JP3066890B2 - Mobile communication propagation delay measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for measuring propagation delay in digital mobile communication, and measures a mobile communication propagation delay in real time using a narrow band signal to measure a delay spread, which is one of indexes indicating the propagation delay. About.

[0002]

2. Description of the Related Art Hitherto, as a method of measuring a propagation delay in a narrowband digital mobile communication, a method of obtaining a value of a delay spread from a demodulated detection output distortion amount has been proposed. Here, an example in which QPSK modulation is used will be described. In Nyquist transmission, there is no intersymbol interference at the sampling timing when there is no propagation delay, but there is intersymbol interference when there is a propagation delay,
Appears as distortion of the detection output.

FIG. 12A shows the positions of signal points on the phase space of two channels, I and Q, which are orthogonal to each other. If there is no propagation delay, the demodulated signal is at the points of phase angles ± 45 ° and ± 135 °. However, if there is a propagation delay, the position of the demodulated signal shifts as shown in FIG. 12B. FIG. 13 shows the positional deviation, that is, the relationship between the amount of distortion and the delay spread. That is, the relationship between the distortion amount and the delay spread is obtained in advance and tabulated and prepared, the distortion amount is actually measured and the delay spread is estimated by using the above table. In this case, the table of the distortion amount and the delay spread created in advance is generally created under the condition that the detection distortion does not occur due to other noise.

[0004] The techniques described above are described in detail in the following references 1 and 2. Literature 1 [Shouhong, Yoshida, Ikegami, "Multiple wave detection by orthogonal channel interferometry", IEICE, B-II Vol. J73-B-II No.
1 pp.10-19 January 1990] Reference 2 [Hirai, Tan. Guan. Ren, Zhou, Takeuchi, Yoshida,
“Prototype of Simple Multiplexed Wave Delay Time Detector for π / 4 Shift QPSK,” IEICE Technical Report RCS 91-14, pp. 53-59. However, as shown in FIG. Since the detection output is distorted due to the thermal noise, the relationship between the detection output distortion amount and the delay spread changes. Therefore, in order to accurately measure the delay spread, it is necessary to remove the influence of thermal noise when the reception level is reduced. As a method of removing the influence of thermal noise, a method is proposed in which a threshold is provided for the reception level, and the detection output distortion is not measured when the reception level falls below the threshold. This technique is described in detail in Document 3 [Ikura et al., Japanese Patent Application Laid-Open No. 6-244881, filed on February 16, 1993, line quality measuring instrument].

[0005]

However, even if a threshold value is provided for the reception level and the influence of thermal noise when the reception level is lower than the threshold value is removed, the reception level is completely changed due to the dynamic change of the reception level. Since it cannot be completely removed, FIG.
As shown in (1), for the same amount of distortion D according to the difference in the reception level, the delay spreads A, B, and C should be originally estimated according to the difference in each reception level. If the characteristic is the characteristic of the curve 3 shown in FIG. 14, the delay spread C is estimated even when the reception level is 10 dBμ and 20 dBμ, which has a disadvantage that an estimation error occurs.

Further, as shown in FIG. 15, in mobile communication, the moving speed (in FIG. 15, the moving speed is set to the maximum Doppler frequency f
_(Shown by _D ), the effect of different moving speeds on the distortion of the detection output is different. Therefore, the conventional method using a single conversion table without considering the difference between the reception level and the vehicle speed has a problem that a large estimation error occurs in the estimated value of the delay spread.

[0007]

According to the present invention, there is provided an apparatus for measuring a propagation delay spread using a detection output distortion amount in digital mobile communication, wherein a plurality of detection output signals are provided in advance according to a difference in reception level and a difference in vehicle speed. A conversion table of distortion amount versus delay spread is prepared, an optimum conversion table is selected according to the measured difference in reception level and vehicle speed, and a delay spread value is calculated from the distortion amount. Therefore, according to the present invention, the conversion of the distortion amount and the delay spread can be optimized according to the difference between the reception level and the vehicle speed.

