JPS6364417A - Radio digital communication system - Google Patents

Abstract

PURPOSE:To make quality supervision in a radio digital communication system accurate by detecting the difference of the value of a demodulated base band signal and a decided value to supervise the quality of the wireless channel, and switching the channel when the quality is below the standard. CONSTITUTION:Modulated signals received by an antenna 1 are converted to base band signals by a demodulator 2, and the base band signals are sampled using a deciding circuit 3 driven by a clock 12 synchronously with it, and decision of '0', '1' is made, and the result is outputted from an output terminal 4. The band signals of the circuit 2 are digitized by an A/D converter 5, and a reference value is outputted from a reference signal generating circuit 6. Then, the difference of output of the converter 5 and circuit 6 is calculated by a subtracter circuit 7, and held in a register 8, and a square mean value is calculated by a square mean circuit 9. Then, the value and a predetermined reference value is compared by a controlling circuit 10, and when the value exceeds the reference value, an channel switching signal is sent to an output terminal 11.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to wireless digital communication systems.

[Conventional technology]

In a mobile communication system such as a car phone, the service area is divided into several parts, each base station is installed to cover the divided area, and the same frequency is repeatedly used between base stations that do not cause interference. By doing so, we aim to make effective use of frequency resources. However, since radio channels for mobile communications fluctuate drastically with fading due to the influence of multiple wave propagation, it is difficult to completely avoid the influence of co-frequency interference. In order to provide high quality services under such conditions, it is necessary to monitor the state of the wireless channel and control it so that a predetermined quality is obtained.

For this purpose, the quality of the wireless channel is monitored by measuring the interference level using the beam component of the received wave envelope generated by co-frequency interference, and the channel is switched if the quality is below a predetermined value. The method is well known in the art. Specifically, the radio channel quality monitoring method is implemented as follows. When co-frequency interference occurs, the square-law detection output of the envelope R,(t) of the received wave is expressed as follows.

R2(t) −Rs 2(t) −1−R, + 2(t)
+2Rs (t) R+ (t) cosφ
(1; ) −(1,) where Rs(t) and Rt
(t,) represents the envelope of the desired wave and interference wave. Also φ
(1) does not represent the phase difference between the desired wave and the interference wave. The speed at which R,,s (t) and R1(t) change due to fading is about several tens of Hz, whereas the phase difference φ(
The speed of variation in 1) depends on the data rate of the modulation signal, but is generally several kHz or more. Therefore, R,2(
It is possible to separate the low frequency component Rs”(t)+R+2 (t) of t) from the high frequency component 2Rs(t)Rt(t) cosφ(1) using a filter.The average value of the low frequency component is detected. By (Rs 2 (f;)
＞ + <Rt 2 (Sat, )> increases the high frequency component by 2
2 (Rs 2
(t)><R, + 2 (t)> are obtained, respectively. By calculating using these outputs, the power of the desired wave versus the interference wave is calculated as R52(t)>/<R, + ” (
1> can be found. (Published by the Society of Automobile Telephone Electronics and Communication Engineers, ppl, 08-ppl O9).

[Problem that the invention seeks to solve]

However, the conventional radio channel monitoring method has the drawback that accurate quality monitoring is difficult because the received wave envelope fluctuates not only due to co-frequency interference but also due to the influence of fading.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wireless digital communication system that performs accurate wireless channel quality monitoring that overcomes the drawbacks of the prior art.

[Means for solving problems]

The wireless digital communication system of the present invention monitors the quality of the wireless channel by detecting the difference between the value of the decoded baseband signal and the determined value, and switches the channel if the quality is below the standard. I do.

[Effect]

When co-frequency interference occurs in a radio channel, the baseband signal output from the demodulation circuit at the time of determination does not maintain a constant value but fluctuates, causing errors. The higher the level of the interference wave with respect to the desired wave, the larger the fluctuation range and the worse the PPI error rate, so this fluctuation range is an appropriate indicator of the quality of the radio channel.

In the present invention, the variation width is measured by detecting the difference between the value of the demodulated baseband signal and the judgment value,
If this fluctuation range exceeds a reference value, it is determined that the quality of the wireless channel is likely to deteriorate, and the channel is switched.

[Embodiment] Next, the present invention will be explained in detail with reference to the drawings.1 Fig. 1 does not show an embodiment of the present invention. A modulated signal received by a receiving antenna 1 is converted into a baseband signal by a demodulation circuit 2. A determination circuit 3 driven by a clock 12 synchronized with this baseband signal samples the baseband signal, determines 0.1, and outputs the result to an output terminal 4.

A method for monitoring the quality of wireless channels is described below.
A /D (analog-to-digital) converter 5 digitizes the baseband signal output from the demodulation circuit 2.

On the other hand, the reference signal generation circuit 6 outputs O1 of the output of the determination circuit 3.
] Outputs the reference value according to the value. The subtraction circuit 7 is
A/I) Calculate the difference between the outputs of converter 5 and reference signal generation circuit 6. The register 8 sequentially receives the output of the subtraction circuit 7 and holds a plurality of values. The mean square circuit 9 calculates the mean square value of the plurality of values held in the register 8. The control circuit 10 compares the output of the root mean square circuit 9 with a preset reference value, and outputs a channel switching signal to the output terminal 11 if the output exceeds the reference value. A/D converter 5, reference signal generation circuit 6,
The subtraction circuit 7, register 8, mean square circuit 9, and control circuit 10 are driven by a clock 12.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a radio channel control method that accurately monitors the quality of a radio channel.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. 2... Demodulation circuit, 3... Judgment circuit, 5... A/D
Converter, 6... Reference signal generation circuit, 7... Subtraction circuit, 8... Register, 9... Root mean square circuit, 1
o...control circuit. 1 piece of foil

Claims (1)

[Claims] A wireless digital communication system characterized in that the quality of a wireless channel is monitored by detecting a difference between the value of a demodulated baseband signal and a determination value, and the channel is switched if the quality is below a standard.