JP2003163623A - Digital modulation radio repeater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital modulation radio repeater capable of measuring accurate BER at all times even during a relay operation. <P>SOLUTION: In a digital modulator 1, by a multiplex circuit 4, PRBS signals supplied from a PRBS signal generator are time-division-multiplexed to digital input signals DI. In a digital demodulator 2, the PRBS signals are demultiplexed and taken out from digital signals transmitted through a radio channel 9 by a demultiplex circuit 7 and a bit error detector 8 measures a bit error rate BER generated in the radio channel 9 by the PRBS signals. Thus, while relaying the digital signals, the bit error rate BER is measured in real time. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for digitally modulating a binary signal and wirelessly relaying it, and more particularly to a digital modulation wireless relaying apparatus using microwaves.

[0002]

2. Description of the Related Art In recent years, a microwave radio relay system of a digital modulation system has been widely used for transmission of digital signals. At this time, deterioration of transmission characteristics due to fading or the like can be avoided even in a transmission line by microwaves. Therefore, a bit error occurs in the transmitted digital data.

Therefore, in such a microwave radio relay system, conventionally, a technique of compensating for line deterioration by providing an automatic equalizer in a digital demodulator has been adopted, and an error correction technique is applied to bit errors of digital data. It is applied and measures are taken to reduce the effect of bit errors.

However, in spite of the above measures, it is still difficult to secure a line without bit error, and therefore,
Generally, a transmission system switching technique such as a space diversity system is used to ensure the reliability of data transmission by a wireless line.

By the way, it has been general that the switching control of the space diversity system is performed according to the received electric field strength. However, in the case of such a digital transmission system, bit error of the transmitted data is generated. Rate (B
ER: Bit Error Rate) is a problem, and therefore the quality of the transmission system should be evaluated essentially by the BER. Therefore, the switching control of the spatial diversity is also performed by this BER. Is desirable.

In order to meet this demand, therefore, in the prior art, a predetermined PRBS (pseudo random code) signal is sent from the transmission side of the microwave radio repeater of the digital modulation system to the transmission line, and this is transmitted on the repeater side. The BER was measured by receiving and collating.

Further, in another conventional technique, when the digital demodulator is provided with an automatic equalizer, the BER is equivalently estimated from the equalization residual data obtained from the automatic equalizer. I was trying to meet the request.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
No consideration has been given to the fact that the transmission system occupies the transmission of the BS signal, and there is a problem in that there is a gap in the original relay operation and the data transmission efficiency is reduced.

This is because, in this prior art, when measuring the BER, the PRBS is replaced with the original digital signal.
This is because the original relay operation cannot be performed at this time because the signal must be transmitted.

Further, the above-mentioned other prior art does not take into consideration that it is premised on the equipment of an automatic equalizer, so that the relay system to which it is applied is limited and the response to the change in BER is caused. There was a problem of low sex.

This is because the other conventional techniques cannot be applied to a system which is not equipped with an automatic equalizer, so that the relay system to be applied is limited, and the automatic equalizer is also applied. This is because, in the case of using an instrument, only an average bit error can be estimated, and it is not possible to follow a sudden change in BER.

It is an object of the present invention to provide a digital modulation radio repeater capable of always measuring the BER accurately even during the repeat operation.

[0013]

SUMMARY OF THE INVENTION The above object is to provide a digital modulation radio relay apparatus for measuring a bit error rate on a transmission system by using a pseudo random signal received through the transmission system. The signal is achieved by time-division multiplexing the digital signal to be wirelessly relayed and transmitting the signal.

Further, in the above-mentioned object, in the digital modulation radio relay apparatus which measures the bit error rate on the transmission system by the pseudo random signal received via the transmission system, the pseudo random signal is wireless. This can also be achieved by time-division-multiplexing and transmitting the digital signal to be relayed by the interleave method.

At this time, a data error correction method using a correction code may be applied to the digital modulation radio relay apparatus.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A digital modulation radio relay apparatus according to the present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a microwave radio relay system.
Reference numeral 1 is a digital modulator which is installed on the transmitting side of the microwave radio relay system and is supplied with a digital input signal DI.

Next, 2 is a digital demodulator, which is also installed on the repeater side of this microwave radio repeater system and outputs the digital output signal DO relayed from this.

First, in the digital modulator 1, the digital input signal DI is input to the digital modulator 3, where the microwave carrier is modulated by a predetermined digital modulation method, and the microwave carrier 9 is passed through the microwave radio line 9. And is transmitted to the digital demodulation device 2.

At this time, in this embodiment, the digital input signal DI is input to the multiplexing circuit 4 before being supplied to the digital modulator 3, where the PRBS (pseudo random code) generated by the PRBS signal generator 5 is generated. ), And then input to the digital modulator 3.

At this time, the time division multiplexing method is used for the PRBS multiplexing method with respect to the digital input signal DI. Therefore, the micro-BS in which the PRBS signal is time-division multiplexed from the digital modulator 1 to the digital input signal DI is used. Waves of radio waves are transmitted by the microwave radio line 9, received by the digital demodulation device 2, and the multiplexed digital input signal DI and PRBS signal are wirelessly relayed.

