JPS61289739A - Digital multiplex transmission system - Google Patents

Abstract

PURPOSE:To separate accurately a multiplexing signal without inserting a frame pulse by applying coding violated against the CMI code only to a part in a multiplexing signal corresponding to specific digital signal subjected to multiplexing periodically. CONSTITUTION:Parts 1d, 2d in a multiplexing signal (a) before transmission line coding correspond to two series of digital signals subjected to multiplexing and in converting the multiplexing signal into a transmission line code, the coding of the CMI code rule violation is applied with a prescribed interval only to the part 1d corresponding to the 1st digital signal as shown in chain lines. In separating the code, the 1st and 2nd digital signals subjected to multiplexing are separated surely without mis-recognition by detecting the part 3v of the code rule violation. Thus, no frame pulse insertion is required.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a system for multiplexing and transmitting a plurality of series of digital signals, and particularly relates to a method for multiplexing and transmitting digital signals of multiple series.
The present invention relates to a digital multiplex transmission system that uses modified Mark Inversion codes.

(Prior Art) In the case of digital multiplex transmission in which multiple series of digital signals are multiplexed and transmitted, it is necessary to make it possible to accurately separate the multiplexed signal series. The method used is to regularly insert pulses called frame pulses in addition to a plurality of multiplexed digital signals.

Part 31i4 shows an example of the configuration of a multiplexed signal according to the conventional method when two series of digital signals are multiplexed.
In the figure, parts ld and 2d are parts of two series of digital signals to be multiplexed, and part 3f is a part of a frame pulse.

When separating the multiplexed signal shown in Figure 3 and restoring it to the original two series of digital signals, the frame pulse acts as a delimiter, and the first digital signal and the second digital signal may be mistakenly recognized. Separation can be performed accurately without any problems.

[Problem that the invention seeks to solve]

However, the conventional method of inserting frame pulses described above requires a device that performs demultiplexing.

A disadvantage of so-called digital multiplex converters is that they require speed conversion circuits.

In the multiplexed signal of FIG. 3, the information rate of the two multiplexed digital signals is of course equal to the original information rate on average, but momentarily different from the original information rate. For this reason, a digital multiplex converter requires a speed conversion circuit for adjusting the information speed of the multiplexed signal to the information speed in the multiplexed signal.

Since this speed conversion circuit occupies a considerable portion of a digital multiplex converter, conventional multiplexing systems are a major factor in the complexity of the digital multiplex converter, and are extremely disadvantageous in this respect.

[Means for solving problems]

The digital multiplex transmission system of the present invention uses a CMI code as a transmission path code, and a part of the multiplexed signal corresponding to a specific one of multiplexed digital signals is assigned a CMI code rule. This method eliminates the need for frame pulse insertion and makes the information speed of the multiplexed digital signal the same before and after multiplexing by periodically performing violating encoding and forcing the code rule to be violated. be.

Multiplexed signals are rarely transmitted as is; they are usually converted to a code suitable for the transmission path before being transmitted.
I (Coded Mark Inversion)
The code is one such transmission line code.

According to the CMI code side, for example, as shown in Figure 2 (a), every time information "1" appears, it is converted alternately to "l" level and "0" level, and information "θ" is The time slot (time interval occupied by one code) is converted into one in which there is a rise from the "O" level to the "1" level at the center of ts.

In addition, violation of CMI coding rules means, for example, Fig. 2 (b)
), and encode it like the part of 1 ma. In other words, in the case of information "1", as shown by the arrow, the previous information "1"
”, and in the case of information ``0'', convert it to one with a fall from the ``1'' level to the ``θ'' level at the center of that time slot) ts. be.

The present invention periodically performs coding that violates the CMI coding rule only on a portion of a multiplexed signal that corresponds to a specific one of the multiplexed digital signals, thereby converting frame pulses into This makes it possible to accurately separate multiplexed signals without insertion.

〔Example〕

Next, the present invention will be described by way of examples with reference to the drawings. FIG. 1 shows an example of the configuration of a multiplexed signal according to the method of the present invention. Here, as in FIG. 3, a case is shown in which two series of digital signals are multiplexed.

FIG. 1(a) is an example of a multiplexed signal before transmission line encoding is performed, and ld and 2d are parts corresponding to two columns of digital signals to be multiplexed, respectively.

Further, FIG. 1(b) is an example of a multiplexed signal after transmission path encoding, and the 3rd column is a portion where encoding is performed that violates the CMI coding rule.

In FIG. 1(a), portions ld and 2d correspond to two-tree digital signals to be multiplexed, and
When converting this multiplexed signal into a transmission path code, the CM■ coding rule violation is encoded only in the portion 1d corresponding to the first digital signal and at regular intervals as shown by the chain line.

When separating, by detecting the part 3 that violates the coding rule, separation can be performed reliably without misidentifying the multiplexed first digital signal and second digital signal. Therefore, insertion of frame pulses becomes unnecessary.

Although the case where two digital signals are multiplexed is illustrated here, the present invention can also be applied to the case where three or more digital signals are multiplexed.

〔Effect of the invention〕

As explained above, the present invention uses CMI as a transmission path code.
This method eliminates the need to insert frame pulses because the CMI coding rule is periodically encoded only in the portion of the multiplexed signal that corresponds to a specific one of the multiplexed digital signals. As a result, the information speed of the multiplexed digital signal is equal to that of the original digital signal both on average and instantaneously, so a speed conversion circuit is not required in the digital multiplex converter, resulting in a significantly simpler configuration. There is. In other words, the information speeds of the digital signals to be multiplexed can be matched after multiplexing, resulting in the effect that the speed conversion circuit of the digital multiplex converter becomes unnecessary.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a multiplexed signal according to the present invention, FIG. 2 is a diagram showing encoding that violates the CMZ coding rule and the CMI coding rule, and FIG. 3 is a diagram showing the configuration of a multiplexed signal according to the conventional method. It is a figure which shows an example. 1d: Portion corresponding to the first series of digital signals to be multiplexed. 2d: Portion corresponding to the second series of digital signals to be multiplexed. 3ma: Part where encoding is performed that violates the CMI coding rules.

Claims (1)

[Claims] In digital multiplex transmission in which a CMI code is used as a transmission line code and multiplexed digital signals are transmitted, a specific one of the multiplexed digital signals is transmitted. A digital multiplex transmission system characterized in that only a portion of a corresponding multiplexed signal is periodically encoded in a manner contrary to the CMI coding rule.