JPH0879161A - Fading pitch estimation device - Google Patents

Abstract

PURPOSE: To provide a fading pitch estimation device which can improve its detection accuracy of the fading pitch in a mobile communication system. CONSTITUTION: A sampling means 1 samples the receiving levels of received signals in each prescribed cycle, and a difference calculation means 2 calculates the difference between the sampled receiving levels. An integration means 3 integrates the calculated differences in a prescribed period of time to obtain the integration value. It is already known that the integration value of differences calculated between those sampled receiving levels has the correlation with the fading pitch value. Thus a fading pitch estimation means 4 converts the integration value into a fading pitch based on the correlation. As this integration value sensitively changes in response to the value of the preceding difference, the detection accuracy of the fading pitch is improved compared with the conventional method that is insensitive to the difference value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fading pitch estimating device in a mobile communication system, and more particularly to a fading pitch estimating device for detecting a received level fluctuation of a received signal to estimate a fading pitch. In the present specification, the "fading pitch" means a fading frequency.

[0002] In recent years, the demand for mobile communication systems has increased, and many radio frequencies are inevitably required.
However, there are limits to the radio frequencies that can be used. Therefore, introduction of dynamic channel allocation control or the like is being considered in order to effectively use the radio frequency. In dynamic channel allocation control, it is pointed out that call movement speed information plays an important role, and it is necessary to obtain the call movement speed, that is, the movement speed of the mobile station. The moving speed of the mobile station can be easily calculated by detecting the fading pitch.

[0003]

2. Description of the Related Art Conventionally, as a fading pitch estimating device in a mobile communication system, there is, for example, a "moving speed detecting device in a mobile communication system" (International Application No. PCT-JP93-01714) by the applicant. In such a device, as shown in FIG. 16, first, the receiver 101 receives a transmission radio wave, and the reception level of the reception signal is detected by the level detection unit 10 for each timing signal of a predetermined cycle T.
2 is detected, and the A / D converter 103 converts it into a digital value for sampling. Based on the sampled reception level, a difference between the reception level sampled this time and the reception level sampled last time is obtained at each sampling by the difference detection unit 104 having a built-in storage device. The comparison unit 105 compares this difference with a threshold value, and causes the counter 106 to count up when the difference is larger than the threshold value. The counter 106 counts this for a predetermined time, and the conversion unit 107 converts the count value into a fading pitch and further into the moving speed of the mobile station. The conversion unit 107 experimentally obtains and stores beforehand a correlation table between the count value and the fading pitch, and performs conversion by referring to the correlation table. The fading pitch f _d and the moving speed v of the mobile station have a relationship represented by the following equation.

V = f _d × λ (λ is the wavelength of the received signal) Based on this equation, the moving speed of the mobile station is calculated.

[0005]

However, as described above, the comparison unit 105 compares the difference obtained by the difference detection unit 104 with a threshold value, for example, 3 dBμ, and when the difference is larger than the threshold value, counts only one in the counter 106. Up is performed, and if the difference is larger than the threshold value, uniformly,
The counter 106 is made to count up only one. That is, even if the difference is 5 dBμ, or 3d
The treatment is the same even if it is slightly larger than Bμ. Therefore, there is a problem that the detection accuracy is low at the fading pitch detected by such a device.

Further, the value of the reception level on which the difference is calculated by the difference detection unit 104 may be very small, and the reception level in such a case is often buried in noise. However, in the past, even when the reception level was very small, the difference was calculated based on such reception level, so the calculated difference was not always a reliable value, and therefore, it was detected based on such difference. There is a problem that the reliability of fading pitch is low.

Further, although the fading pitch value is the same, the count value obtained by the counter 106 varies depending on the magnitude of the received electric field strength. The fading pitch detection has a problem that the detection accuracy cannot be increased.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a fading pitch estimating apparatus for improving the accuracy of fading pitch detection.