Therefore, although not shown, the microwave radio line 9 is composed of a microwave transmitter and a transmitting antenna on the digital modulation side, and a microwave receiving antenna and a receiver on the digital demodulation side. Will be.

Next, in the digital demodulation device 2, the received signal input from the radio line 9 is demodulated into a digital signal by the digital demodulator 6. After that, this digital signal is input to the separation circuit 7, where Is separated into the original digital signal and the PRBS signal by the digital input signal DI.

The original digital signal is output as it is from the digital demodulation device 2 as a digital output signal DO, whereby the function as a radio relay system is fulfilled.

On the other hand, the PRB separated by the separation circuit 7
The S signal is supplied to the bit error detector 8 where the PRB
The bit error is detected using the S signal and the BER is calculated based on the detection result, and the BER is output from the outside to be used for the switching control of the space diversity system.

Therefore, the operation of the bit error detector 8 at this time will be described. First, bit errors occurring in the PRBS signal are sequentially detected, counted, and integrated at regular time intervals.

Then, the bit error rate, that is, BER is calculated from the integrated value. At this time, the multiplexing rate at the time division multiplexing described above, that is, the original digital input signal DI within the time division period is used. Consider the ratio of digital signal period to PRBS signal period.

Now, if this ratio is 9: 1, that is, the original digital signal period in the time division period is 90%, PR
Suppose that the multiplexing circuit 4 of the digital modulator 1 time-division-multiplexes so that the BS signal period becomes 10%. At this time, assuming that an error occurs randomly in the transmission system in time. It can be estimated that, on average, 10 times as many bit errors as the number of errors accumulated in the received PRBS signal period have occurred in the transmission system.

Therefore, the bit error detector 8 integrates the number of errors detected in each time-division period of the PRBS signal period and multiplies the integration result by 10 to obtain the BER of each time-division period. Is configured to be output as.

Therefore, according to this embodiment, the BER can be measured almost in real time in parallel with the transmission of the original digital signal, and as a result, the transmission efficiency of the original digital signal is lowered. B that does not correspond to the bit error actually occurring in the data on the transmission path
ER can be measured.

Therefore, by using the BER output from the bit error detector 8 for the space diversity switching control, it is possible to always obtain an accurate space diversity switching, and the reliability of data transmission by the wireless line. Can be maintained high enough.

Next, FIG. 2 shows another embodiment of the present invention, in which 12 is an interleave circuit.
Reference numeral 3 is a deinterleave circuit, and other configurations are the same as those in the embodiment of FIG.

First, the interleave circuit 12
The PRBS signal is converted into the digital input signal DI by the multiplexing circuit 4.
It inputs the time-division-multiplexed digital signal to the input terminal, randomizes the bit arrangement order of the digital signal by the convolutional interleave method, and then supplies the digital signal to the digital modulator 3.

On the other hand, the deinterleave circuit 13 inputs the digital signal received via the wireless line 9 and demodulated by the digital demodulator 6, and sets the bit arrangement order randomized by the interleave circuit 12 on the transmission side. , Restore by the same convolutional interleave method,
It works to restore the original bit order.

Therefore, in the embodiment of FIG. 2, in the transmission system from the digital modulator 3 on the transmitting side to the digital demodulator 6 on the receiving side via the wireless line 9, the bit arrangement order of the digital signals is randomized. In other words, the original digital signal and the PRBS signal are transmitted in a state of being interleaved with each other within the time division period.

Then, in the embodiment of FIG. 2, the other operations are the same as those of the embodiment of FIG. 1 except for the difference in the data format in the transmission system including the wireless line 9, and therefore the operation of FIG. Also according to the embodiment, the BER can be measured almost in real time in parallel with the transmission of the original digital signal, and as a result, the transmission efficiency of the original digital signal is not actually reduced in the transmission path. It is also the same that the BER that corresponds well to the bit error occurring in the data can be measured.

Here, in the embodiment described with reference to FIG. 1, as described above, in the calculation of the bit error rate, it is assumed that errors occur randomly in the transmission system with respect to time. Generally does not cause much problems, and the BER can be measured with sufficient accuracy in practical use.

However, in an actual wireless line, a bit error of data may occur in a burst (abrupt) due to fading or the like. In this case, in the embodiment of FIG. There may be an impact.

According to the embodiment of FIG. 2, however, the bit arrangement order of the digital signals is randomized on the transmission system including the wireless line 9, and the original digital signal and the PRBS signal are within the time division period. The signals are transmitted in an interleaved state.

As a result, when a burst-like bit error occurs, the bit error does not occur only in one of the original digital signal and the PRBS signal, but occurs randomly. Therefore, in FIG. According to the embodiment, there is no fear that the measurement accuracy of the BER will be lowered, and sufficient accuracy can be maintained.

By the way, the digital modulation radio relay apparatus targeted by the present invention may be provided with a transmission error correction function. Therefore, an embodiment of the present invention in which the embodiment of FIG. 2 is provided with this transmission error correction function will be described with reference to FIG.

