JP4677864B2 - Area evaluation display program and apparatus considering influence of shadowing - Google Patents

Description

  The present invention relates to an area evaluation display program and apparatus in consideration of the influence of shadowing in a wireless communication system.

  FIG. 1 is an explanatory diagram of propagation characteristics in a wireless communication system.

  In a wireless communication system such as a cellular system, generally, a cell coverage is constructed in which the height of an antenna of a base station is set higher than that of a surrounding building and the radius is several kilometers or more. The base station can communicate with a plurality of mobile stations, and the reception level at the mobile station depends on propagation distance characteristics (long-term fluctuation). The propagation distance characteristic means that the reception level of the mobile station decreases as the distance between the base station and the mobile station increases. FIG. 1 shows attenuation (propagation loss) dB corresponding to the distance between the base station and the mobile station. The attenuation increases as the distance increases.

The long interval variation m (d) with respect to the distance d can be approximated by the following equation, for example.
m (d) = 10 · log (Ad ^−α )
A and α are propagation constants depending on transmission power, frequency, transmission / reception antenna height, building height, and the like, and α = 3 to 4 in a standard urban area.

  On the other hand, the propagation path between the base station and the mobile station cannot always obtain a line of sight, and is affected by buildings and topography. Therefore, in reality, even for mobile stations located at the same distance from the base station, the average value of the reception level varies gently. This is based on the spatial variation caused by the shielding effect (hereinafter referred to as “shadowing”) of buildings and terrain around the mobile station.

ｘ：受信電力の短区間平均値（短区間変動）
Ｘ：ｘの対数値（＝１０・ｌｏｇｘ）
ｍ：Ｘの平均値（長区間変動平均値）
σ：標準偏差ｄＢ
ｐ(Ｘ)：Ｘの確率密度関数 The variation in the average value of the reception level due to the influence of shadowing when the distance between the base station and the mobile station is fixed is calculated by, for example, the following propagation model equation.

x: Short-term average value of received power (short-term fluctuation)
X: Logarithm of x (= 10 · logx)
m: Average value of X (long interval fluctuation average value)
σ: standard deviation dB
p (X): Probability density function of X

  The fluctuation of the short interval average value of the received power represents the short interval fluctuation. In short-term fluctuation, even if a mobile station is located at the same distance from the base station, the average value of the short-term received power fluctuates gently because the line of sight cannot be obtained due to the influence of buildings and topography. The speed of short-term fluctuation is moderate, about 1 / several hundreds, compared to the speed of instantaneous fluctuation. In this book, the phenomenon that causes short-term fluctuations is called shadowing.

  FIG. 2 is an area evaluation screen in the prior art.

  The cell coverage of one base station is represented by a vertical line on the map. The map is divided into a plurality of areas around the base station. The evaluation area is displayed as a vertical line only when the propagation loss average value for each evaluation area (the average value of the short section of received power divided by the transmission power) allows the allowable propagation loss specified in advance. The

  According to FIG. 2, the cell coverage represented by the vertical lines around the base station represents a range in which allowable propagation loss is allowed. For example, assuming that the allowable propagation loss is 100 dB, an area where the propagation loss is 100 dB or less is represented by a vertical line. As described above, only the area that satisfies the predetermined allowable propagation loss with respect to the base station is clarified on the area evaluation screen, and is extremely important information in the determination of the arrangement of the base station or the movement of the mobile station.

Murakawa Junyuki, “Radio Wave Propagation Handbook”, Chapter 15 Propagation of Land Mobile Communications, pages 200-216, published by Realize Inc., 1999

  The attenuation amount with respect to the distance is actually affected by shadowing and causes short-term fluctuation. Nevertheless, in the propagation model formula, the propagation loss in the evaluation area is only specified by the long interval average value, and the influence of shadowing is not considered at all.

  Accordingly, an object of the present invention is to provide an area evaluation display program and apparatus for displaying the propagation loss for each evaluation area around the base station on the screen in consideration of the influence of shadowing.

According to the present invention, in an area evaluation display program for causing a computer to function so as to display a propagation loss for each area divided around a base station on a screen,
Normal distribution data accumulating means for accumulating normal distribution data based on the standard deviation σ of the short interval variation with respect to the frequency f;
An evaluation range deriving unit that associates the average propagation loss value of the area with the average value of the normal distribution data, and derives the best value and the worst value of the propagation loss in the specified confidence interval from the normal distribution data;
Area evaluation means for determining the display pattern of the area depending on whether the best value, the average value, and the worst value each allow a specified allowable propagation loss;
The computer is caused to function as user interface means for displaying cell coverage of a base station by superimposing a display pattern for each area on map information.

