JP3050160B2 - Line quality monitoring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line quality monitoring system and, more particularly, to a primary group digital hierarchy which is asynchronous with each other in a line configuration including an intermediate relay station between a transmitting terminal and a receiving terminal.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line quality monitoring method in a digital multiplexing transmission / reception apparatus that performs time division multiplexing transmission / reception with a key signal as input .

[0002]

2. Description of the Related Art Conventionally, as a line quality monitoring method in a digital multiplex radio transmission / reception apparatus, for example, in a device constituting a reception demodulation system, a frame synchronization signal or a parity signal generated in a frame synchronization stage from a reception demodulated signal. A method of extracting and monitoring is used, for example, based on the monitoring result of the frame synchronization signal and the monitoring result of the parity signal, controlling the wireless device having the backup configuration to switch to the backup configuration. AIS without an auxiliary configuration is an AIS (Alarm Indication) which is an alarm display signal for notifying the occurrence of some trouble.
Signal) signal is output.

Further, in a digital multiplexing transmission / reception apparatus adopting a circuit configuration including an intermediate relay station, when a signal is passed through, separated, and inserted in the intermediate relay station, and a failure occurs in front of the intermediate relay station, The signal set in the through mode is configured to be transmitted to the lower station as an alarm display signal. For example, in the invention disclosed in Japanese Patent Application Laid-Open No. Hei 5-236030, the contents for the purpose of improving the detection time at the time of parity detection described above are described. Further, in the invention disclosed in Japanese Patent Publication No. 62-32664, an AIS signal transmission is described in which an alarm display signal transmission method for preventing a pulse break and an erroneous recognition of an AIS signal is described.

Further, in the invention disclosed in Japanese Patent Application Laid-Open No. 62-299129, in a digital micro multiplex communication system including an intermediate relay station, when a failure occurs in a line between the intermediate relay station and its higher station. However, this document describes a restoring circuit that can extract a signal inserted in the intermediate relay station normally in the lower station if the line between the intermediate relay station and the lower station is in a normal state.

Next, a description will be given of a conventional line quality monitoring method for a digital multiplex transmission / reception apparatus including an intermediate relay station. FIG. 3 is a block diagram showing a configuration of a conventional line quality monitoring system of a digital multiplex transmission / reception apparatus including an intermediate relay station. The line quality monitoring method shown in FIG.
5, an intermediate relay station 217, and a receiving terminal station 224. In the transmitting terminal station 205, a primary group digital hierarchy signal of n columns, which is asynchronous with each other, for example, ch (channel)
The transmission rate converters 203 and 204 each convert the rate of the asynchronous primary-group digital hierarchy signal of two channels 1 and 2 by the well-known stuff synchronization, and the time-converted signal is time-multiplexed by the time-division multiplexing section 201. Divided and multiplexed,
Then, the primary group digital hierarchy signals ch1 and ch
Parity information is added by a parity multiplexing unit 202 to a signal obtained by time-division multiplexing of 2 and transmitted.

[0006] The signal transmitted from the transmitting terminal station 205 is transmitted to the intermediate relay station 217, the frame synchronization of which is ensured by the frame synchronization section 206, the time division multiplexing is separated by the time division separation section 208, and the reception rate conversion sections 210 and 211 convert the signal. Each is destuffed, restored to a primary group digital hierarchy signal of two columns of ch1 and ch2, and output.

In this case, the transmitting terminal station 205 and the intermediate relay station 2
17 and whether the line quality is degraded due to the effects of fading or the like is determined based on the parity detection result by the parity detection unit 207, and when it is determined that the line quality is degraded, The separated signal after time-division separation is A
The AIS control unit 209 performs AIS control for performing IS control and outputting as an AIS signal. Also, the intermediate relay station 217
Then, through transmission in which the main signal is output as it is or insertion transmission in which a new signal is inserted are arbitrarily selected as follows.

