JPH0754936B2 - Concentration distribution system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a concentrating distribution system in which a plurality of terminal devices arranged at various places are connected to a central apparatus via a concentrating distribution terminal. .

(Prior Art) When a plurality of terminal devices such as telephones are connected to an exchange to form a network, it is very laborious to directly wire-connect each terminal device and the exchange, and Equipment costs will be high. Therefore, for example, a concentrating distribution terminal is provided for each of a plurality of buildings or different floors, and these concentrating distribution terminals and a central device including the exchange are connected to signal cables (first transmission path and second transmission path). There is a system in which the terminal equipment is connected to the central device via the line concentrating distribution terminal by connecting each terminal device to the line concentrating distribution terminal closest to the facility location.

According to such a system, not only the installation work of the signal cable between the central device as the backbone and the plurality of concentration distribution terminals becomes easy, but also by connecting the terminal device to the nearest concentration distribution terminal. Since it is good, it is possible to flexibly construct a network.

By the way, in such a system, signal transmission is performed between a plurality of concentration distribution terminals and a central device via a common transmission path. Further, the respective line concentrating / distributing terminals are respectively connected to different positions of the transmission line. For this reason, the transmission line length between each concentration distribution terminal and the central device is different for each concentration distribution terminal, and as a result, there is a difference in the signal transmission time of the signal transmitted between each concentration distribution terminal and the central device. Occurs. Therefore, if the signal transmission is performed without considering the difference in the transmission delay time, there occurs a problem that the signals transmitted between the respective distribution lines collide with each other on the transmission path.

Therefore, in JP-A-61-145995, the round-trip propagation delay time between the central unit and the line distribution terminal is measured using a dedicated time slot, and the line distribution terminal transmits a signal to the transmission line based on the measurement result. We have proposed a method to control the timing of sending out. Further, Japanese Patent Application Laid-Open No. 62-241451 proposes a method of improving the previous proposal and measuring a round-trip propagation delay time in a central device.

However, in these methods, it is necessary to provide a time slot dedicated to system control for realizing the above-described method in the frame, in addition to the time slot for communication. Furthermore, when a new concentrating / distributing terminal for which delay measurement is not performed is connected, the round-trip propagation delay time between the concentrating / distributing terminal and the central unit is unknown, so the window frame of the time slot for system control is The duration of the period should be long enough. That is,
In order to increase the operating radius, it is necessary to lengthen the time length of the system control time slot. As a result, there arises a problem that the number of communication time slots is reduced.

Further, in order to improve these points, in JP-A-62-241451, a round-trip propagation delay time between each concentration distribution terminal and the central device is roughly measured using a frequency channel dedicated to control in advance, A method has been proposed in which the length of the system control time slot is minimized by measuring the propagation delay time in the channel of the communication time slot selected and designated according to the rough measurement result.

However, even with this method, a time slot dedicated to system control is still required, and it is unavoidable that the communication time slot is reduced accordingly.

(Problems to be Solved by the Invention) In such a concentrating distribution system conventionally proposed, the difference in transmission delay time generated between each concentrating distribution terminal and the central unit is determined by a time dedicated to system control. Since the measurement is performed using slots, there is a problem that it is inevitable that the communication time slots will decrease.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a concentrating distribution system capable of accepting a new entry of a concentrating distribution terminal without lowering communication efficiency.

[Structure of the Invention] (Means for Solving the Problems) According to the present invention, a central unit to which an exchange is connected and a plurality of concentration distribution terminals to which terminals are connected are connected via first and second transmission lines. A time slot signal for communication from the central line distribution terminal to the central device is time-divisionally transmitted via the first transmission path, and a time slot signal for communication from the central device to the central line distribution terminal is the first signal. In a concentrating distribution system that is time-divisionally transmitted via two transmission lines, the central device is a communication time slot signal composed of a data signal transmitted from the concentrating / distributing terminal via the first transmission line. Means for sampling with a plurality of clocks which are generated from a predetermined reference clock and have different phases including the reference clock, and the communication timing based on these sampling results. Means for knowing bit error information of a slot signal, wherein the concentrating / distributing terminal determines the reference based on a phase difference between the reference clock and the sampling clock with the least bit error of the communication time slot signal. There is provided means for controlling the transmission timing of the communication time slot signal to the first transmission line so that the bit error of the communication time slot signal sampled by the clock is minimized.

