JPS5840382B2 - Communication line quality monitoring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line quality monitoring system that can obtain highly accurate error rates with a simple circuit configuration.

In a digital signal transmission line such as a PCM communication line, the line quality is evaluated by the error rate of a pulse train.

This error rate is a value obtained by measuring the number of error bits in a signal transmitted over a certain period of time and dividing it by the total number of transmitted pulse signals.The smaller the value, the better the line quality. It shows.

Although it is a desirable condition to measure error rates quickly,
Normally, the error rate of a line is extremely small, so in order to accurately determine the error rate, measurements must be carried out over a long period of time.

The time required to measure the error rate is reduced by increasing the number of error bits by a predetermined number and estimating the actual number of error bits in the line from the measurement results.

The expanded error rate (this is called the pseudo error rate)
In order to obtain this, the conventional means carried out in a communication line using m-phase PSK (phase shift key ink) modulation are (1) inserting a known special code pattern sequence into the transmission code sequence, and (2) determining the identification of the baseband signal. An example of this is to shift the level so that the error rate is a dog.

Although method 1) is accurate, it requires some modification to the transmission code string, and has the disadvantage that the code string used as data becomes less useful as the special code is inserted.

The latter method (2) has the disadvantage that measurement accuracy deteriorates because the input level itself fluctuates.

SUMMARY OF THE INVENTION An object of the present invention is to provide a line quality monitoring system that can improve the above-mentioned drawbacks and measure error rates with high precision in a short time with a simple circuit configuration.

Embodiments of the present invention shown in the drawings will be described below.

As shown in FIG. 1, in a block diagram for receiving a four-phase PSK wave, DET is a synchronous detector section, which includes a biblit circuit 1 and phase detectors 2 and 3.

Note that a regenerated carrier wave such as eO8ωt1sinωt is applied to the phase detectors 2 and 3 after being regenerated from the received signal of the 4-phase PSK wave as in the prior art.

The input signal a of the hybrid circuit 10 is a received signal, and is a 4-phase P
In the case of the SK wave, it has a signal vector as shown in Figure 2, so
If this is now COS (ωt+θ), the phase detector 2,
The outputs S and c of 3 become COS θ and sin θ, respectively.

So this demodulated signal. Take out a part of C and use coefficient multiplier 6
By multiplying by an appropriate coefficient by 9 to 9 and performing addition and subtraction operations using adders and subtracters 10 and 11, a baseband operation signal f2g is obtained.

That is, the father ctl, α2 is a constant Perform the operation to obtain .

08 (--α1), 5in (--α1), cos (-+α2), and 4 sin (-+α2) correspond to the coefficient values of coefficient multipliers 6 to 9.

The signals f and g after this calculation are discriminated and reproduced by the discriminators 12 and 13, and then the demodulated signals S and c of the main path are discriminated and reproduced by the discriminators 4 and 5, resulting in a signal d.

e is compared by exclusive OR circuits 14 and 15, and the output Jtk of exclusive OR circuits 14 and 15 is inputted to exclusive OR circuit 16 to obtain a pseudo error pulse l.

FIG. 3 shows the process of obtaining the pseudo-error pulse l, and FIG. 4 shows the pseudo-error determination area.

π 3π 5π The phase angle θ−−1 444 7π − indicated by a circle in FIG. 3 is the phase of a signal that does not include a noise valve, that is, has no error.

When the phase θ of the signal vector is swayed by noise and enters the shaded area in FIG. 4, a pseudo error occurs.

This pseudo error rate P is given by the following equation.

Pp#-;erfc (sin dl) +〒erfc
(sin d2) When this pseudo error rate P is obtained, the error rate P of the actual line.

The relationship between P and P is as shown in FIG. 5A, with the ratio of carrier power C to noise N on the horizontal axis and the error rate on the vertical axis.

The correspondence relationship between and P is as shown in FIG. 5B.

Therefore, when the pseudo error rate Pp can be measured, the error rate Pe of the actual line can be estimated.

Next, FIG. 6A shows a simplified circuit of FIG. 2, in which only one of the signals g and f, which have been calculated as described above, is used to calculate L.

Measuring the pseudo error rate and estimating the error rate is the same as in the case of FIG.

The only area that is determined to be an error is the shaded area in FIG. 6B.

The pseudo error rate P is given by the following formula Pp#r erfc
(・i・α・) In this way, the present invention has the advantage that it is not affected by reception level fluctuations, and even when a signal is being transmitted, it is possible to use the baseband signal after demodulation in a relatively low frequency band. Since signals are used, the circuit configuration is simple, there is no need to take the line offline, and line quality can be monitored at low cost.

Furthermore, when measuring the pseudo error rate, by adjusting the value of the coefficient multiplier, a value that is easy to measure can be selected, and therefore rapid measurement is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure shows each signal vector of the 4-phase PSK wave, FIG. 3 shows the signals of each part of FIG. 1 and explains the process of obtaining a pseudo-error pulse, and FIG. 4 shows the pseudo-error determination area. Figure 5A is a diagram showing the curve of pseudo error rate and main line error rate, Figure 5B is a diagram showing the relationship between true error rate and pseudo error rate, and Figure 6 is a circuit diagram of a simplified method. and shows the pseudo-error region. DET... Synchronous detector, 1... Hybrid circuit, 2, 3... Phase detection, 4, 5,
12, 13...Identification regenerator, 6, 7, 8, 9...
... Coefficient unit, 10.11 ... Signal combiner, 14, i5.16 ... Exclusive OR circuit.

Claims (1)

[Claims] 1 In a method of measuring the error rate of a communication line from the received signal and monitoring the line quality, a baseband signal with increased errors is obtained by multiplying the baseband original signal obtained from the received signal by a coefficient, and A communication line quality monitoring method characterized in that the quality of a communication line is monitored by detecting a mismatch between a signal after multiplication and an original signal to obtain a pseudo error signal.