  According to another embodiment of the program of the present invention, the area evaluation means firstly determines the first display pattern in an area where the best value allows the allowable propagation loss, and secondly, the average value is allowable. It is also preferable that the computer function so that the second display pattern is determined in an area where the propagation loss is allowed, and thirdly, the third display pattern is determined in an area where the worst value allows the allowable propagation loss.

  According to another embodiment of the program of the present invention, it is preferable that the confidence interval in the evaluation range deriving unit is specified by a standard deviation.

  According to another embodiment of the program of the present invention, it is also preferable to cause the computer to function so that the propagation loss of the area in the evaluation range deriving means is an actually measured average value or a value based on a propagation model equation.

According to the present invention, in the area evaluation display device that displays on the screen the propagation loss for each area divided around the base station,
Normal distribution data accumulating means for accumulating normal distribution data based on the standard deviation σ of the short interval variation with respect to the frequency f;
An evaluation range deriving unit that correlates the average propagation loss value of the area with the average value of the normal distribution data, and derives the best value and the worst value of the propagation loss in the specified confidence interval from the normal distribution data;
Area evaluation means for determining the display pattern of the area depending on whether the best value, the average value, and the worst value each allow a specified allowable propagation loss;
User interface means for displaying cell coverage of a base station by superimposing a display pattern for each area on map information.

  According to another embodiment of the apparatus of the present invention, the area evaluation means firstly determines the first display pattern in an area where the best value allows the allowable propagation loss, and secondly, the average value is allowable. It is also preferable to determine the second display pattern in an area where propagation loss is allowed, and thirdly, determine the third display pattern in an area where the worst value allows allowable propagation loss.

  According to another embodiment of the apparatus of the present invention, it is also preferable that the confidence interval in the evaluation range deriving unit is specified by a standard deviation.

  Furthermore, according to another embodiment of the apparatus of the present invention, it is also preferable that the propagation loss of the area in the evaluation range deriving means is a measured average value or a value based on a propagation model equation.

  ADVANTAGE OF THE INVENTION According to this invention, the influence of shadowing can be considered in the area evaluation of a radio | wireless communications system. In particular, it is effective for evaluation of communication between a base station and a mobile station using a high frequency band that is easily affected by shadowing. According to the present invention, it is possible to evaluate the short-term fluctuation due to shadowing in accordance with the probability model of the normal distribution with respect to the propagation loss of the area calculated from the propagation model equation. Area evaluation can be performed practically by superimposing and displaying these evaluations on a map.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 3 is a logarithmic graph showing the standard deviation σ with respect to the frequency f with respect to the short interval variation.

  The magnitude of the shadowing effect depends on the frequency band used. That is, the higher the frequency band f used, the greater the standard deviation σ. This means that the higher the frequency, the larger the short-term fluctuation of the propagation loss due to the effect of shadowing. Of course, this logarithmic graph differs depending on whether the environment around the base station is an urban area or a suburban area with good visibility.

  According to FIG. 3, when the frequency band is about 800 MHz, the standard deviation in the logarithmic normal distribution model of shadowing is about 6.5 dB. However, at 2 GHz, it is about 7.5 dB. Thus, as the frequency band increases, the amount of fluctuation due to shadowing tends to increase. In the wireless communication system, it is expected that a high frequency band will be used in the future, and the influence of shadowing will not be negligible in the area evaluation.

  The data as shown in FIG. 3 is ideally an average value actually measured for each evaluation area. This is because even in the same base station, the distribution of short-term fluctuation varies depending on the evaluation area. However, the burden required for actual measurement is extremely large. Actually, it may be obtained from past statistical data around the base station. Even if the short-term fluctuation for each evaluation area changes somewhat, it is possible to consider the distribution of short-term fluctuation from the average value of the long-term fluctuation around the base station.

  FIG. 4 shows normal distribution data with respect to FIG.

  In a section in which the distance between the base station and the mobile station can be considered to be constant, the fluctuation of the received power average value of several hundred wavelengths follows a normal distribution when the received power value is expressed logarithmically. Therefore, normal distribution data as shown in FIG. 4 can be derived with respect to FIG. According to the present invention, the population average of the normal distribution data is associated with the average propagation loss actually measured in the evaluation area or the propagation loss derived from the propagation model equation.

  In order to evaluate the area, an allowable propagation loss and a confidence interval or standard deviation are required. These parameters may be input by a user who evaluates the area, or may be set in advance.