For example, when through transmission is selected, AI
The signal subjected to the S control is time-division multiplexed, the parity information is rewritten, and the intermediate relay station 217 to the receiving terminal station 22
4 is transmitted. Such signal transmission to the receiving terminal station 224 is processed through the selection unit 214A and the selection unit 214B, the time division multiplexing unit 215, and the parity calculation unit 216. On the other hand, for example, the transmitting terminal station 205 and the intermediate relay station 217
When the insertion transmission is selected in order to grasp the deterioration of the line quality of the data transmission route between the two , a new one of (ch1) and (ch2) is selected.
The next group digital hierarchy signal is transmitted to the transmission rate converter 2
After the stuff synchronization is ensured by the selectors 12 and 213, the stuff is selected by the selectors 214 A and 214 B and transmitted to the receiving terminal 224 through the time division multiplexer 215 and the parity calculator 216.

In the receiving terminal station 224, the frame synchronization is performed by the frame synchronization section 21 in the same manner as in the receiving system of the intermediate relay station 217.
8, the signal is time-division-separated by the time-division separation unit 220, AIS control is performed based on the parity detection result by the parity detection unit 219, and the reception rate conversion unit 222,
In 223, the stuff synchronization is performed, and the primary group digital hierarchy signals (ch1) and (ch2) are restored and output.

[0010]

The above-described conventional line quality monitoring method for signal transmission in a digital multiplex transmission / reception apparatus including an intermediate relay station has the following problems. The first problem is described in, for example,
As in the case of the invention described in JP-A-99129,
In the IS signal transmission system, if slight deterioration of the line quality continues so as not to be judged as a line failure,
This means that the receiving terminal station determines that there is no abnormality in the line quality even though the main signal contains a failure of the line quality deterioration.

The reason is that the line quality of the main signal gradually deteriorates in each section during multi-stage transmission. And a so-called DSC (Digital Service Channel) bit is rewritten, which allocates a desired auxiliary signal to this gap.
This is because the parity bit is rewritten each time, so that it is determined to be normal in the case of a slight line failure.

The second problem is that in order to solve the first problem described above, a circuit becomes complicated in configuring a frame format. The reason is that, when performing time division multiplexing, it is necessary to allocate parity information dedicated to the transmitting terminal station and parity information dedicated to the intermediate relay station on a frame format.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and in a line quality monitoring system for a digital multiplex radio transmission / reception apparatus, to ensure reliable line quality monitoring even if a radio line failure occurs twice or three times. And to provide a line quality monitoring method that can ensure both of the above and the simplification of the device configuration.

[0014]

