JPH0746816B2 - Digital communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention is a digital communication in which signals from various terminals are switched and input by a private branch exchange, encoded into digital signals, and transmitted to a partner terminal via a digital transmission line. Regarding the scheme.

“Prior Art” Conventionally, in a method of converting an analog signal into a digital signal and transmitting the digital signal, an encoder is fixedly used for an input as shown in FIG. That is, the terminal signals from the terminals 10 ₁ to 10 _l are switched by the circuit switch 11 and encoded into digital signals by the encoders 13 _{1 to} 13 _n through the interface circuits 12 _{1 to} 12 _n . The digital signals from the encoders 13 _{1 to} 13 _n are multiplexed by the multiplexing unit 14 and transmitted to the digital transmission line 16 composed of the digital lines 15 ₁ to 15 _n . Here, the digital lines 15 ₁ to 15 _n are generally time-division multiplexed on one digital transmission line 16, but the encoders 13 _{1 to} 13 _n are respectively multiplexed lines 15 ₁ to 15 on the digital transmission line 16. because it associated with the 15 _n, a digital line 15 ₁ to 15 _n are arranged in parallel to illustrate this point.

On the receiving side, the demultiplexing unit 17 demultiplexes the multiplexed signal of the digital transmission line 16 into the signals of the digital lines 15 ₁ to 15 _n , supplies them to the decoders 18 ₁ to 18 _n , respectively, decodes them, and outputs their respective composite outputs. Is supplied to the circuit switch 21 through the interface circuits 19 _{1 to} 19 _n , and is switched to the terminals 22 _{1 to} 22 _l and transmitted there. Although the signal transmission from the left to the right has been described in the above description, the signal transmission from the right to the left is performed in the same manner.

By the way, a high-efficiency encoder focuses on the characteristics of voice and compresses the band by removing the redundancy to reduce the transmission speed for transmission. When the signal from the above) is encoded by this encoder, the quality deterioration becomes more remarkable than that of the voice signal. Therefore, for example, for modem signals 32 kb / s ADPCM (adaptive prediction PCM, CCITT compliant) is 4800 b / s or less, 16 kb / s APC-AB
In (adaptive prediction adaptive bit allocation coding), application of 1200 b / s or less is the limit, and higher speed modem signals cannot be coded and transmitted using these encoders.

Therefore, when applying a high-efficiency encoder to the conventional encoder-fixed method for a configuration in which voice signals, facsimile signals, and other signals with different properties such as signals from a private branch exchange are transmitted on the same line. Has the drawback that its use is restricted.

It is an object of the present invention to provide a digital communication system which can eliminate restrictions on application of a high-efficiency encoder, and thus apply a high-efficiency encoder to enable efficient use of a line.

[Means for Solving Problems] According to the present invention, a high-efficiency encoder (low-speed encoder) suitable for voice signals and a high-speed encoder suitable for modem signals are provided, and the characteristics of signals from terminals are provided. The low-speed encoder and the high-speed encoder are switched and used according to. A working digital line is fixedly assigned to support a low-speed encoder, a digital signal from the low-speed encoder is transmitted through these, and when using a high-speed encoder, one of the working digital lines and a shortage of capacity on that line are reserved. It is transmitted by using a digital line.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 4 are designated by the same reference numerals. In this embodiment, the circuit switch 11 uses the interface circuits 12 _{1 to} 12 _n to generate a coding unit 23.
Connected to ₁ to 23 _n respectively. Each coding unit 23 ₁ ~ 23 _n, slow encoder for encoding the high efficiency with respect to the audio signal as shown in the coding unit 23 ₁ (rate of encoded digital signal is slow) 24 ₁ And a high-speed encoder suitable for encoding modem signals (the speed of encoded digital signals is faster than the output of the encoder 24 ₁ ) 25 _1, and the terminal signal from the interface circuit 12 _{1 is} supplied. It is switched by the switching switch 26 ₁ and supplied to the encoder 24 ₁ or 25 ₁ . The coded output of the low-speed encoder 24 _{1 and a part} of the coded output of the high-speed encoder 25 ₁ (the same capacity as the code output of the low-speed encoder 24 ₁ ) are switched and output by the switching switch 27 _1. To be done.

