JPS5858859B2 - Line identification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line identification system for received signals in a plurality of PCM signal transmission lines.

Since PCM signal transmission using a carrier wave is modulated by a digital signal, it has the advantage of strong resistance to interference noise. We are trying to make effective use of frequency bands.

In such signal transmission in the same frequency band, if the received signal from the regular line is cut off, the signal from another line using the same carrier wave will be received, so in reality the line is Since there is a possibility that the receiving side cannot detect a fault even though it is a fault, a line identification function is required to identify whether or not the received signal is from a legitimate line.

Conventionally, as a line identification method for such transmission paths, a pilot pulse insertion method has been used in which different distinguishable pilot patterns are inserted into the baseband PCM signal on the transmitting side and identified by monitoring them on the receiving side. be.

Furthermore, in the case of transmission using signals of four or more values, such as four-phase phase modulation, there is also a method in which different pilot patterns are not necessarily inserted into the PCM signal of each line.

That is, in order to perform multilevel modulation of a carrier wave using a PCM signal to be transmitted, the PCM signal requires serial-parallel conversion, and when inserting a pilot pattern into each of the serial-parallel converted parallel PCM signals. This is because, by distinguishing the combinations of the relative phases and polarities of the inserted pilot patterns, the signals of each line can be given distinctiveness.

However, the conventional method for monitoring pilot pattern insertion as described above requires a pilot pattern generation circuit and an insertion circuit on the transmitting side, and a pilot pattern generation circuit, a pilot pattern detection circuit, and a removal circuit on the receiving side equipment. The configuration becomes complex and expensive.

An object of the present invention is to transmit a series of PCM signals that are input signals to a device on the transmission line transmitting side with respect to the transmission of a PCM signal using a multilevel code of four or more values.
The frame synchronization pulse of the CM signal (this frame synchronization pulse is, for example, a frame synchronization pulse for demultiplexing in carrier terminal equipment) has a pattern of 2 bits or more, and this synchronization pulse is transmitted over the transmission line. When the serial-to-parallel conversion operation in the side equipment does not cause concentration on one line of the parallel PCM signals, a line identification method and device with an extremely simple device configuration that does not require the pilot pattern insertion supervision operation as in the conventional system is proposed. This is what we provide.

According to the present invention, in a line in which a serial PCM signal having a frame synchronization pattern of multiple bits is converted into a parallel PCM signal and transmitted as a multilevel signal, the relative phase shift amount and polarity of the parallel PCM signal can be determined on the transmitting side. Transmit the multilevel signal with line identification through signal conversion using at least one of the selected signals, and detect the frame synchronization pattern by performing conversion complementary to the signal conversion on the receiving side. Thus, a line identification system is obtained which is characterized by distinguishing between signals from a regular line and signals from other lines on a transmission path.

An embodiment of the line identification method according to the present invention will be described in detail below with reference to the drawings.

That is, FIG. 1 shows a block diagram of a device configuration according to an embodiment of the line identification system according to the present invention, particularly in the case of four-level PCM signal transmission having a serial-to-two-column conversion circuit, where a indicates a transmission line transmitting side device, and b indicates a transmission line transmitting side device. Shows the transmission line receiving side device.

Figure 2 is a PC used to explain the principle of the method shown in Figure 1.
The figure shows a time chart of an M signal, and particularly shows an example of a time chart of a PCM signal when input signals on the transmission line transmission side have a 2-bit frame synchronization pattern in adjacent time slots.

Now, in FIG. 1a, a PCM signal 16 having a frame synchronization pulse as shown in FIG. 2a is converted by the serial-to-parallel conversion circuit 11 into two lines of PCM signals 17 and 18 having a time chart as shown in FIG. .

In this embodiment, as shown in FIG. 2a, frame synchronization pulses F1. i and F2. i is separated by the serial-to-parallel conversion operation as shown in FIG. 2 without concentrating on a particular pulse train of the parallel PCM signal.

Parallel PC with frame sync pulses separated in this way
The M signals 17 and 18 are processed by delay circuits 12 and 13 having a predetermined delay time of bits, and the relative phase between the parallel PCM signals is changed as shown in FIG. 2C.
converted to 20.

The main PCM signals 19, 20 are used as signals PCM1. It becomes PCM221.22.

On the receiving side of the transmission line, the PCM signals 36 and 37 in FIG. 1 obtained by demodulating the carrier wave are polarized by a polarity selection circuit 3L32.

This polarity conversion is performed by the transmitting side polarity selection circuit 14 in FIG. 1a.
This is performed to cancel the polarity conversion by 15.

Thus, by 3L32 the signal 19.20 at the transmitter
A signal 38,39 with the same polarity as is recovered.

The PCM signal 38.39 has the same relative phase as 17.18 of FIG. 1a, as shown in FIG. signal 40.41.

Furthermore, the main signal 40.degree. 41 is converted by the parallel-to-serial conversion circuit 35 into a signal 42 having the same frame synchronization pulse as the transmitting side serial PCM signal 16 shown in FIG. 2a.

If the transmitting and receiving sides have completely complementary relative phase and polarity selection circuits for parallel PCM signals converted from serial to parallel in this way, the serial PCM pulse train on the receiving side will reproduce the correct frame synchronization pattern. This enables the receiving device to establish frame synchronization of this signal.

If the combination of relative phase and polarity of this serial-parallel converted parallel signal is differentiated for each line in a transmission line using the same frequency band, complementarity will not be satisfied on the receiving side.When receiving signals from other lines. , the frame synchronization pattern of the parallel-to-serial converted serial signal does not match the frame synchronization pattern of the transmitting side serial signal, making it impossible to establish frame synchronization on the receiving side, and thus the received signal differs from the normal received signal. This makes it possible to identify the line.

In the above explanation, signal conversion is performed by combining the relative phase of the output signal 17.18 by the serial-parallel converter 11, the amount of phase shift by the delay circuit 12.13, and the polarity selection by the polarity selection circuit 14.15. It is clear that the object of the present invention can be achieved more simply by converting the signal using at least one of them and transmitting it from the transmitting device.

In this case, it is clear that the receiving device only needs to use circuits that are complementary to the transmitting device.

The system of the present invention having the line identification function as explained above can easily implement the delay circuit and polarity selection circuit required to add the line identification function to the transmission signal using a normal digital IC. This method has the advantage that the configuration of the device can be significantly simplified compared to a method of inserting a pilot pattern into a transmission signal, such as the above method.

[Brief explanation of the drawing]

1A and 1B are block diagrams showing an embodiment of the line identification system according to the present invention, and FIG. 2 is a time chart of PCM signals for explaining the principle of the line identification system shown in FIG. 11: Series-parallel conversion circuit; 12, 13, 33° 34:
Delay circuit; 14, 15, 31. 32: Polarity selection circuit: 3
5: Parallel-serial conversion circuit.

Claims (1)

[Claims] 1 Serial P with multi-bit frame synchronization pattern
In a line that converts a CM signal into a parallel PCM signal and transmits it as a multilevel signal, the transmission side converts the parallel PCM signal by signal conversion using at least one of the relative phase, phase shift amount, and polarity selection. The multilevel signal is transmitted with line identification, and the receiving side performs conversion complementary to the signal conversion to detect the frame synchronization pattern and distinguish it from the signal from the regular line on the transmission path. A line identification method that distinguishes signals from lines.