Also, different feature selection criteria can be used depending on the propagation estimation formula used. For example, in the statistical propagation estimation formulas such as the Okumura-Kashiwa formula and the like, a specific feature is not taken into consideration, so that a high feature that blocks the propagation path is likely to be an error factor in the propagation estimation. Therefore, in such a case, it is desirable to consider the influence by using the high relative height based on the height of the propagation path of the above-mentioned direct line-of-sight wave as a reference for selecting a feature. . On the other hand, deterministic propagation estimation methods such as ray-tracing methods already consider features that have a sufficiently high relative height to obstruct the propagation path in order to consider features around the propagation path. Therefore, it is hard to become an error factor. However, there is a possibility that the propagation loss of a feature having a height similar to the height of the propagation path of the line-of-sight direct wave greatly varies depending on whether or not the line-of-sight direct wave is actually blocked. In particular, when the height information of the feature is not accurate and, for example, only the floor information of the building can be obtained as the height information, an error in such a situation is likely to occur. Therefore, in the deterministic propagation estimation method such as ray tracing method, selecting a feature whose relative height is close to zero with reference to the height of the propagation path of the line-of-sight direct wave is to specify the error factor. Is desirable.

  Furthermore, it is possible to select a plurality of features as features that consider the influence of radio wave shielding around the propagation path. Hereinafter, an example in which the influence of radio wave shielding by a plurality of features is considered will be described.

  FIG. 8 is a diagram of another evaluation area in the second embodiment, and particularly shows the evaluation area 10 when considering a plurality of features. FIG. 8 shows an example in which a feature 35 and a feature 36 are selected as features considering the influence of radio wave shielding among the features around the propagation path from the transmission point 12 to the evaluation point 13. The evaluation area 10 is divided into a plurality of evaluation areas. The evaluation area shielded by both the feature 35 and the feature 36 is A1, the evaluation area shielded only by the feature 35 is A2, and the evaluation area shielded only by the feature 36 is A3. Assume that B is an evaluation area that is not affected by shielding. It is assumed that the measurement point 19, the measurement point 18, the measurement point 20, and the measurement point 21 belong to the evaluation areas A1, A2, A3, and B, respectively. In this case, it is assumed that the evaluation point 13 exists in the evaluation area A1.

  In such a case, a different measurement reliability function is used for each evaluation area. For example, the measurement reliability ρa1 (θ) is used for the measurement point 19 belonging to the evaluation area A1, and the measurement reliability ρa2 (θ) is used for the measurement point 18 belonging to the evaluation area A2. The measurement reliability ρa3 (θ) is used for the measurement point 20 belonging, and the measurement reliability ρb (θ) is used for the measurement reliability belonging to the evaluation area B. Here, each measurement reliability function ρa1 (θ), ρa2 (θ), ρa3 (θ), ρb (θ) is set to a value corresponding to each similarity with the propagation environment of the evaluation point 13. Specifically, for example, ρa1 is set so that the measurement reliability of the evaluation area A1 having the highest similarity to the propagation environment of the evaluation point 13 is higher than the measurement reliability of the other evaluation areas A2, A3, and B. Set (θ). Here, each function ρa1 (θ), ρa2 (θ), ρa3 (θ), ρb (θ) is the above-described relationship (at least the measurement reliability of the evaluation area A1 having the highest similarity to the propagation environment of the evaluation point 13). Any function may be used as long as the degree satisfies the relationship (in which the degree is higher than the measurement reliability of the other evaluation areas A2, A3, and B). For example, similar to the function ρ (θ) shown in FIG. 3, the characteristics obtained from the experimental results and the like can be converted into functions, or can be a predetermined calculation formula. Further, for example, in the functions ρa1 (θ), ρa2 (θ), ρa3 (θ), and ρb (θ), in each of the evaluation areas A1, A2, A3, and B, the measurement reliability decreases as θ increases. It can be a function. Alternatively, the functions ρa1 (θ), ρa2 (θ), ρa3 (θ), and ρb (θ) may be functions that output a constant value in each evaluation area A1, A2, A3, and B (of course, In this case, the measurement reliability in the evaluation area A1 is set higher than the measurement reliability in the other evaluation areas).

  In the second embodiment described above, when the reception level estimation value at the evaluation point is actually measured and corrected, the measurement reliability considering the radio wave shielding caused by the features around the propagation path from the transmission point to the evaluation point is used. Since the actual measurement correction is performed, effective correction that more reflects the similarity of the propagation environment between the measurement point and the evaluation point becomes possible.

  Further, more effective correction can be performed by selecting a feature considering the influence of radio wave shielding using the height of the feature as a selection criterion.

  Propagation estimation by blocking direct waves by selecting features that consider the effects of radio wave shielding, using the relative height of the features based on the height of the propagation path of line-of-sight direct waves as a selection criterion. Effective correction considering the influence of errors becomes possible.

In the actual measurement correction, not only the path loss error angle correlation but also the measurement error variance and the path loss error variance at the time of actual reception level measurement can be taken into consideration as in the first embodiment.
[Third Embodiment]
In the first and second embodiments described above, the radio wave propagation characteristic estimation system is the system that performs the actual measurement correction. On the other hand, such actual measurement correction is also useful in a cognitive radio system that performs communication by sharing the frequency of an existing radio system. In the cognitive radio system, it is necessary to estimate how much interference is caused to the existing radio system so that the interference to the existing radio system due to own transmission does not affect the existing service. This embodiment describes a cognitive radio system that performs the actual measurement correction described in the first and second embodiments in order to grasp interference.

  FIG. 9 is a configuration diagram of a radio communication system according to the third embodiment of this invention. This wireless communication system includes a cognitive wireless system (hereinafter referred to as a secondary system) and an existing wireless system (hereinafter referred to as a primary system). The primary system includes a transmitting station 50 having coverage 52 (hereinafter referred to as a primary transmitting station 50) and a receiving station 51 (hereinafter referred to as a primary receiving station). The secondary system includes a transmission station 55 (hereinafter referred to as a secondary transmission station) and a monitoring station 56.

  In FIG. 9, the radio waves of the secondary transmission station 55 transmitted in the same frequency band as the primary system are interference with the primary reception station 51. Here, the primary receiving station 51 is located at the area end of the coverage 52 and is the primary receiving station having the highest interference level from the secondary transmitting station 55 among the primary receiving stations in the coverage 52. In the secondary system, by controlling the amount of interference with the primary receiving station 51, control is performed such as setting the interference level below an allowable value so as not to affect the existing service of the primary system.

  The monitoring station 56 is one of secondary system reception stations located around the primary reception station 51 and measures radio waves transmitted from the secondary transmission station 55 and causing interference to the primary reception station 51. By using this measurement data, the level of interference with the primary receiving station 51 is accurately measured and corrected.

  In other words, in the present embodiment, the evaluation point that is the reception level estimation target is the position of the primary receiving station 51, and the measurement point is the position of the monitoring station 56. The actual reception level value used for the actual measurement correction is the interference level measured by the monitoring station 56.

  FIG. 10 is a block diagram illustrating a configuration example of the secondary system illustrated in FIG. 9. The secondary system includes a secondary transmission station 55, a monitoring station 56, a core network 57, a geographic database 58, and a spectrum manager 59.

  The core network 57 is a network for communicating with the secondary transmission station 55, the monitoring station 56, the geographic database 58, and the spectrum manager 59.

  The geographic database 58 holds information related to the primary system (transmission power, transmission antenna gain, coverage, reception antenna height and reception antenna gain). Information on the primary system held in the geographic database 58 is used by the secondary transmission station 55 and the spectrum manager 59 via the core network 57.

  The spectrum manager 59 controls the interference level from the secondary transmission station 55 and the frequency band to be used so as not to affect the existing service of the primary system. Further, the spectrum manager 59 calculates an interference level from the secondary transmission station 55 to the primary reception station 51 in order to perform the interference level control. Specifically, first, the spectrum manager 59 acquires information on the primary system from the geographic database 58, and specifies the position where the interference from the secondary transmission station 55 is maximum (that is, the position of the primary receiving station 51). . Next, the spectrum manager 59 calculates a reception level estimation value at the position of the primary reception station 51 using a predetermined propagation estimation formula. Further, the spectrum manager 59 determines the measurement reliability. Then, the spectrum manager 59 uses the measured interference level in the monitoring station 56 and the measurement reliability to actually correct the received level estimation value to calculate the interference level. The interference level calculated here is sent to the secondary transmission station 55. For example, the secondary transmission station 55 performs transmission control such that the interference level is equal to or less than an allowable value. Thereby, it is possible to prevent the service of the secondary system from affecting the existing service of the primary system.

  FIG. 11 is a flowchart for explaining an operation example (mainly an operation example relating to the interference level calculation) of the spectrum manager 59 shown in FIG.