[0009]

In order to achieve the above object, the present invention provides a sampling means 1 for sampling the reception level of a reception signal at a predetermined cycle as shown in FIG.
, A difference calculating means 2 for calculating a difference between the sampled reception levels, an integrating means 3 for integrating each calculated difference over a predetermined time, and a fading for estimating a fading pitch based on the integrated value. A fading pitch estimating device is provided, which comprises: pitch estimating means 4;

Further, the difference calculating means 2 compares at least one of the two reception levels continuously sampled by the sampling means 1 with a predetermined level, and if at least one of the reception levels is equal to or higher than a predetermined level. If there is, the difference between the two reception levels is calculated.

Further, it further comprises an average reception level detection means 5 for detecting the average reception level of the reception levels, and the fading pitch estimation means 4 detects the integrated value obtained by the integration means 3 and the average reception level detection means 5. The fading pitch is estimated based on the average received level.

[0012]

In the above structure, the sampling means 1 samples the reception level of the reception signal at a predetermined cycle, and the difference calculating means 2 calculates the difference between the sampled reception levels. Then, the integrating means 3 integrates the calculated differences over a predetermined time to obtain an integrated value. It is known that the integrated value of the difference over the predetermined time has a correlation with the value of the fading pitch. Therefore, based on such correlation, the fading pitch estimation means 4 determines that the integrated value To the fading pitch.

By the way, since the integrated value is a value that sensitively changes according to the magnitude of the difference, the detection accuracy is improved as compared with the conventional fading pitch detection which is insensitive to the magnitude of the difference.

Further, the difference calculating means 2 compares at least one of the two reception levels continuously sampled by the sampling means 1 with a predetermined level. By setting this predetermined level to a value slightly larger than the noise level, if at least one of the reception levels is above a predetermined level, this reception level is recognized as a significant value, and at this time, for the first time, The difference between the two reception levels is calculated. As a result, the calculated difference becomes a reliable value, and therefore the fading pitch detection accuracy is improved. The technique of comparing the reception level with a predetermined level can also be applied to a conventional fading pitch detection device using a count value.

Further, the fading pitch estimating means 4 is
A plurality of correlation tables for different average reception levels are prepared in advance, the average reception level detecting means 5 detects the average reception level, and the fading pitch estimating means 4 detects the average reception level detecting means 5. A correlation table corresponding to the average received level is selected, and the integrated value obtained by the integrating means 3 is converted into a fading pitch using this correlation table. As a result, the fading pitch is detected in consideration of the average reception level, and therefore the fading pitch detection accuracy is improved.
The technique for detecting the fading pitch in consideration of the average reception level can also be applied to the conventional fading pitch detection device based on the count value.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a fading pitch estimating apparatus of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of the first embodiment of the present invention. In the figure, the receiver 11 receives a transmission radio wave, the level detection unit 12 detects the reception level of the reception signal based on a timing signal of a predetermined cycle, and the A / D converter 13 converts the received signal into a digital value to perform sampling. Done. The reception level sampled last time is held in the storage unit 14 for each sampling, and the difference detection unit 15 calculates the difference between the reception level sampled this time and the reception level sampled last time for each sampling. It is calculated and output to the integrating unit 16.
The integrating unit 16 integrates each difference that is sequentially sent over a predetermined time (for example, 1 sec) to obtain an integrated value. This integrated value will be described with reference to FIGS. 3 and 4.

FIGS. 3 and 4 are graphs showing changes in the reception level with time. The curve C1 of FIG. 3 shows the reception level when the fading pitch is high, and the curve C2 of FIG. 4 shows the case where the fading pitch is low. Shows the reception level of. In the figure, if it is assumed that n timing signals having a predetermined cycle are generated during the above-mentioned predetermined time, the reception levels are timings t0, t2 ,. ． It will be sampled at tn. Since the timing intervals are constant, the areas of the triangles indicated by diagonal lines in the figure are proportional to the respective differences, and therefore the total area of the triangles is proportional to the integrated value calculated by the integrating unit 16. . On the other hand, FIG.
Also, from FIG. 4, it can be seen that the higher the fading pitch, the larger the total area of the shaded areas. From these facts, it is possible to detect the fading pitch based on the integrated value by obtaining the integrated value.

