JPH0286343A - time division multiplexer - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a time division multiplexing device using a pulse stuff-ink method in digital communications.

[Prior art] As a conventional technology, for example, the collection of recommendations (in RED Boo) published by C (: rTT (International Telegraph and Telephone Advisory Committee))
, 742 TABLE 1, stuff bits (Bits from tributar in the table)
ies available for Justific
The position is a specific position in the frame structure, and whether or not the stuff bit is used is determined by the stuff specification bit (Justification in the table).
There is a pulse stuffing method specified by control bits).

Note that whether or not stuff bits are used is as follows. In other words, using stuff bits means inserting meaningless bits with no information into the data area to reduce the data transmission speed, and not using stuff bits means using the entire data area for data transmission and reducing the data transmission speed. It is to raise the

[Problems to be Solved by the Invention] Conventional methods of this type used stuff bits fixed at specific positions within a long frame length (usually several hundred bits or more), which is caused by the use of the pulse stuffing method. There was a problem in that stuff jitter (waiting time jitter) increased and communication quality deteriorated.

That is, FIG. 2(a) shows the input section of a multiplexer (in the synchronization section buffer of the present invention, which will be described later) in the conventional pulse stuffing method (FIG. 2(b) shows the pulse stuffing method according to the present invention, which will be described later). This shows how the amount of data changes over time. In the figure, for the sake of simplicity, one
This shows a case in which stuff bits are inserted twice (the probability that a stuff bit is inserted per frame is called the stuffing rate, and in this case, the stuffing rate is #l/2).

Now, in Fig. 2(a), since the stuff bit position is fixed within the frame, the envelope of the fluctuation of the amount of data in the input section occasionally as shown at point A in the figure (indicated by the dotted line in the figure) changes discontinuously. In this case, this amount of change is 172 bits, which causes low frequency jitter called stuff jitter.

If the stuffing rate is generally expressed as a rational number M/N, the above stuffing jitter is 17N[UT]
(DI: Unit Interval) Since it is known that when N is small, the stuff jitter 1/N becomes large and the transmission quality deteriorates.

An object of the present invention is to provide a time division multiplexing device that solves the above problems.

[Means for Solving the Problems] The present invention is a time division multiplexing device using pulse stuffing, which includes a detection means for detecting the amount of data in the synchronization section buffer, and a frame configuration of a human signal based on the result of the detection means. and inserting means for inserting stuff bits at arbitrary positions within the data area.

[Operations] According to the present invention, stuff jitter is suppressed by inserting stuff bits at arbitrary positions within the data area of the frame structure.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The multiplexing device shown in FIG. 1(a) time-division multiplexes low-speed data of four channels and converts it into high-speed data.The demultiplexing device shown in FIG. 1(b), on the contrary, It extracts 4 channels of low-speed data from the data. Since the low-speed data of the four channels is asynchronous with the clock of the multiplexer, a pulse stuffing method is used to synchronize it with the clock of the multiplexer.

A multiplexer using this pulse stuffing method will be explained below.

In FIG. 1(a), the low-speed data 7 is the low-speed clock 8.
are sequentially written into the synchronization section buffer 1. On the other hand, the data written in this way is read out by a clock 9 with a blank clock from the control circuit 5 (a clock with blank clocks in this part because the frame synchronization signal 11 and the pointer 13 are added later).

Under normal conditions, the read clock is slightly faster than the write clock, so the amount of data in the synchronizer buffer 1 gradually decreases. If the amount of data falls below a fixed threshold, the buffer information line 15 is
The control circuit 5 is notified, and the circuit 5 eliminates one of the missing clocks and inserts a stuff bit (meaningless bit without information) into this position as described below.
Insert. As a result, the amount of data in the synchronizer buffer 1 increases by one bit. On the other hand, the control circuit 5 stores the address of the position where the stuff bit is to be inserted (simply put, the information about the position counting from the first bit of the frame).

Next, the frame synchronization signal 11 . Stuff bit 12 (entered when there is a request from the synchronization section buffer), pointer 1
3 (input the address value of the stuff bit position stored in the control circuit) is added. This addition is performed in the multiplexer 2, and the selection information for each signal 10, 11, 12, 13 in the multiplexer 2 is given from the selector 4 which receives a command from the control circuit 5.

The signal 14 of channel (ch) 1 outputting from multiplexer 2 is multiplexed with the signals of the other three channels (ch 2 to 4), and both are input to the barrel/serial converter, where it is converted to high-speed data 16 and output. Ru.

6 is a counter, and the high-speed clock from here is
It is applied to the control circuit 5, the parallel/serial converter 3 and the separation device.

[Operation of the separation device] As shown in FIG. 1(b), the high-speed data 26 input to the separation device enters the frame synchronization circuit 18, where frame synchronization is performed based on the high-speed clock 27 (the start of the frame is To detect). The frame-synchronized signal is
It is separated into four channels by a serial/parallel converter 19. The chi signal 28 sent out from here is sent to the demultiplexer 20 as data 30, frame synchronization signal 31 . Stuff bit 32. It is divided into pointers 33. A select signal to the demultiplexer 20 for this purpose is given from a selector 24 that receives a command from the control circuit 22. In particular, the position where the stuff bit 32 is taken out is the channel where the control circuit 22 outputs from the serial/parallel converter 19.
It is detected by reading the address value 29 in the pointer from the signal 28 of i. High speed clock 27 is applied to counter 23, and the clock from counter 23 is applied to serial/parallel converter 19 and control circuit 22.

The data 30 output from the demultiplexer 20 is missing, and in order to convert it into low-speed data 35 at a constant speed, a separator buffer 21 that receives a clock from the control circuit 22 is used. The clocks are phase locked.

FIG. 2(b) shows how the amount of data in the synchronizer buffer changes over time in this embodiment. From this (b),
Since a stuff bit is inserted every time the amount of data in the synchronization section buffer falls below the intermediate value, discontinuous changes like in the conventional example (a) above do not occur, and therefore the stuff jitter becomes a negligible value. (There is no problem because the periodic fluctuation component within the envelope can be removed by the separator buffer 21 and PLL 25 in the separator).

It is effective when used in cases such as when connecting in stages).

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a multiplexing device and a demultiplexing device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a stuffing method in the conventional method and in the present invention. Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] 1) A time division multiplexing device using pulse stuffing, which includes a detection means for detecting the amount of data in the synchronization part buffer, and a detection means for detecting the amount of data in the frame structure of the input signal based on the result of the detection means. 1. A time division multiplexing device comprising: inserting means for inserting a stuff bit into an arbitrary position within a region. 2) The time division multiplexing apparatus according to claim 1, wherein the inserting means specifies the stuff bit position by the value of a pointer placed at a specific location in the frame configuration.