JP3075222B2 - Communications system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system provided with an equalizer for removing transmission distortion of a digitally transmitted signal, and more particularly to a communication system in which the line quality of a working line during communication deteriorates. The present invention relates to a communication system that switches to a protection line and continues this communication.

[0002]

2. Description of the Related Art Various equalizers or equalization circuits are used to remove transmission distortion of digitally transmitted signals and obtain a shaped waveform that can be directly input to a logic circuit. As a prior art relating to such an equalizer or an equalizing circuit, for example, Japanese Unexamined Patent Publication No.
A “transversal type automatic equalizer” disclosed in Japanese Patent No. 6219 and an “automatic equalizer circuit” disclosed in Japanese Patent Application Laid-Open No. 2-217014 are known.

[0003] The former transversal automatic equalizer is
A plurality of serially connected delay circuits for receiving an input signal;
A weighting coefficient circuit connected to the input and output of these delay circuits, an adder for adding the outputs of these weighting coefficient circuits, and comparing the output of the adder with an optimum value that minimizes the waveform distortion A first discriminating circuit for transmitting an output signal, wherein a transversal type automatic equalizer configured to change a weight coefficient value of the weight coefficient circuit to remove waveform distortion of the output signal; A second identification circuit identical to the first identification circuit, a third identification circuit for comparing the adder output with a value smaller than the optimum value, and a second / third identification circuit.
An error monitor constituted by an exclusive OR circuit connected to the output of the identification circuit is provided, and the weight system value of the weight coefficient circuit is controlled so that the error occurrence rate of the error monitor is minimized. According to this transversal type automatic equalizer, control can be automatically performed even when the delay time of the delay circuit is a time other than one time slot, and power consumption is reduced and the delay circuit is shortened. It is possible.

The latter automatic equalizing circuit includes a waveform equalizing circuit using a transversal filter, a coefficient setting circuit for setting a coefficient value of each tap of the transversal filter from an input and an output of the waveform equalizing circuit, And a coefficient monitoring circuit for prohibiting all coefficient values from being changed when the coefficient value exceeds a predetermined range. According to this automatic equalization circuit, when an abnormal signal including a non-input signal is input, the coefficient setting operation can be limited to a predetermined range to suppress fluctuations from the standard characteristics, It is possible to prevent the error rate of the signal from being unnecessarily degraded due to the setting of the coefficients.

Therefore, if such a transversal type automatic equalizer or automatic equalizing circuit is used, the characteristics of the equalizer are always optimized in accordance with the characteristics of the digitally transmitted signal. Signal transmission distortion can be almost certainly removed.

However, when the above-mentioned transversal type automatic equalizer or automatic equalizing circuit is applied to a communication system using a wireless line as a transmission line, the line quality of the wireless line changes due to changes in weather or movement of a communication person. It is much more susceptible to such effects. For this reason, even if the characteristics of these equalizers or the equalizer circuits themselves are optimized according to the characteristics of the signals, practical communication cannot be maintained if the line quality deteriorates to such an extent that it cannot be compensated. there were. Therefore, a communication system applied to a digital mobile phone and the like which has been widely spread in recent years always monitors the line quality of a wireless line during communication, that is, a working line. When the line quality is degraded from the specified quality, the line is switched from the working line to the protection line, and this communication is continued without interruption, via the protection line. Next, a conventional example of such a communication system will be described.

FIG. 4 shows an example of a conventional digital communication system. The first to N-th working radio lines and one protection radio line for performing modulation and demodulation by the multilevel quadrature amplitude modulation method are shown in FIG. FIG.

In FIG. 1, an input terminal 11₁~ 11_NInput from
The output data signals are sent to the transmission line switch 12 respectively.
And the transmission line switching unit 12
In a good normal case, the control signal from the sending end line controller 13
According to the input terminal 11 ₁~ 11_NData from
Signal from the pilot signal generator 14 to the working line.
Output the pilot signal to the protection line.
You. Output to the working line or protection line in this way
Each signal is transmitted to the working line 15₁~ 15_NStrange belonging to
Controller 16₁~ 16_NAnd protection line 15_BModulation belonging to
Table 16_BAfter being modulated by the corresponding transmitter 17₁~ 17
_NAnd transmitter 17_BIs output to the wireless transmission path by
It has become. Each signal output to the wireless transmission path is
Each working line 15₁~ 15_NReceiver 18 belonging to₁
~ 18_NAnd protection line 15_BReceiver 18 belonging to_BTo
Thus, after being received, the respective demodulators 19₁~
19_NAnd demodulator 19_BDemodulated to the original signal
The received original signal is input to the receiving-end line switch 20,
According to the control signal from the receiving line switching controller 21,
Output terminal 22₁~ 22_NAnd pilot signal receiver 2
3 is output.

Next, the operation of the digital radio communication system shown in FIG. 4 will be described.

[0010] For example, the data signal inputted from the first input terminal 11 _1, if it is not output the control signal from the sending-end line controller 1, first through the feed edge line switching unit 12 1
Is input to the modulator 16 ₁ belonging to the working line 15 ₁ .
The modulator 16 _1, and the speed converting an input data signal at high speed, after framed by inserting additional bits, such as frame synchronization bits and parity check bits, and outputs the modulated signal obtained by performing modulation I do. The modulated signal is transmitted via the transmitter 17 ₁ belonging to the first working line 15 ₁ to the first working radio transmission path of the line. The receiver 18 ₁ belonging to the first working line 15 ₁ receives this radio signal, converts it into a predetermined frequency and level, and then inputs it to the corresponding demodulator 19 ₁ . The demodulator 19 ₁ belonging to the first working line 15 ₁ detects the frame synchronization bit inserted in the demodulated data signal obtained by performing the demodulation, synchronizes the frames, and then receives the demodulated data signal at the receiving end. Input to the line switch 20. Further demodulator 19 ₁ obtains a code error rate by performing a parity operation using the parity check bits in the demodulated data signal only if the value of the bit error rate is not exceed the preset value Then, a bit error rate alarm is output to the receiving end line controller 21 as an error detection signal. The receiving end line controller 21
The working line 15 ₁ of the line quality is good, if the bit error rate alarm is not output, the first working line 15 the demodulated data signal input from the demodulator 19 ₁ belonging to ₁ to the receiving end line switcher 20 is 1st output terminal 2
As it is outputted to the 2 _1, and outputs a control signal to the receiving end line switching unit 20.

