JP2549342B2 - Multiple channel measurement method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple channel measurement system in mobile communications, and more particularly, to an amplitude frequency characteristic (ie spectrum) of a radio channel with a high signal noise ratio (C).
/ N ratio).

[0002]

2. Description of the Related Art Recently, with the digitization of modulation schemes in mobile communications and the speeding up of digital signals, deterioration of transmission characteristics due to multiple propagation paths has become a problem. It has become necessary to elucidate the delay spread with high accuracy and measure the bit error rate. conventionally,
A delay profile, which is a characteristic in which a delay amount and a power value are associated with each other, is measured to obtain a delay spread of multiple propagation paths. However, this requires a very wide transmission band and a sufficiently high transmission power. Considering the expected radio wave interference in the future, it is almost impossible to measure the delay spread with high accuracy. Is becoming. Further, in order to measure the bit error rate, the band must be the same as the band at the time of service, and the power must be the same as the power at the time of service. Therefore, it is necessary to permit the use of radio waves, and it is becoming difficult to perform the measurement itself. As a conventional radio wave propagation path measurement method, a method has been adopted in which a coded signal having an excellent autocorrelation characteristic is used and a delay spread is measured from a cross-correlation between a signal on the transmission side and a received signal. However, the measurement accuracy of this method is limited by the chip rate (time length of one symbol of the modulated wave), and the approximate measurement accuracy is 1 / T (T: chip rate). A chip rate of 100 Mbps is required to obtain the measurement accuracy.
There is a problem that about 300MHz is required in the band. In addition, there is a drawback that it is necessary to overcome wideband noise in order to improve reception accuracy, and thus it is necessary to increase transmission power. For this reason, the applicant has proposed a multiple channel measurement method capable of measuring delay spread in a normal use band and at low transmission power (see Japanese Patent Application No. 4-262710).

[0003]

However, in the above-mentioned multiple channel measurement method proposed by the applicant, the amplitude-frequency characteristic (that is, spectrum) of the radio channel measured by the receiving system is measured.
It has been a problem that it is difficult to measure at a high signal-to-noise ratio. The present invention has been made to solve the above problems, and provides a multiple channel measurement method capable of measuring the amplitude frequency characteristic (spectrum) of a radio channel at a high signal-to-noise ratio (C / N ratio). The purpose is to do.

[0004]

In order to solve the above-mentioned problems, the multiple channel measurement system according to the present invention comprises a transmission system and a reception system in mobile communication, and the transmission system has a frequency stability A pseudo clock pattern generator and a pseudo random pattern generator circuit are used to generate a pseudo random pattern of an arbitrary repetition period, then band limitation is performed, and then a digital modulator circuit and a carrier wave generator with high frequency stability are used to Digital modulation is performed using a pseudo-random pattern, and the modulated wave thus modulated is transmitted as a transmission wave using an RF band amplifier. In the reception system, the RF band band limiting circuit, the IF band converter, and the frequency stability A high reception local signal generator is used to receive the delayed modulated wave in which the transmitted modulated wave is delayed by the multiple propagation path, and the band control of the received wave is performed. By converting the band-limited received wave into an intermediate frequency band received wave, and then using a fast Fourier transform analysis circuit and a sampling time / frame generator with high frequency stability Fast Fourier transform analysis of a repeating cycle is performed, and then fast Fourier transform analysis data of the received wave is processed by using a polar coordinate converter, a phase compensation circuit, and an analytic addition circuit, and the fast Fourier transform of the processed received wave is performed. It is configured to measure an amplitude frequency characteristic having a high signal-to-noise ratio from analysis data.

[0005]

According to the multiple channel measurement system of the present invention having the above-mentioned structure, in the transmission system, a clock signal generator having a high frequency stability, a pseudo random pattern generation circuit,
Using a carrier wave generator, a digital modulation circuit, and an RF band amplifier, in the receiving system, a receiving local signal generator with high frequency stability, a sampling time / frame generator with high sampling frequency stability, and a fast Fourier transform Since the analysis circuit, the polar coordinate converter, the phase compensation circuit, and the analysis addition circuit are used, the amplitude frequency characteristic (spectrum) of the radio wave propagation path can be measured with a high signal-noise ratio (C / N ratio).

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a mobile communication system according to an embodiment of the present invention. As shown in the figure, this mobile communication system includes a transmission system 1 and a reception system 2.

Further, the transmission system 1 includes a coded signal generation circuit 5 which is a pseudo random pattern generation circuit, a clock signal generator 8, a band limitation circuit 6, an RF band digital modulation circuit 7, and a carrier wave generator 9. And an RF band amplifier 10. Further, the receiving system 2 includes an RF band band limiting circuit 11
An IF band converter 12, a receiving local signal generator 29,
FFT (FFT: Fast Fourier Transform) analysis circuit 24, sampling time / frame generator 30, phase compensation circuit 28, and analysis addition circuit 2
5, the analysis addition holding circuit 23, the delay spread estimation
It has a code error rate estimation circuit 27 and a comparison circuit 26. Further, the phase compensation circuit 28 is provided with a polar coordinate converter (not shown).

In this case, in the transmission system 1, the clock signal generator 8 and the carrier wave generator 9 have high frequency stability (frequency stability of a value of about 10 −10).
In the receiving system 2, the receiving local signal generator 29,
For the sampling time / frame generator 30,
The one with high frequency stability (the value with frequency stability of about 10-10) is used.

Next, the procedure of the multiple channel measurement method in the above mobile communication system will be described with reference to FIG.

First, the encoded signal generation circuit 5 of the transmission system 1
Generates and outputs a pseudo random pattern (PN pattern) based on the clock signal from the clock signal generator 8. Next, the band limiting circuit 6 limits the power of the transmission RF band to a certain band. Then, in the RF band digital modulation circuit 7, B
PSK (Binary Phase Shift Keying) and QPSK (Qu
The digital modulation such as adratur Phase Shift Keying) is performed and output.

In this case, the PN pattern is represented by g (t) and the clock frequency is represented by fc.
The digital modulation output a (t) from

[Equation 1] It is represented by. In the above equation (1), ωo represents the initial angular frequency, θo represents the initial phase difference, and the frequency stability of fc is a value of about 10 -10.

On the other hand, in the receiving system 2, the receiving local signal generator 29 is used to limit the received RF band wave to the measurement frequency bandwidth by the RF band band limiting circuit 11, and then I
Intermediate frequency band (IF band) measured by F band converter 12
Convert to.

Next, the transmitted wave passes through the frequency converter 12 and is then FFT-analyzed by the FFT analysis circuit 24.
The analysis addition holding circuit 23 adds M T times and stores and holds it. By adding in this way, the power spectrum is smoothed and measured and stored as a reference signal.

In addition, when measuring the delay modulation wave spectrum, the transmission side FFT analysis result at the frequency fn is obtained by γ.
Let T (fn) be the result of addition and holding Yn
Is

[Equation 2] It is represented by. In the above formula (2), MT represents the number of measurements, and MT is about 10,000 times.

In this case, R to the RF band band limiting circuit 11
F input b (t) is

(Equation 3) It is represented by. In the above equation (3), hn (t) represents the time waveform of the impulse generated by the transmission / reception system, τ n represents the delay time, and N (t) represents the noise component.

Next, similarly to the reference signal measurement, the FFT
In the analysis circuit 24, FFT analysis is performed based on the frame from the sampling time / frame generator 30. In this case, assuming that the frequency is 1, the m-th Fourier cosine transform Cm output from the FFT analysis circuit 24.
(L) is the following formula

[Equation 4] It is represented by. In the above equation (4), T represents the sample time length of the Fourier transform (the repeating period of the Fourier transform analysis).

The m-th Fourier sine transform Sm (l), which is the output from the FFT analysis circuit 24, is

(Equation 5) It is represented by.

Next, the phase compensation circuit 28 performs phase compensation. In this case, the m-th Fourier cosine transform C'm (l) output from the phase compensation circuit 28 is

(Equation 6) It is represented by.

In the above equation (6), θl is the following equation

(Equation 7) It is represented by. In the above equation (7), Tt represents the frame time length of the PN pattern (the repetition period of the pseudo random pattern).

However, in the above equation (7), T is represented by the following equation T = ko / fo (8) and Tt is represented by the following equation T = kc / fc ... ... (9) In the above formulas (8) and (9), ko represents an integer, fo represents a carrier frequency, and kc represents an integer.

The m-th Fourier sine transform S'm (l), which is the output from the phase compensation circuit 28, is expressed by the following equation.

(Equation 8) It is represented by.

