JPH0113260B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a two-wire circuit that is inserted into a two-wire line using time-division direction control in which a burst digital signal is transmitted in both directions, and is regenerated and relayed in both directions. Concerning improvements to repeaters.

[Description of prior art]

In digital communication networks, two-wire line transmission using time-division direction control is being considered. For example, this uses a two-wire line as a subscriber line on which burst digital signals are transmitted bidirectionally.A two-wire line is installed between the station equipment and the home equipment, and the station equipment When a digital signal with a burst length of When received, the station device again transmits a digital signal of a predetermined burst length to this two-wire line, and this is repeated to perform two-way communication. If this two-wire line is long and the transmitted signal is attenuated, making reception identification difficult, a repeater is required to relay and amplify the signal transmitted over the line.

FIG. 1 shows a block diagram of a conventional repeater for this purpose. This is JP Andry, et al: A long Burst Time−
shared Digital Transmission System for
Subscriber Loops, ISSLS (International
Symposium on Subscriber Loops and
Service) This was published in a 1980 document.

FIG. 1 shows a state in which two-wire lines 3, 3' are installed between the station equipment 1 and the home equipment 2, and a two-way repeater 4 is inserted between the two-wire lines. In this repeater 4, the upper line connection terminal 11 is connected to the upper side switching circuit 12, and the lower line connection terminal 13 is connected to the lower side switching circuit 14, and these two switching circuits 12 and 14 are indicated by solid lines in FIG. It is configured to perform bidirectional relay by alternately and synchronously switching between the state shown and the state shown by the broken line.

That is, the burst digital signal arriving at the upper line connection terminal 11 is transmitted to the upper line switching circuit 1.
2, is identified and regenerated by the downstream receiving circuit 16, is amplified to the line transmission level by the downstream transmitting circuit 17, and is transmitted to the lower side switching circuit 14.
is transmitted from the transmission terminal T to the lower line connection terminal 13. When this relay transmission in the downstream direction is completed, the control circuit 20 switches the upper side switching circuit 12 to the transmission terminal T.
The lower side switching circuit 14 is connected to the receiving terminal R, respectively.
Switch to the passage indicated by the broken line in the figure, and
The upstream burst-like digital signal temporarily stored in 1 is read out and transmitted from the transmitting circuit 23 to the upper line connection terminal 11. During this time, if a signal arrives at the lower line connection terminal 13, the lower side switching circuit 1
The uplink receiving circuit 24 receives this from the receiving terminal R of 4, performs identification and reproduction, and sends it to the frame synchronization circuit 2.
5, this signal is temporarily stored in the buffer circuit 21.

This operation is shown in the time chart of FIG. 2A to 2D show signals at points A to D shown in FIG. 1, respectively. That is, in this conventional method, when a downlink signal arrives at the upper line connection terminal 11 as shown in FIG. 2B, it is received and regenerated by the receiving circuit 16, and as shown in FIG. 2C. At the same time, the signal is transmitted as a downstream transmission signal from the transmission circuit 17. On the other hand, regarding the upstream signal, as shown in FIG. 2B, when the burst of the downstream reception signal ends, the upstream transmission signal is transmitted after the guard time Tg has elapsed. During this time, as shown in Fig. 2D, the home device 2 transmits the transmission signal after the guard time Tg' has elapsed after the burst of the received signal ends, so in Fig. 2B, the upstream transmission signal is being transmitted. Then, the upstream received signal arrives at the receiving circuit 24.

The level of the signal transmitted by the transmitting circuit 23 is line 3.
This is a high level considering transmission loss. On the other hand, the level of the signal received by the receiving circuit 24 is
This is a signal that has been attenuated on line 3' and is at a low level.
Therefore, the output of the transmitting circuit 23 and the receiving circuit 24
If the output signal of the transmitting circuit 23 leaks into the input signal of the receiving circuit 24 due to a slight wrap-around between the input signal and the input of the receiving circuit 24, noise will be generated in the received signal of the receiving circuit 24. In order to reduce this wraparound, it is necessary to take design considerations into circuit shielding, power circuit division, etc., but there is a limit to reducing this wraparound with repeaters of limited shapes. Therefore, if we try to reduce the influence of noise due to this wraparound, it is impossible to increase the difference between the transmission level of the transmission circuit 23 and the reception level of the reception circuit 24, that is, the relay interval of this repeater 4 cannot be increased. This means that it will not be possible to make it larger.

