JPH0480573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field of the Invention The present invention relates to output level adjustment, particularly to a network termination used in a so-called information network system (INS) and each terminal. The present invention relates to an output level adjustment method for adjusting the output level so that channels associated with each terminal can be output at the correct output level in frame information used for communication.

(B) Technical background and problems Recently, the so-called INS concept has been considered, and the uplink (T line) and downlink (R line) are wired from the network termination, and various terminals (terminal equipment) is configured to communicate with the network termination using the channel in the frame information on the T line or R line, and the network termination is, so to speak, between the external line and the various terminals. Consideration is being given to having the device function as a transmission mediating function device.

FIG. 1 shows the connection between the network termination and each terminal, FIG. 2A shows conventional frame information on the R line, and FIG. 2B shows conventional frame information on the T line.

In Figure 1, 1 is the network termination, 2 is the external line, 3 is the R line (down line), and 4 is the network termination.
represents the T line (up line), and 5-1, . . . , 5-N represent terminals. Each terminal 5-1,...5-N is at an arbitrary distance l from network termination 1.
It is installed at 1,...lN so that its position can be changed.
And network termination 1 is
As shown in FIG. 2A, frame information having a frame synchronization signal F and a plurality of channels CH1, CH2... is sent out on the R line, while each terminal, for example, 5-
Based on the reception of the frame synchronization signal F, i operates to place information on the channel CHj assigned to it at the timing of the channel j assigned to it, as shown in FIG. 2B. In other words, the network termination 1 is adapted to detect frame information such as that shown in FIG. 2B being transmitted on the T line.

In the conventional mode as described above, since the distance l1, . . . at which each terminal 5 is installed from the network termination 1 is different, each terminal is assigned a channel
Assuming that the information is listed above, the multiplexed frame information received at the reception point of network termination 1 has different amplitude depending on the channel as shown in Figure 3, and When attempting to identify the frame information using a fixed threshold, it is difficult to set the threshold, and in some cases it may be impossible to set an appropriate threshold. If the above fixed threshold is set according to the level of information from the terminal farthest from the network termination, the threshold will be unnecessarily too low for the level of information from the nearest terminal, and the information will be superimposed on the signal. There is a risk that the noise may be picked up. AGC (Automatic Gain Control) has traditionally been used as a receiving circuit that can respond to changes in input signal level.
Circuits and ATC (Automatic Threshold Control)
Although there are circuits, these are effective when the time constant of the input signal level change is large, but they are difficult to apply when the time constant is short such that the level changes within the same frame as described above. This has traditionally been addressed by fixed thresholds and by placing certain limits on the distance from the network termination to the farthest terminal. On the other hand, from the standpoint of a user using a terminal, such distance restrictions that impose restrictions on the wiring configuration of the terminal are not desirable.

(C) Object and Structure of the Invention The present invention aims to solve the above-mentioned problems, and the output level adjustment method of the present invention includes a network termination connected to an external line, and A plurality of terminals are branched to a common uplink and downlink to the network termination, and communication between each terminal and the network termination is connected to the uplink and downlink. In a communication system configured to perform communication using a channel on frame information carried on the uplink, each terminal has an uplink monitor pattern corresponding to a predetermined timing in the frame information on the uplink. an uplink monitor pattern insertion mechanism for inserting an uplink monitor pattern; a downlink monitor that detects a downlink monitor pattern in which the uplink monitor pattern is folded back at a predetermined timing in frame information on the downlink in the network termination; - A pattern detection mechanism and an output level adjustment mechanism for adjusting the output level of information output on the uplink are provided, so that the uplink monitor pattern inserted from the own terminal can be correctly detected as the downlink monitor pattern. The present invention is characterized in that the output level in the output level adjustment mechanism is adjusted as follows. This will be explained below with reference to the drawings.

(D) Embodiment of the invention FIG. 4 shows the configuration of an embodiment of the present invention, FIG. 5A shows frame information of an embodiment on the R line, and FIG. 5B shows frame information of an embodiment on the T line. . Further, FIG. 6 is a configuration example of the network termination shown in FIG. 4, FIG. The figure shows the configuration of an embodiment of the terminal shown in FIG.

In Fig. 4, the symbols 1, 2, 3, 4, and 5 are the first
Corresponding to the figure, 6 represents an up line monitor pattern insertion mechanism, 7 represents a down line monitor pattern detection mechanism, 8 represents an output level adjustment mechanism, and 9 represents a monitor pattern folding mechanism.

In the case of the present invention, an output level adjustment mechanism 8 is provided in the terminal 5-i to eliminate differences in network termination reception levels depending on the installation position of each terminal, and the output level from each terminal is adjusted to match the network termination reception level. The output level adjustment mechanism 8 can be adjusted so as to have a constant amplitude at a certain point. This specific method will be explained below.