[0011] In contrast, in channel quality to such fading occurs in the first radio transmission path of the working line 15 ₁ is deteriorated, the demodulator 19 ₁ belonging to the first working line 15 ₁
When the value of the bit error rate calculated by the parity operation exceeds a preset value, the receiving end line controller 21
A bit error rate alarm is output to In response to this bit error rate alarm, the receiving end line controller 21
Transmits an instruction signal instructing the channel switching from the first working line 15 ₁ to the protection line 15 _B to the feed edge line controller 1. Feed edge line controller 1 that receives this instruction signal, outputs a control signal to the feed edge line switching unit 12, in place of the pilot signal from pilot signal generator 14, corresponding to the first working line 15 ₁ first data signal from the input terminal 11 ₁ is to be output to the modulator 16 _B belonging to the protection line 15 _B. As a result, the protection line 15 data signals from the modulator 16 a first input terminal 11 _{1, B} belonging to _B is modulated, is output as a modulation signal by a corresponding transmitter 17 for _B to the wireless transmission path of the protection line 15 _B You. The modulated signals are received by a receiver 18 _B belonging to the protection line 15 _B, after being demodulated into the original signal in the corresponding demodulator 19 _B, is input to the reception terminal line switcher 20. Receiving end line switching unit 20, on the combined phase of each channel signal by performing a line switching from the working line ₁₅₁ to the protection circuit 15 _B without interruption, from the first input terminal 11 ₁ is input and outputs the data signals transmitted via a wireless transmission path protection line 15 _B to the first output terminal 22 _1.

[0012] Here, the channel quality of the first working line 15 ₁ of the radio transmission path is described the operation of the line switching in the case of deterioration, line quality of the radio transmission path of the working line M2～15 _N is degraded The same applies to the case.

As described above, when the line is switched from the working line to the protection line due to the deterioration of the line quality of the working line, the signal transmitted via the protection line before and after the line switching is performed. Instantaneously switches from the pilot signal to the data signal. At this time, switched when two there is considerable difference in frequency between the signals, the frequency response characteristic of the clock synchronization circuit provided to a demodulator 19 _B belonging to the protection line 15 ₁ is the rapid change of frequency due to line switching It may not be able to keep up and lose clock synchronization. When such a clock synchronization loss occurs, the completion of the line switching is delayed until the phase synchronization between the working line in which the line quality has deteriorated and the protection line to be switched is determined, and the line quality is already reduced. The use of the deteriorated working line must be continued, and the risk of causing a momentary interruption of communication due to the occurrence of deeper fading before the completion of the line switching increases.
Therefore, it is necessary to always feed back the characteristics related to the line quality of the working line to the protection line so that the above-mentioned clock synchronization is not lost when the line is switched from the working line to the protection line.

FIG. 5 shows an example of the internal configuration of the demodulator belonging to the protection line in FIG. 4, and shows a block diagram of an example of the digital signal demodulator capable of performing the above-mentioned feedback. In the demodulator 19 _B, the clock synchronization circuit 1
By 14 belonging to the working line 15 ₁ to 15 _N demodulator 1
A channel alarm, which is a bit error rate alarm from 9 _{1 to} 19 _N, and a frame pulse of a radio signal are monitored by the frame synchronization determination circuit 115.
Then, the demodulator 19 ₁ belonging to the working line 15 ₁ to 15 _N
~ 19 If the channel alarm from one of the _N is output, and at the same time performs line switching as described above, by performing the control to increase the bandwidth of the bandwidth variable loop filter 33 provided in the clock synchronization circuit 114, The frequency response characteristics of the clock synchronization circuit 114 are improved. By taking such considerations, the conventional communication system prevents clock synchronization from being lost when the above-described line switching is performed. The reason for not expanding the bandwidth of the bandwidth variable loop filter 33 from the beginning is to prevent a steady bit error rate (BER) from deteriorating due to an increase in jitter due to the expansion of the bandwidth, and to prevent the protection line 15 _B
This is to maintain the same line quality as the working wireless line even after the line is switched.

[0015]

However [0005] In the communication system shown in FIG. 4, when the channel alarm from one of the demodulators 19 ₁ ~ 19 _N belonging to the working line 15 ₁ to 15 _N is output, the preliminary a control to increase the bandwidth of the bandwidth variable loop filter 33 provided in the clock synchronization circuit 114 of the demodulator 19 _B belonging to the line 15 _B, and the control of the line switching to the protection line are simultaneously performed from a working line . For this reason, when the line quality of the working line deteriorates considerably rapidly due to fading or the like, the bandwidth of the variable bandwidth loop filter 33 cannot be increased in time for the line switching, and clock synchronization is lost. There is a drawback that the current working line may be momentarily interrupted and communication may be interrupted.

Accordingly, an object of the present invention is to provide a communication system capable of suppressing occurrence of loss of clock synchronization when a line is switched to a protection line when the line quality of a working line is deteriorated.

It is another object of the present invention to provide a communication system capable of suppressing occurrence of loss of clock synchronization when switching between two types of signals having a considerable frequency difference.