(Operation) According to the present invention, since the delay measurement is performed by using the communication time slot of the system control dedicated frequency channel or the communication frequency channel, it is not necessary to provide the control dedicated time slot in the communication frequency channel. Therefore, the number of time slots of the communication frequency channel can be maximized, and a new entry of the line distribution terminal can be accepted without lowering the communication efficiency.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a concentrating distribution system according to an embodiment of the present invention.

In this system, as shown in the figure, a central device 1 including an exchange and a plurality of concentrating distribution terminals 2a, 2b ... 2n are tree-connected via a first transmission line 3 and a second transmission line 4 which are signal cables. Connected to each other.

The concentration distribution terminals 2a, 2b ... 2n are provided, for example, for each of a plurality of buildings or for different floors. Various terminals 5 such as a telephone, a facsimile, a data terminal, etc. are connected to the line concentrating / distributing terminals 2a, 2b ... 2n closest to the place where they should be installed.

FIG. 2 is a diagram showing the configuration of the central device 1 described above.

The central unit 1 shown in the figure has a switch 6, a plurality of communication time slot control circuits 7 corresponding to the respective frequency channels for communication, and a phase for each communication time slot control circuit 7 based on a clock from the switch 6. , A multi-phase clock generator circuit 8 for supplying a plurality of different clocks, an initial setting module circuit 9 corresponding to a frequency channel dedicated to system control, and transmission lines 3 and 4 and each communication time slot control circuit 7 or initial stage. It is composed of a diplexer 10 for interfacing with the setting module circuit 9.

In the communication time slot control circuit 7, the frame generation circuit 11 generates a communication frame from the data signal from the exchange 6, the control information from the call control circuit 18 and the signal from the frame check sequence (FCS) addition circuit 12. , Which is sent to the second transmission path 4 (communication frequency channel) via the modulator 13 and is sent from the first transmission path 3 (communication frequency channel) and demodulated via the demodulator 14 for communication The necessary mime slots are extracted from the frame by the selector 15, and these are disassembled by the frame disassembly circuit 16 and sent to the exchange 6. Further, the sampling circuit 17 inserted between the demodulator 14 and the selector 15 samples the communication time slot signals by a plurality of types of clocks having different phases supplied from the multi-phase clock generation circuit 8, respectively. By sending this sampling signal to the frame check sequence (FCS) adding circuit 12, it contributes to the realization of delay control described later. Further, the call control circuit 18
Is connected to each section (each call control circuit) of the central apparatus 1 via a call control bus, and controls the frame generation circuit 11 or the frame disassembly circuit 16 based on the communication procedure of the entire apparatus.

In the initial setting module circuit 9, the initial delay control circuit 19 sends a control signal to the second transmission line 4 (frequency channel dedicated to system control) via the modulator 20, and in response to this, the line concentrating distribution terminals 2a, 2b. 2n, that is, the control signal transmitted from the first transmission path 3 (frequency channel dedicated to system control) is demodulated via the demodulator 21, and between the central device 1 and the line distribution terminals 2a, 2b. Measure the round trip propagation delay time. In addition, the control signal is used to exchange predetermined data described later with the concentration distribution terminals 2a, 2b ... 2n. Further, the call control circuit 22 is connected to each unit (each call control circuit) of the central apparatus 1 via the call control bus and controls the initial delay control circuit 19 and the like based on the communication procedure of the entire apparatus, as described above. There is.

FIG. 3 is a diagram showing a configuration of the above-mentioned concentration distribution terminals 2a, 2b ... 2n.