  First, the spectrum manager 59 specifies the position of the primary receiving station 51 (that is, the position of the “evaluation point”) at which the interference level is maximum within the coverage 52 (step S20).

  Next, in order to obtain measurement data used for actual measurement correction, the spectrum manager 59 is a monitoring station 56 (a receiving station of a secondary system located around the primary receiving station 51, and the position is referred to as a “measurement point”. In response, the monitoring instruction for measuring the radio wave transmitted from the secondary transmission station 55 is transmitted (step S21).

  Subsequently, the spectrum manager 59 receives measurement data from the monitoring station 56 after the monitoring station 56 measures the interference level (step S22).

  The spectrum manager 59 calculates a propagation loss from the secondary transmission station 55 to the primary reception station 51 using a predetermined propagation estimation formula. Then, the spectrum manager 59 uses the propagation loss, the transmission power and transmission antenna gain of the secondary transmission station 55, and the reception antenna gain of the primary reception station 51 to estimate the interference level to the primary reception station 51 ( ("Received level estimation value" in the first and second embodiments) is calculated (step S23).

  The spectrum manager 59 determines the interference level based on the angle between the line segment connecting the transmission point (secondary transmission station 55) and the evaluation point (primary reception station 51) and the line segment connecting the transmission point and the measurement point (monitoring station 56). Calculate the measurement reliability for the correction of the estimated value. Then, the spectrum manager 59 performs actual measurement correction of the interference level estimation value using the interference level actual measurement value according to the measurement reliability (step S24).

  That is, the spectrum manager 59 has a function related to the actual measurement correction of the radio wave propagation characteristic estimation system in the first and second embodiments, and corrects the estimated value of the interference level to the primary receiving station 51 using the actual measurement correction.

  According to the third embodiment described above, in the cognitive radio system that performs communication while sharing the frequency band with the existing radio system, the propagation environment of the measurement points and the evaluation points is the same as in the first and second embodiments. It is possible to perform effective actual measurement correction in accordance with the similarity of. This is because the interference level as the basis of the interference control is a line connecting the transmission point (secondary transmission station 55) to the evaluation point (primary reception station 51) and the transmission point to the measurement point (monitoring station 56). This is because the calculation is performed by actual measurement correction in consideration of the measurement reliability calculated based on the angle formed by the minute.

  In the third embodiment described above, the spectrum manager 59 performs the interference level estimation using the propagation estimation formula and the actual measurement correction using the actual measurement value of the interference level. It is also possible to carry out with other devices. For example, the secondary transmission station 55 may perform the interference level estimation and the actual measurement correction.

  Further, in the third embodiment described above, the actual correction using the actual measurement value of the interference level is targeted. However, the monitoring station 56 transmits the signal transmitted from the primary transmitting station 50 and received by the primary receiving station 51 ( In the following, it is also possible to measure the radio wave of the primary signal. In this case, the spectrum manager 59 estimates the reception level of the primary signal received by the primary reception station 51 using the propagation estimation formula, and uses the actual measurement value of the primary signal obtained by the measurement of the monitoring station 56. By correcting, it is possible to accurately estimate the coverage 52 of the primary system. Further, the spectrum manager 59 calculates the carrier-to-interference power ratio in the primary receiving station 51 by performing both the actual correction regarding the interference level and the actual correction regarding the primary signal, and uses it for controlling the interference level. Also good.

  In summary, in the first to third embodiments described above, when the estimated value of the reception level at the evaluation point is actually corrected, the validity of the measurement data used for the actual correction is a line connecting the transmission point and the evaluation point. Since the measurement reliability is determined according to the angle between the minute, the transmission point, and the line segment connecting the measurement points, effective measurement correction reflecting the similarity of the propagation environment between the measurement points and the evaluation points becomes possible.

  The first to third embodiments described above can also be embodied as predetermined hardware, for example, a circuit.

The first to third embodiments described above can be controlled and operated by a computer circuit (for example, a CPU (Central Processing Unit)) (not shown) based on a control program. In this case, these control programs are stored in, for example, a storage medium (for example, ROM (Read Onl) in the apparatus or the system.
y Memory), a hard disk, etc.) or an external storage medium (for example, a removable medium, a removable disk, etc.), and read and executed by the computer circuit.