Therefore, a correlation table between the fading pitch value and the integrated value is obtained in advance by an experiment,
The fading pitch detection unit 17 uses the correlation table to convert the integrated value obtained by the integration unit 16 into a fading pitch. Since the integrated value is obtained by integrating the difference over a predetermined time, the integrated value slightly changes according to the magnitude of the difference, and therefore the fading pitch is detected with high accuracy. It becomes possible.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing the configuration of the second embodiment. Since the configuration of the second embodiment is basically the same as that of the first embodiment, the same parts are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

In the second embodiment, the difference between the reception level sampled this time and the reception level sampled last time is sent from the difference detection unit 15 to the comparison unit 18 at every sampling, and the comparison unit 18 sends the difference. Each obtained difference is compared with the threshold value sent from the threshold value output unit 19. Then, only the difference equal to or larger than the threshold value is sent to the integrating unit 16. The integrating unit 16 integrates the difference sent from the comparing unit 18 over a predetermined time to obtain an integrated value.

That is, not all the differences are sent to the accumulator 16, but as shown in, for example, FIGS. 6 and 7 (assuming that the second embodiment also has the same reception level as in FIGS. 3 and 4). As a result of comparison with the threshold value, when the fading pitch is high, only six differences (corresponding to the six shaded areas in FIG. 6) become the threshold value or more and are sent to the integrating unit 16, while the fading pitch is low. In this case, only the three differences (corresponding to the three shaded portions in FIG. 7) become the threshold value or more and are sent to the integrating unit 16. Therefore, compared with the first embodiment, the integrated value when the fading pitch is high,
The difference from the integrated value when the fading pitch is low appears clearly, and the fading pitch can be detected with higher accuracy.

Next, a third embodiment of the present invention will be described. FIG. 8 is a block diagram showing the configuration of the third embodiment. Since the configuration of the third embodiment is basically the same as that of the first embodiment, the same parts are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

In the third embodiment, the foot level level output unit 22 is connected to the difference detection unit 21 to supply the foot level. The foot level is set to a value slightly higher than the noise level included in the reception level. The operation of the difference detection unit 21 will be described with reference to FIG.

FIG. 9 is a flow chart showing the procedure of the difference detection processing performed by the difference detection unit 21. Hereinafter, description will be given along the steps shown in the drawing. [S1] A timer for measuring a predetermined time is started.

[S2] The control variable n of this processing is set to 0. [S3] Level detector 12 and A / D converter 13
Performs sampling at a cycle T, and the sampled reception level is sent to the difference detection unit 21 at every sampling.

[S4] The reception level R (t + nT) sampled last time is compared with the foot level. As a result, if the reception level R (t + nT) is equal to or higher than the foot level, the process proceeds to step S5, and if it is lower than the foot level, the process proceeds to step S7.

[S5] The reception level R {t + (n + 1) T} sampled this time is compared with the foot level. As a result, if the reception level R {t + (n + 1) T} is equal to or higher than the foot level, the processing proceeds to step S6, and if it is lower than the foot level, the processing proceeds to step S7.

[S6] The difference between the reception levels sampled last time and this time is calculated and sent to the fading pitch detection processing section 23. [S7] If the timer value has reached the predetermined time (for example, 1 sec), this process is terminated, and if it has not reached the predetermined time, the process proceeds to step S8.

[S8] The control variable n is increased by 1 to prepare for the next difference calculation. As described above, since both the previous sampling reception level and the current sampling reception level provided for the difference calculation in step S6 are equal to or higher than the foothold level, these reception levels are significant values clearly distinguished from noise. Can be considered. Since the difference is detected based on such a reception level, the difference becomes a reliable value.

The fading pitch detection processing section 23 has the same configuration as the accumulating section 16 and the fading pitch detecting section 17 of the first embodiment, operates in the same manner as in the first embodiment, and is not disturbed by noise. Realize more accurate fading pitch detection using reliable difference.