The present invention has the following means in order to achieve the above object. That is, the first configuration of the present invention relating to the line quality monitoring system is a time-division multiplexing method in which n columns of a primary group digital hierarchy signal that are asynchronous with each other are speed-converted by stuff synchronization and parity information as line quality monitoring information is added. Monitoring the line quality in a system configuration including an intermediate relay station between a transmitting terminal and a receiving terminal of a digital multiplex transmission / reception apparatus for performing radio transmission by performing conversion on every n columns of a primary group digital hierarchy signal. This is a characteristic line quality monitoring method, and has the following configurations (a) to (c). (A) A transmission rate conversion unit for n columns, which performs rate conversion of n columns of primary group digital hierarchy signals that are asynchronous with each other by a stuff synchronization method, and line quality monitoring information for every n columns of the primary group digital hierarchy signals A parity multiplexing unit for n columns for adding parity information as
A transmitting terminal station having a time-division multiplexing unit for performing parallel / serial conversion on the n-column output signal of the parity multiplexing unit for the columns and time-division multiplexing and transmitting related information such as frame information; A frame synchronization section for extracting frame synchronization information from an output signal of the time division multiplexing section of the terminal station to establish frame synchronization, and time-division-multiplexing the signal time-division multiplexed at the transmitting terminal station based on the frame synchronization information. A time division demultiplexing unit that separates the signal into n columns, a parity detection unit for n columns that detects parity information added at the transmitting terminal from the signal separated into n columns by the demultiplexing unit and determines the line quality. A reception speed conversion unit for n columns that restores the signal separated into n columns by the time division separation unit into a primary group digital hierarchy signal by destuffing synchronization, and a parity determination result for n columns of the parity detection unit To An AIS control unit for n columns that performs AIS control for outputting a primary group digital hierarchy signal restored by the reception speed conversion unit and outputting an AIS signal that is an alarm display signal when a line abnormality occurs, AIS
A transmission rate conversion unit for n columns which converts the rate of n columns of a newly input asynchronous primary digital hierarchy signal to provide an output at the time of signal output by a stuff synchronization method; A parity multiplexing unit for n columns for adding parity information as line quality monitoring information to an output of the conversion unit, a signal separated by the time division demultiplexing unit, and an output signal of the parity multiplexing unit for the n columns And a time-division multiplexing unit that performs parallel / serial conversion on the signal selected by the selection unit, time-division multiplexes related information such as frame information, and sends out as an n-column output signal. (C) a frame synchronization section for extracting frame information from an output signal of the time division multiplexing section of the intermediate relay station to establish frame synchronization, and the frame synchronization information A time-division multiplexing unit that separates the time-division multiplexed signal in the intermediate relay station based on the time division multiplexing and sends out as an n-sequence signal; and detects the parity information of the n-sequence signal separated by the time-division multiplexing unit. A parity detector for n columns for determining channel quality, and reception for n columns for restoring the n column signals separated by the time division demultiplexer into n columns of primary group digital hierarchy signals by destuffing synchronization. A speed conversion unit, and outputs a primary group digital hierarchy signal of n columns restored by the reception speed conversion unit based on a parity determination result of the parity detection unit for the n columns, and an alarm display signal when a line abnormality occurs AIS
A receiving terminal station having AIS control units for n columns for performing AIS control for outputting a signal

According to a second aspect of the present invention, in the first aspect, the line quality is monitored in a digital multiplex transmission / reception apparatus in which the intermediate relay station and the transmitting and receiving end stations are based on the same apparatus. Things.

According to a third configuration of the present invention, in the first or second configuration, the line quality is monitored in a digital multiplex transmission / reception device having a configuration in which the intermediate relay stations are connected in multiple stages.

[0017]

Next, embodiments of the present invention will be described with reference to the drawings. Referring to FIG. 1, in the first embodiment of the present invention, a digital multiplex radio system is roughly composed of a transmitting terminal station 106, an intermediate relay station 121, and a receiving terminal station 130. Next, the internal configuration will be described. First, the transmission terminal station 106 transmits two rows of primary-group digital hierarchy signals asynchronous to each other as an example, and as an example, the transmission rate conversion for converting the primary-group digital hierarchy signal ch (channel) 1 by stuff synchronization. And a parity multiplexing unit 1 that performs parity operation on an output signal of the transmission rate conversion unit 104 and multiplexes parity information.
02 and a transmission rate conversion unit 105 that converts the rate of the primary group digital hierarchy signal ch2 asynchronous with the primary group digital hierarchy signal ch1 by stuff synchronization.
And a parity multiplexing unit 103 for performing parity calculation on the output signal of the transmission rate conversion unit 105 and multiplexing the parity information, a parity multiplexing unit 102, and a parity multiplexing unit 103. And a time division multiplexing unit 101 for performing time division multiplexing of bits and the like.

The inside of the intermediate relay station 121 is roughly divided into a receiving system and a transmitting system. The receiving system includes a frame synchronization unit 10
7, a time-division demultiplexing unit 108 for returning the time-division multiplexed signal on the transmission side of the upper station to the original parallel signal sequence, a parity detection unit 109 for detecting the parity of the primary group digital hierarchy signal ch1, A reception rate conversion unit 111 for converting the rate by destuffing synchronization of the primary group digital hierarchy signal ch1, and an AIS based on a parity detection result.
AIS control unit 113 for controlling, parity detection unit 110 for detecting parity of primary group digital hierarchy signal ch2, primary group digital hierarchy signal c
It is provided with a reception speed conversion unit 112 that converts the speed by destuffing synchronization of h2, and an AIS control unit 114 that performs AIS control based on the parity detection result.