[0008]

In the present invention, a plurality of conversion tables of the detection output distortion amount to the delay spread are prepared corresponding to the difference in the reception level and the vehicle speed, and the conversion table most suitable for the measured reception level and the vehicle speed is selected. Because the influence of thermal noise and the like on the detection output distortion amount is taken into account, the accuracy of delay spread estimation can be improved.

FIG. 1 shows an embodiment of the present invention. In this embodiment, a delay detection circuit 11, a reception level detection circuit 12,
Vehicle speed detection circuit 13, distortion amount detection circuit 14, and control unit 15
The control unit 15 includes a conversion table storage unit 16 and a conversion circuit 17. First, a method of creating a conversion table will be described. FIG. 2 shows an example of a method for creating a plurality of conversion tables. The transmitter 21 sets the level L _(i) , and the multipath fading simulator 22 sets the vehicle speed V and the delay spread value S. In FIG. 2, the vehicle speed V is set to the maximum Doppler frequency f.
_{Expressed as D.} When the delay wave model is a double spike model having a delay profile as shown in FIG. 3, the detection circuit 23 calculates the delay time difference between the two waves as a delay time Td (S = Td) corresponding to the delay spread value S. In this case, signals having the same average power level of each wave and undergoing independent Rayleigh fading are input.

Under these conditions, the detection output distortion D is detected by the distortion detection circuit 24 from the output of the detection circuit 23 when the delay spread value S is changed by the multipath fading simulator 22, and the setting is made. Delay spread value S and distortion amount D at reception level L, vehicle speed V
Find the conversion table of Here, the reception level L _(i) is L _(i) = L ₀ + ΔL × i (i = 1, 2,..., N), and the vehicle speed V _(k) is V _(k) = V ₀ + ΔV × k (k = 1,2,…,
m) and n × m are set, and a relation between the delay spread value S and the distortion amount D is obtained under each condition to create a plurality of conversion tables as shown in FIG. To memorize.

Next, the operation of the delay spread measurement will be described with reference to FIG. Specifically, the reception phase modulation wave is subjected to delay detection in the delay detection circuit 11, and an in-phase detection output I and a quadrature detection output Q are generated. The generated one detection component I or Q is input to the distortion amount detection circuit 14, and the distortion amount D corresponding to the delay spread value S is detected. For simplicity, an example of detecting the distortion of the in-phase detection output I will be described. The positive and negative detection output values in an ideal state where there is no influence of noise such as thermal noise and there is no distortion are set as reference values. The detection output distortion amount D is obtained by averaging the absolute value of the difference between the detection output value and the detection output value over the set measurement time. For details, refer to “Line quality measuring instrument” described in JP-A-6-244881.

The output from the distortion detection circuit 14 is supplied to the control unit 15 together with the output from the reception level detection circuit 12 and the output from the vehicle speed detection circuit 13. Conversion circuit 1 in control unit 15
7 from a plurality of tables in the conversion table storage unit 16 that are created in advance according to the vehicle speed V _(k) and level L _(i), the condition of the inputted reception level L _(i) and the vehicle speed V _(k) The table created under the closest condition is selected as the optimum table, and the distortion amount is converted into the delay spread value S by using this selected table.

In the above embodiment, a conversion table is created for the two parameters of the reception level L _(i) and the vehicle speed V _(k) , and the optimum conversion table is selected. A conversion table may be created using only L _(i) as a parameter. In this case, as shown in FIG. 5, a delay detection circuit 11, a reception level detection circuit 12, a distortion amount detection circuit 14, and a control unit 15 including a conversion table storage unit 16 and a conversion circuit 17 are provided.

Although FIG. 1 shows the case of single branch reception, the delay spread value S can be estimated by the same procedure in the case of diversity reception. However, the conversion table in the case of performing the measurement by diversity reception is selected from the conversion table created by performing the diversity reception. The modulation and demodulation method is QPS
Although the case of the K modulation / delay detection method is shown, BPSK
The same measurement can be performed using another digital modulation method such as modulation, and other demodulation methods such as a synchronous detection method can be used for demodulation.