The threshold of the receiver circuit at the network termination is set in advance to 1/2 of the input level from the farthest terminal. The terminal that wishes to make the adjustment first inserts "0" into the monitor pattern insertion position MT in FIG. 5B, and sends it to the T line. Network termination 1 receives this and returns it to the R line as MR. At this time
MR is naturally returned as "0". Next, at the terminal, the signal is increased by a minute level ΔV and sent to the T line (by the output level adjustment mechanism). At the network termination, turn around as before.
Repeat this operation and check the number of times the output level increases until MR on the R line at the terminal becomes "1" for the first time. Assuming that this is K times, the final "1" code output level is set to an amplitude corresponding to 2K times (Vout(1)=
2K・△V). The above operation ensures that the "1" code output level from the terminal is twice the receiver threshold of the network termination at the network termination receiving point, regardless of the distance of the terminal from the network termination. This means that the signal has been adjusted to be received as an amplitude, which satisfies the above requirement.

FIG. 6 shows an embodiment of the configuration of a portion where MT on the T line is folded back to MR on the R line at the network termination, and FIG. 7 shows its time chart. When frame information is input from the T line 4, it is first identified by the receiver 11 with the fixed threshold mentioned above and taken in as transmission multiplexed information as shown in FIG.・Pattern MT
is latched and becomes one input of the selector 14. The other input of the selector 14 is received multiplexed information D as shown in FIG. 7D, and the MT and received multiplexed information are selected by the selection signal shown in FIG.
It is turned back to the R line as MR (FIG. 7F). FIG. 8 shows the configuration of an embodiment of the terminal of the present invention. When frame information is input from the R line, it is first identified by the normal receiver circuit 21.
A clock is extracted by the PLL 22, and frame information is transferred to the flip-flop 2 by the clock.
It is played in 3. The reproduced frame information is subjected to frame synchronization by the frame synchronization circuit 24 and is taken into the terminal as received information. On the other hand, the clock circuit 25 uses the clock from the PLL 22 and the frame synchronization signal from the frame synchronization circuit 24 to generate various control clocks for the entire circuit. The flip-flop 26 extracts the monitor pattern MR from the received frame information and latches it. Counter 28, ROM 30, flip-flop 29, latch 31, and selector 32 are circuits for controlling output level adjustment circuit 34. The ROM 30 uses the output of the counter 28 as an address, and writes data for controlling the switch so that the output level increases by the above-mentioned ΔV every time the address increases by 1 on the a side, and on the a side, data is written in order from address 0.On the other hand, on the side b On the side, data is written to perform switch control such that the output level increases by 2 △V every time the address increases by 1 (address 0 is written such that the output level becomes 0 for both a and b). (contains switch control data). Also,
The selector 33 is for selecting transmission multiplexing information and transmission monitor pattern MT. The output level adjustment circuit 34 is composed of a variable amplifier using an operational amplifier, and switches 14-1, . . . 14-
The gain is adjusted by controlling m. The operation of each part during output level adjustment is as follows.

In the initial state of output level adjustment, the counter 28,
The flip-flop 29 has been reset and the selector 32 has selected the a side. Therefore, 0 is sent to the first MT. If this is returned as MR at the network termination and latched at flip-flop 26, the result is 0.
NOR gate 27 increments counter 28 through the clock. As a result, the ROM 30 outputs switch control data such that the output level increases by ΔV, and the next MT becomes ΔV. If the above operation is repeated and, for example, the output MR of the flip-flop 26 becomes "1" for the first time at the Kth time, the counter 28 is prohibited from incrementing at this time, and the latch 31 latches the output of the b side of the ROM 30. , and the flip-flop 29 is set and the selector 32 is controlled to select the b' side. The switch control data b' at this time is such that the output level becomes 2K·ΔV, and the output level is thereafter fixed at this value and the output level adjustment is completed.

(E) Effects of the Invention According to the present invention, a receiver circuit in a network termination can be realized using a fixed threshold system with a simple configuration, and the distance between the network termination and the terminal can be kept sufficiently large. This has the effect of providing flexibility in the wiring configuration of user terminals.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams explaining the conventional aspect, FIG. 4 shows the configuration of one embodiment of the present invention, FIG. 5A shows one embodiment of frame information on the R line, and FIG. 5B shows the T 10 shows an example frame information on a line. FIG. 6 is a configuration example of the network termination shown in FIG. 4, FIG. 7 is a time chart illustrating an aspect of folding back the monitor pattern according to the present invention in the configuration shown in FIG. 6, and FIG. FIG. 4 shows an embodiment of the configuration of the illustrated terminal.

Claims (1)

[Claims] 1 Network connected to external line
and a plurality of terminals branched to a common uplink and downlink to the network termination, and communication between each terminal and the network termination is provided. In a communication system configured to use a channel on frame information carried on the uplink and downlink, each terminal has a channel that corresponds to a predetermined timing in the frame information on the uplink. up line monitor
an uplink monitor pattern insertion mechanism that inserts a pattern, and a downlink monitor pattern that detects a downlink monitor pattern in which the uplink monitor pattern is folded back at a predetermined timing in frame information on the downlink in the network termination. A line monitor pattern detection mechanism and an output level adjustment mechanism for adjusting the output level of information output on the uplink are provided, and the uplink monitor pattern inserted from the own terminal is correctly used as the downlink monitor pattern. An output level adjustment method, characterized in that the output level in the output level adjustment mechanism is adjusted so that the output level can be detected.