JPS62213322A - Operating state supervisory method of receiver having viterbi decoder - Google Patents

Abstract

PURPOSE:To supervise accurately the operating state by supervising a difference between the maximum and minimum values of a path metric obtained from a branch metric whose output is limited to a preset value or supervising the change in the path metric value. CONSTITUTION:A reception signal is inputted to a Viterbi decoder 2 after through an automatic equalizer 1. A branch metric calculation circuit 21 of the decoder 2 calculates a branch metric from a reception signal and gives the result to a Add Compare Select ACS circuit 23. Then the circuit 23 reference outputs of the circuit 21 and a pathmetric storage circuit 25 to select a remaining path and to update the content of the result of storage. Then a supervisory circuit 3 receives a path metric from the circuit 25 to supervise the timewise increasing rate of the minimum value of the path metric. When the increasing rate is larger than the setting value, a divergence detection signal of an automatic equalizer is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for monitoring the operating state of a receiver having a Viterbi decoder.

[Conventional technology]

Conventionally, as an example of monitoring the operating state of a receiver from the operating state of a Viterbi decoder, there is a method in which this is used to monitor out-of-synchronization of a code synchronization circuit of a convolutional code. This is a method in which, when the operating state of the Viterbi decoder is abnormal, it is determined that the code synchronization circuit is in an out-of-synchronization state, and the code synchronization circuit shifts to synchronization hunting.

At this time, an abnormality in the operating state of the Viterbi decoder can be determined based on, for example, the rate of increase over time of the minimum path metric, the difference between the maximum and minimum values of the path metric, or the continuity of the maximum likelihood path. , Principles of Digital Communication and Coding (t'rinciples) by Viterbi et al.
of Digital CommunicaLio
-n and Coding) on pages 258 and below.

[Problems to be Solved by the Invention] In the conventional method for monitoring the operating state of a receiver having a Viterbi decoder as described above, the code synchronization circuit monitors the operation of the portions of the receiver after the hard decision unit or the soft decision unit. However, there has never been an example in which information on the operating state of a Viterbi decoder is used for the purpose of previous operations, such as detecting divergence in an automatic equalization layer.

On the other hand, for example, a method for detecting divergence in an automatic equalizer is to obtain the difference between the input and output of a judge that performs a hard decision as an error signal, use it to modify the tap coefficient, and monitor the average power of the error signal. Something like this has been done. However, in situations where the S/N ratio of the transmission line is low, where the Viterbi decoder is particularly effective, the results of this hard decision itself are not reliable, and therefore the average power of the error signal is also There is a problem in that it does not necessarily accurately reflect the operating state of the converter.

An object of the present invention is to provide a method for monitoring the operating state of a receiver having a Viterbi decoder, which more accurately monitors the operating state of a portion before a hard decision unit or soft decision unit such as an automatic equalizer. be.

[Means for solving problems]

A method for monitoring the operating state of a receiver having a Viterbi decoder according to the first aspect of the present invention selectively adds branch metrics calculated from received signals, and monitors changes in values of path metrics obtained as a result of the addition. and is configured to monitor the operating state before the hard decision device or the soft decision device.

A method for monitoring the operating state of a receiver having a Viterbi decoder according to a second aspect of the present invention includes output-limiting the value of a branch metric calculated from a received signal to a preset value; is selectively added, the difference between the maximum value and the minimum value of the path metric obtained as a result of the addition is monitored, and the operating state of the portion before the hard decision unit or the soft decision unit is monitored.

[Effect]

A first aspect of the present invention is to monitor the operating state of the Viterbi post-determiner to determine the operating state of the portion before the hard decision unit or the soft decision unit. Note that in all of the following explanations, the metric is defined as the square of the Euclidean distance. Therefore, the bus with the smallest metric is selected as the decoding result.

The path metric is a value indicating how much noise power a certain bus, that is, a signal point sequence has experienced. This noise power includes not only noise caused by the transmission path but also a portion caused by deviations from the ideal state of operation of each part of the receiver, that is, deviations from the ideal state of the tap coefficients of the automatic equalizer.

Therefore, by monitoring changes in the value of the path metric, etc., it is possible to monitor the operating state of a portion before the hard decision device or soft decision device, such as an automatic equalizer.

As long as the Viterbi decoder does not make errors, the value of the minimum path metric accurately represents the integral value of the noise power. On the other hand, the noise power estimated from the error signal obtained from a decider that performs hard decisions is only accurate as long as the hard decisions do not cause errors. Since the error rates of the two methods differ by the coding gain obtained by the Viterbi decoder, the information obtained by the former method is more useless as a means of determining whether the operation of the receiver is normal or abnormal.

