JPS61144936A - Time division direction control transmission system - Google Patents

Abstract

PURPOSE:To eliminate the need for a status information bit by transmitting a burst frame while inhibiting number exchange at each burst with a polarity of a head bit during training period and allowing an opposite party to detect the end of the training period from the start of polarity inversion at each burst of the said polarity. CONSTITUTION:Line terminators 2, 4 have the same constitution. A burst signal transmitted on a subscriber line 3 is subject to switching control by a switch 31, decoded and a frame pattern is separated in a multiplex separation circuit 13 and the result is fed to a burst control circuit 30. On the other hand, a clock signal is generated based on the timing extracted by a timing extraction circuit 15. A frame synchronism circuit 17 discriminates the presence of synchronism establishment with the opposite party depending whether the frame pattern is detected or not at a prescribed point of time based on the said clock signal and an output of a decoder 12. Further, a polarity detection line 18 detects the end point of time of the training period by detecting the start of inversion of the polarity of the head bit in the frame pattern transmitted from the opposite party at each burst during the training period.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a time division direction control transmission system for transmitting and receiving digital signals in a burst frame configuration via a two-wire transmission line.

Conventional technology Via a two-wire subscription circuit of the public telecommunications network.

There is a 9-time division direction control transmission method as one of the transmission methods for digital communication between subscriber terminals and exchanges.

This time-division direction control transmission method writes continuous transmission information into a buffer memory and reads it from the buffer memory at a predetermined period called the burst period and at a speed that is more than twice the writing speed. The burst signal sent from the other party is converted into a continuous signal in a buffer memory and then received. The above time division direction control transmission method is 1 normal.

It is also called a ping-pong transmission method because the subscriber terminal side and the station side send out bursts alternately.

On the other hand, when establishing a physical link (line connection) for each call, in order to speed up the process, it is necessary to easily and reliably notify and detect the status of the nine line termination devices.

According to a paper by Mano et al. entitled "Configuration of Digital Subscriber Line Transmission System" published in Research and Practical Application Report Vol. 32, No. 11 of Denka Communication Research Institute, the burst frame configuration shown in Figure 5 is Proposed.

That is, one burst frame consists of an 8-bit frame pattern indicating the beginning of the burst frame, a 4-bit status notification bit for monitoring or housekeeping, and 20 words of 11 bits each. The frame pattern consists of a leading bit that is fixed to “1” for both uplink and downlink, one bit (M) that is alternated every burst frame to avoid pseudo synchronization, and six bits that are fixed to “0”. It is configured. This frame pattern is used to establish synchronization.

A configuration is adopted in which a part of the status notification bits is used to notify each other whether synchronization has been established.

Problems to be Solved by the Invention In the conventional method described above, the processing is complicated because the status notification bit and the bit M in the frame pattern are controlled independently. is not detected correctly by the other party,
There is a waste of securing that bit area and transmitting it.

Structure of the Invention The method of the present invention which solves the problems of the prior art described above includes a transmission circuit that transmits burst frames while prohibiting alternation of the polarity of the leading bit for each burst during the training period, and a transmission circuit that transmits burst frames transmitted by the other party. By providing a receiving circuit that detects the end of the training period from the start of the alternation of the polarity of the first bit in each burst, it is configured to eliminate the need for a status notification bit for notifying the other party of the end of the training period. .

Hereinafter, the effects of the present invention will be explained in detail with reference to nine examples.

Embodiment FIG. 1 is a block diagram showing the configuration of a transmission system to which a time division direction control transmission system according to an embodiment of the present invention is applied.

This transmission system includes a subscriber terminal 1, a line termination device on the subscriber terminal side 2. a two-wire subscriber line 3. It consists of a line termination device 4 on the subscriber exchange side and a subscriber exchange 5.

Both line termination devices W2 and W4 have the same configuration as shown in FIG.

That is, a burst signal sent onto the subscriber line 3 by the other party is supplied to the receiver 11 via a switch 31 which is controlled by a burst control circuit to be described later. The burst signal equalized and amplified by the receiver 11 is
It is decoded by the decoder 12, and the frame pattern and call information (words #1 to #20 in FIG.
). The demultiplexed frame pattern is supplied to the burst control circuit 30, and the remaining call information is written into the buffer memory 14. The call information written in the buffer memory is read out continuously at a speed less than half the writing speed according to the timing supplied from the burst control circuit 30, and is sent to the subscriber terminal or the subscriber exchange via the output terminal 19. Supplied.

In parallel with this, the timing extraction circuit 15.

Extract the timing from the output of receiver 11.

Based on this, the clock signal generation circuit 16 generates a clock signal. The frame synchronization circuit 17 is.

The clock signal of the clock signal generation circuit 16 and the decoder 1
Based on the output of step 2, whether or not synchronization with the other party is established is determined based on whether a frame pattern can be detected at a predetermined time. Furthermore, the polarity detection line 18 detects the end point of the training period by detecting the start of alternation of the polarity of the first bit in the frame pattern transmitted from the other party during the training period for each burst.

