JPH07264145A - Propagation delay measurement method - Google Patents

Abstract

PURPOSE:To attain the measurement with a small error by fitting each antenna to a transmitter and a receiver, obtaining a delay spread value according to a specific equation from a delayed profile through transmission reception of a radio wave and using the corrected delay spread as a measurement value. CONSTITUTION:A radio wave whose input level is known is given to a receiver to generate a calibration curve. Then a transmitter and the receiver are connected directly with a cable to measure a delayed profile of a transmission waveform. Then the delayed profile is sampled and the level is calibrated, then the delay spread So is obtained, Then an antenna is connected respectively to the transmitter and the receiver and the delayed profile is obtained by sending/receiving the radio wave to the antennas. Similarly the level is calibrated to obtain a delay spread Sm. The delay spread Sm is corrected by the delay spread So according to equation I to obtain a corrected value Sc. Thus, the measurement error is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a delay spread measuring method which affects the transmission quality of digital mobile communications.

[0002]

2. Description of the Related Art In digital mobile communication, transmission quality deteriorates due to propagation delay. Propagation delay is a wave that directly arrives when a radio wave is transmitted and received by the receiving side (direct wave or head wave), or a wave that arrives after a time delay by reflecting on a building or mountain (delay). Wave), and the radio wave is divided into a number of propagation paths in this way, and each radio wave arrives with a certain delay time.

FIG. 4 shows an example of a propagation delay situation in an urban area. a is a direct wave, and b1 and b2 are delayed waves delayed in time from the direct wave a. FIG. 2 shows the reception level waveform caused by the propagation delay. 1a is a transmission waveform, and 2
a is a received waveform. In particular, the reception waveform of 2a is called a delay profile.

As described above, the propagation delay is the same as the situation where a kind of echo is applied to the transmitted radio wave, and when transmitting a digital signal at a high speed, it has an adverse effect of quality deterioration. A delay spread is used as a value indicating the degree of this propagation delay. Delay spread S is delay profile P
It can be calculated from (t) by the following equation.

[0005]

[Equation 2]

The principle of the propagation delay measuring machine is such that the impulse waveform 1a shown in FIG. 2 is transmitted, and the delay profile is obtained from a plurality of delayed waves delayed on the receiving side. There is also a method of using a PN code instead of the impulse waveform, but this corresponds to transmitting one impulse radio wave by dividing it into a plurality of small impulses (PN code).

Here, in order to improve the measurement accuracy of the delay spread, the width of the impulse waveform or the PN code width may be narrowed. However, in order to make a sharp impulse waveform, a wide frequency band must be taken, and the band cannot be easily widened due to restrictions on the radio license. Therefore, the impulse waveform to be transmitted becomes a waveform having a certain spread (width), which limits the measurement accuracy of the delay spread. In particular, when trying to measure a delay spread that is about the same as or less than the spread of the transmission impulse waveform, the measurement error becomes large.

Further, if there is reflection of radio waves in the measuring system on the transmitting side, the waveform finally transmitted becomes dull, which causes a large measurement error. FIG. 3 shows a received waveform (delay profile) when the transmitted waveform is distorted. 1b is a transmission waveform and 2b is a delay profile.

[0009]

In order to improve the measurement accuracy of the delay spread, a wide frequency band to be used is taken as a sharp impulse waveform, or matching in the measurement system is removed so that unnecessary reflected waves are not generated. Measures can be considered.

However, when measuring a delay spread smaller than the spread of the impulse waveform actually transmitted, a measurement error will occur. There is a demand for a method of improving the measurement accuracy by correcting a delay spread smaller than the spread of the impulse waveform from the measured value.

The present invention solves the above problems, and an object thereof is to reduce the measurement error that occurs when measuring a delay spread smaller than the spread of the impulse waveform actually transmitted and improve the measurement accuracy. It is to provide a propagation delay measuring method.

