JPH03244238A - Multiple stuff conversion device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stuff multiplex conversion device that performs transmission at a constant stuff rate regardless of frequency fluctuations of low-order group signals.

[Conventional technology]

Figure 2 shows, for example, ``Easy Digital Transmission'' (Showa 5).
Figure 1 is a block diagram showing a conventional staff multiplex conversion device shown in April 1999, published by Ohmsha Co., Ltd., P. 108).
In the figure, 1 is the transmitting device, 2 is the receiving device,
Reference numeral 3 denotes a transmission line connecting the transmitting device 1 and the receiving device 2.

In the transmitter 1, 11 is a buffer memory into which data signals of low-order group signals input from the outside are written in accordance with a clock signal WC of the low-order group signals. 12
is a multiplexing circuit that reads out the data signal from the buffer memory 11 in accordance with the read clock signal RC, multiplexes the synchronized data signal d, and sends the generated high-order group signal to the transmission line 3. Reference numeral 13 denotes a high-order group oscillator that supplies the multiplexing circuit 12 with a clock signal CK that is the basis of the read clock signal RC. 14 compares the phase of the clock signal WC for writing the data signal to the backup memory 11 and the phase of the read clock signal RC for the multiplexing circuit 12 to read the synchronized data signal d from the buffer memory 11, and based on the comparison result. This is a phase comparator that generates a stuffing request signal in response to the stuff request signal.

In the receiving device 2, a demultiplexing circuit 21 demultiplexes the high-order group signal and the synchronized data signal d received from the transmitting device 1, and generates a write clock signal WC. 22 is a synchronized data signal d demultiplexed by the separation circuit 21 according to the write clock signal WC.
is stored in the buffer memory and read out as a data signal of the lower order group signal according to the read clock signal RC. 23 is a phase comparator that compares the phase of the write clock signal WC of the buffer memory 22 and the read clock signal RC; 124 is this phase comparator 2;
This is a low-pass F-wave filter that filters the output signal of No. 3.

25 receives the output signal of the phase comparator 23 filtered by the low frequency filter 24, and
This is a voltage controlled oscillator whose oscillation frequency is controlled by the voltage value of the signal from 4, and its oscillation output is supplied to the buffer memory 22 as the read clock signal RC.

Next, the operation will be explained. Here, in such a stuff multiplex conversion device, the low-order group signals to be multiplexed usually consist of a plurality of channels, but for the sake of simplicity, only a single channel is illustrated here.

When an external low-order group signal is input to the transmitter 1, the data signal of the low-order group signal is temporarily stored in the buffer memory 11 in accordance with the clock signal WC. On the other hand, the multiplexing circuit 12 receives the clock signal CK generated by the high-order group oscillator 13 and sends the read clock signal RC generated based on this clock signal CK to the buffer memory 11. The data signal stored therein is read out from the buffer memory 11 as a synchronized data signal d in accordance with the read clock signal RC, and the multiplexing circuit 12 multiplexes the read synchronized data signal d and performs 7-raming. and sends it out to the transmission line 3 as a higher-order group signal.

Here, when the clock signal WC of the low-order group signal and the read clock signal RC from the multiplexing circuit are asynchronous, in order to read the low-order group signal of each channel without omission, the frequency of the read clock signal RC must be set as follows. It is necessary to make the frequency as high as the sum of the frequencies of the clock signals WC of the low-order group signals of each channel. However, when such frequency settings are made, the phases of the clock signal WC for writing and the clock signal RC for reading from the buffer memory 11 gradually approach each other, creating the possibility that the same data signal will be read twice. Therefore, the phases of both are constantly monitored by the phase comparator 14, and when the phase difference approaches a preset prescribed phase difference, the phase comparator 14 outputs the stuffing request signal S.
Generate T.

When the multiplexing circuit 12 receives the stuff request signal ST, it executes stuff ink and makes one pulse of the read clock signal RC supplied to the buffer memory 11 to prevent the data signal from being read twice.

When the receiving device 2 receives the higher-order group signal from the transmission path 3, the demultiplexing circuit 21 demultiplexes the synchronized data signal d of each channel and outputs the demultiplexed signal to the buffer memory 22. At the same time, this separation circuit 21 generates a clock signal synchronized therewith and supplies it to the buffer memory 22 as a write clock signal WC. The synchronized data signal d is temporarily stored in the buffer memory 22 in accordance with the write clock signal RC, and is sequentially read out in accordance with the read clock signal RC generated by the voltage controlled oscillator 25. The read data signal is sent to the outside as a low-order group signal together with the read clock signal RC.

On the other hand, the phase comparator 23 compares the phases of the write clock signal WC and the read clock signal RC of the buffer memory 22, and sends the comparison result to the voltage controlled oscillator 25 via the low-frequency p-wave generator 24.

The voltage controlled oscillator 25 oscillates at a frequency corresponding to the voltage value of the output signal of the low-frequency F wave generator 24, and generates the read clock signal RC. The phase-locked loop (PLL) formed by the phase comparator 23, the low-frequency F wave generator 24, and the voltage-controlled oscillator 25 continuously outputs the destuffed write clock signal WC. The read clock signal RC is sent to the buffer memory 22.

Here, the stuff ink in the transmitting device 1 is determined by the frequency difference between the write clock signal WC and the read clock signal RC of the buffer memory 11. The larger the frequency difference, the more stuff ink is used. In addition, the receiving device 2 detects the stuffed ink and performs destuffing, but when the destuffing is performed, the write clock signal WC to the buffer memory 22 becomes an incomplete clock signal. becomes. Therefore, jitter generally occurs in the read clock signal RC of the buffer memory 22 that is synchronized with the write clock signal WC.