[0018]

According to the first aspect of the present invention, there is provided (a) a modulating means for generating, based on a given original signal, a digitally modulated signal including a restoration control signal used for the restoration thereof; Transmitting means for transmitting the modulated signal generated by the modulating means to a predetermined transmission path; receiving means for receiving the modulated signal transmitted via the transmission path; and A clock synchronization unit that extracts a predetermined clock component from the restoration control signal and performs clock synchronization, and a demodulation unit that generates a first intermediate restoration signal that identifies and demodulates the modulated signal according to the clock synchronization performed by the clock synchronization unit. And a transmission distortion equalizing unit that generates a second intermediate restoration signal equalizing transmission distortion included in the first intermediate restoration signal, and the second restoration signal based on the restoration control signal. And a transmission error detection unit that detects a transmission error of the intermediate restoration signal and outputs an error detection signal according to the degree of the transmission error, and corrects the transmission error from the second intermediate restoration signal to generate the restoration control signal. One or a plurality of working lines each including: an original signal reproducing unit for obtaining the removed original signal; and a working demodulation unit having a distortion compensation amount monitoring unit for outputting a compensation degree signal corresponding to a distortion compensation amount in the transmission path. (B) a modulating means for generating a digitally modulated signal including a restoration control signal used for restoration based on a given original signal; and transmitting the modulated signal generated by the modulation means to a predetermined transmission path. Transmitting means for receiving the modulated signal transmitted through a transmission path, and a predetermined clock signal from the restoration control signal in the modulated signal received by the receiving means. And a demodulation unit for generating a first intermediate restoration signal that identifies and demodulates the modulated signal according to the clock synchronization by the clock synchronization unit, and generates a first intermediate restoration signal. A transmission distortion equalizer for generating a second intermediate restored signal equalizing the included transmission distortion and a transmission error of the second intermediate restored signal are detected based on the restoration control signal, and a degree of the transmission error is detected. A transmission error detection unit that outputs a corresponding error detection signal; and an original signal reproduction unit that obtains the original signal obtained by correcting the transmission error from the second intermediate restoration signal and removing the restoration control signal, and responding to the original signal. A backup demodulation unit whose characteristics are determined according to the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation unit belonging to the working line. Designating a communication line to be used for a transmission line for transmitting each of a plurality of data signals given as the different original signals from one or more protection lines and (c) the working line and the protection line. (D) sending-end line switching means for sending the plurality of data signals to a specific communication line designated by the sending-end control signal; A) receiving an output destination of the plurality of data signals, which are the original signals demodulated and reproduced from the modulated signal, based on the restoration control signal in the modulated signal transmitted through each of the communication lines; Receiving end line control means for outputting an end control signal,
(F) pass / fail boundary storage means for preliminarily storing a pass / fail boundary value of the line quality for each of the communication lines;
(G) determining whether or not the error detection signal output from the transmission error detection unit of the working demodulation means belonging to each of the working lines has exceeded the boundary value stored in the pass / fail boundary storage means; Pass / fail judgment instruction means for outputting a switching instruction signal for instructing line switching to the transmission line control means when an error detection signal exceeds the boundary value,
(H) receiving-end line switching means for outputting the plurality of demodulated and reproduced data signals to the output destination specified by the receiving-end control signal.

That is, according to the first aspect of the present invention, the protection line follows the compensation degree signal output from the distortion compensation amount monitoring section of the working demodulation means provided in the working line according to the distortion compensation amount of the transmission line. The response characteristic of the preliminary demodulation means provided in the step is determined in real time. On the other hand, the pass / fail judgment instruction means
Whether the error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detection unit of the working demodulation means belonging to each working line has exceeded the line quality pass / fail boundary value stored in the pass / fail boundary storage means. Judgment is performed, and when the error detection signal exceeds the boundary value, a switching instruction signal for instructing line switching is output. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already optimized according to the communication performed via the working line. In addition, the occurrence of clock loss due to line switching is suppressed.

According to a second aspect of the present invention, in the first aspect of the present invention, (a) the plurality of working lines and the protection line are wireless communication lines for performing communication via a wireless transmission line. .

That is, according to the second aspect of the present invention, it follows the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means provided for the working line which is a wireless line according to the amount of distortion compensation of the transmission line. As a result, the response characteristics of the preliminary demodulation means provided for the backup line, which is a wireless line, are determined in real time. On the other hand, the pass / fail judgment instructing means outputs an error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detecting section of the working demodulation means belonging to each working line. And outputs a switching instruction signal for instructing line switching when the error detection signal exceeds the boundary value. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already optimized according to the communication performed via the working line. In addition, the occurrence of clock loss due to line switching is suppressed.

According to a third aspect of the present invention, in the first or second aspect of the present invention, (a) the transmission distortion equalizing sections of the working demodulation means belonging to each of the plurality of working lines are each provided with a transformer. Has a versal filter,
(B) The distortion compensation amount monitoring unit outputs a value of a tap coefficient obtained by monitoring the transversal filter as the compensation degree signal.

In other words, according to the third aspect of the present invention, the compensation degree signal, that is, the value of the tap coefficient, output from the distortion compensation amount monitor section of the working demodulation means provided in the working line in accordance with the distortion compensation amount of the transmission line. Following this, the response characteristics of the standby demodulation means provided in the standby line are determined. On the other hand, the pass / fail judgment instructing means outputs an error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detecting section of the working demodulation means belonging to each working line. And outputs a switching instruction signal for instructing line switching when the error detection signal exceeds the boundary value. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already optimized according to the communication performed via the working line. In addition, the occurrence of clock loss due to line switching is suppressed.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, (a) the response characteristics of the spare demodulation means belonging to the protection line are the response characteristics of the working demodulation means belonging to the plurality of working lines. It is characterized in that the distortion compensation amount is determined in accordance with a compensation degree signal having the maximum distortion compensation amount among the compensation degree signals output from the distortion compensation amount monitoring unit of the demodulation means.

That is, according to the fourth aspect of the present invention, of the compensation degree signals output from the distortion compensation amount monitoring units of the working demodulation means provided for the plurality of working lines in accordance with the distortion compensation amount of the transmission line, The response characteristic of the spare demodulation means provided in the spare line is determined following the compensation degree signal having the largest compensation amount. On the other hand, the pass / fail judgment instructing means outputs an error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detecting section of the working demodulation means belonging to each working line. And outputs a switching instruction signal for instructing line switching when the error detection signal exceeds the boundary value. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already adjusted to the communication performed via the working line whose line quality is most deteriorated. Due to the optimization, occurrence of clock loss due to line switching is suppressed.