The coded outputs from the coding units 23 ₁ to 23 _n are multiplexed by the multiplexing unit 14 and supplied to the digital transmission line 16, but the low-speed coded output, that is, the outputs of the switching switches 27 _{1 to} 27 _n are They are fixedly assigned to the working digital lines 15 ₁ to 15 _n in the digital transmission line 16. On the other hand, the remaining coded output that is not supplied to the switching switches 27 _{1 to} 27 _n during the coded output of the high-speed encoders 25 _{1 to} 25 _n is passed through the multiplexer 14 to the digital transmission line.
It is switched and supplied to one or a plurality of spare digital lines 28 _{1 to} 28 _{m in} 16 of them.

The interface circuits 12 _{1 to} 12 _n are connected to the detection circuits 29 _{1 to} 29 _n , respectively, and identify whether the signal from the terminal is a voice signal or a modem signal. Therefore, the modem signal can be identified by detecting the carrier wave. Detection circuit 29
The identification outputs of _{1 to} 29 _n are input to the control circuit 31, and the control circuit 31
When a modem signal is input, the corresponding coding unit 23 _i
(I = 1,2, ... n) switching switches 26 _i and 27 _i are controlled to be encoded by a high-speed encoder 25 _i , and the encoded output is transmitted through the switching switch 27 _i through the working digital line 15 _i . The spare digital line 28 _{1 to} 28 _m
To transmit. The control signal indicating this switching is transmitted to the other party through the control signal transmission / reception circuit 32, for example.

Demultiplexed digital signals of the working digital lines 15 ₁ to 15 _n in the demultiplexer 17 on the receiving side is fixedly supplied to the switching switch 34 ₁ to 34C _n decoding units 33 ₁ ~ 33 _n respectively. The switching switches 34 _{1 to} 34 _n have their inputs at a slow decoder 35.
_{1 to} 35 _n and high-speed decoders 36 _{1 to} 36 _n are switched and supplied. Decoder outputs of slow decoders 35 _{1 to} 35 _n and fast decoders 36 _{1 to} 3
Each decoded output of 6 _n are switched respectively by switching switches 37 ₁ to 37 _n are supplied to the in tough ace circuit 19 ₁ ~ 19 _n. The spare digital lines 28 _{1 to} 28 _m are connected to the high speed decoders 36 _{1 to} 36 _n through the demultiplexing unit 17 by switching. The control signal transmission / reception circuit 38 is connected to the control circuit 39, and sends a signal indicating switching of the switching switches 26 _i , 27 _i from the other party to the control signal transmission / reception circuit 38.
And the switching switches 34 _i and 37 _i are controlled accordingly.

Although not shown in the figure, signals from terminals 22 _{1 to} 22 _l
For transmission to 10 ₁ to 10 _l, in tough Ace circuit 19 ₁ to 1
9 _n detection circuits 41 ₁ to 41 _n that identifies the nature of the terminal signals are connected to, the same encoding function and the encoding unit 23 ₁ ~ 23 _n are provided to the decoding section 33 _to 333 in _n, also The same decoding function as the decoding units 33 _{1 to} 33 _n is provided in the encoding units 23 ₁ to 23 _n .

When the signal from the terminal in the configuration described above of the audio signal using the low-speed encoder 24i, line in digital transmission path 16 using the encoder 24 _i to permanently assigned working digital line 15 _i To do.

If the signal from the terminal is a modem signal, etc., a high-speed encoder 25
switching to use _i, and a high-speed encoder 25 _i, for example, 32 kb / s this working digital lines 15 _i and 16 kb / s spare digital lines fixedly allocated 16 kb / s the output of Divided into two and transmitted.

FIG. 2 shows temporally the transmission / reception of signals between the opposite devices and the control within the device for realizing the encoder switching, the multiplexer control by detecting the modem signal and the like on the transmission side. In Fig. 2, the signal from the terminal (for example, the carrier signal of the modem)
Is detected at the position of the interface circuit 12 _i , and on the basis of the signal, the transmitting side coding unit 23 _i controls the control signal from the pattern generator in the control signal transmission / reception circuit 32 (fixed pattern or pseudo random pattern of constant length). Specific pattern)
To the line 15 _i fixedly assigned to the coding unit 23 _i .

On the receiving side, the control signal from the pattern generator is detected by the control signal transmission / reception circuit 38, and the decoder switching and line changing of the decoding unit 33 _i (both the fixed allocation line 15 _i and the protection line are performed by the high speed decoder 36 _i ). Connect to _i )).