This jitter amount and frequency are determined by the frame structure, stuff rate,
It is known that it varies depending on the circuit configuration, etc.

FIG. 3 is an explanatory diagram showing the relationship between the amount of jitter and the stuff rate. As shown in the figure, the amount of jitter changes spot-wise with respect to fluctuations in the stuffing rate.

[Issues that Hikata tries to solve]

Conventional stuff multiplexing converters are configured as described above, so even if the stuffing rate is set in advance to a point with a small amount of jitter, the stuffing rate will change when the frequency of the low-order group signal changes. This poses a problem in that the amount of jitter increases, making it difficult to perform stable communication.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a stuff multiplex conversion device that can perform stable communication even when the frequency of a low-order group signal fluctuates.

[Means to solve the problem]

The stuff multiplex conversion device according to the present invention includes a transmitting device that includes:
The stuffing rate is detected based on the phase comparison result of the phase comparator, the detected stuffing rate is compared with a preset reference value, and the output frequency of the high-order group oscillator is controlled based on the comparison result. It is equipped with a stuff rate detection circuit.

[Effect]

The stuffing rate detection circuit according to the present invention detects changes in the stuffing rate due to frequency fluctuations of low-order group signals from the phase comparison result of the phase comparator of the transmitting device, and sets the detected stuffing rate to a preset reference value. If the two are different, the output frequency of the high-order group oscillator is adjusted to maintain a constant stuffing rate, so that even if the frequency of the low-order group signal fluctuates, the stuffing rate does not change. To realize a stuff multiplex conversion device capable of performing stable communication without changing the amount of jitter.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a transmitting device, 2 is a receiving device, 3 is a transmission line, 11.22 is a buffer memory, 13 is a high-order group oscillator,
12 is a multiplexing circuit, 14.23 is a phase comparator, 21 is a separation circuit, 24 is a low-frequency F-wave generator, and 25 is a voltage controlled oscillator. Since this is a considerable portion, detailed explanation will be omitted.

Reference numeral 15 is located in the transmitting device 1, and detects a stuffing rate due to frequency fluctuation of the low-order group signal based on the phase comparison result of the phase comparator 14, and compares the stuffing rate with a preset reference value. In comparison, when the standard value is large, the output frequency of the high-order group oscillator 13 is lowered, and when it is small, the output frequency of the high-order group oscillator 13 is increased, thereby controlling the stuffing rate to be constant.

Next, the operation will be explained. Since the basic operation is the same as the conventional case shown in FIG. 2, the operation of the stuff rate detection circuit 15 will be mainly explained.

As a result of the phase comparison between the writing clock signal WC and the reading clock signal RC of the buffer memory 11 by the phase comparator 14, when the phases of the two gradually approach each other and become less than a preset prescribed phase difference, the multiplexing circuit 12 At the same time, the stuffing request signal ST is also input to the stuffing rate detection circuit 15. The stuffing rate detection circuit 15 detects the stuffing rate based on the inputted stuffing request signal ST, and compares the detected stuffing rate with a preset standard stuffing rate. As a result, if the detected stuffing rate is different from the reference stuffing rate, a control signal C8 for controlling the output frequency of the high-order group oscillator 13 is generated and sent to the high-order group oscillator 13.

For example, when the detected stuffing rate is larger than the standard stuffing rate, the control signal C8 is transmitted to the high-order group oscillator 13.
If the detected stuffing rate is smaller than the reference stuffing rate, the output frequency is increased.

Upon receiving this control signal C8, the high-order group oscillator 13 generates a clock signal CK whose frequency is adjusted according to the control signal C8, and supplies it to the multiplexing circuit 12. In this way, even if the frequency of the low-order group signal fluctuates, the frequency of the clock signal CK input to the multiplexing circuit 12 changes to follow the fluctuation, and the read clock signal RC based on it changes.
The data signal stored in the buffer memory 11 is read out, and therefore its stuffing rate is always controlled to be constant.

〔Effect of the invention〕

As described above, according to the present invention, the change in the stuffing rate due to the frequency fluctuation of the lower order group signal is detected based on the phase comparison result of the write clock signal and the readout clock signal on the transmitting device side, and the detected stuffing rate is determined in advance. The configuration is configured to compare the set reference value and adjust the output frequency of the high-order group oscillator if the two differ, so even if the frequency of the low-order group signal fluctuates, the stuffing rate is controlled to be constant. This has the effect of providing a stuff multiplex conversion device that can perform stable communication without changing the amount of jitter.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a stuff multiplexing device according to an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional stuffing multiplexing device, and FIG. 3 is an explanation showing the relationship between the stuffing rate and the amount of jitter. It is a diagram. 1 is a transmitter, 3 is a transmission path, 11 is a buffer memory, 1
2 is a multiplexing circuit, 13 is a high-order group oscillator, 14 is a phase comparator, and 15 is a stuff rate detection circuit. In the diagrams, the same symbols indicate the same or equivalent parts.

Claims (1)

[Claims] a buffer memory in which a data signal of a received low-order group signal is written in accordance with a clock signal of the low-order group signal; and the data signal is read out from the buffer memory in accordance with a read clock signal, multiplexed, and sent to a transmission path as a high-order group signal. a high-order group oscillator that provides the multiplexing circuit with a clock signal that is the basis of the read clock signal, and a phase comparator that compares the phase of the clock signal of the low-order group signal and the read clock signal. In the stuffing multiplex converter having a transmitting device, the transmitting device detects a stuffing rate based on the phase comparison result of the phase comparator, compares the stuffing rate with a preset reference value, and compares the stuffing rate with a preset reference value. A stuff multiplex conversion device comprising a stuff rate detection circuit that controls the output frequency of the high-order group oscillator based on the result.