[0012]

A characteristic of the present invention for achieving the above object is to transmit a pseudo random code or an impulse waveform from a transmitter in order to measure a propagation delay characteristic when a radio wave propagates, In the propagation delay measuring method for obtaining the delay spread value from the delay profile of the electric wave received by the receiver, the delay spread value S _m is obtained from the delay profile obtained by attaching the antenna to the transmitter and the receiver and transmitting and receiving the electric wave,

[0013]

[Equation 3]

In the method of measuring the propagation delay, the delay spread value corrected by is used as the measurement value.

The constant S ₀ is a delay spread value obtained from a delay profile measured by connecting the output of the transmitter and the input of the receiver with a cable.

[0016]

FIG. 5 shows the relationship between the transmission waveform, the true delay profile, and the measured delay profile when the phase of the reception level is not taken into consideration. 1 m is a transmission waveform, 3 m is a true delay profile, and 2 m is a measured delay profile. The measured delay profile 2m is obtained by adding the spread of the transmission waveform 1m to the true delay profile 3m. This indicates that the measured delay profile can be obtained by convolving the transmission waveform and the true delay profile. In the convolutional integration, assuming that the two delay spread values before the convolutional integration are S ₁ and S ₂ , the delay spread value S _c obtained by the convolutional integration is as follows.

[0017]

[Equation 4]

Correcting the delay spread can be obtained by performing the correction according to the equation (1) from the relation of the equation (5).

However, in reality, since the transmission waveform and the delay profile have a phase component, convolution integration with a complex number including the phase is performed in the measurement. FIG. 6 shows the state of complex convolution. 1c is a complex transmission waveform, 3
c is the true complex delay profile, 2c is the measured complex delay profile. In the complex convolution integral, the relation of Expression (5) is not mathematically established.

What kind of relationship does complex have? Let's see the relationship by computer simulation. The phases of the delayed waves forming the true complex delay profile 3c are considered to be independent of each other, and thus the phases are set randomly. The envelope of the true delay profile is an exponential type or a square type, and the transmission waveform is a normal type (Gaussian type). FIG. 7 shows each waveform. 1d is a normal transmission waveform, 3d is an exponential delay profile, and 3e is a rectangular delay profile.

FIGS. 8A and 8B show computer simulation results. In (a), the delay profile is exponential,
(B) is a square type. In FIG. 8, the delay spread of the transmission waveform is normalized as 1. The solid line in the figure is the true delay spread and the delay spread S _m obtained by measurement.
And the dotted line S _c is the case where the delay spread value obtained by the measurement is corrected by the equation (1). It can be seen that the measurement error increases when the true delay spread becomes about the same as the delay spread of the transmission waveform. But,
The measurement error is improved by correcting the equation (1). From this, it can be understood that the relationship of Expression (5) does not hold mathematically in the case of complex numbers, but the measurement error due to the transmission waveform can be reduced by using the relationship of Expression (5).

[0022]

1 shows the algorithm of the method according to the invention. Radio waves having a known input level are input to the receiver to create a calibration curve (S ₄ ). The transmitter and the receiver are directly connected by a cable and the delay profile of the transmission waveform is measured (S ₁ ). After the delay profile is sampled (S ₃ ) and the level is calibrated (S ₅ ), the delay spread S ₀ is calculated by the equations (2) to (4) (S ₆ ). A delay profile is obtained by connecting an antenna to each of the transmitter and the receiver and transmitting and receiving radio waves (S ₂ ). The level spread is calibrated in the same manner as described _above to obtain the delay spread S _m (S ₈ ). The delay spread S _m is corrected by the delay spread S _{0 as shown} in Expression (1) to obtain the correction value S _c (S ₉ ).

FIG. 9 shows a measuring device according to an embodiment of the present invention. Reference numeral 11 is a transmitter and 4 is a receiver. 5 is a receiver, 6
Is a level calibration unit, 7 is a calculation unit, 8 is a storage unit, 9 is a display device, 10 is an antenna, and 12 is an external power amplifier.