The above explanation was about the minimum value of the path metric, but as shown in the above-mentioned literature, other information obtained from the Viterbi decoder, such as the difference between the maximum and minimum value of the path metric, etc. , it is easy to confirm that the same argument holds even if we use the continuity of the maximum likelihood bus.

Next, the second aspect of the present invention is to more accurately monitor the operating state of the portion before the hard decision unit or the soft decision unit by limiting the output of the branch metric to a preset value.

Among the information obtained from the Viterbi decoder, when the difference between the maximum value and the minimum value of the smetric is used, the following problem may occur. In other words, when a signal with an extremely large amplitude is input to the Viterbi decoder due to abnormal operation of an automatic equalizer, etc., the difference between the maximum and minimum values of Pasta 1~Risk, which should normally be small during abnormal operation, is The value becomes as large as it would be during normal operation, or even larger.

For example, if binary modulation of +1 and -1 is performed and a signal of value X is received, the values of the branch metric are (X-1>2 and (X+1)2. ...The difference in Tsuku is 4X, and this value is
If it gets bigger, it will get bigger accordingly. Since the path metric is an accumulation of branch metrics, at this time the difference between the maximum value and the minimum value of -Pasta I. Rick also becomes large.

However, such a situation can be easily avoided by setting an upper limit on the value of the branch metric. In other words, if the upper limit is Y, then when X is sufficiently large, all branch metric values are equal to Y, so the difference between the maximum and minimum path metrics approaches zero, and the automatic equalizer It is possible to correctly detect frequent buying behavior such as.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an operating state monitoring device for a receiver having a Viterbi decoder according to an embodiment of the first aspect of the present invention.

In FIG. 1, a received signal is input to a Viterbi decoder 2 after passing through an automatic equalizer 1.

In the Viterbi decoder 2, the branch metric calculation circuit 21
The branch metric is calculated from the received signal by A
The signal is supplied to a CS (Add Compare 5 select) circuit 23. The AC3 circuit 23 refers to the outputs of the branch metric calculation circuit 21 and the path metric storage circuit 25, selects a surviving path, and updates the contents of the path metric storage circuit 25. The path memory 24 stores the surviving paths and outputs the decoding results.

The monitoring circuit 3 receives the Pasta I Rick from the path metric storage circuit 25, monitors the temporal increase rate of the minimum value of the path metric, and when this value is greater than a predetermined setting value, automatically Outputs the divergence detection signal of the converter.

FIG. 2 is a block diagram of an operating state monitoring device for a receiver having a Viterbi decoder according to an embodiment of the second aspect of the present invention.

In FIG. 2, the received signal passes through an automatic equalizer 1 and then is input to a Viterbi decoder 2'.

The Viterbi decoder 2' is obtained by adding a hard limiter circuit 22 to the Viterbi decoder 2 shown in FIG.
Limit the output of branch metrics from to a preset value. Viterbi decoder 2 excluding hard limiter circuit 22
The operation of ' is similar to that of the Viterbi decoder 2 described above.

The monitoring circuit 4 receives the path metric from the path metric storage circuit 25, monitors the difference between the maximum value and the minimum value of the pasta I-rick, and when this value is smaller than a predetermined value, performs an automatic operation, etc. Outputs the divergence detection signal of the converter.

〔Effect of the invention〕

As explained above, according to the present invention, changes in the value of the path metric are monitored, or the maximum and minimum values of the pasta I-lick obtained from the branch metric whose output is limited to a preset value are monitored. By monitoring the difference between , it is possible to realize a method for monitoring the operating state of a receiver having a Viterbi decoder that can accurately monitor the operating state of the portion before the hard decision unit or soft decision unit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an operating state monitoring device for a receiver having a Viterbi decoder according to an embodiment of the first aspect of the present invention;
FIG. 2 is a block diagram of an operating state monitoring device for a receiver having a Viterbi decoder according to a second embodiment of the present invention. 1... Automatic equalization layer, 2, 2'... Viterbi decoder, 3
．． 4... Monitoring circuit, 21... Branch metric calculation circuit, 22... Hard limiter circuit, 23... A
C8 circuit, 24... bus memory, 25... path metric storage circuit. Figure 2

Claims (2)

[Claims] (1) Selectively add branch metrics calculated from received signals, monitor changes in the path metric value obtained as a result of the addition, and monitor the operating state of the part before the hard decision unit or soft decision unit. A method for monitoring the operating state of a receiver having a Viterbi decoder, characterized in that: (2) Output-limiting the branch metric value calculated from the received signal to a preset value, selectively adding the output-limited branch metric, and the maximum and minimum values of the path metric obtained as a result of the addition. 1. A method for monitoring the operating state of a receiver having a Viterbi decoder, characterized in that the operating state of a portion before a hard decision unit or a soft decision unit is monitored.