In the above embodiment, the vehicle speed V_(k)
Is detected, but this vehicle speed V _(k)Diagram of detection method
6 is shown. In the case of FIG.
The distance pulse accompanying the rotation is acquired from the rotation sensor 42,
The vehicle speed V according to the value_(k)Is calculated by the vehicle speed detection circuit 43.
You. (Equivalent to obtaining the vehicle speed directly from the vehicle speed meter). one
On the other hand, there is also a method of detecting the vehicle speed based on the fluctuation of the received wave level.
is there. In mobile communication, the reception level is instantaneous according to the vehicle speed.
Suffer fading that fluctuates greatly. In this case,
The maximum value of the dynamic speed is generally the maximum Doppler frequency f_DCalled
Frequency (wavelength λ) and vehicle speed V_(k)
Function f_D= (V_(k)/ Λ) cos θ_i(Θ_iIs the arrival of radio waves
Angle between the incoming direction and the moving direction of the moving object)
it can. That is, the maximum Doppler frequency f_DMeasure
Conversely, the vehicle speed V_(k)Can be estimated. FIG. 7 shows the maximum
Doppler frequency f_DThe configuration for directly measuring is shown. This structure
As a result, a receiver 51, a reception level detection circuit 52,
A comparator 53, a counter 54, a controller 55, and a threshold
It can be constituted by the value generator 56. Comparator
At 53, the reception level input from the reception level detection circuit 52 is output.
Bell signal 57 crosses threshold E as shown in FIG.
Pulse P every_SGenerate. Generated in comparator 53
Pulse P_SIs input to the counter 54 and counted for a certain period of time.
Let it. The count value of the counter 54 is shown in FIG.
Conversion curve to maximum Doppler frequency f_DIs calculated.
Frequency f_DVehicle speed V using_(k)Convert to That's all
Vehicle speed V_(k)Can be detected.

FIG. 10 shows a delay spread estimation algorithm of this embodiment. In this embodiment, the amount of distortion D is detected from the detected output in step S3, and the detected amount of distortion D is averaged to determine the average amount of distortion for each measurement time. On the other hand, in steps S1 and S2, the reception level L _(i)
And the vehicle speed V _(k) are detected, and a table created under the condition of the most suitable level and vehicle speed is selected from a plurality of tables prepared in advance in step S4. Using this optimum table, the distortion amount D is converted into a delay spread value S in step S5, and the delay spread value S is estimated and output in step S6.

FIG. 11 shows again the averaged output characteristic with respect to the delay spread value S shown in FIG.
Here, if the measurement is performed when the actual delay spread is 5 μs, the selection of the conversion table is performed optimally for the reception level L _(i) and the vehicle speed V _(k) .
The vehicle speed V _(k) and the reception level L _(i) are respectively V _(k) = 5
0 km / h, L _(i) = 10 dBμ, 50 km / h, L _(i) = 20 dB
μ, 50Km / h, L ( i) = in the case detection output distortion quantity of the character is D _1, D _2, D ₃ each conditions 30dBμ, L of Figure 11 corresponding to each condition _(i) = 10 dBμ, L _(i) = 20 dBμ,
Each table of L _(i) = 30 dBμ is selected,
It can be estimated as 5 μs, which is equal to the actual delay spread value S.

Also, when the vehicle speed V _(k) changes, the delay spread value S can be accurately estimated by referring to the optimum conversion table.

[0019]

As described above, the conventional estimation of the delay spread value S is performed when the measurement is performed under the same reception level L _(i) and vehicle speed V _(k) as when the conversion table was created. Although the error is minimized and the estimation error increases as the difference with the condition at the time of creating the conversion table increases, according to the present invention, a plurality of conversions are performed in accordance with different reception levels L _(i) and vehicle speeds V _(k). There is an advantage that the estimation error does not increase even under a variety of different conditions because the configuration is designed to deal with this by having a table.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a block diagram for explaining a method of creating a conversion table used in the embodiment shown in FIG.