The difference detecting section 21 may perform the difference detecting process shown in FIG. 10 instead of the procedure of the difference detecting process shown in FIG. FIG. 10 shows the difference detection unit 2.
6 is a flowchart showing the procedure of another difference detection process that can be performed in 1. In this flowchart, step S1
1 to S13 and steps S16 to S18 correspond to steps S1 to S3 and step S6 in the flowchart of FIG.
~ S8 is the same as each. Therefore, description of the same steps is omitted, and only different steps S14 and S15 will be described.

[S14] The reception level R (t + nT) sampled last time is compared with the foot level. As a result, if the reception level R (t + nT) is equal to or higher than the foot level, the processing proceeds to step S16, and if it is lower than the foot level, the processing proceeds to step S15.

[S15] The reception level R {t + (n + 1) T} sampled this time is compared with the foot level. As a result, if the reception level R {t + (n + 1) T} is equal to or higher than the foot level, the processing proceeds to step S16, and if it is lower than the foot level, the processing proceeds to step S17.

That is, in this difference detection process, the difference is calculated if at least one of the reception levels sampled last time and this time is equal to or higher than the foothold level.

In the third embodiment, the fading pitch detection processing unit 23 is the integrating unit 16 of the first embodiment.
The fading pitch detecting section 17 has the same configuration as that of the fading pitch detecting section 17, but instead, the fading pitch detecting processing section 23 is the same as the comparing section 105, the counter 106, and the converting section 107 of the conventional apparatus shown in FIG. You may make it consist of a structure.

Next, a fourth embodiment of the present invention will be described. FIG. 11 is a block diagram showing the configuration of the fourth embodiment. Since the configuration of the fourth embodiment is basically the same as that of the first embodiment, the same parts are designated by the same reference numerals, the description thereof will be omitted, and only different parts will be described.

In the fourth embodiment, the difference detecting section 25 is the difference detecting section 104 and the comparing section 1 of the conventional apparatus shown in FIG.
In the same configuration as 05, the difference between the reception level sampled this time and the reception level sampled last time is obtained at each sampling, and this difference is compared with a predetermined threshold value (for example, 3 dBμ). Then, the drive signal is output to the counter 26. The counter 26 counts the number of input drive signals over a predetermined time and outputs the count value after the predetermined time to the fading pitch detector 29.

On the other hand, the sampling value of the reception level output from the A / D converter 13 is also sent to the adding section 27 and the dividing section 28, where the reception level is averaged and the average reception level is adjusted to the fading pitch. It is sent to the detection unit 29.

The fading pitch detecting section 29 stores a correlation table between the count value of the counter 26 and the fading pitch depending on whether the received electric field strength is high or low.
First, it is created and stored in advance based on experiments.

FIG. 13 is a diagram showing such a correlation table. A curve C3 is a correlation table when the received electric field strength is high, and a curve C4 is a correlation table when the received electric field strength is low.

Returning to FIG. 11, the fading pitch detector 29 detects the fading pitch based on the count value sent from the counter 26 and the average reception level sent from the divider 28. The operation of the fading pitch detector 29 will be described with reference to FIG.

FIG. 12 shows a fading pitch detecting section 29.
6 is a flowchart showing a procedure of a fading pitch detection process performed in step S4. The steps will be described below. [S21] The average reception level sent from the dividing unit 28 is compared with a predetermined level (for example, 20 dBμ). If the average reception level is equal to or higher than the predetermined level, the process proceeds to step S22, and if it is less than the predetermined level, the process proceeds to step S23.

[S22] Using the curve C3 of FIG. 13 which is the correlation table when the received electric field strength is high, the counter 2
The count value sent from 6 is converted into a fading pitch.

[S23] Using the curve C4 of FIG. 13 which is the correlation table when the received electric field strength is low, the counter 2
The count value sent from 6 is converted into a fading pitch.

As described above, the fading pitch is detected in consideration of the average reception level, and therefore, the fading pitch detection accuracy is higher than that of the conventional apparatus which uniformly converts the count value into the fading pitch regardless of the received electric field strength. Is improved.

Although only two correlation tables are prepared in the fourth embodiment, three or more correlation tables may be prepared according to the received electric field strength.
This can be expected to further improve the detection accuracy of the fading pitch.