On the other hand, continuous call information supplied to the terminal 21 from the subscriber terminal 1 or the switching center 5 is written into the buffer memory 22 and then in accordance with the timing from the burst control circuit 30 in a burst period and at a writing speed. The data is read out at twice the speed or more and supplied to the multiplexing circuit 23. After this call information is multiplexed with the frame pattern supplied from the burst control circuit, the encoder 24 outputs +1. It is converted into a bipolar signal consisting of O, -1 and sent to the subscriber line 3'' through the driver 26 and switch 31.

Note that normally, a scrambling circuit is installed between the buffer memory 22 and the multiplexing circuit 23.

Correspondingly, the demultiplexing circuit 13 and the buffer memory 1
A descrampling circuit is installed between 4 and the multiplexing circuit 23, but is omitted in FIG. 2 for the sake of simplicity.

In this example. As shown in Figure 3, the structure of the burst signal consists of an 8-bit frame pattern and each subsequent
It consists of call information consisting of 20 words of 1 bit. During steady transmission, the polarity of the leading bit in a frame pattern is alternated for each burst to avoid pseudo synchronization. On the other hand, the first bit in this frame is
During the training period, alternation of polarity between bursts is prohibited1
will be played.

The operations from activation to establishment of a physical link upon call origination or incoming call will be explained based on the signal sequence shown in FIG. 4.

After the subscriber terminal side, the switching center side, and each line termination device are activated according to well-known procedures, the burst control circuit 30 of the first line termination device 4 generates a frame pattern al+a2 in which the leading bit is fixed to +1 of positive polarity, for example.・・・・・・
, multiplexing circuit 23. Encoder 24, driver 26. The data is sequentially sent to the line termination device 2 on the subscriber terminal side via the switch 31 and the subscriber line 3 at burst intervals.

In the line termination device 2 on the subscriber terminal side, the frame synchronization circuit 17 receives the 2m-th burst frame am by repeatedly receiving the burst frame described in
Detect establishment. The burst control circuit 30 of the line termination device 2, which has received the notification of the synchronization establishment, transfers the burst frame b1 whose leading bit is fixed to +1 to the multiplexing circuit 23.
Encoder 24, polarity inversion circuit 25. Driver 26. It is sent to the line termination device 4 on the switching center side via the switch 31 and subscriber line 3.

In this way, burst frames b, , b2 .
b, . . . are also sent from the line terminating device 4 as burst frames with the leading bit fixed to positive polarity +1 am ++ + Awl+z * A1+3 .
are sent out alternately, and when one line terminating device 4 receives the burst frame b3, synchronization on the line terminating device 4 side is established.

Burst control circuit 30 of line termination device 4 with established synchronization
notifies the end of the training period by controlling the encoder 24 to send to the line terminating device 2 a burst frame A in which the first bit is inverted with respect to the first bit in the immediately preceding burst frame.

The polarity detection circuit 18 of the line termination bag w2 detects the polarity inversion of the first bit of the received burst frame A, knows the end of the training period, and transmits the burst frame B with the polarity of the first bit inverted to the line termination device 4. Send. The polarity detection circuit 18 of the line termination device 4 detects the polarity reversal of the first bit of the received burst frame B, and confirms the end of the training period. After that, 1 line terminal device 2 and 4
Burst frames in which the polarity of the leading bit is alternated for each burst are sent from both sides, and a physical link is established.

Effects of the Invention As explained in detail above, the time division direction control transmission system of the present invention prohibits alternation of the polarity of the leading bit of a burst frame during the training period. In order to notify the other party of the end of the training period by providing a transmitting circuit that sends L, and a receiving circuit that detects the end of the training period from the start of alternation of the polarity of the first bit of the burst frame sent by the other party. Since the configuration is such that the status reporting bit of the frame pattern is unnecessary, the IJ? of the status reporting bit and bit M in the frame pattern. 11 It eliminates the need for complicated processing to be performed completely independently, and also eliminates the waste of securing and transmitting a bit area even though the status report bit is not correctly detected by the other party in a state where synchronization is not established immediately after startup. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a transmission system to which an embodiment of the present invention is applied, FIG. 2 is a block diagram showing an example of the configuration of line termination devices 2 and 4 in FIG. 1, and FIG. Conceptual diagram showing the burst configuration in the above embodiment, No. 4
The figure is a signal sequence for explaining the operation from startup to establishment of a physical link, and FIG. 5 is a conceptual diagram for explaining the conventional burst configuration and problems. 1...Subscriber terminal, 2...Line termination device on the subscriber terminal side, 3...2-wire transmission line, 4...Line termination device on the switching center side, 5...Switching center, 11...Receiver 912...Decoder, 17...Frame synchronization circuit, 18...Polarity detection circuit,
24...Encoder, 26...Driver, 30...Burst Il? I11 circuit, 31... switch.

Claims (1)

[Claims] In a time-division direction control transmission method in which digital information in a burst frame structure is transmitted and received via a two-wire transmission line, and during steady transmission, the first bit in each burst frame is alternated and transmitted for each burst frame. , a transmission in which a binary code transmission signal is encoded according to the bipolar rule, and transmitted while prohibiting alternation of the polarity of the first bit in the burst frame during the steady transmission for each burst frame during the training period from startup to physical link establishment. and a receiving circuit that decodes the received signal into a binary signal and detects the start of alternation of the polarity of the first bit in the burst frame transmitted by the other party for each burst frame to detect the end of the training period. A time-division direction control transmission system characterized by: