JP3765615B2 - Audio transmission device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention performs voice line exchange processing with a voice transmission apparatus that compresses and encodes a voice band signal into a cell, outputs it to a transmission line, and disassembles a cell received from the transmission line, compresses and decodes it to a voice band signal. The present invention relates to a voice transmission device in a voice band signal transmission system having an exchange.
[0002]
[Prior art]
In an audio band signal transmission system, when an audio signal is transmitted, high-efficiency audio compression coding / decoding is performed in order to effectively use the line capacity. Conventionally, one channel is assigned to one line of audio compression signal by time division multiplexing. In time division multiplexing, the channel is occupied even in a no-call state, so that a line is wasted. In order to use the line efficiently, the compression-coded voice is divided into frames to form a cell 31 as shown in FIG. The cell 31 includes a header area 32 indicating additional information such as an address and a data type, and a data area 33 including a compression-coded audio signal or the audio signal itself.
[0003]
A method of statistically improving transmission efficiency has been performed by transmitting this cell and not transmitting the cell when there is no sound so that other lines can use the transmission line when there is no call. . In addition, unlike voice signals, voice band data signals such as FAX and modem cannot be compressed and encoded, so they are converted into cells without being compressed and transmitted.
[0004]
FIG. 4 shows a configuration diagram of a relay transmission system when a large-scale network is configured. The voice band signal between the telephones 40 and 41 as exemplified in FIG. 4 is transmitted from the voice transmission devices 43, 45, which are composed of the exchanges 42, 46, 50, the voice decoding unit a, and the voice encoding unit b. 47, 49 and transmission paths 44, 48, etc., are transmitted to the telephone of the other party of the call. However, since it is the exchanges 42, 46, 50 that exchange the voice line at the relay base, the voice transmission devices 43, 45 , 47, and 49, it is necessary to decode the cell-based voice and pass it to the exchange. Therefore, in a communication network that performs relay transmission, as shown in FIG. 4, compression encoding / decoding of an audio signal is repeated a plurality of times in an audio transmission device, which causes a deterioration in audio quality.
[0005]
[Problems to be solved by the invention]
In the case of a large-scale network as described with reference to FIG. 4, when a voice signal is compressed and encoded, converted into cells and transmitted, the cells are once decomposed, compressed and decoded at a relay base, and circuit-switched by an exchange. The data is compressed, encoded, and transmitted again. Repeating compression encoding / decoding of an audio signal a plurality of times degrades the audio quality, and further increases the delay time due to processing delay, cellization, and cell decomposition processing delay associated with the compression decoding processing.
[0006]
The present invention solves such a conventional problem, and compresses, decodes, decodes, and assembles and disassembles a speech signal once regardless of how many steps of relay exchange are performed, thereby deteriorating speech quality and increasing delay time. The purpose is to improve the call quality by preventing the call.
[0007]
[Means for Solving the Problems]
In order to solve the above problems and achieve the object, the present invention inserts a predetermined identification signal into a voice band signal obtained by decomposing and compressing and decoding a cell , and outputs the identification signal to the exchange. An identification signal detection unit for detecting that a predetermined identification signal is included in the voice band signal, and a changeover switch for switching when the identification signal detection unit recognizes that the voice transmission device is connected to the voice transmission device of the relay connection partner. In order to generate a signal in which cells are inserted in the signal band to be output to the switch, voice compression is used when switching between a plurality of voice compression methods and uncompressed voice band signals depending on the use efficiency of the transmission path and the type of voice band signal to be transmitted. The cell insertion part that changes the method of inserting cells depending on the method and compression, and the relay connection of the insertion position, compression method, and compression of the inserted cell To retrieve a cell relay signal generator for chromatic cell type signal insertion unit for transmitting to the hand of the audio transmission device, the cell being inserted into the signal band from the exchange, the cell that receives the cell type signal from the signal received from the exchange type signal receiving unit, and a cell extraction unit that have a cell extracting portion for changing the method of extracting the cells by cell type, using the channel conditions, the control of switching the audio compression encoding method depending on the type of voiceband signal from the exchange And a control unit to perform .
