JPH07212348A - Bit error measuring device of communication line - Google Patents

Abstract

PURPOSE:To eliminate the influence on the error at the time of an analog conversion by modulating a bit level digital signal by a first modem, transmitting the signal by plural codecs in digital and analog lines and demodulating the signal in a second modem. CONSTITUTION:A modem 2A modulates the outputs 0 and 1 of a randam code generator 1 to frequencies fa and fz. After this modulation signal is converted into a byte level digital signal in a codec 3A and a D/A conversion is performed for the signal in a codec 3B via a digital line 4A, an A/D conversion is performed for the signal in a codec 3C via an analog line 5 and a byte level digital signal 13 is outputted. A D/A conversion is performed for this signal in a codec 3D and the signal is demodulated in a modem 2B. Namely, because a digital signal 11 is modulated into frequencies fa and fz in the modem 2A and the signal is modulated into 0 and 1 again in the modem 2B by defining the signal as the object of the conversions of the codecs 3A to 3D, a bit error can be measured if this exists, even if the frequencies fa and fz levels corresponding to 1 and 0 change between signals 11 and 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bit error of a communication line when a digital signal of a digital line is converted into an analog signal by a codec (a combination of an encoding unit and a decoding unit) and the analog signal is transmitted. It relates to a measuring device.

[0002]

2. Description of the Related Art Next, the principle of bit error measurement will be described with reference to FIG. FIG. 5A is an example of transmission data in which a digital signal is represented by a bit level, which is "1", "0",
"1" and "0" are transmitted. FIG. 5A shows an example of the received data of FIG. 5A, which is “1”, “1”, “1”, “0”. Figure 5c shows the comparison data of Figure 5a and Figure 5a.
The error bit "1" is measured.

Next, a configuration diagram for measuring the bit error in FIG. 5C will be described with reference to FIG. In FIG. 6, 7 is a comparator, 16 is a reference pattern, and 17 is a reception pattern. The reference pattern 16 is the same as the transmission data of FIG. 5A, and the reception pattern 17 is the reception data of FIG. Reference pattern 1
By putting 6 and the reception pattern 17 in the comparator 7,
The error bit of FIG. 5C is obtained from the output of the comparator 7.

Next, a bit error measurement system diagram of a digital line will be described with reference to FIG. In FIG. 7, 1 is a random code generator, 4A is a digital line, and 6 is a code error measuring device. In FIG. 7, the random code of the bit level is sent from the random code generator 1 to the digital line 4A, and the output of the digital line 4A is input to the code error measuring device 6.
The bit error is measured by comparing the received pattern with the reference pattern as shown in.

Next, a block diagram of a bit error measuring device for a communication line according to the prior art will be described with reference to FIG. 3B in FIG.
Is a codec for D / A conversion, 5 is an analog line,
3C is a codec for A / D conversion, 4B is a digital line, and others are the same as those in FIG. As shown in FIG. 8, when the digital lines 4A and 4B and the analog line 5 are used, the codec 3B converts them into analog signals, and the codec 3C converts them into digital signals again. Is different. Further, the random code is affected by the level fluctuation due to the analog line 5 and the cable loss.

Next, the conversion contents by the codec are shown in FIG.
Will be described. 9A shows a byte-level waveform obtained by encoding a sine wave, and FIG. 9A shows a decoded waveform of FIG. 9A. FIG. 9C is a byte-level waveform obtained by encoding FIG. 9A. Considering the delay caused by transmission, the sampling points are different between FIGS. 9A and 9C. Therefore, since the coded waveforms are different between FIG. 9A and FIG. 9C, the transmission side digital signal and the reception side digital signal due to the codec differ in bit level.

[0007]

The present invention relates to a first modem and a first modem for modulating a random code between a random code generator 1 and a digital line 4A of FIG. 8 at a bit level to frequency, phase or amplitude. A first codec for encoding the output of the modem at the byte level is arranged, and the output of the digital line 4B is decoded at the byte level into frequency, phase or amplitude between the digital line 4B and the code error measuring device 6 of FIG. By placing a second modem that demodulates the output of the second codec and the output of the second codec to "0" and "1" of the bit level, there is no influence due to the difference in the conversion content at the byte level by the codec. An object is to provide a bit error measuring device for a communication line.