The transmission system is the same as the asynchronous channels ch1 and ch2 newly inserted from the intermediate relay station 121.
A transmission rate converter 115 for converting the rate of the next group digital hierarchy signal (ch1) by stuff synchronization in the same manner as in the transmission terminal station 106, and a transmission rate converter 115
And a parity multiplexing unit 117 that multiplexes parity information by performing a parity operation on the output signal of the first group and a transmission that converts the rate of a primary group digital hierarchy signal (ch2) asynchronous with the primary group digital hierarchy signal (ch1) by stuff synchronization. A rate conversion section 116, a parity multiplexing section 118 for performing parity calculation on the output signal of the transmission rate conversion section 116 and multiplexing parity information, and transmitting the separated signal from the time division demultiplexing section 108 as it is as it is, Selection sections 119A and 119B for selecting whether to insert the signal of section 117 and parity multiplexing section 118, through or insertion
And the signals selected by the selection units 119A and 119B
06, and a time division multiplexing unit 120 for time division multiplexing.

The internal configuration of the receiving terminal station 130 includes a frame synchronizing unit 122 similar to the receiving system of the intermediate relay station 121,
A time division demultiplexing unit 123 that demultiplexes and returns the time division multiplexed signal on the transmission side, a parity detection unit 124 that detects the parity of the signal on the first column side of the time division demultiplexing unit 123, The reception speed conversion unit 126 that converts the speed of the signal on the first column side by destuffing synchronization, the AIS control unit 128 that performs AIS control based on the parity detection result, and the parity of the signal on the second column side of the time division separation unit 123 A parity detection unit 125 for detecting, a reception speed conversion unit 127 for converting the speed by destuffing synchronization of the signal on the second column side of the time division separation unit 123, and an AIS control unit 129 for performing AIS control based on the parity detection result. It is composed.

The digital multiplexing transmission / reception apparatus including the transmitting terminal, the intermediate relay station, and the receiving terminal as described above allows the digital multiplexing transmission / reception apparatus to determine the parity due to the difference in the data transmission route between the stations.
It is a basic feature of the present invention that based on the difference between the errors, the line quality can be reliably monitored even if the radio line failures occur repeatedly, and the simplification of the system configuration can be ensured.

[0022]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of a line quality monitoring system according to the present invention, and FIG. 2 is a diagram showing a frame configuration in the embodiment of FIG. First, the transmitting terminal station 106
Will be described. As the primary group digital hierarchy signals ch1 and ch2 as input signals, primary group digital hierarchy signals of, for example, 1.544 Mbps (hereinafter referred to as 1.5M signal) which are asynchronous with each other are input (ch1 and ch2 in FIG. 2). ch2). The input 1.5M signal is subjected to rate conversion by well-known stuff synchronization in transmission rate conversion sections 104 and 105, and parity bits are multiplexed in parity multiplexing sections 102 and 103 on the signals after the rate conversion (FIG. 2a, b). Parity multiplexer 10
The output signals 2103 are subjected to parallel / serial conversion in the time division multiplexing unit 101, and are output with frame information added thereto (c in FIG. 2).

Next, the operation of the intermediate relay station 121 will be described. The output signal of the transmitting terminal station 106 is
Are received (d in FIG. 2), frame synchronization is established by the frame synchronization unit 107, and serial / parallel conversion is performed by the time division separation unit 108 (e and f in FIG. 2). The parallel-converted signal is further branched into a through transmission signal and a separated output signal, respectively, and the through signal is divided into selectors 119A and 119B.
And the separated output signals are sent to the parity detectors 109 and 110.
Connected to The separated output signals that have been time-divided and split into two branches are passed through parity detectors 109 and 110 and received by the receiving speed converters 111 and 112 to be speed-converted by destuffing synchronization and restored to 1.5 M signals.

The reconstructed 1.5 M signal is sent to the AIS control units 113 and 114 by the parity detection unit 1 described above.
Control is performed on whether or not to use an alarm display signal (AIS signal) based on the respective determination results of 09 and 110, and the signal is output. In the intermediate relay station 121, (ch1), (ch
As 2), similarly to the transmitting terminal station 106, the same 1.5M asynchronous signal as ch1 and ch2 can be newly input.

The operation is the same as that of the transmitting terminal station 106. The transmission rate conversion sections 115 and 116 perform rate conversion, and the parity multiplexing sections 117 and 118 add parity, respectively. Then, the selectors 119A and 119B select the two-way split through signal of the time-division separator 108 or newly input (ch1),
(Ch2) is speed-converted and parity information is added, and either one of the signals (hereinafter referred to as an insertion signal) is arbitrarily selected, connected to the time division multiplexing section 120, and transmitted to the transmission terminal station 106.
Similarly, parallel / serial conversion is performed, and frame information is added to the output of the intermediate relay station 121.

Next, the operation of the receiving terminal station 130 will be described.
Upon receiving the output signal of the intermediate relay station 121, the intermediate relay station 12
1, the frame synchronization is established by the frame synchronization unit 122, and the time division separation unit 123 performs serial / parallel conversion. The signal converted into the parallel data is connected to parity detection units 124 and 125, and the parity detection units 124 and 125
The signal is converted to a 1.5M signal by the destuffing synchronization in the reception speed conversion units 126 and 127 after passing through 125. The restored 1.5M signal is sent to the AIS controllers 128 and 129 by the parity detectors 124 and 12.
According to the respective determination results of 5, the control is performed as to whether or not to generate an alarm display signal (AIS signal), and the signal is output.

Here, the selector 119 of the intermediate relay station 121
A case where A and B are used for insertion signal (ch1, ch2) selection will be described. Now, the transmitting terminal station 106 and the intermediate relay station 1
In the line between the relay station 21 and the relay station 21, when a severe line quality is deteriorated due to fading or the like and an error occurs in the bit of the “x” part as shown in FIG. The .5M signal is determined as an AIS signal output by the parity detection units 109 and 110, and the AIS control units 113 and 1
The AIS control is performed at 14, and the output signals of ch1 and ch2 at the intermediate relay station 121 become AIS signal outputs.

Then, in the intermediate relay station, (ch1) and (ch2) are newly inserted as 1.5M signals (g and h in FIG. 2). The inserted 1.5M signal is transmitted to the transmitting terminal 1
As in the case of 06, the data is subjected to speed conversion, parity is added, parallel / serial conversion is performed, and frame information is added and transmitted from the intermediate relay station 121.

Here, the intermediate relay station 121 and the receiving terminal station 13
If there is a slight degradation in the line quality between the transmission end station 106 and the intermediate relay station 121 between 0 and 0 (only the bits in the “y” portion cause an error as shown in i of FIG. 2). At the receiving end station)
5 is judged to be normal line quality, and 1.5 without AIS control.
Output M signal. This operation itself is the same in the conventional system.

Next, the selector 119 of the intermediate relay station 121
A case where A and B are used for through signal selection will be described. When severe line quality degradation occurs due to fading or the like in the line between the transmitting terminal station 106 and the intermediate relay station 121 and an error occurs in the bit of the “x” portion as shown in FIG. The 1.5M signal output from the station 121 is determined to be an AIS output by the parity detectors 109 and 110, and the AIS controller 113 and 114 determines the AIS output.
Control is performed and the AIS signal is output. On the other hand, the transmission signal from the intermediate relay station 121 is the same signal as that of d in FIG. 2 since the through signals are selected and transmitted by the selection units 119A and 119B.