[0008]
According to the present invention, it is recognized by the voice transmission apparatus itself that the voice transmission apparatuses are connected, and voice transmission is performed in the state of the cell without performing compression coding / decoding of the voice signal, cell decomposition, and cell assembly. Since relay transmission is performed between devices, no matter how many stages of relay exchange are performed, compression coding / decoding, cell assembly, and disassembly of voice signals are performed once, preventing deterioration of voice quality and increase in delay time, and large scale It has the effect of improving the call quality in a simple network.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
[0010]
(Embodiment)
FIG. 1 is a block diagram showing a configuration of an audio transmission device 11 according to an embodiment of the present invention. In FIG. 1, 12 is a transmission line interface unit for transmitting / receiving cells to / from the transmission line, 13 receives a voice band signal from the exchange, and an exchange interface unit for transmitting the voice band signal to the exchange, and 14 is received from the transmission line. A cell decomposing unit for decomposing the cell into auxiliary information and audio compression signal, 15 has one or a plurality of audio compression methods, and performs compression decoding by switching the audio compression method so that there is no cell header, or uncompressed audio compression decoding unit passing it, 16 of the voice band signal and the 64k bit / s from the audio compression decoder 15 by detecting the state of the identification signal from the identification signal detecting section 18 to be described later A changeover switch for switching and outputting a signal in which a cell is inserted in a band, and 17 is an identification signal inserting unit for inserting a predetermined identification signal into a voice band signal to be output to an exchange
[0011]
The above-described identification signal detection unit 18 detects a predetermined identification signal from the voice band signal received from the exchange. Reference numeral 19 denotes a cell relay signal generation unit that generates a cell relay signal in which a cell is inserted in the signal band to the exchange, and includes a cell insertion unit 20 and a cell type signal insertion unit 21. Here, the cell insertion unit 20 inserts only the cell or the cell data area into the signal band to be output to the exchange side. The cell type signal insertion unit 21 inserts a cell type signal indicating the cell insertion position, compression method, and presence / absence of compression inserted by the cell insertion unit 20.
[0012]
Reference numeral 22 denotes a cell extraction unit that extracts cells inserted in the signal band received from the exchange side, and includes a cell type signal reception unit 23 and a cell extraction unit 24. Here, the cell type signal receiving unit 23 receives the cell type signal when the signal from the exchange includes a cell. The cell extraction unit 24 extracts a cell when the cell is included in the signal from the exchange. 25 is a control unit for controlling the switching of the voice compression coding system according to the use condition of the transmission path and the type of the voice band signal from the exchange, and 26 has one or a plurality of voice compression systems and performs compression coding of the voice signal. A speech compression encoding unit that performs or passes the speech signal without compression, 27 is a cell assembly unit that divides the speech compression encoded signal into frames and adds a header that is auxiliary information such as a compression method to assemble a cell, 28 This is a changeover switch for switching the cell from the cell extraction unit 24 and the cell from the cell assembly unit 27 according to the detection state of the identification signal from the identification signal detection unit 18.
[0013]
Next, the operation of FIG. 1 having the above configuration will be described with reference to the cell relay signal (compression method A (1), compression method B (2) and data area only (3)) shown in FIG.
[0014]
In the initial state, the changeover switch 16 outputs the voice band signal from the voice compression decoding unit 15 to the exchange side, and the changeover switch 28 outputs the cell from the cell assembly unit 27 to the transmission line side. When voice transmission devices are connected by an exchange, the identification signal detection unit 18 detects that the signal from the voice transmission device of the relay connection partner includes a predetermined identification signal, and the changeover switch 16 is connected to the cell relay. The changeover switch 28 is switched to the cell from the cell extraction unit 22 to the output from the signal generation unit 19, and the cell relay transmission operation is started. Similarly, the voice transmission device of the relay connection partner also enters the cell relay transmission operation.
[0015]
In the cell relay transmission operation, the cell relay signal generator 19 generates a cell relay signal by inserting the cell received from the transmission path into a part of the 64 kbit / s band to the switch, and the identification signal inserter 17 inserts the identification signal. After that, it outputs to the exchange side. Conversely, the cell extraction unit 22 extracts a cell embedded in the 64 kbit / s band from the signal received from the voice transmission device of the relay connection partner via the exchange, and outputs it to the transmission line side. While the relay connection is established, the identification signal is always detected by the identification signal detector 18, and the cell relay operation is maintained.
[0016]
After the call is finished, the exchange unit disconnects the audio transmission devices, so that the identification signal is not detected by the identification signal detection unit 18, and the changeover switch 16 is used as the output from the original voice compression decoding unit 15, and the changeover switch 28 is used as the source. The output from the cell assembly unit 27 is switched. When the voice transmission device is connected to a telephone, facsimile, or modem by an exchange, since the identification signal is not detected, the selector switch 16 is set to the output from the original voice compression decoding unit 15, and the selector switch 28 is set to the cell assembly. The output from the unit 27 is subjected to voice compression coding, decoding, cell assembly, and cell decomposition.