[0008]

To achieve this object, in the present invention, a digital line 4A for transmitting a digital signal, a codec 3B for D / A converting the output of the digital line 4A, and an output of the codec 3B are provided. A / the analog line 5 for transmission and the output of the analog line 5
A communication line including a codec 3C for D conversion and a digital line 4B for transmitting the output of the codec 3C,
In a device for measuring bit error, a random code generator 1 for generating a random code of "0" and "1", and a modem 2A for modulating the output of the random code generator 1 at a bit level into frequency, phase or amplitude. , Digital line 4A
To the codec 3A that encodes the output of the modem 2A at the byte level and the output of the digital line 4B as input, and decodes the frequency, phase or amplitude at the byte level to the codec 3D and the frequency of the output of the codec 3D. A modem 2B for demodulating the phase or amplitude into "0" and "1", and a code error measuring device 6 for measuring "0" and "1" from the output of the modem 2B and measuring a bit error.

[0009]

Next, the configuration of the bit error measuring device for a communication line according to the present invention will be described with reference to FIG. 2A and 2B of FIG.
Are modems, 3A and 3D are codecs, and others are the same as those in FIG. That is, FIG. 1 shows that the modem 2A is provided between the random code generator 1 and the digital line 4A of FIG.
And codec 3A are arranged, and the digital line 4 in FIG.
A codec 3D and a modem 2B are arranged between B and the code error measuring device 6.

The modem 2A modulates the output of the random code generator 1 at the bit level into frequency, phase or amplitude. In FIG. 1, a modem is used as a frequency modulation modem and a codec is a 64 Kbit codec as an example.
The modem 2A modulates the output "0" of the random code generator 1 to the frequency fa and the output "1" to the frequency fz.
The codec 3A encodes the output of the modem 2A at the byte level. In FIG. 1, the frequencies fa and fz are encoded into a code such as 8 bytes.

The codec 3D decodes the output of the digital line 4B at the byte level into frequency, phase or amplitude. In FIG. 1, as an example, the output of the digital line 4B is decoded into a frequency fa · fz. The modem 2B demodulates the frequency, phase or amplitude of the output of the codec 3D into "0" and "1" at the bit level.

In FIG. 1, a random code generator 1 generates a random code, and a modem 2A modulates the random code into an analog signal. For example, bit “0” is set to frequency fa =
Frequency-modulates to 1300 Hz, and bit "1" is frequency fz =
Frequency modulated to 2100Hz. The signal frequency-modulated by the modem 2A is converted into a byte-level digital signal by the codec 3A and sent to the digital line 4A. The output of the digital line 4A is D / A converted by the codec 3B and enters the analog line 5.

Reference numeral 11 in FIG. 1 indicates a bit level "0".
"1" digital signal, 21 is the modulated frequency fa
Fz analog signal, 12 byte-level encoded digital signal, 22 analog signal, 13 byte-level digital signal, 14 decoded analog signal of frequency fa · fz, 15 demodulated It is a digital signal of bit level "0" and "1".

Next, the relationship between the modem 2A and the modem 2B will be described with reference to FIG. Modem 2A uses digital signal 11A
The bit "0" of the above is modulated to the frequency fa, and the bit "1" is modulated to the frequency fz. The signals of frequencies fa and fz are demodulated into a digital signal 11B by the modem 2B. Modem 2
Since B demodulates the frequency fa into the bit “0” and the frequency fz into the bit “1”, it can be converted into the original bit.

Comparing the digital signal 11A and the digital signal 11B in FIG. 2, the digital signal 11A is correctly converted into the digital signal 11B. Therefore, when the digital signal 11A has the PN pattern, the digital signal 11B is correctly reproduced in the PN pattern, and the bit error can be measured.

Next, the modem 2A and the codec 3 shown in FIG.
The relationship of A will be described with reference to FIG. When the digital signal 11 is input to the modem 2A, the modem 2A generates the frequency fa when the bit is "0" and the frequency f when the bit is "1".
generate z. Analog signal 2 of this frequency fa · fz
When 1 is input to the codec 3A, the frequency fa · fz
Analog signal 21 is a byte-level digital signal 1
Converted to 2. Byte level digital signal 12
Is different from the bit-level digital signal 11, one bit of the digital signal 11 is converted into the analog signal 21 of the frequency fa · fz by the modem 2A, and the frequency fa
The fz analog signal 21 is changed to the byte level digital signal 12.