After transmitting the specific pattern, the transmitting side anticipates the time t ₁ required for the pattern detection in the receiving side decoding unit 33 _i , controls the encoder switching and the line change with timing, and sends it to the high-speed encoder 25 _i . Realization of switching.

Figure 3 is transmitting all signals by using a slow encoder 24 _i, the signal from the receiving terminal is monitored during the time t ₁ at the receiving side, the code under the control of the receiving side if there is no response It shows the control for switching the vessel. The control after the response signal cannot be detected by the receiving side is the operation of the transmitting side and the receiving side in FIG. 2 reversed, and at time t ₂ the signal sent from the receiving side pattern generator (specific Pattern) indicates the time required to detect the control signal transmission / reception circuit 32 on the transmission side, and switches the encoder on the reception side with timing.
Control the line change.

By performing the above-described control within the time period during which the terminal establishes synchronization, it is possible to realize communication in which the high-efficiency encoder is switched and used according to the property of the signal.

As is clear from this result, it is possible to select the most suitable encoder for the configuration in which voice and modem signals are transmitted on the same line where the application of the highly efficient encoder is limited in the conventional method. At the same time, there is an effect that transmission can be performed with a line capacity suitable for the signal to be transmitted.

Although two types of encoders having different encoding rules or encoding speeds are provided in each encoding unit in the above description, more types of encoders may be provided. Further, one encoder may be provided and the encoding law or the encoding speed may be changed.

"Effects of the Invention" As described above, according to the present invention, the high-efficiency encoder can be switched and used according to the characteristics of the signal, and the digital line for the high-speed encoder secures its insufficient capacity as a spare. Since the number of lines can also be made smaller than the fixed number of digital lines by sharing, there is an advantage that it is not necessary to limit the application of the high efficiency encoder and the digital lines can be efficiently used.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital communication system according to the present invention, FIGS. 2 and 3 are flow charts showing transmission and reception of information and control signals between transmission and reception, and FIG. 4 is a conventional digital communication system. It is a block diagram shown. 10 ₁ to 10 _l , 22 _{1 to} 22 _l : Various terminals, 11,21: Circuit switch, 12 ₁
~ 12 _n , 19 ₁ ~ 19 _n : Interface circuit, 14: Multiplexing unit, 15 ₁
~ 15 _n : Working digital line, 16: Line 15 ₁ to 15 _n and line 1
Digital transmission line in which 8 ₁ to 18 _m are multiplexed, 17: Demultiplexing unit, 23 ₁ to 23 _n : Encoding unit whose coding rule can be changed, 24 _{1 to} 24 _n :
Low speed encoder, 25 _{1 to} 25 _n : High speed encoder, 26 _{1 to} 26 _n , 27 ₁
〜 27 _n , 34 ₁ 〜 34 _n , 37 ₁ 〜 37 _n : Switching switch, 28 ₁ 〜 28 _m : Spare digital line, 29 ₁ 〜 29 _n , 41 ₁ 〜 41 _n : Detection circuit, 3
1,39: Control circuit, 32,38: Control signal transmitting / receiving circuit, 33 _{1 to} 33 _n :
Decoding unit, 35 _{1 to} 35 _n : low speed decoder, 36 _{1 to} 36 _n : high speed decoder.

Claims (1)

[Claims] 1. A digital communication system for encoding signals from a plurality of opposing terminals and transmitting and receiving the signals via a common digital transmission line, wherein a low-speed encoder provided for each digital line of the digital transmission line. And a coding unit having a high-speed encoder, and detects the property of a signal from a terminal which is provided for each of the above-mentioned coding units and is input to the coding unit, and accordingly, the low-speed encoder and the high-speed encoder of the coding unit are detected. Detection switching means for switching and supplying the input signal to any of the encoders, and when the detection switching means supplies the input signal to the low speed encoder, the encoded output of the low speed encoder is encoded. When the input signal is supplied to the high-speed coder by supplying it to one of the digital circuits corresponding to the section, the amount that can be sent by the low-speed transmission in the encoded output of the high-speed coder is And a multiplexer for supplying the rest of the encoded output of the high-speed encoder to the auxiliary digital line in the digital transmission line, while supplying to one of the digital lines corresponding to the encoding unit. The characteristic digital communication method.