[0017]
In the case of cell transmission using a plurality of voice compression methods as illustrated in FIGS. 2 (1) and 2 (2) according to the use state of the transmission path and the type of signal to be transmitted, or illustrated in FIG. 2 (3). If the data is transmitted without being compressed, the compression method of the cells received from the transmission line side during the cell relay transmission operation, the proportion of cells inserted into the 64 kbit / s band output to the switch side depending on the presence or absence of compression The insertion position will change.
[0018]
The cell header area has information on the voice compression method and the presence / absence of compression, the cell decomposition unit 14 recognizes the voice compression method and the presence / absence of compression, and the cell insertion unit 20 changes the cell insertion method. The cell type signal insertion unit 21 inserts a cell type signal indicating the insertion position of the inserted cell and the presence or absence of compression. Also, the cell type signal receiving unit 23 receives the cell type signal inserted in the 64 kbit / s band from the signal from the exchange, and the cell extracting unit 24 inserts the 64 kbit / s band in accordance with the cell position and compression. Extraction of existing cells.
[0019]
In FIG. 2, the cell insertion method is changed in the band of 64 kbit / s according to the voice compression method A (1) or B (2) of the cell to be relayed as shown in the signal example of the cell relay signal. In other words, when a cell having a 64 kbit / s data area that is not compressed is relayed, the entire cell including the header area cannot be embedded in the 64 kbit / s band, so only the 64 kbit / s data area is inserted. I do. The least significant bit (LSB) position includes a cell type signal indicating the insertion position of the cell and the presence or absence of compression. The least significant bit always contains an identification signal.
[0020]
【The invention's effect】
As described above, the audio transmission apparatus according to the present invention compresses and encodes an audio signal into a cell, and when the audio transmission apparatus is connected by an exchange, the audio signal is compression-encoded and decoded. By performing relay transmission between voice transmission devices without disassembling and cell assembling, voice compression encoding / decoding and cell assembling / disassembling are performed once, regardless of the number of relay exchanges. Thus, deterioration of voice quality and increase in delay time can be prevented, and call quality in a large-scale network can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an audio transmission apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of signals to be relayed and transmitted in the present invention.
FIG. 3 is a diagram illustrating a configuration example of a cell.
FIG. 4 is a configuration diagram of a relay transmission system in the case of a large-scale network configuration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Audio | voice transmission apparatus, 12 ... Transmission path interface part, 13 ... Switch interface, 14 ... Cell decomposition part, 15 ... Voice compression decoding part, 16, 28 ... Changeover switch, 17 ... Identification signal insertion part, 18 ... Identification signal Detection unit, 19 ... Cell relay signal generation unit, 20 ... Cell insertion unit, 21 ... Cell type signal insertion unit, 22 ... Cell extraction unit, 23 ... Cell type signal reception unit, 24 ... Cell extraction unit, 25 ... Control unit, 26 ... Audio compression coding unit, 27 ... Cell assembly unit.

Claims (1)

And cells of the compression coded audio band signal which is provided to the audio band signal transmission system with exchange to exchange processing of the audio line output to the transmission path, also audio compression decoding decomposes cell received from the transmission path Oite the voice transmission equipment back to the band signal,
An identification signal insertion unit for outputting to the exchange by inserting a predetermined identification signal to the audio band signal which is obtained by compressing decoded decomposing the cell,
An identification signal detecting unit that detects that it contains the predetermined identification signal to the audio band signal from the exchange,
A changeover switch that switches when the identification signal detection unit recognizes that it is connected to the voice transmission device of the relay connection partner ,
In order to generate a signal in which cells are inserted into the signal band to be output to the exchange , the voice compression is used when switching between a plurality of voice compression methods and uncompressed voice band signals depending on the use efficiency of the transmission path and the type of voice band signal to be transmitted. A cell insertion unit that changes the method of inserting a cell according to the method and the presence / absence of compression, and a cell type signal insertion unit that conveys the insertion position, compression method, and presence / absence of compression of the inserted cell to the voice transmission device of the relay connection partner a cell relay signal generation unit,
For taking out the cells that are inserted in the signal band from the exchange, with a cell extracting portion for changing the method of extracting the cells by the cell type signal receiving unit, and the cell type that receives a cell type signal from the received signal from the exchange A cell take-out section ;
A voice transmission apparatus comprising: a control unit that performs control to switch a voice compression coding system according to a use situation of a transmission line and a type of voice band signal from an exchange .

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