According to a fifth aspect of the present invention, there is provided (a) a modulating means for generating a digitally modulated signal including a restoration control signal used for restoring the signal based on a given original signal; Transmitting means for transmitting the modulated signal to a predetermined transmission line, receiving means for receiving the modulated signal transmitted via the transmission path, and a predetermined signal from the restoration control signal in the modulated signal received by the receiving means. And a demodulation unit for generating a first intermediate restoration signal that identifies and demodulates the modulated signal in accordance with the clock synchronization by the clock synchronization unit, and a first intermediate A transmission distortion equalizing unit that generates a second intermediate restoration signal equalizing transmission distortion included in the restoration signal, and the second intermediate restoration signal based on the restoration control signal A transmission error detection unit that detects a transmission error and outputs an error detection signal corresponding to the degree of the transmission error, and the original signal obtained by correcting the transmission error from the second intermediate restoration signal and removing the restoration control signal (B) one or a plurality of working lines each comprising: an original signal reproducing unit for obtaining the signal; and a working demodulation means having a distortion compensation amount monitoring unit for outputting a compensation degree signal corresponding to the distortion compensation amount in the transmission line.
A modulating means for generating a digitally modulated signal including a restoration control signal used for restoration based on a given original signal; a transmitting means for transmitting the modulated signal generated by the modulating means to a predetermined transmission path; Receiving means for receiving the modulated signal transmitted via a transmission path, and a clock synchronization unit for extracting a predetermined clock component from the restoration control signal in the modulated signal received by the receiving means and performing clock synchronization And a first signal obtained by identifying and demodulating the modulated signal according to the clock synchronization by the clock synchronization unit.
A demodulation unit that generates an intermediate restored signal of the first intermediate restored signal, a transmission distortion equalizer that generates a second intermediate restored signal equalizing the transmission distortion included in the first intermediate restored signal, and the second A transmission error detection unit for detecting a transmission error of the intermediate restoration signal of No. 2 and outputting an error detection signal according to the degree of the transmission error; and correcting the transmission error from the second intermediate restoration signal to obtain the restoration control signal. An original signal reproducing unit for obtaining the original signal from which the signal has been removed, and a response characteristic of the original signal reproducing unit is determined according to the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means belonging to the working line. (C) a plurality of data signals respectively provided as the different original signals from the working line and the protection line; Sending-end line control means for outputting a sending-end control signal designating a communication line to be used for a transmission line for transmitting a signal, and (d) generating a monitoring signal for constantly generating a predetermined monitoring signal used for monitoring the state of the communication line Means and (e)
Sending-end line switching means for sending the plurality of data signals and the monitoring signal to a specific communication line designated by the sending-end control signal output from the sending-end line control means, and (f) the communication line Receiving the plurality of data signals, which are the original signals demodulated and reproduced from the modulated signal, and the output destination of the monitoring signal, based on the restoration control signal in the modulated signal transmitted through each of the Receiving line control means for outputting an end control signal; (g) good or bad boundary storage means for storing in advance a boundary value of good or bad line quality for each of the communication lines; Determining whether or not the error detection signal output from the transmission error detection unit of the working demodulation means belongs to the boundary value stored in the pass / fail boundary storage means; Pass / fail judgment instruction means for outputting a switching instruction signal for instructing the transmission-end line control means to switch the line when the signal exceeds the boundary value, and (r) the plurality of demodulated and reproduced data signals and the monitoring Receiving line switching means for outputting a signal to each of the output destinations specified by the receiving end control signal.

In other words, according to the fifth aspect of the present invention, the protection line follows the compensation degree signal output from the distortion compensation amount monitoring section of the working demodulation means provided in the working line according to the distortion compensation amount of the transmission line. The response characteristic of the preliminary demodulation means provided in the step is determined in real time. On the other hand, the pass / fail judgment instruction means
Whether the error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detection unit of the working demodulation means belonging to each working line has exceeded the line quality pass / fail boundary value stored in the pass / fail boundary storage means. Judgment is performed, and when the error detection signal exceeds the boundary value, a switching instruction signal for instructing line switching is output. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already optimized according to the communication performed via the working line. In addition, the occurrence of clock loss due to line switching is suppressed. Further, for example, the line quality of the protection line can be confirmed by the monitor signal generated by the monitor signal generating means.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, (a) the plurality of working lines and the protection lines are wireless communication lines for performing communication via a wireless transmission line. .

That is, according to the invention of claim 6, the compensation degree signal is output from the distortion compensation amount monitoring section of the working demodulation means provided in the working line which is a wireless line according to the amount of distortion compensation of the transmission line. As a result, the response characteristics of the preliminary demodulation means provided for the backup line, which is a wireless line, are determined in real time. On the other hand, the pass / fail judgment instructing means outputs an error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detecting section of the working demodulation means belonging to each working line. And outputs a switching instruction signal for instructing line switching when the error detection signal exceeds the boundary value. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already optimized according to the communication performed via the working line. In addition, the occurrence of clock loss due to line switching is suppressed. Further, for example, the line quality of the protection line can be confirmed by the monitor signal generated by the monitor signal generating means.

According to a seventh aspect of the present invention, in the fifth or sixth aspect of the present invention, (a) the transmission distortion equalizers of the working demodulation means belonging to each of the plurality of working lines are each provided with a transformer. Has a versal filter,
(B) The distortion compensation amount monitoring unit outputs a value of a tap coefficient obtained by monitoring the transversal filter as the compensation degree signal.
That is, according to the seventh aspect of the present invention, the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means provided in the working line according to the distortion compensation amount of the transmission line, that is, the value of the tap coefficient. The response characteristics of the standby demodulation means provided on the standby line are determined. On the other hand, the pass / fail judgment instructing means outputs an error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detecting section of the working demodulation means belonging to each working line. And outputs a switching instruction signal for instructing line switching when the error detection signal exceeds the boundary value. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already optimized according to the communication performed via the working line. In addition, the occurrence of clock loss due to line switching is suppressed. Further, for example, the line quality of the protection line can be confirmed by the monitor signal generated by the monitor signal generating means.

In the invention according to claim 8, in the invention according to claims 5 to 7, (a) the response characteristic of the protection demodulation means belonging to the protection line is such that the response characteristics belonging to the plurality of working lines respectively. It is characterized in that the distortion compensation amount is determined in accordance with a compensation degree signal having the maximum distortion compensation amount among the compensation degree signals output from the distortion compensation amount monitoring unit of the demodulation means.

That is, in the invention according to claim 8, the distortion compensation signal output from the distortion compensation amount monitoring section of the working demodulation means provided for a plurality of working lines in accordance with the amount of distortion compensation of the transmission line. The response characteristic of the spare demodulation means provided in the spare line is determined following the compensation degree signal having the largest compensation amount. On the other hand, the pass / fail judgment instructing means outputs an error detection signal corresponding to the degree of the transmission error of the signal output from the transmission error detecting section of the working demodulation means belonging to each working line. And outputs a switching instruction signal for instructing line switching when the error detection signal exceeds the boundary value. Therefore, when the line is switched from the working line to the protection line in response to the switching instruction signal, the response characteristics of the protection demodulation means are already adjusted to the communication performed via the working line whose line quality is most deteriorated. Due to the optimization, occurrence of clock loss due to line switching is suppressed. Also,
For example, the line quality of the protection line can be confirmed by the monitor signal constantly generated by the monitor signal generating means.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail based on examples.

FIG. 1 shows an overall configuration of a communication system according to the present embodiment. N working radio channels (first radio channels) for transmitting and receiving radio signals modulated and demodulated by a multi-level quadrature amplitude modulation system are shown. Working line 101 ₁ , second working line 101 ₂ ,..., Nth working line 101 _N ) and 1
It represents a digital radio communication system having a pre-radio line 101 _B of the line in the block diagram. Here, the same components as those of FIG. 4 used in the description of the related art are denoted by the same reference numerals.

The first input terminal 11 ₁ , the second input terminal 1
1 _2, ..., the data signal is a raw signal inputted from the input terminal 11 _N of the N is outputted to the feed edge line switching unit 12, the sending end line switching device 12, the working line 1 of N line
In the normal case where the line qualities of 01 _{1 to} 101 _N are all good, the data signals from the input terminals 11 _{1 to} 11 _N are respectively transferred to the corresponding working lines 101 _{1 in} accordance with the transmission terminal control signal from the transmission line controller 13. and outputs to to 101 _N, a pilot signal generator 1 is a monitoring signal generating means
4 becomes a monitor signal or a pilot signal is generated to be outputted to the protection line 101 _B. Thus working lines 101 ₁ to 101 _N and the protection line 101 the signals output to _B, a modulator 16 ₁ belonging to the modulator (the first working line 101 ₁ which belongs to the line, a second working line 101 modulator 16 ₂ belonging to the _2, ..., the working line 101 modulator 16 belonging to _{N N} of the N, high speed is speed conversion in the protection line 101 modulator 16 _B belonging to _B), the frame synchronization bits and parity check bits after being framed by the insertion of additional bits, such as is output as modulated by the modulation signal, the transmitter 17 ₁ this modulated signal, belonging to the transmitter (first working line 101 ₁ which belongs to the line,
Transmitter 17 ₂ belonging to the second working line 101 _2, ...,
Transmitter 17 _N belonging to the working line 101 _N of the N, and is output to the appropriate radio transmission channel by the transmitter 17 _B) belonging to the protection line 101 _B. Each signal outputted to the radio transmission path, the radio transmission path receiver belonging to the corresponding line (the receiver 18 ₁ belonging to the first working line 101 _1, receiver 1 second belongs to the working line 101 ₂
8 ₂ ,..., Receiver 1 belonging to the N-th working line 101 _N
8 _N , after being received by the receiver 18 _B belonging to the protection line 101 _B and converted to a predetermined frequency and level, a demodulator (first working line 101 ₁ ) belonging to that line is received.
Demodulator 102 ₁ which belongs to, demodulator 102 ₂ belonging to the second working line 101 _2, ..., demodulator 102 _N belonging to the working line 101 _N of the N, by belonging demodulator 102 _B) to the protection line 101 _B An original signal, that is, an original data signal or a pilot signal, is demodulated into an original signal. , Output terminals 22 _{1 to} 22 _N and a pilot signal receiver 23. Here, the receiving end line controller 21 also serves as receiving end line control means, pass / fail boundary storage means, and pass / fail judgment instructing means.

The demodulators 10 belonging to the respective working lines
2₁~ 102_N(Working demodulator) is the radio of the working line.
Fading occurs on the transmission line, deteriorating the line quality.
Is determined by the amount of distortion compensation in the transmission path.
Always monitor and reserve a compensation level signal according to this distortion compensation amount.
Line 101_BDemodulator 102 belonging to_BTo the data signal
Received line switching controller for error detection signal that detected transmission error
21 to the receiving end line switching controller 21
Is output from the demodulator belonging to any of the working lines.
If the error detection signal exceeds the line quality threshold,
From the working line to the protection line 101_BSwitch line to
Sends a switching instruction signal to instruct the transmitting end line switching controller 13
It is supposed to. Protection line 101_BDemodulation belonging to
Vessel 102 _B(Preliminary demodulator), as described later,
When the switch completion signal is output from the line switch 20,
The compensation degree signal output from the demodulator belonging to the working line of
Variably control the receiving bandwidth accordingly
I have.

FIG. 2 shows the internal configuration of the demodulator belonging to the protection line in FIG. 1. The demodulator of the digital signal capable of feeding back the characteristics relating to the line quality of the working line to the protection line is shown. One example is represented by a block diagram.

The demodulator 102 _B performs a demodulation circuit 111 for discriminating and reproducing a signal received by the receiver 18 _B and converted to a predetermined frequency and level, and an automatic adaptation circuit for equalizing signal distortion generated in a radio transmission path. When the switching completion signal is output from the pattern equalizer 112 and the receiving end line switch 20, the above-described bandwidth is varied according to the compensation degree signals output from the demodulators 102 ₁ to 102 _N belonging to the respective working lines. logic circuit 113 which outputs a variable instruction signal instructing the controller, receiver 18 _B clock for clock synchronization based on a clock component is extracted from the output signal synchronization circuit 1
14, transmission errors that occur when a frame synchronization determination circuit 115 for automatic adaptive equalizer 112 takes the frame-synchronization by detecting a frame pulse from being output signal, line quality of the transmission path of the protection line 101 _B is deteriorated detect and parity error detection circuit 116, the protection line 101 _B belonging to the modulator 16 _B by the added additional bit removed original signal to output an error detection signal (usually at a pilot signal)
Is provided. The clock synchronization circuit 114, a clock component extraction circuit 114a for extracting a clock component from the signal in the receiver 18 _B is output, the phase comparator 114b, the voltage controlled oscillator 1
14c, a variable bandwidth loop filter 114d.

FIG. 3 shows the internal structure of the demodulator belonging to the working line in FIG. 1. The demodulator of the digital signal capable of feeding back the characteristics relating to the line quality of the working line to the protection line is shown. One example is represented by a block diagram. Here, the same components as those in FIG. 2 are denoted by the same reference numerals.

The demodulator 102₁~ 102_NIs the receiver 18
₁~ 18_NThe demodulation circuit 111 receives the
Automatic adaptive equalizer 12 for equalizing signal distortion generated in the transmission path
1. Receiver 18₁~ 18_NExtracted from the signal output by
Clock synchronization based on the clock component
Clock synchronization circuit 122, frame synchronization determination circuit 11
5. Parity error detection circuit 116, additional bit removal circuit
117. Then, the automatic adaptive equalizer 121
Is a transverser used to equalize the original signal distortion.
Together with the filter 121a,
The tap coefficient is calculated as the above-mentioned compensation degree signal that changes
Output tap coefficient monitor circuit 121b (distortion compensation
Quantity monitoring unit), and the clock synchronization circuit 122
Is the receiver 18 _BFrom the signal output by
Clock component extraction circuit 122a to be extracted, phase comparator 1
22b, voltage-controlled oscillator 122c, having a predetermined bandwidth
A loop filter 122d is provided.

Next, an example of the line switching operation in this embodiment will be described with reference to FIGS.

(Control of Response Characteristics of Protection Line) When fading or the like occurs in any one of the wireless transmission lines of the working line and the line quality deteriorates, the automatic adaptive equalizer 121 in FIG. The amount of distortion compensation at increases in accordance with this deterioration,
In accordance with this increase, the value of the tap coefficient output from the tap coefficient monitor circuit 121b as the compensation degree signal also increases. As described above, the compensation degree signal, that is, the tap coefficient, obtained for the wireless transmission path of each working line is shown in FIG.
Is output to the demodulator 102 _B (preliminary demodulator) belonging to the protection line 101 _B, and the tap coefficient value is input to the logic circuit 113 in the demodulator 102 _B. Therefore, N working lines 101 _{1 to} 101 _N
If the logic circuit 113 is configured in advance so that the above-mentioned variable instruction signal is output according to the tap coefficient having the maximum value among the tap coefficients output from The bandwidth of the variable bandwidth loop filter 114d in the synchronization circuit 114 is expanded and set in accordance with the working line whose line quality is most deteriorated.

(Control of Line Switching) When the line quality of the working line is further deteriorated, a transmission error is detected by the parity error detection circuit 116 in FIG. When the value increases beyond a predetermined value, a bit error rate alarm is output to the receiving-end line switching controller 21 as the above-described error detection signal. Receiving end line switching controller 21, when the bit error rate alarm is input, a sending end line switching controller 13 the switching instruction signal for instructing the line switching to the protection line 101 _B of the appropriate working line reception terminal Output to the line switch 20. Feed edge line switching controller 13 which has received the switching instruction signal, so that the bit error rate alarm data signal that would otherwise be transmitted through the detected working line is transmitted via the protection line 101 _B Next, the transmission line switching unit 12 is controlled. The data signal is speed converted at a high speed modulator 16 _B belonging to the protection line 101 _B, after being framed by the insertion of additional bits such as a frame sync bit and a parity check bit, the protection line as modulated by the modulation signal transmitter 1 belonging to 101 _B
It is output to the radio transmission path of the protection line 101 _B by 7 _B. The modulated signals are received by receiver 18 _B belonging to the protection line 101 _B, after being converted to a predetermined frequency and level, demodulator 102 _B belonging to the protection line 101 _B
Is demodulated to the original data signal by the receiving end line switch 2
Input to 0. Receiving end line switching unit 20 in accordance with the switching instruction signal from the receiving end line switching controller 21, outputs the data signal transmitted via a radio transmission path of the protection line 101 _B to the appropriate output terminals.

(Relationship Between Characteristic Control and Line Switching Control)
In this embodiment, before the above-described line switching is performed, the bandwidth of the variable bandwidth loop filter 114d in the clock synchronization circuit 114 is adjusted in accordance with the tap coefficient output from the corresponding working line whose line quality has deteriorated. Enlargement is set. Therefore, when the degree of transmission error due to the working line exceeds a predetermined value and the bit error rate alarm, which is an error detection signal, is output, the clock synchronization circuit 114 of the protection line converts the pilot signal to the data signal. It can sufficiently follow the rapid frequency fluctuation accompanying the switching, and is in a state where clock synchronization is not lost at the time of line switching. Therefore, loss of clock synchronization can be suppressed when switching to the protection line when the line quality of the working line is degraded, and the protection performed quickly and reliably without interrupting communication performed via the working line. A line can be switched to a line.

In this embodiment, a case has been described in which a wireless communication line is used as the working line and the protection line. However, a communication line that does not use wireless communication, for example, ISDN (Integr
Also, the present invention can be applied to a case where a wired digital communication line such as an ated Services Digital Network) is used. Further, as a compensation degree signal that triggers line switching, a tap coefficient value obtained by monitoring a transversal filter provided in an equalizer in a demodulator belonging to a working line is used. As long as the signal is determined according to the distortion compensation amount in the above, other signals can be used as the compensation degree signal.

[0046]

As described above, according to the first aspect of the present invention, when switching the line to the protection line when the line quality of the working line is degraded, the output is made according to the distortion compensation amount of the working line. The response characteristics of the backup demodulation means provided in the protection line are optimized according to the compensation degree signal, and the occurrence of clock synchronization loss in the protection demodulation means can be suppressed. The line can be switched to the backup line reliably and quickly without interruption.

Further, according to the second aspect of the present invention, in addition to the effect of the first aspect, the wireless communication, in which the line quality fluctuates more remarkably than the wired communication and the clock synchronization is liable to occur so far, is interrupted. Since it is possible to continue without fail, reliability of wireless communication can be improved.

According to the third aspect of the invention, in addition to the effects of the first and second aspects, the distortion compensation amount monitor can be a known tap coefficient detector, so that it is easy and inexpensive. A communication system can be realized.

According to the fourth aspect of the present invention, in addition to the effects of the first to third aspects, in addition to the effects of the first to third aspects, the working line having the most deteriorated line quality and the highest possibility of being subject to line switching is provided. In addition, the response characteristics of the protection line can be determined.

According to the fifth aspect of the present invention, when the line is switched to the protection line when the line quality of the working line is degraded, the compensation degree signal output according to the distortion compensation amount of the working line is used. Therefore, the response characteristics of the spare demodulation means provided in the spare line are optimized, and the occurrence of clock loss in the spare demodulation means can be suppressed, so that communication performed via the working line is not interrupted. The line can be switched to the protection line reliably and quickly, and the state of the communication line can be monitored by the monitoring signal.

Further, according to the invention of claim 6, in addition to the effect of claim 5, the wireless communication, which is more likely to lose clock synchronization because the line quality fluctuates more remarkably than the wired communication, is interrupted. Since it is possible to continue without fail, reliability of wireless communication can be improved.

According to the seventh aspect of the present invention, in addition to the effect of the fifth or sixth aspect, the distortion compensation amount monitor can be a known tap coefficient detector, so that it is easy and inexpensive. A communication system can be realized.

Further, according to the invention of claim 8, in addition to the effects of claims 5 to 7, in addition to the working line which is the most degraded in line quality and most likely to be subject to line switching. In addition, the response characteristics of the protection line can be determined.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a communication system according to an embodiment.

FIG. 2 is a block diagram showing an internal configuration of a demodulator belonging to a protection channel in FIG.

FIG. 3 is a block diagram showing an internal configuration of a demodulator belonging to a working line in FIG. 1;

FIG. 4 is a block diagram showing an example of a conventional digital communication system.

FIG. 5 is a block diagram showing an example of an internal configuration of a demodulator belonging to a protection channel shown in FIG.

[Explanation of symbols]

Reference Signs List 12 transmission line switching device 13 transmission line switching controller 14 pilot signal generator 16 _{1 to} 16 _N , 16 _B modulator 17 _{1 to} 17 _N , 17 _B transmitter 18 _B to 18 _N , 18 _B receiver 20 End line switch 21 Receiving line switch controller 23 Pilot signal receiver 101 _{1 to} 101 _N Working line 101 _B protection line 102 _{1 to} 102 _N Demodulator belonging to working line (working demodulator) 102 _B Demodulation belonging to protection line (Preliminary demodulator) 121 Automatic adaptive equalizer 121a Transversal filter 121b Tap coefficient monitor circuit

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04B 1/74 H04B 1/76 H04B 3/04-3/18 H04B 7/005 H04L 1/22

Claims (8)

