JPH0225581B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dependent synchronous relay system of a PCM communication system. In particular, one terminal station, the master station, is equipped with a reference timing signal generation circuit, and the other terminal station, the slave station, is configured to operate in synchronization with a timing signal received from the master station through a transmission path. The present invention relates to the configuration of a repeater used in a synchronous relay method.

[Conventional technology]

FIG. 1 is an explanatory diagram showing the principle of a PCM relay system using a dependent synchronization system. That is, between the master station 1 and the slave station 2, there is a downlink 3 through which signals are transmitted from the master station 1 to the slave station 2, and an uplink 4 through which signals are transmitted from the slave station 2 to the master station 1. A relay system is constructed by arranging a regenerative repeater 5 on the lines 3 and 4, which regenerates and repeats signal attenuation that occurs on the way. A plurality of regenerative repeaters 5 are inserted depending on the lengths of the lines 3 and 4, but only one of them is shown in FIG.

The main station 1, which is one terminal station of this relay system, is equipped with a reference timing signal generation circuit 8.
A signal is transmitted from the transmitting circuit 9 to the downlink 3 in synchronization with the timing signal generated by the transmitting circuit 9. In the slave station 2, which is the other terminal station, the signal received from the downlink 3 is equalized and amplified by an equalization circuit 10, and a timing signal is extracted from the output by a timing extraction circuit 11. The transmission line 12 transmits a signal to the uplink line 4 in synchronization with the timing signal extracted by the timing extraction circuit 11.

The signal reaching the main station 1 from the upstream circuit 4 is equalized and amplified by the equalization circuit 15, and a timing signal is extracted from the output signal by the timing extraction circuit 16. The output of the equalization circuit 15 is sent to the elastic memory 17 in synchronization with this timing signal.
Further, in synchronization with the output timing signal of the reference timing generation circuit 8, the written signal is read out from the elastic memory 17.

FIG. 2 is a block diagram of a conventional regenerative repeater. That is, in each regenerative repeater 5, the signals of the lines 3 and 4 are equalized and amplified by the equalization circuits 20 and 21, and the timing extraction circuit 2 is used from the output thereof.
2 and 23, and the transmitting circuits 24 and 23 respectively synchronize with this timing signal.
The device is configured to transmit signals from 25.

[Problem that the invention seeks to solve]

Such a slave synchronization method has the advantage of being inexpensive since it is not necessary to equip the slave station 2 with a reference timing generation circuit, but since the timing signal is repeatedly extracted and reproduced by each regenerative repeater 5, the accompanying There is a drawback that jitters gradually accumulate. Therefore, the slave station synchronization method cannot be used for lines that require a large number of regenerative repeaters.

The present invention aims to improve this problem, and aims to suppress the jitter that is accumulated during regenerative relay using the dependent synchronization method.

[Means for solving problems]

The present invention provides an elastic memory in a regenerative repeater inserted between a master station and a slave station in a slave synchronization system, and synchronizes the timing of an uplink signal with a timing signal with less jitter in a downlink. It is characterized by reading and transmitting signals.

〔Example〕

FIG. 3 is a block diagram of an apparatus according to an embodiment of the present invention. This can be used in place of the regenerative repeater 5 shown in FIG. 1, and by implementing the present invention, there is no change in both terminal stations. The regenerative repeater 5 according to the embodiment of the present invention has the same equalization circuit 20, timing extraction circuit 22, and transmission circuit 24 for the downlink 3 as the conventional device shown in FIG. 2, but for the uplink 4. In this example, an elastic memory 27 is inserted into the output of the equalization circuit 21, and writing is performed in this elastic memory 27 in synchronization with the timing signal extracted by the timing circuit 23. The feature is that the reading is performed in synchronization with the timing signal extracted by.

That is, after the signal on the uplink 4 is equalized and amplified by the equalization circuit 21, it is written into the elastic memory 27 at the timing of the signal. As can be seen in Fig. 1, the timing of this uplink 4 is the one that has been replayed back by the slave station 2, so compared to the timing of the downlink 3, it has been replayed more times and the amount of accumulated jitter is higher. It's also big. The signal written in the elastic memory 27 has less jitter because it is read out in synchronization with the timing signal extracted from the downlink 3 with less jitter. This signal is further sent out from the transmitting circuit 25 to the uplink.

The regenerative repeater 5 configured in this way is connected to the main station 1.
If only one repeater is used at a repeater located approximately in the middle of the line between the regenerative repeater 5 and the slave station 2, the cumulative jitter will be almost at its maximum at the uplink input of this regenerative repeater 5 or the uplink input of the main station 1. However, the size is about half that of the conventional method.

The regenerative repeater of the present invention is not limited to one location between the main station and the slave station of the line, but can be used at a plurality of locations.

〔Effect of the invention〕

As described above, according to the present invention, the accumulation of jitter caused by regenerative relaying of a transmission path can be suppressed to a small level using a PCM relaying system that uses a dependent synchronization system. In particular, if a downlink transmission timing signal with less jitter is used at an intermediate position between the master station and the slave station, the jitter in the timing signal during signal transmission from the slave station to the master station can be reduced.

As a result, signal errors can be reduced, and an economical dependent synchronization method can be applied to long-distance systems.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the dependent synchronization method. FIG. 2 is a configuration diagram of a conventional device. FIG. 3 is a configuration diagram of an apparatus according to an embodiment of the present invention. 1...Main station, 2...Slave station, 3...Down line, 4
...Uplink, 5...Regenerative repeater, 8...Reference timing signal generation circuit, 9...Transmission circuit, 10...
... Equalization circuit, 11 ... Timing extraction circuit, 12
... Transmission circuit, 15 ... Equalization circuit, 16 ... Timing extraction circuit, 17 ... Elastic memory, 20, 21 ... Equalization circuit, 22, 23 ... Timing extraction circuit, 24, 25 ... Transmission circuit, 5
7...Elastic memory.

Claims (1)

[Claims] 1. A master station includes a reference timing signal generation circuit, and means for transmitting a signal to a slave station in synchronization with a timing signal generated by this circuit, and the slave station receives a timing signal from the master station. and means for transmitting a signal to the master station in synchronization with the timing signal, and a plurality of regenerative repeaters are inserted in a transmission path between the master station and the slave station. In the communication system, the regenerative repeater located at least between the main station and the slave station in the regenerative repeater includes a first regenerative repeater that extracts a timing signal from a downlink through which a signal is transmitted from the master station to the slave station. a second timing extraction circuit that extracts a timing signal from an uplink through which signals are transmitted from the slave station to the main station; and a second timing extraction circuit that is inserted into the uplink. A dependent synchronous relay comprising an elastic memory that writes a transmission signal in synchronization with the output timing signal and reads the transmission signal in synchronization with the output timing signal of the first timing extraction circuit. method.