Next, the relationship among the codec 3B, the analog line 5 and the codec 3C shown in FIG. 1 will be described with reference to FIG. When the byte-level digital signal 12 is input to the codec 3B, the codec 3B converts into an analog signal 22 every 8 bits and sends it to the analog line 5. When the analog signal 22 transmitted through the analog line 5 is input to the codec 3C, the analog signal 22 is converted into a byte-level digital signal 13 for every 8 bits corresponding to the analog signal 22.

The byte-level digital signal 13 A / D-converted by the codec 3C and output is substantially the same as the digital signal 12 in the sense that it is a signal whose frequency is fa · fz. According to the data communication V series recommendation in CCITT's telephone network, an error of ± 10 Hz is allowed. The relationship between the digital signal 12 obtained by encoding the frequencies fa · fz and the frequency fa · fz obtained by decoding the byte-level digital signal 13 is ± 10H.
It can be within z. And digital line 4
The byte-level digital signal 13 is input to the codec 3D via B, D / A converted, and demodulated by the modem 2B.

That is, the digital signal 11 is transferred to the modem 2
The frequency fa · fz is modulated by A, the frequency fa · fz is used as the conversion target of the codecs 3A to 3D, and the frequency fa · fz is demodulated to “0” or “1” by the modem 2B to obtain the digital signal 11. Even if the levels of the frequencies fa · fz corresponding to “1” and “0” change slightly between the digital signals 13, if there is a bit error, the bit error can be reliably measured.

In the modems 2A and 2B of FIG. 1, the frequency fa
-Although modulation / demodulation is performed to fz, it goes without saying that modulation other than frequency modulation such as phase modulation and amplitude modulation can be used.

[0021]

According to the present invention, when a digital signal on a digital line is converted into an analog signal by a codec and transmitted on the analog line, the first modem converts the bit-level digital signal into frequency, phase or amplitude. Modulation and transmission of this modulated output by digital code and analog line by multiple codecs, and demodulation of frequency, phase or amplitude by the second modem eliminates the influence of errors in analog signal conversion by codec. Therefore, it is possible to reliably measure the bit error.

[Brief description of drawings]

FIG. 1 is a block diagram of a bit error measuring device for a communication line according to the present invention.

FIG. 2 is an explanatory diagram of a relationship between a modem 2A and a modem 2B of FIG.

FIG. 3 is an explanatory diagram of a relationship between a modem 2A and a codec 3A in FIG.

FIG. 4 is a diagram for explaining the relationship between the codec 3B, the analog line 5 and the codec 3C in FIG.

FIG. 5 is a principle diagram of bit error measurement.

FIG. 6 is a configuration diagram for measuring the bit error of FIG. 5C.

FIG. 7 is a bit error measurement system diagram of a digital line.

FIG. 8 is a bit error measurement system diagram of a communication line according to a conventional technique.

FIG. 9 is an explanatory diagram of conversion contents by codec.

[Explanation of symbols]

 1 Random Code Generator 2A / 2B Modem 3A / 3B / 3C / 3D Codec 4A / 4B Digital Line 5 Analog Line 6 Code Error Tester

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Kenji Nishizawa, 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Takahiro Nakamura, 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corp. (72) Inventor Issei Sotojima 5-1027 Minamiazabu, Minato-ku, Tokyo Anritsu Co., Ltd. (72) Inventor Koji Sahara 4-19-7 Kamata, Ota-ku, Tokyo Ando Electric Co., Ltd.

Claims (1)

[Claims] 1. A first digital line (4A) for transmitting a digital signal and an output of the first digital line (4A) are D
A second codec (3B) for A / A conversion, an analog line (5) for transmitting the output of the second codec (3B), and a third codec (A) for converting the output of the analog line (5) 3C) and a device for measuring bit error in a communication line provided with a second digital line (4B) for transmitting the output of the third codec (3C), generating a random code of "0" and "1" Input the random code generator (1), the first modem (2A) that modulates the output of the random code generator (1) to the frequency, phase or amplitude at the bit level, and the first digital line (4A). , The first modem (2A)
Codec that encodes the output of a byte at the byte level
(3A) and the output of the second digital line (4B) as an input, and the fourth codec (3D) that decodes to frequency, phase or amplitude at the byte level, and the output of the fourth codec (3D) Measure "0" and "1" from the output of the second modem (2B) and the second modem (2B) that demodulates the frequency, phase or amplitude into "0" and "1",
A bit error measuring device for a communication line, comprising: a bit error measuring device (6) for measuring a bit error.