FIG. 10 shows a connection diagram at the time of calibration. Reference numeral 13 is a variable attenuator. The calibration is performed via the variable attenuator 13 between the transmitter and the receiver with the transmission power amplifier attached.
In the calibration, the transmitter 11 outputs a constant output and the variable attenuator 1
At 3, the input level to the receiver 4 is changed at regular steps. Each time, the level calibration unit 6 stores a known input level and creates a calibration curve. In the calibration, the delay profile of the transmission waveform is measured in addition to the level, and the delay spread S ₀ is calculated and stored in the storage unit 8. By calibrating with a transmission power amplifier, it is possible to perform calibration that includes all characteristics of the transmission power amplifier, such as amplifier distortion and filters. The transmission waveform is 1 in Fig. 3 by the filter of the transmission power amplifier.
Even if it is slightly distorted as shown in b, it can be corrected by obtaining the delay spread of the transmission waveform.

FIG. 11 shows a diagram for explaining the measuring method.
14 is a building and 15 is a measuring vehicle. If the transmitter 11 is installed on the roof of a building and measurement is performed while traveling with a measuring vehicle 15 equipped with a receiver, delay spread characteristics in urban areas can be obtained. The delay profile obtained by the receiving unit 5 for each running is calibrated by the level calibrating unit 6, the calculating unit 7 calculates the delay spread value S _m by the equations (2) to (4), and the S ₀ value of the storage unit 8 is used. The correction of Expression (1) is performed. The correction value is displayed on the display 9.

[0026]

As described above, according to the present invention, when measuring a delay spread which is close to the measurement limit of a propagation delay measuring machine, correction is performed based on the transmission waveform, so that the measurement error can be reduced. Although the delay spread in a building is generally smaller than that in an outdoor area such as an urban area, the propagation delay measuring instrument made for outdoor also has an advantage that it can perform measurement with less error by adding the correction function of the present invention. is there.

Further, the correction based on the transmission waveform determined by the condition of the measurement system at the time of measurement and the measuring instrument on that day means that the error factors are collectively processed and the measurement error is It is effective in reducing it.

[Brief description of drawings]

FIG. 1 shows an operation flow of a propagation delay measuring method according to the present invention.

FIG. 2 shows a transmission waveform and a delay profile.

FIG. 3 shows a delay profile when a transmission waveform is distorted.

FIG. 4 shows a state of propagation in an urban area.

FIG. 5 shows a transmission waveform and a delay profile when the phase of the reception level is not considered.

FIG. 6 shows complex convolution.

FIG. 7 shows waveforms used in computer simulation.

FIG. 8 shows results of computer simulation.

FIG. 9 shows a propagation time measuring device according to an embodiment of the present invention.

FIG. 10 shows the connection of the device during calibration.

FIG. 11 is a diagram illustrating a measuring method of the present invention.

[Explanation of symbols]

 a direct wave b1, b2 delayed wave 1a transmission waveform 2a delay profile 1b transmission waveform 2b delay profile 1m transmission waveform 3m true delay profile 2m measurement delay profile 1c complex transmission waveform 3c true complex delay profile 2c measurement complex delay profile 1d normal type Transmission waveform of 3d Exponential delay profile 3e Square delay profile 4 Receiver 5 Receiver 6 Level calibration unit 7 Calculation unit 8 Storage unit 9 Display unit 10 Antenna 11 Transmitter 12 Power amplifier 13 Variable attenuator 14 Building 15 Measuring vehicle

Claims (2)

[Claims] 1. A propagation delay in which a pseudo-random code or an impulse waveform is transmitted from a transmitter and a delay spread value is obtained from a delay profile of a radio wave received by the receiver in order to measure a propagation delay characteristic when the radio wave propagates. In the measurement method, the delay spread value S _m is obtained from the delay profile obtained by attaching antennas to the transmitter and the receiver and transmitting and receiving radio waves, respectively, A propagation delay measuring method characterized in that a delay spread value corrected by is used as a measurement value. 2. The propagation delay measuring method according to claim 1, wherein the constant S ₀ is a delay spread value obtained from a delay profile measured by connecting an output of the transmitter and an input of the receiver with a cable.