Further, the difference detecting section 2 of the above-mentioned fourth embodiment.
5 and the counter 26, the storage unit 14 of the first embodiment,
The difference detecting unit 15 and the integrating unit 16 may have the same configuration, and the fading pitch detecting unit 29 may convert the integrated value into the fading pitch in consideration of the average reception level.

Next, a fifth embodiment of the present invention will be described. The fifth embodiment is a modification of the method of calculating the average reception level of the fourth embodiment. FIG. 14 is a block diagram showing the configuration of the fifth embodiment. Since the configuration of the fifth embodiment is basically the same as that of the fourth embodiment,
The same portions will be denoted by the same reference numerals and the description thereof will be omitted, and only different portions will be described.

In the fifth embodiment, a timer 30 and a switch 31 driven by the timer 30 are newly provided, and the receiver 32 adopts an antenna selection diversity system. In the receiver 32, the antenna that has received the signal having the highest reception level is selected from the same signals received by the plurality of antennas, and the actual reception is performed via the selected antenna. Such antenna selection is performed for each frame of the received signal, for example, for every 6.6 ms. The timer 30 is for outputting an ON signal after a predetermined short time from the switching time when the antenna is switched by the receiver 32, and the switch 31 is for transmitting the ON signal. Only the reception level which is conductive and is output from the A / D converter 13 immediately after the ON signal is input is sent to the addition unit 27.

That is, when the antenna is switched in the receiver 32, the reception level sampled in the first time immediately after the switching is, of course, a considerably high level, and the fading pitch becomes high or low. There is almost no difference due to it. The reception level sampled at the next second time is generally lower than the reception level sampled at the first time, and the degree of the decrease is larger as the fading pitch is higher. Therefore, when such reception levels are averaged, a phenomenon occurs in which the higher the fading pitch, the lower the average reception level, even if the same average reception level should be obtained. Therefore, in the fifth embodiment, a timer 30 and a switch 31 are provided, and when calculating the average reception level, only the reception level sampled for the first time immediately after the antenna switching is used, and the addition unit 27 and The average reception level calculated by the divider 28 is not influenced by the fading pitch.

The operation of the fifth embodiment is the same as that of the fourth embodiment except that the method of calculating the average reception level is different. Each of the above embodiments can be combined with two or three of them. This can be expected to further improve the detection accuracy of the fading pitch. The sixth embodiment, shown in FIG.
These are three examples and are a combination of the first, third, and fourth embodiments.

In any of the above embodiments,
Although only the fading pitch is detected, the detected fading pitch may be further multiplied by the wavelength of the received signal to calculate the moving speed of the mobile station.

[0054]

As described above, according to the present invention, the integrated value of the fluctuation amount (difference) of the reception level is obtained, the fading pitch is estimated from the integrated value, and the significant reception which can be distinguished from the noise. You can use the level to calculate the difference,
Also, the fading pitch may be estimated in consideration of the average reception level. Thereby, it becomes possible to detect the fading pitch with high accuracy, and therefore, it is possible to accurately estimate the moving speed of the mobile station, which is an important parameter in the mobile communication system, and as a result,
It has become possible to improve the quality of wireless line control and service control.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a block diagram showing a configuration of a first embodiment.

FIG. 3 is a graph showing a temporal change of a reception level when a fading pitch is high.

FIG. 4 is a graph showing a temporal change of a reception level when a fading pitch is low.

FIG. 5 is a block diagram showing a configuration of a second exemplary embodiment.

FIG. 6 is a graph showing a temporal change of a reception level when a fading pitch is high.

FIG. 7 is a graph showing a temporal change of a reception level when a fading pitch is low.

FIG. 8 is a block diagram showing a configuration of a third exemplary embodiment.

FIG. 9 is a flowchart showing a procedure of difference detection processing.

FIG. 10 is a flowchart showing the procedure of another difference detection process.

FIG. 11 is a block diagram showing a configuration of a fourth exemplary embodiment.

FIG. 12 is a flowchart of a fading pitch detection process.

FIG. 13 is a diagram showing a correlation table.

FIG. 14 is a block diagram showing a configuration of a fifth exemplary embodiment.