Next, the analysis and addition circuit 25 adds the above analysis results. Then, the above-mentioned analysis addition circuit 2
The output P (l) from 5 is

[Equation 9] It is represented by.

Next, a case where the amplitude frequency characteristic (spectrum) of the received wave is measured by the above procedure will be described using actual numerical values.

The PN pattern, which is a pseudo-random pattern, has 11 stages, and the clock frequency fc = 4.047 MHz.
And Therefore, the frame time length Tt is calculated by the following equation: Tt = (211-1) ÷ (4.047 × 10 6) = 10 -6 = 1 (μsec) (12)

In this case, the sample time length T of the Fourier transform (repetition period of the Fourier transform analysis) is T = 1 μs.
When set to ec and matched with the frame time length Tt of the PN pattern (repeat cycle of the pseudo random pattern),
From the above equation (7), θl = -2π (13)

Therefore, the above equations (6) and (10)
Therefore, C'm (l) = Cm (l) ... (14) S'm (l) = Sm (l) ... (15) Therefore, phase compensation becomes unnecessary and facilitated. .

When the carrier frequency fo in this case is calculated,
When ko = 1000, fo = ko / T = ko × 10 6 = 1 GHz ... (16)

The C / N ratio in the above case is calculated by the following equation.

[Equation 10] And m / 1000 times, the C / N ratio is 30
It is improved by dB.

In addition to the above, in order to compensate for the imperfections of the transmission / reception system, in the reception system 2, on the one hand, the amplitude frequency characteristic (spectrum) of the modulated wave output from the FFT analysis circuit 24 is detected. The modulated wave spectrum is measured, on the other hand, the delayed modulated wave spectrum which is the amplitude frequency characteristic of the delayed modulated wave which is the output of the FFT analysis circuit 24 is measured, and the modulated wave spectrum and the delayed modulated wave spectrum are measured. It is also effective to cancel the characteristics of the transmission / reception system by taking the ratio of

Further, the receiving system 2 is configured so that, in the RF band band limiting circuit 11, the bandwidth for measuring the amplitude frequency characteristic is expanded and the measured amplitude frequency characteristic is smoothed by C / C. It is effective in improving the N ratio.

The analytical addition in the analytical addition circuit 25 is performed MR times. By adding in this way, the measured amplitude frequency characteristic is smoothed and the measurement accuracy is improved.

In the above, when the reception side FFT analysis result at the point of frequency fn is γ R (fn), the added and held result Rn is

[Equation 11] It is represented by. In the above formula (18), MR represents the number of measurements, and MR is a number of about 10,000 times.

Next, the above-mentioned Yn and Rn are compared by the comparison circuit 26.
Are compared. This comparison is

(Equation 12) It is represented by.

Next, based on the above comparison result Pn, the delay spread estimation / code error rate estimation circuit 27 measures the power drop within the band of the power spectrum and the power value of the power drop. Then, the delay spread estimation / code error rate estimation circuit 27 described above logically estimates the delay spread from the number of power drops.

The procedure of the above delay spread estimation will be described below. First, when the level of the drop from the average level in the band is r, the average value q of the number of drops to the r level
(R)

(Equation 13) It shall be represented by Here, N represents the number of times the r level drops in the band, L represents the number of times of measurement while the moving body moves a distance of 10λ (λ: wavelength), and B represents the band bandwidth. .

Next, the error is

[Equation 14] It is represented by.

Next, the reference x (r, α) is determined so as to minimize the above error. Where x (r,
α) is the following formula

(Equation 15) And is represented by a polynomial having each coefficient of Expression (22) calculated in advance from the broadband infinite multiple wave model. Since α corresponds to the delay spread, the delay spread α is estimated from this x (r, α).

Here, the broadband infinite multiple wave model refers to an electric field of an incoming wave in contrast to a conventional infinite multiple wave model (a model in which an infinite wave having the same electric field strength arrives at a moving body from a direction of 360 °). This is a model in which the intensity has an exponential distribution and the arrival delay amount has a uniform distribution.

Next, from the above power drop value, the number of drops, and the delay spread, the delay spread estimation /
The code error rate estimation circuit 27 measures the code error rate.

The code error rate is given by

[Equation 16] Required by. Here, kr is determined by the actual measurement value.

The analysis / estimation unit 3 is provided with an adaptive equalization circuit, and measures the frequency position of the power spectrum drop and the characteristic of the power value (drop level) after the adaptive equalization. , The code error rate after the adaptive equalization is estimated by associating the code error rate estimated from the frequency position of the drop of the power spectrum and its power value with the characteristic after the adaptive equalization. May be.

That is, first, the code error rate is estimated from the frequency position of the drop of the power spectrum and its power value (drop level). Next, the frequency position of the drop of the power spectrum and the distribution of the power value thereof are adaptively equalized to obtain the characteristic. Then, the code error rate after demodulation / equalization is estimated from the above-mentioned code error rate and the above characteristics in correspondence with the drop frequency position.

Further, in the above mobile communication system, the receiving system 2 is provided with a plurality of sequences of space diversity receiving system, and the analysis and estimation unit, which is a logic unit, receives from the plurality of sequences of FFT analysis data after reception by space diversity. The code error rate may be estimated.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any device having the same function and effect can be realized by the present invention. It is included in the technical scope of the invention. For example, a software program processes the same function as the above.

[0045]

As described above, according to the multiple channel measurement system of the present invention having the above configuration, in the transmission system, a clock signal generator with high frequency stability, a pseudo random pattern generation circuit, and a carrier wave are provided. In the receiving system, using a generator, etc., digital modulation circuit, and RF band amplifier,
Radio wave propagation because a local signal generator with high frequency stability, a sampling time / frame generator with high sampling frequency stability, a fast Fourier transform analysis circuit, a polar coordinate converter, a phase compensation circuit, and an analysis addition circuit are used. Amplitude-frequency characteristics (spectrum) of a high signal-to-noise ratio (C
/ N ratio).

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a mobile communication system which is an embodiment of the present invention.

[Explanation of symbols]

 1 transmitting system 2 receiving system 5 coded signal generating circuit 6 band limiting circuit 7 RF band digital modulation circuit 8 clock signal generator 9 carrier wave generator 10 RF band amplifier 11 RF band band limiting circuit 12 IF band converter 23 analysis addition hold Circuit 24 FFT analysis circuit 25 Analysis and addition circuit 26 Comparison circuit 27 Delay spread estimation / code error rate estimation circuit 28 Phase compensation circuit 29 Reception local signal generator 30 Sampling time / frame generator

Claims (5)

(57) [Claims] 1. In mobile communication, a transmission system and a reception system are provided, and the transmission system uses a clock signal generator and a pseudo random pattern generation circuit having high frequency stability to generate a pseudo random pattern with an arbitrary repetition period. Generated, then band-limited, then digitally modulated by the pseudo-random pattern using a digital modulation circuit and a carrier generator with high frequency stability, and then the modulated wave modulated using an RF band amplifier. Is transmitted as a transmission wave, and in the reception system, an RF band band limiting circuit, an IF band converter, and a reception local signal generator having high frequency stability are used to delay the transmitted modulated wave by a multiple propagation path. Received delayed modulated wave, band-limit the received wave, convert the band-limited received wave to intermediate frequency band received wave, and then -Fourier transform analysis circuit and high-frequency-stable sampling time / frame generator are used to perform fast Fourier transform analysis of the received wave of the intermediate frequency band with an arbitrary repetition period, and then polar coordinate converter, phase compensation circuit, and analysis addition circuit Multipath propagation characterized by processing the fast Fourier transform analysis data of the received wave using, and measuring the amplitude frequency characteristics with a high signal-to-noise ratio from the fast Fourier transform analysis data of the processed received wave. Road measurement method. 2. The multiple channel measurement method according to claim 1, wherein the repetition period of the pseudo-random pattern and the repetition period of the fast Fourier transform analysis are matched to facilitate the phase compensation. 3. The receiving system measures a modulated wave spectrum which is an amplitude frequency characteristic of the modulated wave on one side and a delayed modulated wave spectrum which is an amplitude frequency characteristic of the delayed modulated wave on the other side. Then, the characteristic of the transmission / reception system is canceled by taking the ratio of the modulated wave spectrum and the delayed modulated wave spectrum. 4. The receiving system widens a bandwidth for measuring the amplitude frequency characteristic, and smoothes the measured amplitude frequency characteristic.
The multiple channel measurement method described in. 5. The multiple channel measurement system according to claim 1, wherein the amplitude frequency characteristic is smoothed by adding power again to the outputs of the analysis and addition circuit a plurality of times.