DESCRIPTION OF SYMBOLS 10 Evaluation area 11 Transmission station 12 Transmission point 13 Evaluation point 14, 16, 17, 18, 19, 20, 21 Measurement point 30, 31, 32, 33, 34, 35, 36 Feature 40 Assumed antenna of evaluation point 41 Transmission Station antenna 50 Primary transmission station 51 Primary reception station 52 Coverage 55 Secondary transmission station 56 Monitoring station 57 Core network 58 Geographic database 59 Spectrum manager 200, 300 Radio wave propagation characteristic estimation system 202 Propagation estimation unit 203 Measurement data determination unit 204 Measurement data storage unit 205, 301 Angle-specific reliability calculation unit 207 Actual correction unit 302 Feature data storage unit

Claims (10)

A system that corrects the actual reception level estimated value of the radio wave transmitted from a transmission point of the transmitting station using the actual received level value measured at the measurement point at any evaluation point within the evaluation area for estimating the radio wave propagation characteristics. Because
A propagation estimation unit that calculates a reception level estimation value at the evaluation point using a predetermined propagation estimation formula;
Based on the reliability indicating the relationship between the propagation loss at the evaluation point and the propagation loss at the measurement point of the radio wave transmitted from the transmission point, an actual measurement correction unit that actually corrects the reception level estimation value;
An angle-specific reliability calculation unit that calculates the reliability based on an angle formed by a line segment connecting the transmission point and the evaluation point, and a line segment connecting the transmission point and the measurement point;
A radio wave propagation characteristic estimation system comprising:   A feature data storage unit that stores data related to the features in the evaluation area is further provided, and the reliability by angle calculation unit uses the feature data held in the feature data storage unit to transmit the transmission point. 2. A feature in the vicinity of a propagation path from the evaluation point to the evaluation point is selected, and the reliability is set to a different value according to the degree of radio wave shielding at the measurement point by the feature. Radio wave propagation characteristic estimation system.   3. The radio wave propagation characteristic estimation system according to claim 2, wherein the selection of the feature is based on a height of a feature around the propagation path as a selection criterion.   The selection of the feature is based on the relative height of the feature based on the height of the propagation path of the line-of-sight direct wave propagating from the transmitting station antenna at the transmission point to the assumed antenna at the evaluation point. The radio wave propagation characteristic estimation system according to claim 2.   5. The angle-specific reliability calculation unit sets the reliability to a different value according to the number of features that shield radio waves when a plurality of features are selected. The radio wave propagation characteristic estimation system according to claim 1.   6. The reliability according to claim 1, wherein the reliability is calculated based on a path loss error correlation that is a correlation between a path loss estimation error at the evaluation point and a path loss estimation error at the transmission point. The described radio wave propagation characteristic estimation system.   7. The radio wave propagation characteristic estimation system according to claim 6, wherein the reliability is calculated using, in addition to the path loss error correlation, a measurement error variance at the time of reception level measurement and a variance of a path loss estimation error. .   The actual measurement correction unit corrects the reception level estimation value at the evaluation point using a value obtained by multiplying the difference between the reception level estimation value at the measurement point and the reception level actual measurement value by the reliability. The radio wave propagation characteristic estimation system according to any one of claims 1 to 7. A method of actually correcting the estimated reception level of a radio wave transmitted from a transmission point of a transmitting station using an actual reception level measured at a measurement point at an arbitrary evaluation point within an evaluation area for estimating radio wave propagation characteristics Because
Calculate a reception level estimation value at the evaluation point using a predetermined propagation estimation formula,
Based on the reliability indicating the relationship between the propagation loss at the evaluation point and the propagation loss at the measurement point of the radio wave transmitted from the transmission point, the reception level estimation value is actually corrected,
The radio wave propagation characteristic estimation method, wherein the reliability is calculated based on an angle formed by a line segment connecting the transmission point and the evaluation point and a line segment connecting the transmission point and the measurement point. A computer that actually corrects the estimated reception level of radio waves transmitted from a transmission point of a transmitting station at an arbitrary evaluation point within the evaluation area for estimating radio wave propagation characteristics using the actual reception level measured at the measurement point. A program,
Processing for calculating a reception level estimation value at the evaluation point using a predetermined propagation estimation formula;
Based on the reliability indicating the relationship between the propagation loss at the evaluation point and the propagation loss at the measurement point of the radio wave transmitted from the transmission point, the process of actually correcting the reception level estimate,
Processing for calculating the reliability based on an angle formed by a line segment connecting the transmission point and the evaluation point and a line segment connecting the transmission point and the measurement point;
Is executed by a computer.

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