FIG. 3 is a waveform chart for explaining the operation of the embodiment shown in FIG. 2;

FIG. 4 is a block diagram for explaining a configuration of a conversion table storage unit used in the embodiment shown in FIG. 2;

FIG. 5 is a block diagram for explaining a modified embodiment of the present invention.

FIG. 6 is a block diagram for explaining an example of a vehicle speed detection circuit shown in FIG. 1;

FIG. 7 is a block diagram illustrating an example of a vehicle speed detection circuit illustrated in FIG. 6;

FIG. 8 is a waveform chart for explaining the operation of the vehicle speed detection circuit shown in FIG. 7;

9 is a graph showing the number of counters used in the vehicle speed detection circuit shown in FIG. 7 versus the maximum Doppler frequency conversion curve.

FIG. 10 is a diagram showing an estimation algorithm used in the embodiment of the present invention.

FIG. 11 is a diagram showing an example of a plurality of conversion tables representing the relationship between the amount of detection output distortion and delay spread, and an estimated delay spread value when using the plurality of conversion tables.

FIG. 12 is a diagram showing signal points on a phase space of a QPSK demodulated signal which is one of the phase modulation signals.

FIG. 13 is a diagram illustrating a relationship between a detection distortion amount and a delay spread.

FIG. 14 is a diagram for explaining the reason why different delay spreads have to be estimated according to the difference in the reception level.

FIG. 15 is a diagram for explaining the reason why different delay spreads must be estimated according to the difference in vehicle speed.

[Explanation of symbols]

1 Relationship between delay spread and distortion at reception level 10 dBμ 2 Relationship between delay spread and distortion at reception level 20 dBμ 3 Relationship between delay spread and distortion at reception level 30 dBμ 4 Delay at maximum Doppler frequency f _D = 0 Hz Relationship between spread and distortion amount 5 Relationship between delay spread and distortion amount when maximum Doppler frequency f _D = 1 Hz 6 Relationship between delay spread and distortion amount when maximum Doppler frequency f _D = 10 Hz 11, 31 Delay detection circuit 12, 32, 52 reception level detection circuit 13, 43 vehicle speed detection circuit 14, 24, 33 distortion amount detection circuit 15, 34 control unit 16, 25, 35 conversion table storage unit 17, 36 conversion circuit 21 transmitter 22 multipath fading simulator 23 detection circuit 26 Delay wave model 41 Axle 42 Rotation sensor 51 Receiver 53 Comparator 54 Counter 55 Controller 56 Threshold value generator 61 Conversion table when reception level is 10 dBμ 62 Conversion table when reception level is 20 dBμ 63 Conversion table when reception level is 30 dBμ or more

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 17/00 G01R 29/00 H04B 7/26 H04L 27/18

Claims (2)

(57) [Claims] 1. A relation between a detection output distortion amount due to intersymbol interference caused by a propagation delay and a delay spread value is prepared in a table, and a propagation delay amount is estimated from the detected distortion amount using the table. In a device for measuring propagation delay in digital mobile communication, a plurality of the above tables are prepared according to the reception level, and an optimum table is selected according to the reception level measured for the detected detection output distortion amount, and the delay spread value is selected. A mobile communication propagation delay measuring device in digital mobile communication, characterized in that: 2. A relation between a detection output distortion amount due to intersymbol interference caused by a delay spread and a delay spread value is prepared in a table, and a propagation delay amount is estimated from the detected distortion amount using the table. In an apparatus for measuring a delay spread value in digital mobile communication, a plurality of the above tables are prepared according to a reception level and a vehicle speed, and an optimum table is selected according to a reception level and a vehicle speed measured with respect to a detected detection output distortion amount. A mobile communication propagation delay measuring device for digital mobile communication, wherein the delay spread value is calculated.