JP2000299708A - Modem receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a modem receiver that can accurately decide the quality of its channel. SOLUTION: An error correction device 3 and a decoder 4 recover a binary code corresponding to a signal from a receiving point subjected to error correction processing a receiving signal point discrimination device 5 recovers a binary code corresponding to the signal from the receiving point not subjected to error correction processing, a comparator 6 obtains a difference between the binary codes recovered in this way, and a channel quality decision device 7 discriminates propriety of quality of a channel according to the result of the comparison.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to ITU-T Recommendation V. 17, V.I. 32, or V.I. The present invention relates to a modem receiver for performing data communication using a convolutional code, such as a modem 34.

[0002]

2. Description of the Related Art As is well known, in a conventional modem receiver, the line quality is determined, and the result of this determination is used, for example, in facsimile communication to determine the necessity of fallback.
Computer communication was used to determine the need for falldown and retraining.

FIG. 2 is a diagram showing ITU-T Recommendation V. 7.2 of 17
This is a constellation for kbps communication. The transmitting side generates one bit of a convolutional code based on the transmission code,
This is mapped, modulated, and transmitted to one of the 16 points in FIG. 2 according to the data.

[0004] On the receiving side, the receiving point is shifted as shown in FIG.
It is distorted like. At this time, if the reception point is received within the area surrounded by the broken line, no determination error occurs. However, if a distortion exceeding this region occurs, a determination error may occur.

[0005] A determination error is a data error due to erroneous determination of a receiving point as another receiving point. For this reason,
As described above, the modem monitors the line quality, and when the data error is likely to exceed the allowable range, the transmission rate is reduced (fallback, falldown), and the equalizer is retrained to improve the error rate. Aim.

FIG. 4 shows each area of two receiving points A and B, where the distance between signal points AB is d. When communication is performed using the points A and B, if the signal point A is transmitted, and if the reception point of the signal A is distorted d / 2 or more toward the signal B, the signal A is shifted to an area where the signal A is determined to be B. There is a possibility of entering and causing a judgment error.

As shown in FIG. 5, the horizontal axis represents the distance between the transmission point (ideal point) and the reception point A, and the vertical axis represents the probability density indicating the probability of occurrence. the probability density and S _A0, when the probability density of the region outside the (d / 2 or more) and S _A1, in this case, if S _A1 is 0, the line quality is good, whereas there are S _A1 If it exceeds the allowable value, it is determined that the line quality is bad.

However, since the portion of S _A1 belongs to the region S _B0 of the adjacent point and the signal originally transmitted as the signal B of the adjacent point exists, it is difficult to simply measure only the portion of S _A1. Can not.

Conversely, S_A0For the part of
The signal originally transmitted as signal B at the adjacent point is distorted
S in the area shifted by d / 2 or more_B1Will be included
S _A0It is also not possible to simply measure only the portion of.

FIG. 6 shows such a situation. That is, even if the average value of S _A1 (or S _A0 ) of the signal A is measured and this measurement result is compared with a certain reference value to determine the line quality, the S _B0 (or S _B1 ) of the signal B is determined. And the problem that accurate judgment cannot be made arises.

[0011]

The conventional modem receiver has a problem that the line quality cannot be determined accurately. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a modem receiver capable of accurately determining the line quality.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a modem receiver for receiving a signal generated by adding error correction information and performing modulation processing. A first information reproducing means for reproducing the information corresponding to the phase of the data, and a second processing for reproducing the information by applying error correction processing and processing for reproducing the information corresponding to the phase to the received signal in a predetermined order. The information reproduced by the information reproducing means, the information reproduced by the first information reproducing means, and the information reproduced by the second information reproducing means are compared with each other. And a line quality judging means for judging.

In the modem receiver having the above-described configuration, information is reproduced from the received signal by phase demodulation, information is reproduced by phase demodulation and error correction processing, and the information is compared. Is determined.

Therefore, according to the modem receiver having the above-described configuration, even if the received signal is demodulated to erroneous information due to poor line quality, the error-corrected information is reproduced and reproduced. , The deterioration of the line quality can be determined, so that the line quality can be accurately determined.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a modem receiver according to an embodiment of the present invention. In FIG. 1, the configuration relating to the features of the present invention is mainly shown, and the configuration for controlling the reception timing and the like are omitted.