FIG. 15 is a block diagram showing a configuration of a sixth exemplary embodiment.

FIG. 16 is a block diagram showing a configuration of a conventional device.

[Explanation of symbols]

 1 Sampling Means 2 Difference Calculating Means 3 Accumulating Means 4 Fading Pitch Estimating Means 5 Average Reception Level Detecting Means

Front page continuation (72) Inventor Kazuo Kawabata 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Kenji Suda 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Tadao Takami 2-10-10 Toranomon, Minato-ku, Tokyo NTT Mobile Communications Network Co., Ltd.

Claims (10)

[Claims] 1. A fading pitch estimation device in a mobile communication system, sampling means for sampling a reception level of a reception signal at a predetermined cycle, difference calculation means for calculating a difference between the sampled reception levels, and the calculation. A fading pitch estimating device comprising: an integrating means for integrating each of the obtained differences over a predetermined time; and a fading pitch estimating means for estimating a fading pitch based on the integrated value. 2. A comparison means for comparing each difference calculated by the difference calculation means with a predetermined threshold value and sending only a difference equal to or more than the predetermined threshold value to the integration means. 1. The fading pitch estimation device according to 1. 3. The difference calculation means compares the two reception levels sampled continuously by the sampling means with a predetermined level, and if the two reception levels are equal to or higher than the predetermined level, the difference calculation means The fading pitch estimating apparatus according to claim 1, wherein a difference between two reception levels is calculated. 4. The difference calculating means calculates the difference between the two reception levels if at least one of the two reception levels continuously sampled by the sampling means has a reception level equal to or higher than a predetermined level. The fading pitch estimating apparatus according to claim 1, wherein the fading pitch estimating apparatus calculates the fading pitch. 5. An average reception level detection means for detecting an average reception level of the reception levels is further provided, and the fading pitch estimation means detects the integrated value obtained by the integration means and the average reception level detection means. The fading pitch estimating apparatus according to claim 1, wherein the fading pitch is estimated based on the averaged reception level. 6. The apparatus further comprising a receiver adopting an antenna selection diversity system, wherein the average reception level detecting means is
The fading pitch estimating apparatus according to claim 5, wherein the average reception level is detected using only the reception level detected immediately after the antenna switching based on the antenna selection diversity method. 7. A fading pitch estimation device in a mobile communication system, comprising: sampling means for sampling a reception level of a reception signal at a predetermined cycle;
If the reception level of at least one of the two reception levels is equal to or higher than a predetermined level, a difference calculation means for calculating a difference between the two reception levels, and each calculated difference is compared with a predetermined threshold, A comparison unit that outputs a drive signal when the drive signal is equal to or greater than a predetermined threshold value, a count unit that receives the drive signal and counts the number of input drive signals over a predetermined time period, and the count unit operates over the predetermined time period. And a fading pitch estimating means for estimating a fading pitch based on the value counted by the fading pitch estimating device. 8. The difference calculating means compares the two reception levels continuously sampled by the sampling means with a predetermined level, and if the two reception levels are equal to or higher than the predetermined level, the difference calculation means 8. The fading pitch estimation device according to claim 7, wherein the difference between the two reception levels is calculated. 9. A fading pitch estimation device in a mobile communication system, sampling means for sampling a reception level of a reception signal at a predetermined cycle; difference calculation means for calculating a difference between the sampled reception levels; Comparing each difference with a predetermined threshold and outputting a drive signal when the difference is equal to or greater than the predetermined threshold, and a count for inputting the drive signal and counting the input number of the drive signal over a predetermined time. Means, an average reception level detection means for detecting an average reception level of the reception levels, and a fading based on a value counted by the counting means over the predetermined time and an average reception level detected by the average reception level detection means. Fading pitch estimating means for estimating the pitch, and E over managing pitch estimation apparatus. 10. A receiver employing an antenna selection diversity system is further provided, wherein the average reception level detecting means uses only the reception level detected immediately after antenna switching based on the antenna selection diversity system. 10. The fading pitch estimation device according to claim 9, wherein the level is detected.