  For example, if the confidence interval is 80%, it means “a range including 80% of the variation in the average propagation loss value”. The confidence interval means between the best value dB and the worst value dB, which are boundaries that occupy 80% of the normal distribution data shown in FIG.

  For example, it is assumed that the average value 100 dB in a certain evaluation area is calculated from the normal distribution data to be the best value 90 dB and the worst value 110 dB. At this time, if an allowable propagation loss of 100 dB is specified, it can be understood that the evaluation area is an area that is allowed for the average value (and the best value) but is not allowed for the worst value of 110 dB.

  The parameter designated by the area evaluator may be the standard deviation σ instead of the confidence interval. For example, the standard deviation from the average value to the best side and the standard deviation from the average value to the worst side can be designated.

  FIG. 5 is a functional configuration diagram of the area evaluation display device according to the present invention.

  The area evaluation display device 1 is a device that displays on a screen the propagation loss for each area divided around the base station. Regarding the area evaluation display device 1, a functional unit described below may function by causing a computer to execute a program.

  The area evaluation display device 1 includes an area average value collection unit 100, a normal distribution data storage unit 101, an evaluation range derivation unit 102, an area evaluation unit 103, a map information storage unit 104, and a user interface unit 105. .

  The area average value collection unit 100 collects the propagation loss average value for each evaluation area. These propagation loss average values are treated as propagation loss average values. The average value for each area may be a measured average value or a value calculated from a propagation model equation.

  The normal distribution data accumulation unit 101 accumulates normal distribution data based on the standard deviation σ of short-term fluctuation with respect to the frequency f. Normal distribution data as shown in FIG. 4 is accumulated.

  The evaluation range deriving unit 102 associates the average value of the propagation loss for each evaluation area as the average value of the normal distribution data. In addition, the evaluation range deriving unit 102 acquires the confidence interval% or the standard deviation dB from the area evaluator. Thereby, the evaluation range deriving unit 102 derives the best value and the worst value of the propagation loss for the range satisfying the confidence interval or the standard deviation from the normal distribution data.

The area evaluation unit 103 acquires an allowable propagation loss for evaluation. The area evaluation unit 103 evaluates whether the best value, the average value, and the worst value each allow the designated allowable propagation loss. For example, the order is determined in the order of the first display pattern, the second display pattern, and the third display pattern as follows.
(S1) When the best value allows the allowable propagation loss, the first display pattern is displayed.
(S2) Next, when the average value allows the allowable propagation loss, the second display pattern is displayed. Even in the evaluation area where the first display pattern has already been specified, the second display pattern is specified.
(S3) Further, when the worst value allows the allowable propagation loss, the third display pattern is displayed. Even in the evaluation area in which the second display pattern has already been specified, the third display pattern is specified.

  The map information accumulation unit 104 accumulates map information around the base station to be displayed.

  The user interface unit 105 displays the cell coverage around the base station by superimposing the display pattern for each area on the map information acquired from the map information storage unit 104.

  FIG. 6 is an evaluation screen showing propagation loss for each area.

  According to FIG. 6, the average value of the propagation loss is represented for each evaluation area. The propagation loss average value is, for example, an actually measured average value or a value derived from a propagation model equation. In this case, the area one area away from the base station is 100 dB, and the area three areas away from the base station is 120 dB. Here, assuming that the allowable propagation loss is 100 dB, only an area having a propagation loss average value of 100 dB or less is displayed as a vertical line. According to FIG. 6, a vertical line is displayed up to an area one area away from the base station.

  For each evaluation area, the propagation loss average value is made to correspond to the population average of the normal distribution data described above. Then, the best value and the worst value are derived from the normal distribution data by specifying the confidence interval% or the standard deviation σ by the area evaluator.

  According to FIG. 6, regarding the worst value of propagation loss, the area one area away from the base station is 110 dB, and the area three areas away from the base station is 130 dB. Here, assuming that the allowable propagation loss is 100 dB, only an area having a propagation loss average value of 100 dB or less is displayed as a vertical line. According to FIG. 6, only the area where the base station exists is displayed with vertical lines.

  Further, according to FIG. 6, regarding the best propagation loss value, the area one area away from the base station is 90 dB, and the area three areas away from the base station is 110 dB. Here, assuming that the allowable propagation loss is 100 dB, only an area having a propagation loss average value of 100 dB or less is displayed as a vertical line. According to FIG. 6, vertical lines are displayed up to an area two areas away from the base station.

