JPS61239736A - Bit steal system - Google Patents

Abstract

PURPOSE:To reduce necessary transmission capacity per channel, to easily branch and couple a transmit signal, and to reduce the circuit scale of a device by multiplexing a sound and a control signal together with a frame synchronous signal for discriminating the sound and control signals by a bit steal system for transmitting the sound signal and control signal. CONSTITUTION:The voice input signal (a) is converted by an 8-bit digital signal, which is encoded and sent to a signal coupler 8. Signaling input information (b), on the other hand, is converted into a digital signal, which is sent to the signal coupler 18 as well as the sound signal. This signal coupler 18 couples frame information from a frame pattern generator 17, the encoded sound signal, and the signaling signal into a signal sequence, which is sent out to a multiplexing part 12. The multiplexing part 12 multiplexes voice and signaling information of 24 channels into a signal sequence (d) of 1.544Mb/s (193 bits), which is sent out to a transmission line. A reception side operates exactly reversely to the transmission side.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bit stealing method for transmitting audio signals and control signals in a digital communication network.

(Prior art) As a device to which the conventional bit steal method is applied, for example, "Wired Transmission Engineering" supervised by Mitsuharu Maeda
o) There is a PCM-24B terminal device disclosed in IEICE, P. 400-409. This device uses a bit-stealing method to multiplex an 8-bit encoded voice signal and control signals (signaling) necessary for switching functions into a single digital signal string. are doing. This bit stealing method refers to the case where a digital signal stream is divided into 12 frames based on the frame synchronization (FAS) signal of the digital signal stream and the corresponding audio signal (8 bits) is multiplexed only once in each frame. For the frame 1 and the 12th frame, the audio signal has 7 bits, and the remaining 1 bit is allocated for signaling.

Furthermore, recent 6.3 Mb/s PCM terminal equipment employs a system in which bits for signaling transmission are specified and assigned to bits other than the 8-bit audio signal.

(Problems to be Solved by the Invention) However, in the above-described method, frame identification is required to perform bit stealing.

For this purpose, one bit is provided for the multi-frame synchronization signal in addition to the audio signal bits (8 bits).

Therefore, in order to transmit voice signals and signaling information in one channel, 8Kb/S x 8 bits + cib/5 = 64Kb
When trying to multiplex a large number of channels onto a line that requires a transmission capacity of /s + σb/s and has a fixed transmission band, there is a problem in that the information band is wide, which is disadvantageous in terms of reducing the number of channels. .

Also, when dividing a transmission signal into two transmission lines, for example,
It was necessary to take this multi-frame information into consideration, separate audio and signaling, convert them to baseband, and further multiplex them. Similarly, when combining transmission signals from two transmission lines, this multiframe information is taken into account, audio and signaling are separated, and the signals are converted to baseband.
Further multiplexing was necessary.

The present invention eliminates the above-mentioned problems, reduces the necessary transmission capacity per channel, makes it easy to branch and combine transmission signals, and reduces the circuit scale of the device. It provides a method.

(Means for solving the problem) In order to solve the above problem, the present invention frames a part of the audio signal and a control signal in a part of the audio signal encoded into a digital signal. In the bit steal method in which signals are switched and multiplexed in units, a frame synchronization signal for identifying the audio signal and the control signal is also multiplexed.

(Function) According to the present invention, since the bit steal method is configured as described above, it functions as follows. It acts on a part of the audio signal (for example, the LSB of an 8-bit audio signal) by switching and multiplexing a part of the audio signal (LSB information) and a control signal on a frame-by-frame basis. The frame synchronization signal is also multiplexed so that the signal and the control signal can be distinguished. Therefore, since the control signal can be multiplexed into the audio signal, the necessary transmission capacity per channel can be reduced. In addition, the audio signal, the control signal, and the frame synchronization signal may be in the same signal sequence (for example,
Since it is included in a 64 Kb/s signal train), it is possible to branch and combine each signal train, and it is possible to reduce the circuit scale for branching and joining processing.

(Example) The present invention will be explained in detail using FIGS. 1 and 2.

FIG. 1 is a diagram showing an example of a frame structure to which the bit stealing method according to the present invention is applied, in which 8 bits of an audio signal encoded into a digital signal are shown in frame 1. This is to digitize the input audio signal, so it is 8KH.
The data is sampled at a period of z and encoded into 8 bits.

Therefore, the information capacity of Di (MSB) to D8 (LSB) is 8
Kb/sX 8 bits = 64 Kb/s and 1
The period is 125 μsec. Of this encoded signal, D8 (LSB), which has the least influence, is
The structure of frame 2 is taken for each c. Frame 2 is 125μ
Fl, F2. . . . is a signal train having a period of 24 frames (F24). F of this frame 2 is
This is a frame synchronization signal for identifying a 24-frame period.

Also, ■ is the LSB itself of the audio signal encoded into 8 bits. Further, S is a bit for control information (eg, signaling). In this way, the frame synchronization signal, the encoded audio signal, and the control information signal are multiplexed in D8 (LSB) in a time-division manner. According to this method, the deterioration of the audio signal is the P shown in the above document.
It is equivalent to the CM-24B device (bit steal every 6 frames), and the information capacity of control information bit S is 8kb/
sX3/24 = 1 kb/+, and there is no problem in transferring normal signaling information. This frame structure is just one example, and may vary depending on frame synchronization characteristics by F bit, voice quality, amount of control information, etc. Frame configurations can be considered.