Concentration distribution terminals 2a, 2b ... 2n shown in the figure include a communication time slot control circuit 23, an initial setting module circuit 24, and a transmission line.
It is composed of a diplexer 25 for interfacing the communication time slots control circuit 23 with the communication circuits 3, 4, and a subscriber circuit 26.

In the initialization module circuit 24, the initialization / call control circuit
When 27 receives a control signal sent from the central unit 1, that is, the second transmission line 4 (frequency channel dedicated to system control) via the demodulator 28, in response to this, the control signal is sent via the modulator 29. It is sent to the first transmission line 3 (frequency channel dedicated to system control) and contributes to the measurement of the round-trip propagation delay time described above. Further, this control signal is used to exchange predetermined data described later with the central device 1.

In the communication time slot control circuit 23, the second transmission line 4
Time slot extraction circuit from the communication frame sent from (communication frequency channel) and demodulated through the demodulator 30
The necessary time slots are extracted by 31 and sent to the subscriber circuit 26, and the time slot generation circuit
32 generates a time slot from the data signal from the subscriber circuit 26 and sends it to the first transmission line 3 (communication frequency channel) via the modulator 33. Further, the transmission timing control circuit 34 controls the transmission timing of the time slot generation circuit 32. Further, the frame check sequence (FCS) generation / comparison circuit 35 performs delay control described later.

FIG. 4 shows the above-mentioned frequency channels, and these channels are set by dividing the frequency band of the signal cables forming the first transmission path 3 and the second transmission path 4 into a plurality of parts. For example, the frequency band f0 is assigned to a frequency channel dedicated to system control, and the frequency bands f1 to fn are assigned to each frequency channel for communication. Further, each frequency channel for communication is composed of a plurality of time slots for communication which are time-division multiplexed.

FIG. 5 shows such a communication time slot.

As shown in the figure, the first transmission line 3 and the second transmission line 4
Of a signal for transmitting 1 is composed of a plurality of communication time slots (eg, 96 sets). The communication time slots transmitted from the central unit 1 to the line concentrating distribution terminals 2a, 2b ... 2n are composed of control bits and communication bits. 2n transmitted from the line concentrating / distributing terminals 2a, 2b ... 2n to the central unit 1 are composed of reference bits and communication bits.

Next, the procedure of delay control by this system will be described.

First, when the concentration distribution terminal 2n is newly connected to the transmission line of this system, the round-trip propagation delay time between the concentration distribution terminal 2n and the central device 1 is roughly measured using the frequency channel dedicated to system control. . This is measured by exchanging control signals between the initialization module circuit 9 of the central unit 1 and the initialization / call control circuit 27 of the line concentrating distribution terminal 2n using a frequency channel dedicated to system control.

Next, the central unit 1 uses the control signal of the frequency channel dedicated to system control to the concentration distribution terminal 2n to determine the communication frequency channel and time slot number used for notification / confirmation of the call or the call and communication. It is specified.

After that, the central line distribution terminal 2n sends the original time to the central unit 1 at the timing based on the round-trip propagation delay time roughly measured as described above using the time slot of the communication frequency channel designated as described above. A test time slot signal shorter than the slot signal is transmitted. That is, as shown in FIG. 6, the round-trip propagation delay time roughly measured as described above may be slightly different from the designated communication frequency channel due to the difference in the frequency band. The time slot length of the test time slot signal is set shorter than the original communication time slot length so that, for example, even if there is a deviation, the adjacent time slots that are already in use will not be adversely affected.

Next, the central unit 1 instructs the concentration distribution terminal 2n to finely adjust the transmission timing of the test time slot signal so that the carrier detection timing for this test time slot signal falls within the specified range.

Then, after the carrier detection timing falls within the designated range, the concentration distribution terminal 2n sends out a normal-length communication time slot.