This modem receiver comprises an equalizer 1 and a phase P
An LL circuit 2, an error corrector 3, a decoder 4, a received signal point determiner 5, a comparator 6, and a channel quality determiner 7 are provided.

The equalizer 1 receives a baseband signal obtained by demodulating a received signal by a demodulator (not shown). The equalizer 1 is an adaptive equalizer such as a transversal filter, and removes group delay distortion included in the baseband signal. Note that the tap coefficient of the equalizer 1 is updated by information notified from the error corrector 3 described later.

The phase PLL circuit 2 receives a baseband signal from which the group delay distortion has been removed by the equalizer 1, and removes a frequency offset and a jitter from this signal to remove a phase error. As a result, a signal is developed to the coordinates shown in FIG. 2 described above, and this signal is output to the error corrector 3 and the received signal point determiner 5.

The error corrector 3 performs an error correction process by Viterbi decoding on the signal input from the phase PLL circuit 2. Then, the tap coefficient of the equalizer 1 is updated so as to compensate for the group delay distortion from the processing result. Also,
The error corrector 3 determines a reception point based on the result of the error correction processing, and outputs the result of the determination to the decoder 4.

The decoder 4 performs a decoding process on the above determination result to decode it into a binary code. This binary code is
In addition to being output to the comparator 6, the redundant bits added by the convolutional encoder on the transmission side are removed and output to the subsequent data processing unit (not shown) as received data.

The received signal point judging device 5 includes a phase PLL circuit 2
The received point is determined for the input signal, and is converted into a binary code corresponding to the result of the determination. The comparator 6
The binary code obtained by the received signal point determiner 5 and the binary code decoded by the decoder 4 are compared, and a match / mismatch between corresponding codes is determined.

The line quality judgment unit 7 judges the line quality according to whether or not the judgment of the mismatch within a predetermined time exceeds a preset threshold based on the judgment result of the match / mismatch of the comparator 6. .

That is, in the modem receiver having the above configuration,
In the comparator 6, a binary code (output of the received signal point determiner 5) corresponding to a reception point on which no error correction processing has been performed;
The binary code (output of the decoder 4) corresponding to the reception point on which the error correction processing has been performed is compared, and the line quality determination unit 7 determines whether the line quality is good.

Therefore, according to the modem receiver having the above-described configuration, the quality of the received signal point can be determined based on the result of the error correction processing, so that the line quality can be accurately determined.

The present invention is not limited to the above embodiment. In addition, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0026]

As described above, according to the present invention, information is reproduced from a received signal by phase demodulation, information is reproduced by phase demodulation and error correction processing, and the information is compared. The line quality is determined from the result.

Therefore, according to the present invention, even if demodulated to erroneous information due to poor line quality in reproducing a phase-modulated received signal, error-corrected information reproduced and reproduced The comparison between the two indicates that the line quality has deteriorated, so that a modem receiver capable of accurately determining the line quality can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of an embodiment of a modem receiver according to the present invention.

FIG. 2 shows ITU-T Recommendation V. 17 is a diagram showing a constellation at the time of 7.2 kbps communication in FIG.

FIG. 3 is a diagram for explaining a variation on the receiving side of the constellation shown in FIG. 2;

FIG. 4 is a view for explaining an area of a reception point shown in FIG. 2;

FIG. 5 is a diagram for explaining a probability density of receiving each of two signal points.

FIG. 6 is a view for explaining a probability density distribution actually measured based on the probability density distribution shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Equalizer 2 ... Phase PLL circuit 3 ... Error corrector 4 ... Decoder 5 ... Received signal point discriminator 6 ... Comparator 7 ... Line quality discriminator

Claims (2)

[Claims] A first information reproducing means for reproducing information corresponding to a phase of a received signal in a modem receiver for receiving a signal generated by applying error-correction information and performing modulation processing; A second information reproducing means for performing error correction processing and a processing for reproducing information corresponding to the phase on a signal received in a predetermined order to reproduce the information; and information reproduced by the first information reproducing means. And the second
And a line quality judging means for judging the line quality between the transmitting side and the own apparatus based on a result of the comparison with the information reproduced by the information reproducing means. 2. The first information reproducing means reproduces information from a phase and an amplitude of a received signal, and the second information reproducing means performs an error correction process and information corresponding to the phase and the amplitude. 2. The modem receiver according to claim 1, wherein the reproduction is performed on a signal received in a predetermined order to reproduce the information.