First, in FIG. 3, 14 is an error correction code circuit, 15 is an error decoding circuit, 16 is a second PRBS signal generation circuit, 17 is a second bit error detection circuit, 18 is a second interleave circuit, Reference numeral 19 is a second deinterleave circuit, 20 is a second multiplexing circuit, and 21 is a second demultiplexing circuit. Others are the same as in the embodiment of FIG.

In the case of the embodiment shown in FIG. 3, the output of the multiplexing circuit 4 is not directly supplied to the interleave circuit 12 in the digital modulator 1 on the transmission side, but here, error correction is first performed. It is input to the encoding circuit 14 and an error correction code is added.

The error correction code added at this time is generally a convolutional code, but if higher error correction performance is required, a high performance code such as trellis code is used.

The signal output from the interleave circuit 12 is supplied to the second multiplexing circuit 20 and further time-division multiplexed with the second PRBS signal supplied from the second PRBS signal generating circuit 16. After that, the bit arrangement order is changed again by the second interleave circuit 18, and thereafter, the bit arrangement order is supplied to the digital modulator 3.

The output of the digital modulator 3 is transmitted to the digital demodulator 2 on the receiving side via the radio line 9 and input to the digital demodulator 6. Here, the demodulation of the digital demodulator 6 is also performed. The output is not directly supplied to the deinterleave circuit 13, but is input to the second deinterleave circuit 19, where the order of the bits rearranged by the second interleave circuit 18 on the transmission side is first restored. It

After that, it is further input to the second separation circuit 21, where the second PRBS signal is separated from the original digital signal, and then the digital signal is input to the deinterleave circuit 13.

As a result, the original digital signal in which the order of the bits rearranged by the interleave circuit 12 on the transmission side is restored is supplied to the error decoding circuit 15.

The error decoding circuit 15 corrects and decodes the bit error generated on the transmission path, and the original digital signal with the corrected error is supplied to the separation circuit 7.
At this time, as the error decoding system in the error demodulation circuit 15, the Viterbi decoding system is generally used.

Therefore, according to the embodiment shown in FIG. 3, it is possible to maintain sufficient accuracy without fear that the original digital signal in which the transmission error has been corrected and the BER measurement accuracy are deteriorated. In addition to the same effect as the second embodiment, the reliability is improved by correcting the transmission error and the digital signal can be relayed.

On the other hand, the second PRBS signal separated by the second separation circuit 21 is the second bit error detection circuit 1
7 to the BE by the second PRBS signal
R, that is, BER2 representing the bit error rate due to the digital signal before error correction is measured.

Therefore, according to the embodiment of FIG. 3, the BE on the transmission path before the error correction is performed on the transmitted data is performed.
Both R (BER2) and BER on the data actually used for relay after error correction can be known,
With these comparisons, the adequacy of error correction can be evaluated.

[0053]

According to the present invention, while transmitting a digital signal, at the same time, the data bit error rate actually occurring on the transmission line can be measured. Therefore, the transmission efficiency of the digital signal to be originally transmitted can be improved. Without lowering
It is possible to reliably obtain a highly accurate bit error rate.

As a result, according to the present invention, it is possible to always obtain an accurate space diversity switching,
The reliability of data transmission by wireless relay can be maintained sufficiently high.

Further, according to the present invention, the bit error rate on the transmission path before the error correction is performed on the transmitted data and the bit on the data actually used for the relay after the error correction is performed. Both of the error rates can be known, and the comparison of these makes it possible to evaluate the adequacy of the error correction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a digital modulation wireless relay device according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of a digital modulation wireless relay device according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of a digital modulation wireless relay device according to the present invention.

[Explanation of symbols]

DO digital input signal DI digital output signal 1 Digital modulator 2 Digital demodulator 3 Digital modulator 4 Multiplexing circuit 5 PRBS signal generator 6 Digital demodulator 7 separation circuit 8-bit error detector 9 wireless lines 12 Interleave circuit 13 Deinterleave circuit 14 Error correction code circuit 15 Error demodulation circuit 16 Second PRBS signal generator 17 Second bit error detector 18 Second interleave circuit 19 Second deinterleave circuit 20 Second Multiplexing Circuit 21 Second separation circuit

Claims (3)

[Claims] 1. A digital modulation wireless relay apparatus for measuring a bit error rate on a transmission system by using a pseudo random signal received via the transmission system, wherein the pseudo random signal is a digital signal to be wirelessly relayed. A digital modulation radio repeater characterized by being configured to be time-division multiplexed with a signal for transmission. 2. A digital modulation radio relay apparatus for measuring a bit error rate on a transmission system by a pseudo random signal received via the transmission system, wherein the pseudo random signal is a digital signal to be wirelessly relayed. A digital modulation radio relay apparatus, characterized in that the signal is time-division multiplexed in an interleaved manner and transmitted. 3. The digital modulation radio relay apparatus according to claim 1 or 2, wherein a data error correction method using a correction code is applied.