FIG. 2 is a block diagram showing an embodiment of a 24-channel PCM terminal equipment using the frame structure shown in FIG. In the figure, reference numeral 11 denotes an audio channel section, which has the same configuration for 24 channels #1 to #24. 1
Reference numeral 2 denotes a multiplexing section that multiplexes output signals for 24 channels from the audio channel section 11.

Reference numeral 13 denotes a separation unit that separates the multiplexed signal from the transmission path into each channel and sends the separated signals to the audio channel units 11 from #1 to #24. The voice channel section 11 receives the voice input signal a and the signaling signals from the exchanger and sends them to an encoder 15, a signaling encoder 16 . The first
The signal is converted into a signal sequence with a period of 24 frames as shown in frame 2 in the figure and is transferred to the multiplexer 12. Furthermore, the audio channel unit 11 receives a signal sequence with a period of 24 frames sent from the separation unit 13 through a signal separator 20, a frame synchronization circuit 21. A receiving circuit comprising a decoder 22 and a signaling decoder 23 separates the signal into a voice band signal f and a signaling signal g, and sends the signal to the exchange.

Next, the operation will be explained.

The voice input signal a from the exchange is led to an encoder 15, where it is converted into an 8-bit digital signal. This encoded audio signal is sent to a signal combiner 18. On the other hand, the signaling input information from the exchange is converted into a digital signal in the signaling encoder 16 and then sent to the signal combiner 18 in the same way as the voice signal. This signal combiner 18 combines the frame information (frame synchronization signal F with a period of 24 frames) from the frame pattern generator 17, the encoded audio signal, and the signaling signal as shown in frame 2 in FIG. multiplexer 1
Send to 2. The interface signal C with this multiplexing section 12 is 64 as sending information from the audio channel section 11.
It is a signal capable of transmitting a capacity of K b/s x 24.

In FIG. 2, it is shown in a bus-coupled format.

The multiplexing unit 12, which does not take any form as long as it can transmit the signals of the audio channel unit 11 from #1 to #24,
Multiplexes audio and signaling information for each channel, 1
．． It is converted into a signal sequence d of 544 Mb/5 (193 bits) and sent to the transmission line. The receiving side operates in exactly the opposite way to the sending side described above. The received signal e of 1.544 Mb/s is synchronized with the input signal train by the separation unit 13, and
to #24 are distributed to the audio channel sections 11. On the receiving side of the audio channel unit 11, the signal separator 20
The audio signal and the signaling signal are separated, and the separation operation is performed using synchronization information obtained from the frame synchronization signal F from the frame synchronization circuit 21 and frame information that can separate Fl to F24. The separated voice signal is converted from a digital signal into a voice band signal f by a decoder 22 and sent to the exchange. Similarly, the signaling information is also converted from a digital signal into a signaling signal g in the signaling decoder 23, and sent to the exchange.

It goes without saying that the above-described operation of the receiving side circuit takes into consideration multi-frames, and decodes 7 bits every 6 frames, and decodes the remaining 8 bits, thereby improving the audio characteristics.

In addition, in the embodiment shown in FIG. 2, the frame separation for signaling is performed in the audio channel section, but in order to reduce the size and power consumption of the device, this function is transferred to the multiplexing section 12. ．． It is also possible to transfer the signals to the separation unit 13 and execute the signals for 24 channels in a time-division manner using a multiplexing circuit. In addition, not only audio signals to 64Kb, but also 32Kb
It is also easy to apply to b/s ADPCM (adaptive differential PCM) signals.

(Effect of the invention) According to the present invention, as described above in detail.

Since a control signal (for example, signaling) can be multiplexed into a digitized audio signal, there is an advantage that a large number of channels can be transmitted using a transmission line with a fixed transmission band (for example, 1.544 Mb/s).

This is a great advantage for digital leased line transmission equipment, which has recently been released. Furthermore, since the audio signal, signaling signal, and frame synchronization signal are included in the same signal train (e.g., 64Kb eight signal train), the signal from one transmission path is branched and sent out as two. For devices that provide branching/combining service circuits, it is possible to branch/combine signal strings, making processing within the device extremely easy, making the device smaller, lower power consumption, and more reliable. We can also expect it to improve.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a frame configuration to which the bit steal method according to the present invention is applied, and FIG. 2 is a diagram showing an example of an apparatus using the frame configuration of FIG. 1. 1.2-m-frame, 11-m-audio channel section, 12-m-multiplexing section. 13--1 separation section, 15-11 Symphony Orchestra, 16
---Signaling encoder. 17---Frame pattern generator. 18-m-signal separator; 21-m-frame synchronization circuit. 22--1 decoder, 23--signaling decoder.

Claims (1)

[Claims] In the bit steal method, which switches and multiplexes a part of an audio signal encoded into a digital signal and a control signal on a frame-by-frame basis, the audio signal and the control signal are identified. A bit steal method that is characterized by multiplexing the frame synchronization signal for