As shown in FIG. 7, the central unit 1 sends the communication time slot signal φ sent from the concentrating / distributing terminal 2n to a plurality of clocks φ1 to φ16 which are generated by the multi-phase clock generating circuit 8 and have mutually different phases. Respectively, and bit error information of each demodulated signal is transmitted to the line concentrating / distributing terminal 2n. In concrete terms, the central unit 1 collects several frames of the time slots assigned to the concentration distribution terminal 2n into one block, and checks the frame of each sampling signal by a CRC of, for example, 16 bits for each block. A sequence is generated and transmitted to the concentration distribution terminal 2n using the control bits of the downlink time slot. In the centralized distribution terminal 2n, a frame check sequence by CRC is similarly generated for each block in the central device 1 in advance, and a plurality of different phases transmitted by being carried in the control bit of the downlink signal time slot are different. By comparing each of the 16 frame check sequences for each clock, the occurrence status of the upstream bit error is recorded, and the magnitude relationship of the bit error is calculated.
The concentration distribution terminal 2n has its own signal transmission timing so that the size of the relation is such that the reference clock becomes the minimum if the bit error of the demodulated data by the reference clock is not the minimum among the clocks generated by the central unit 1. Fine-tune.

As described above, in the system of the present embodiment, since the delay measurement is performed using the frequency channel dedicated to system control or the communication time slot, it is not necessary to provide the control frequency time slot in the communication frequency channel. For example, as shown in FIG. 8, the control areas such as ASG and RSP in the communication time slot which have been conventionally required are not necessary. Therefore, the number of time slots of the communication frequency channel can be maximized. That is, it is possible to accept a new entry of the line distribution terminal without lowering the communication efficiency. Furthermore, the delay control is performed to minimize the bit error rate by using the bit error information with respect to the fluctuation of the propagation delay time of the transmission line due to the quantization error or the temperature change which occurs during the delay measurement / control. Because it is done
A minimum bit error rate is guaranteed.

[Effects of the Invention] According to the present invention as described above, the delay measurement is performed using the frequency channel dedicated to system control or the communication time slot, so that it is not necessary to provide a control dedicated time slot in the communication frequency channel. . Therefore, it is possible to accept the new entry of the line distribution terminal without deteriorating the communication efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a concentration distribution system according to an embodiment of the present invention, FIG. 2 is a diagram showing a configuration of a central device in this system, and FIG. 3 is a configuration of a concentration distribution terminal in this system. FIG. 4 is a diagram showing each frequency channel in this system, FIG. 5 is a diagram showing communication time slots in this system, and FIG. 6 is a diagram for explaining test time slots. FIG. 8 is a diagram for explaining a plurality of clocks having different phases,
The figure shows a conventional communication time slot. 1 ... Central device, 2a, 2b ... 2n ... Concentration distribution terminal, 3 ...
1st transmission line, 4 ... 2nd transmission line, 6 ... Exchange, 7
...... Communication time slot control circuit, 8 ...... Multi-phase clock generation circuit, 9 …… Initial setting module circuit, 10 ……
Diplexer, 23 ... Time slot control circuit for communication,
24 …… Initial setting module circuit, 25 …… Diplexer,
26 ... Subscriber circuit.

Claims (1)

[Claims] 1. A central device to which an exchange is connected and a plurality of concentration distribution terminals to which terminals are connected are connected via first and second transmission lines, and for communication from the concentration distribution terminal to the central device. Time slot signals are time-divisionally transmitted via the first transmission line, and communication time slot signals from the central unit to the concentration distribution terminal are time-divisionally transmitted via the second transmission line. In a line-concentration distribution system, the central device generates the communication time slot signal composed of a data signal transmitted from the line-concentration distribution terminal via the first transmission line from a predetermined reference clock, and generates the reference clock. Means for sampling with a plurality of clocks having mutually different phases, and means for knowing bit error information of the communication time slot signal from these sampling results The concentration distribution terminal, based on the phase difference between the reference clock and the sampling clock with the least bit error of the communication time slot signal, the communication time slot sampled by the reference clock A concentrating distribution system comprising means for controlling the transmission timing of the communication time slot signal to the first transmission path so that the bit error of the signal is minimized.