Further, the intermediate relay station 121 and the receiving terminal station 13
In the case where a slight line failure occurs until AIS does not occur between 0 and 0, the transmission signal from the intermediate relay station 121 is j in FIG. Is sent as is. Here, the intermediate relay station 121
As shown in FIG. 2J, the receiving terminal station 130 receives the bit error of the “x” part and the bit error of the “y” part between the receiving terminal station 130 and the receiving terminal station 130, and performs parity detection. The units 124 and 125 determine that there is a line failure and control the AIS control units 128 and 129 to output AIS signals.

In this case, if the selection units 119A and 119B in the intermediate relay station 121 select the insertion signal,
Since only the bit error of “y” is received as shown in i of FIG.
Is output as a slight bit error without considering this as a line fault.

In this manner, the line quality of a digital transmission / reception system that includes a transmitting terminal station, an intermediate relay station, and a receiving terminal station and transmits / receives an n-column primary-group digital hierarchy signal is improved. By monitoring every n columns, each input signal has a parity for each of the n columns of the primary hierarchy digital hierarchy signal sequence, so the intermediate relay station converts the transmission signal into an AIS signal and then transmits it. Since transmission is possible without any problem, the intermediate relay station device and the terminal station device have the same functional configuration, and the parity bit handled by the intermediate relay station and the parity bit handled by the terminal station do not need to be separated. Thus, the device configurations of the terminal station and the intermediate relay station can be secured.

Also, the parity bits added by the transmitting terminal are transmitted to the receiving terminal without being rewritten in the middle of the system. Therefore, when a system in which intermediate relay stations are connected in multiple stages is used, the line quality is simultaneously measured in each section. Even if deterioration occurs, the line quality can be monitored accurately at the receiving terminal station.

Since the circuit configuration for securing the above-mentioned features is extremely simplified, the circuit scale itself is somewhat increased, but by forming a chip using an LSI, the above-described enlargement itself can be achieved. It can be fully compressed.

[0036]

As described above, the present invention monitors the transmission line quality of n columns of primary group digital hierarchy signals transmitted and received between the transmitting terminal and the receiving terminal, including the intermediate relay station, every n columns. Thereby, the following effects can be obtained. The first effect is that the parity bit handled by the intermediate relay station and the parity bit handled by the terminal station do not need to be separated, so that the device configuration of the terminal station and the intermediate relay station can be taken by the same device. The reason is that the input signal, which has a parity for each of the n columns of the primary group of digital hierarchy, can be transmitted without converting the transmission signal into an AIS signal at the intermediate relay station and transmitting it. Therefore, the intermediate relay station device and the terminal station device can be configured with the same functional configuration.

A second effect is that, when a system is configured in which intermediate relay stations are connected in multiple stages, even if line quality is simultaneously degraded in each section, the line quality can be monitored accurately at the receiving terminal station. The reason is that the parity bits added by the transmitting terminal are transmitted to the receiving terminal without being rewritten in the middle of the system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a line quality monitoring method according to the present invention.

FIG. 2 is a diagram showing a frame configuration for explaining the operation of the embodiment of FIG. 1;

FIG. 3 is a block diagram showing a configuration of a conventional line quality monitoring method.

[Explanation of symbols]

 101, 201 time division multiplexing section 102, 103, 202 parity multiplexing section 104, 105, 203, 204 transmission rate conversion section 106, 205 transmission terminal station 107, 206 frame synchronization section 108, 208 time division separation section 109, 110 , 207 Parity detector 111, 112, 210, 211 Reception rate converter 113, 114, 209 AIS controller 115, 116, 212, 213 Transmission rate converter 117, 118 Parity multiplexer 119A, 119B Selector 120, 215 Time division multiplexing unit 121, 217 Intermediate relay station 122, 218 Frame synchronization unit 123, 220 Time division demultiplexing unit 124, 125, 219 Parity detection unit 126, 127, 222, 223 Reception speed conversion unit 128, 129, 221 AIS control Unit 130,224 Receiving terminal station 214A, 214B selector 216 parity calculator