[Purpose of the invention]

The present invention is an improvement on this, and an object of the present invention is to provide a repeater that is free from the influence of loop-around even if the amount of loop-circuit from the transmitting circuit to the receiving circuit in the repeater is allowed to some extent. That is, the present invention
It is an object of the present invention to provide a bidirectional repeater in which the repeating interval is not restricted due to noise caused by looping within the repeater.

[Features of the invention]

In the present invention, a buffer circuit, which was provided only in the upstream signal circuit in the conventional system, is also provided in the downstream signal circuit, so that when the downstream transmitting circuit transmits a signal, the upstream transmitting circuit also transmits at the same time. When the downstream receiving circuit receives a signal, the upstream receiving circuit also receives the signal at the same time, eliminating the time when the transmitting circuit and the receiving circuit operate simultaneously, thereby eliminating the influence of feedback. shall be.

[Explanation based on examples]

FIG. 3 is a block diagram of a device according to an embodiment of the present invention. A two-wire line 3, 3' made of a pair of metal wires is installed between the station equipment 1 and the home equipment 2, and since the line is long, a bidirectional repeater 4 according to the present invention is inserted approximately in the middle thereof. Indicates the condition. The direction of the station equipment 1 is the upper one, the direction of the home equipment 2 is the lower one,
A signal transmitted from the home device 2 to the station device 1 is an upstream signal, and a signal transmitted from the station device 1 to the home device 2 is a downstream signal.

The two-wire line 3 is connected to an upper line connection terminal 11. This terminal 11 is connected to a common terminal of the upper switching circuit 12. On the other hand, the two-wire line 3' on the lower side
is connected to the lower line connection terminal 13, and this terminal 1
3 is connected to a common terminal of the lower side switching circuit 14. A receiving terminal R of the upper switching circuit 12 is connected to an input of the receiving circuit 16. This receiving circuit 16 has a function of identifying and reproducing received signals. Its output is connected to the input of buffer circuit 26. The readout output of this buffer circuit 26 is led to the input of the transmission circuit 17, and its output is connected to the transmission terminal T of the lower side switching circuit 14. In addition, the lower side switching circuit 14
The receiving terminal R of is connected to the input of the receiving circuit 24,
The output of the receiving circuit 24 is applied to the input of the buffer circuit 21 and the frame synchronization circuit 25. This buffer circuit 21 temporarily stores the output signal of the receiving circuit 24 under the control of the frame synchronization circuit 25.
The contents are read out under the control of the control circuit 20 and supplied to the input of the transmitting circuit 23. Transmission circuit 2
The output of No. 3 is connected to the transmission terminal T of the switching circuit 12 on the upper side.

Here, the feature of the present invention is that between the output of the downstream receiving circuit 16 and the transmitting circuit 17,
A buffer circuit 26 is provided to temporarily store downstream signals, and reading from this buffer circuit 26 and the upstream buffer circuit 21 is performed synchronously by the control circuit 20.

The operation of the apparatus of the present invention will be explained in detail using the time chart shown in FIG. 4A to 4D show signal time charts at points A to D of the apparatus according to the embodiment of the present invention shown in FIG.

When a burst signal is sent to line 3 as shown in Figure 4A, it is delayed on line 3 and is shown in Figure 4B.
The signal arrives at the upper line connection terminal 11 of the repeater 4 as shown in FIG. At this time, the switching circuits 12 and 14 are set to the state shown by the solid line in FIG. 3. This signal is transmitted from the receiving terminal R of the switching circuit 12 to the receiving circuit 1.
6, and the signal is identified and reproduced. The frame synchronization of the output of the receiving circuit 16 is detected by the control circuit 20, and the output is stored in the buffer circuit 26 under the control of the control circuit 20.

After the receiving circuit 16 and the buffer circuit 26 have performed reception writing for one burst signal, the control circuit 20 switches the switching circuits 14 and 12 in the direction shown by the broken line in FIG. When the time Tg has elapsed, the signal temporarily stored in the buffer circuit 26 is read out, and the signal is amplified to the line transmission level in the transmission circuit 17, and as shown in FIG.
from there to the lower connection terminal 13.

The in-home device 2 receives this burst signal as shown in FIG. send a signal. This burst signal is delayed in the line 3' and arrives at the lower line connection terminal 13 of the repeater 4 as an upstream received signal shown in FIG. 4C. At this time, the switching circuits 14 and 12 have been switched to the state shown by the solid line in FIG. Remember. At this time, the station equipment 1 also receives the downlink signal.
The next burst-like signal arrives at the upper line connection terminal 11, is identified and reproduced by the receiving circuit 16, and is stored in the buffer circuit 26.

When the reception of this burst signal is completed, the switching circuits 12 and 14 are again switched to the state shown by the broken line in FIG. It is read out and transmitted from transmission 23 at line transmission level. At the same time, the temporarily stored contents are also read from the buffer circuit 26 and transmitted from the transmitting circuit 17 as described above. By repeating this operation, signals are transmitted and received as shown in FIGS. 4A to 4D.

That is, in the repeater of the present invention, when the downlink receiving circuit 16 is receiving the burst signal, the uplink receiving circuit 24 is also receiving the signal and is performing the reception. During this period, no signals are transmitted from the transmitting circuits 17 and 23. Further, while the downlink transmitting circuit 17 is transmitting a signal, the uplink transmitting circuit 23 is also transmitting, and at that time, the receiving circuits 16 and 2
4 is not received. Therefore, the receiving circuit 2
Even if the output signal of the transmitting circuit 23 is passed around to the input of the input circuit 4, the receiving circuit 24 is not performing a receiving operation at that time, so there is no effect of the running around. As for the receiving circuit 16, since the transmitting circuits 17 and 23 are not operating during the receiving operation, the input of the receiving circuit 16 is not affected by unnecessary noise from the transmitting circuit.

Note that in the diagrams shown in FIGS. 4B and 4C, the upstream and downstream receiving operations and upstream and downstream transmitting operations are depicted as completely matching, but this is due to the fact that this repeater 4 is connected to the station equipment 1 and the home. After device 2 is inserted at an intermediate position, the delays of line 3 and line 3' are equal,
In addition, there is a guard time Tg from when the repeater 4 completes receiving the downlink burst signal to when it starts transmitting the uplink signal, and from when the in-home device completes receiving the signal to when it starts transmitting the next signal. An ideal case is shown in which the guard times Tg' until the start are equal. If the repeater 4 deviates from the intermediate position between the station equipment 1 and the home equipment 2, the upstream reception signal shown in FIG. 4C does not necessarily arrive while the downlink signal shown in FIG. 4B is being received. However, this can be absorbed by appropriately providing a guard time Tg so that the reception timing and transmission timing do not overlap. That is, the installation position of the repeater 4 may be shifted from the intermediate position between the station device 1 and the home device 2 within the range of the guard time Tg setting.

As mentioned above, since the transmitting circuits 17 and 23 do not perform the transmitting operation while the receiving circuits 16 and 24 are receiving, the influence of the wraparound in the repeater of the present invention is reduced to the output of the transmitting circuit with a high signal level. It is no longer necessary to consider the loop-around from the signal to the input of the receiving circuit where the signal level is low, and it is only necessary to consider the mutual loop-around between the two receiving circuits 16 and 24 in the upper and lower directions, both of which have low signal levels. In other words, in the conventional device, there is a level difference of 40 dB between the output level of the transmitting circuit and the input level of the receiving circuit, and if you try to remove the difference from the loop signal by 30 dB,
It used to be necessary to provide the hardware with a 70 dB attenuation, but according to the present invention, the hardware only needs to have a 30 dB attenuation under the same conditions, significantly easing the requirements for hardware design and manufacturing. At the same time, it becomes possible to further increase the difference between the input level of the receiving circuit and the output level of the transmitting circuit, and to design and manufacture an efficient repeater capable of relaying over a long distance.

FIG. 5 is a three-dimensional graph for explaining the effects of the present invention. In FIG. 5, the line loss of the upper line is plotted in the x direction, the line loss of the lower line is plotted in the y direction, and the amount of wraparound attenuation of the hardware is plotted in the z direction. All units are dB. The two planes indicated by hatching are for the conventional device explained in FIG. 1, and the two planes showing dots are for the device according to the present invention explained in FIG. 3.