(57) [Claims] 1. Modulation means for generating a digitally modulated signal including a restoration control signal used for restoration based on a given original signal, and a modulation signal generated by the modulation means to a predetermined transmission path. Transmitting means for transmitting, receiving means for receiving the modulated signal transmitted via a transmission path, and clock synchronization by extracting a predetermined clock component from the restoration control signal in the modulated signal received by the receiving means. And a demodulation unit for generating a first intermediate restoration signal by identifying and demodulating the modulated signal in accordance with the clock synchronization by the clock synchronization unit, and a transmission distortion included in the first intermediate restoration signal. The second
And a transmission distortion equalizing unit for generating an intermediate restoration signal, and detecting a transmission error of the second intermediate restoration signal based on the restoration control signal and outputting an error detection signal corresponding to the degree of the transmission error. An output section for correcting the transmission error from the second intermediate restoration signal and removing the restoration control signal from the detection section and the original signal reproduction section for obtaining the original signal, and outputting a compensation degree signal corresponding to a distortion compensation amount in the transmission path; One or more working lines each having a working demodulation means having a distortion compensation amount monitoring unit for generating a digitally modulated signal including a restoration control signal used for restoration based on a given original signal. Modulating means, transmitting means for transmitting a modulated signal generated by the modulating means to a predetermined transmission path, receiving means for receiving the modulated signal transmitted via the transmission path, Means for extracting a predetermined clock component from the restoration control signal in the received modulated signal to perform clock synchronization, and identifying and demodulating the modulated signal in accordance with the clock synchronization by the clock synchronization unit;
A demodulation unit that generates an intermediate restored signal of the first intermediate restored signal, a transmission distortion equalizer that generates a second intermediate restored signal equalizing the transmission distortion included in the first intermediate restored signal, and the second A transmission error detection unit for detecting a transmission error of the intermediate restoration signal of No. 2 and outputting an error detection signal according to the degree of the transmission error; and correcting the transmission error from the second intermediate restoration signal to obtain the restoration control signal. An original signal reproducing unit for obtaining the original signal from which the signal has been removed, and a response characteristic of the original signal reproducing unit is determined according to the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means belonging to the working line. One or a plurality of protection lines each provided with a demodulating means; and a plurality of data signals respectively provided as the different original signals from the working line and the protection line. Sending-end line control means for outputting a sending-end control signal for designating a communication line to be used for a transmission line to be sent; and sending each of the plurality of data signals to a specific communication line designated by the sending-end control signal. End line switching means, and output of the plurality of data signals as the original signals which are demodulated and reproduced from the modulated signal based on the restoration control signal in the modulated signal transmitted through each of the communication lines. Receiving-end line control means for outputting a receiving-end control signal specifying a destination; good / bad boundary storing means for storing in advance a good / bad boundary value of the line quality of each of the communication lines; and belonging to each of the working lines. Determining whether or not the error detection signal output from the transmission error detection unit of the working demodulation unit has exceeded the boundary value stored in the pass / fail boundary storage unit; Is higher than the boundary value, a pass / fail judgment instruction means for outputting a switching instruction signal for instructing the transmission-end line control means to perform line switching, and the plurality of demodulated and reproduced data signals are received by the reception-end control signal. A communication system comprising: a receiving-end line switching unit that outputs to each of the specified output destinations. 2. The communication system according to claim 1, wherein the plurality of working lines and the protection line are wireless communication lines for performing communication via a wireless transmission path. 3. The transmission distortion equalizing sections of the working demodulation means belonging to each of the plurality of working lines each have a transversal filter, and the distortion compensation amount monitoring section monitors the transversal filter. 3. The communication system according to claim 1, wherein a value of the obtained tap coefficient is output as the compensation degree signal. 4. A response characteristic of the protection demodulation means belonging to the protection line, wherein a response characteristic of the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means belonging to each of the plurality of working lines. The distortion compensation amount is determined according to a compensation degree signal having a maximum value.
The communication system according to claim 3. 5. Modulation means for generating a digitally modulated signal including a restoration control signal used for restoration based on a given original signal, and a modulation signal generated by the modulation means to a predetermined transmission path. Transmitting means for transmitting, receiving means for receiving the modulated signal transmitted via a transmission path, and clock synchronization by extracting a predetermined clock component from the restoration control signal in the modulated signal received by the receiving means. And a demodulation unit for generating a first intermediate restoration signal by identifying and demodulating the modulated signal in accordance with the clock synchronization by the clock synchronization unit, and a transmission distortion included in the first intermediate restoration signal. The second
And a transmission distortion equalizing unit for generating an intermediate restoration signal, and detecting a transmission error of the second intermediate restoration signal based on the restoration control signal and outputting an error detection signal corresponding to the degree of the transmission error. An output section for correcting the transmission error from the second intermediate restoration signal and removing the restoration control signal from the detection section and the original signal reproduction section for obtaining the original signal, and outputting a compensation degree signal corresponding to a distortion compensation amount in the transmission path; One or more working lines each having a working demodulation means having a distortion compensation amount monitoring unit for generating a digitally modulated signal including a restoration control signal used for restoration based on a given original signal. Modulating means, transmitting means for transmitting a modulated signal generated by the modulating means to a predetermined transmission path, receiving means for receiving the modulated signal transmitted via the transmission path, Means for extracting a predetermined clock component from the restoration control signal in the received modulated signal to perform clock synchronization, and identifying and demodulating the modulated signal in accordance with the clock synchronization by the clock synchronization unit;
A demodulation unit that generates an intermediate restored signal of the first intermediate restored signal, a transmission distortion equalizer that generates a second intermediate restored signal equalizing the transmission distortion included in the first intermediate restored signal, and the second A transmission error detection unit for detecting a transmission error of the intermediate restoration signal of No. 2 and outputting an error detection signal according to the degree of the transmission error; and correcting the transmission error from the second intermediate restoration signal to obtain the restoration control signal. An original signal reproducing unit for obtaining the original signal from which the signal has been removed, and a response characteristic of the original signal reproducing unit is determined according to the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means belonging to the working line. One or a plurality of protection lines each provided with a demodulating means; and a plurality of data signals respectively provided as the different original signals from the working line and the protection line. Sending-end line control means for outputting a sending-end control signal specifying a communication line to be used for a transmission line to be sent; monitoring signal generating means for constantly generating a predetermined monitoring signal used for monitoring the state of the communication line; A transmission-end line switching unit that transmits the plurality of data signals and the monitoring signal to a specific communication line specified by the transmission-end control signal output from the transmission-end line control unit; Based on the restoration control signal in the modulated signal transmitted, the receiving end control signal specifying the output destination of the plurality of data signals and the monitoring signal, which are the original signals demodulated and reproduced from the modulated signal, respectively. Receiving end line control means for outputting, good or bad boundary storage means for preliminarily storing a line quality good or bad boundary value for each of the communication lines, and each of the working lines It is determined whether or not the error detection signal output from the transmission error detection unit of the working demodulation means belongs to the boundary value stored in the pass / fail boundary storage means, and the error detection signal exceeds the boundary value. A pass / fail judgment instruction means for outputting a switching instruction signal for instructing a line switching to the sending end line control means, and the plurality of demodulated and reproduced data signals and the monitoring signal are specified by the receiving end control signal. And a receiving line switching means for outputting to each of the output destinations. 6. The communication system according to claim 5, wherein said plurality of working lines and said protection line are wireless communication lines for performing communication via a wireless transmission path. 7. The transmission distortion equalizing sections of the working demodulation means belonging to each of the plurality of working lines each have a transversal filter, and the distortion compensation amount monitoring section monitors the transversal filter. 7. The communication system according to claim 5, wherein a value of the obtained tap coefficient is output as the compensation degree signal. 8. The response characteristic of the protection demodulation means belonging to the protection line, wherein the response characteristic of the compensation degree signal output from the distortion compensation amount monitoring unit of the working demodulation means belonging to each of the plurality of working lines is The distortion compensation amount is determined according to a compensation degree signal having a maximum value.
The communication system according to claim 7.