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-319186 (JP, A) JP-A-62-25455 (JP, A) JP-A-2-268037 (JP, A) JP-A-5-265 236030 (JP, A) JP-A-62-299129 (JP, A) JP-A-57-121344 (JP, A) JP-A-2-281834 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) H04J 3/00-3/26

Claims (3)

(57) [Claims] The present invention comprises the following components, and performs time division multiplexing of n columns of a primary group digital hierarchy signal that are asynchronous with each other by stuff synchronization and adding parity information as line quality monitoring information. A line characterized by monitoring line quality in a system configuration including an intermediate relay station between a transmitting terminal and a receiving terminal of a digital multiplex transmitting / receiving apparatus for wireless transmission for every n columns of a primary group digital hierarchy signal. Quality monitoring method. (A) A transmission rate conversion unit for n columns, which performs rate conversion of n columns of primary group digital hierarchy signals that are asynchronous with each other by a stuff synchronization method, and line quality monitoring information for every n columns of the primary group digital hierarchy signals A parity multiplexing unit for n columns for adding parity information as
A transmitting terminal station having a time-division multiplexing unit for performing parallel / serial conversion on the n-column output signal of the parity multiplexing unit for the columns and time-division multiplexing and transmitting related information such as frame information; A frame synchronization section for extracting frame synchronization information from an output signal of the time division multiplexing section of the terminal station to establish frame synchronization, and time-division-multiplexing the signal time-division multiplexed at the transmitting terminal station based on the frame synchronization information. A time division demultiplexing unit that separates the signal into n columns, a parity detection unit for n columns that detects parity information added at the transmitting terminal from the signal separated into n columns by the demultiplexing unit and determines the line quality. A reception speed conversion unit for n columns that restores the signal separated into n columns by the time division separation unit into a primary group digital hierarchy signal by destuffing synchronization, and a parity determination result for n columns of the parity detection unit To An AIS control unit for n columns that performs AIS control for outputting a primary group digital hierarchy signal restored by the reception speed conversion unit and outputting an AIS signal that is an alarm display signal when a line abnormality occurs, AIS
A transmission rate conversion unit for n columns which converts the rate of n columns of a newly input asynchronous primary digital hierarchy signal to provide an output at the time of signal output by a stuff synchronization method; A parity multiplexing unit for n columns for adding parity information as line quality monitoring information to an output of the conversion unit, a signal separated by the time division demultiplexing unit, and an output signal of the parity multiplexing unit for the n columns A selection unit for arbitrarily selecting any one of the following, and time-division multiplexing for subjecting the signal selected by the selection unit to parallel / serial conversion, time-division multiplexing related information such as frame information, and sending out as an n-column output signal. (C) a frame synchronization unit for extracting frame information from an output signal of the time division multiplexing unit of the intermediate relay station to establish frame synchronization, and the frame synchronization information A time division demultiplexing unit that demultiplexes the time-division multiplexed signal by the intermediate relay station based on the time division and sends out as an n-sequence signal, and detects parity information of the n-sequence signal demultiplexed by the time division demultiplexing unit A parity detector for n columns for determining channel quality, and reception for n columns for restoring the n column signals separated by the time division demultiplexer into n columns of primary group digital hierarchy signals by destuffing synchronization. A speed conversion unit, and outputs a primary group digital hierarchy signal of n columns restored by the reception speed conversion unit based on a parity determination result of the parity detection unit for the n columns, and an alarm display signal when a line abnormality occurs. AIS
A receiving terminal station having AIS control units for n columns for performing AIS control for outputting a signal 2. The system according to claim 1, wherein the intermediate relay station and the transmitting and receiving terminal stations are configured to monitor the line quality in a digital multiplex transmitting / receiving apparatus based on the same apparatus.
Line quality monitoring method described. 3. The line quality monitoring method according to claim 1, wherein the line quality is monitored in a digital multiplexing transmission / reception apparatus having a configuration in which the intermediate relay stations are connected in multiple stages.