  As described above, according to FIG. 6, in the probability that the propagation loss average value exists in the confidence interval of 80%, in the worst case, only the area where the base station exists satisfies the allowable propagation loss, and in the best case It can be understood that the allowable propagation loss is satisfied up to an area two areas away from the base station.

  FIG. 7 is an area evaluation screen in the present invention.

According to FIG. 7, it is assumed that the area evaluator has input a confidence interval of 80%. The allowable propagation loss for area evaluation is 100 dB.
(S1) On the map, a left oblique line display pattern is superimposed and displayed in an evaluation area where the best value is an allowable propagation loss of 100 dB or more.
(S2) Next, a vertical line display pattern is superimposed and displayed in the evaluation area where the average value is 100 dB or more of the allowable propagation loss.
(S3) Further, a right oblique line display pattern is superimposed and displayed in the evaluation area where the worst value is 100 dB or more of the allowable propagation loss.

  The area evaluator who viewed the screen display of FIG. 7 not only determines whether the predetermined evaluation area satisfies or does not satisfy the allowable propagation loss, but also at any level (best, center, It is possible to grasp whether it is satisfied with (worst).

  Thus, according to the present invention, the influence of shadowing can be taken into account in area evaluation of a wireless communication system. In particular, it is effective for evaluating the cell coverage of a base station that uses a high frequency band that is susceptible to shadowing.

  According to the above-described various embodiments of the present invention, those skilled in the art can easily make various changes, modifications, and omissions in the technical idea and scope of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is explanatory drawing of the propagation characteristic in a radio | wireless communications system. It is an area evaluation screen in a prior art. It is a logarithmic graph showing the standard deviation (sigma) with respect to the frequency f about short-term fluctuation. Normal distribution data. It is a functional block diagram of the area evaluation display apparatus in this invention. It is an evaluation screen showing the propagation loss for every area in the present invention. It is an area evaluation screen in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Area evaluation display apparatus 100 Area average value collection part 101 Normal distribution data storage part 102 Evaluation range derivation part 103 Area evaluation part 104 Map information storage part 105 User interface part

Claims (6)

In the area evaluation display program that allows the computer to function so as to display the propagation loss for each area divided around the base station on the screen,
Normal distribution data accumulating means for accumulating normal distribution data based on the standard deviation σ of the short interval variation with respect to the frequency f;
In the area , the average value of propagation loss, which is a measured average value or a value based on a propagation model equation, is associated as an average value of the normal distribution data to obtain normal distribution data of propagation loss, and specified from the normal distribution data. Evaluation range deriving means for deriving the best value and the worst value of the propagation loss for the range satisfying the determined confidence interval;
Area evaluation means for determining a display pattern of the area according to whether the best value, the average value, and the worst value each allow a specified allowable propagation loss;
An area evaluation display program for causing a computer to function as user interface means for displaying a cell coverage of the base station by superimposing a display pattern for each area on map information. The area evaluation means first determines a first display pattern in an area where the best value allows the allowable propagation loss, and second, sets the average value as an area where the allowable propagation loss is allowed. 2. The display pattern of 2 is determined, and thirdly, the computer is caused to function to determine the third display pattern in an area where the worst value allows the allowable propagation loss. Area evaluation display program.   The area evaluation display program according to claim 1 or 2, wherein the confidence interval in the evaluation range deriving means is specified by a standard deviation. In the area evaluation display device that displays on the screen the propagation loss for each area divided around the base station,
Normal distribution data accumulating means for accumulating normal distribution data based on the standard deviation σ of the short interval variation with respect to the frequency f;
In the area , the average value of propagation loss, which is a measured average value or a value based on a propagation model equation, is associated as an average value of the normal distribution data to obtain normal distribution data of propagation loss, and specified from the normal distribution data. Evaluation range deriving means for deriving the best value and the worst value of the propagation loss for the range satisfying the determined confidence interval;
Area evaluation means for determining a display pattern of the area according to whether the best value, the average value, and the worst value each allow a specified allowable propagation loss;
An area evaluation display device comprising user interface means for displaying a cell coverage of the base station by superimposing a display pattern for each area on map information. The area evaluation means first determines a first display pattern in an area where the best value allows the allowable propagation loss, and second, sets the average value as an area where the allowable propagation loss is allowed. 5. The area evaluation display device according to claim 4 , wherein a second display pattern is determined, and thirdly, a third display pattern is determined in an area where the worst value allows the allowable propagation loss. 6. The area evaluation display device according to claim 4 , wherein the confidence interval in the evaluation range deriving unit is specified by a standard deviation.

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