In the conventional device, for example, if the line loss of both the upper and lower lines is 40 dB,
At point P, which is 40 dB in the x direction and 40 dB in the y direction, the state in which the level of the receiving circuit input signal and the level of the transmitting circuit output signal mixed in due to looping are equal is the amount of hardware looping attenuation. but
Since it is 40 dB, point Q can be obtained by taking 40 dB in the z direction perpendicularly from point P. Assuming that the line loss of both the upper and lower lines is 0 dB, at this time the origin is O, and when the hardware loop attenuation is 0 dB, the signal is mixed in due to the level of the receiving circuit input signal and loop loop. Since the level of the transmitting circuit output signal becomes equal to that of the transmitting circuit output signal, the state where the level of the transmitting circuit output signal mixed in due to looping becomes equal is the origin O. Furthermore, if the line loss of the upper side line is 40 dB and the line loss of the lower side line is 0 dB, the state in which the level of the transmitting circuit output signal mixed into the receiving circuit input by looping is equal to At point T, if the line loss of the lower line is 40 dB and the line loss of the upper line is 0 dB, similarly, the level of the transmitting circuit output signal mixed into the receiving circuit input by looping is equal to The state becomes point U.
Therefore, under the conditions determined by the space below the space divided by the plane OTQ and the plane OUQ, the signal due to wraparound will exceed the level of the received signal.

On the other hand, in the device of the present invention, the state in which the level of the transmitting circuit output signal mixed into the receiving circuit input by loop-around is equal to the level is represented by the plane OTP and the plane OUP, and the state below these two planes is represented by the plane OTP and the plane OUP. For the first time in space, the signal due to wraparound exceeds the level of the received signal. Therefore, the conditions defined in the space between the hatched plane and the dotted plane in FIG. 5 are the area perfected by the present invention.

〔application〕

In the above embodiment, the repeater of the present invention is inserted into the subscriber line between the station equipment and the home equipment, but the present invention is not limited to the subscriber line. It can be implemented as a repeater that is inserted into a two-wire line with time-division direction control transmitted to the network and performs regenerative relay in both directions. The above-mentioned expressions such as upstream or downstream, upper or lower, etc. are for convenience, and the same implementation can be performed even if the directions and connection lines are changed.

The present invention can be implemented in all kinds of two-wire lines, such as a single coaxial line, a single optical fiber, etc., in addition to a line using a pair of metal wires.

〔Effect of the invention〕

As described above, according to the present invention, the influence of noise caused by signal wraparound occurring inside the repeater is significantly improved. According to the present invention, restrictions on the design and manufacture of repeater hardware are relaxed, an economical repeater device can be obtained, and the output level of the transmitting circuit can be made higher than the input level of the receiving circuit. Therefore, it is possible to obtain an economical repeater that can carry out relays with long repeating intervals.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional device. FIG. 2 is a time chart for explaining the operation of the conventional device. Third
The figure is a block diagram of an apparatus according to an embodiment of the present invention. FIG. 4 is a time chart for explaining the operation of the apparatus according to the embodiment of the present invention. FIG. 5 is a three-dimensional graph explaining the effects of the present invention. 11...Upper line connection terminal, 12...Upper side switching circuit, 13...Lower line connection terminal, 14...Lower side switching circuit, 16...Downlink receiving circuit, 17
...Uplink transmission circuit, 20...Control circuit, 21
...Uplink buffer circuit, 23...Uplink transmitting circuit, 24...Uplink receiving circuit, 25...Frame synchronization circuit.

Claims (1)

[Scope of Claims] 1. An upper line connection terminal connected to the upper two-line line, an upper switching circuit that switches transmission and reception of signals of this terminal, a lower line connection terminal connected to the lower two-line line, A lower-side switching circuit that switches transmission and reception of signals at this terminal; a downstream receiving circuit that receives and identifies and reproduces signals arriving at the receiving terminal of the upper-side switching circuit; and an output of this downstream receiving circuit. a downlink transmitting circuit that amplifies the signal to a line transmission level and transmits it to the transmitting terminal of the lower switching circuit; and an uplink receiving circuit that receives the signal arriving at the receiving terminal of the lower switching circuit and performs identification and regeneration. , an upstream buffer circuit that temporarily stores the output of this upstream receiving circuit, and an upstream buffer circuit that amplifies the readout output of this upstream buffer circuit to a line transmission level and transmits it to the transmission terminal of the upper switching circuit. A two-wire system comprising: a transmitting circuit; and a control circuit including a control means for switching the upper-level switching circuit to the transmitting side at a timing when a received signal does not arrive at the upper-level line connection terminal based on the output of the downstream receiving circuit. In the digital two-way repeater, a downlink buffer circuit is provided that temporarily stores the output of the downlink receiving circuit and provides its readout output to the input of the downlink transmitting circuit, It includes means for controlling the two switching circuits and controlling the read and write timings of the two buffer circuits so that the transmitter circuit transmits at the same time and the two receiver circuits receive at the same time. A two-wire digital two-way repeater characterized by: