JPH10341233A - Fluctuation absorbing system in asynchronous transfer mode compression voice communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a transmission delay time of voice data in a network that applies relay exchange to asynchronous transfer mode ATM digital compression voice data. SOLUTION: When a private branch of digital exchange PBX 20 makes relay exchange, a relay exchange detection section 131 in a cell assembler/ disassembler 10 detects the fact of relay exchange to throw a selector 115 to a position A from a position B and a selector 123 to a position C from a position D respectively. Thus, only a station accommodating a concerned voice terminal 30 conducts fluctuation absorption processing, and storage of cells to fluctuation absorption buffer 111, read of stored cells by fluctuation absorption control signal 112, cell disassembling processing by a cell disassembly section 113, expansion processing by an expansion section 114, cell compression processing by a compression section 121 and cell assembling processing by a cell assembling section 122 in the relay exchange station are omitted. Thus, a cell received from an ATM network is relay-exchanged without any modification and sent to the ATM network again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluctuation absorbing system in ATM compressed voice communication for absorbing delay fluctuation of cells when relaying and switching digital compressed voice data from an ATM (asynchronous transfer mode) network.

[0002]

2. Description of the Related Art Conventionally, in a digital voice communication network in which transmission between stations is performed in cells of an ATM network, ITU-T standard recommendation G. After compressing digital audio to a low bit rate using a compression technique typified by LD-CELP based on 728, the data is often assembled into cells and communicated. When the relay is exchanged, the pre-compression band between the digital PBX and the cell assembling / disassembling device is effectively used, and the digital PBX is used as the digital PBX.
The technique of relaying via BX is used. In this case, in order to absorb the delay fluctuation of the cell generated in the ATM network, the station performing the relay switching stores the cell in the buffer when the cell is received from the ATM network, and stores the cell after the fluctuation absorption time elapses. Delayed reading is performed.

[0003]

In such a conventional method, since the station which performs the relay exchange performs the cell fluctuation absorbing process by accumulating the cell buffer every time, the accumulation time corresponding to the number of relay stages is a delay time. As a result, there is a problem that a delay of a voice signal between call terminals is increased. Accordingly, an object of the present invention is to reduce the transmission delay time of voice data in a network for relaying and switching digital compressed voice data of ATM.

[0004]

In order to solve the above-mentioned problems, the present invention provides a buffer for storing cells received from an ATM network, and a fluctuation absorption control unit for reading out cells of the buffer after a guaranteed cell fluctuation time has elapsed. And a cell processing unit including a cell decomposing unit that decomposes the read cells into digital compressed audio data, a decompression unit that decompresses digital compressed audio data, and exchanges digital audio data from the cell processing device within its own station. A digital PBX (digital exchange) for relaying digital compressed voice data between stations is provided, and a detecting means for detecting the presence or absence of inter-station relay of the digital PBX is provided in the cell processing device; Audio data transmitting means for transmitting digital compressed audio data to the digital PBX when the presence is detected. The cell processing device further comprises a compression unit for compressing the digital audio data from the digital PBX when the detection means detects no inter-station relay to generate digital compressed audio data, and assembling the digital compressed audio data into cells. A
And a cell assembling unit for transmitting to the TM network. Further, the cell processing apparatus is provided with voice data transfer means for transferring digital compressed voice data from the digital PBX to the ATM network when the detection means detects the presence of inter-station relay.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an apparatus to which a fluctuation absorbing system in ATM compressed voice communication according to the present invention is applied. The above-mentioned device is a cell assembling / disassembling device (cell processing device), and the cell assembling / disassembling device 10 includes a fluctuation absorbing buffer 11 for storing cells received from the ATM network.
1, a fluctuation absorption control unit 112 for performing control to read cells from the buffer 111 at fixed time intervals after a guaranteed cell fluctuation time delay in order to absorb delay fluctuations generated in the ATM network, and read from the buffer 111. Cell decomposer 1 that decomposes a cell and reproduces it as digital compressed audio data
13, a decompression unit 114 for decompressing the compressed audio data to the original digital audio data, a selector 115 for switching the output to the digital PBX 20, and a compression unit 12 for compressing the audio data from the digital PBX 20 to a low bit rate.
1, a cell assembling unit 122 for assembling digital compressed voice data into cells, a selector 123 for switching cells to be transmitted to the ATM network, and detecting whether or not the line has been relay-switched by the digital PBX 20 and detecting that the line has been relay-switched. In this case, the relay switching detecting unit 131 switches between the selector 115 and the selector 123.

The digital PBX 20 includes signaling information from the cell assembling / disassembling device 10 and other devices (such as the voice terminal 30) connected to the digital PBX 20 and connection destination identification information in voice data. Input / output circuit)
Switch.

Next, the operation of the cell assembling / disassembling apparatus 10 will be described. In the cell assembling / disassembling apparatus 10 that has received the voice data from the digital PBX 20, the relay exchange detecting unit 131 determines whether or not the digital PBX 20 is performing the relay exchange based on the voice data and the control signal from the digital PBX 20. When detecting that the digital PBX 20 is not performing the relay exchange, the relay exchange detecting unit 131 controls the selector 115 to the B side and the selector 123 to the D side.

On the other hand, when the digital PBX 20 detects that the relay exchange is performed, the relay exchange detecting unit 131 controls the selector 115 to the A side and the selector 123 to the C side. Since the digital PBX 20 does not perform the relay exchange in the voice terminal connection station that does not perform the relay exchange, the selector 115
Is controlled to the B side, and the selector 123 is controlled to the D side.

The audio data from the digital PBX 20 is
The band is compressed by the compression unit 121, assembled into cells by the cell assembling unit 122, and transmitted to the ATM network. Conversely, ATM
Since cells received from the network have delay fluctuations,
In order to reproduce the data as STM (synchronous transfer mode) data, the fluctuation must be absorbed. Therefore, after accumulating the received cells in the fluctuation absorption buffer 111, the fluctuation absorption control unit 112 performs control so as to read out the cells from the fluctuation absorption buffer 111 at a constant time interval after the cell fluctuation time delay to be guaranteed. Fluctuation absorption buffer 1
The cell read from 11 is decomposed by the cell decomposing unit 113, reproduced into digital audio compressed data, and then decompressed by the decompression unit 114 to the original audio data.

In the cell assembling / disassembling apparatus 10 at the station where the relay exchange is performed, the selector 115 is initially controlled to the B side and the selector 123 is controlled to the D side. When the digital PBX 20 performs the relay exchange, the relay exchange detection unit 131 detects the relay exchange, and moves the selector 115 to the A side.
Switch 23 to C side. By this selector control, the cells received by the cell assembling / disassembling apparatus 10 are transmitted to the digital PBX 20 as they are without undergoing the fluctuation absorbing process. In addition, the relayed and exchanged cells are received from the digital PBX 20 performing the relay exchange to the cell assembling / disassembling apparatus 10, and transmitted to the ATM network again. When the communication is completed, the relay exchange is released by the digital PBX 20, and the relay exchange detector 131 detects that the relay exchange operation is completed, and switches the selector 115 to the B side and the selector 123 to the D side.

Next, FIG. 2 is a view showing a second embodiment, and shows an example applied to a network. In the example of FIG. 2, the voice terminal 30a of the communication station 40a is
b and the communication station 40a
This is an example of a case where the voice terminal 30a of the communication station 40d and the voice terminal 30d of the communication station 40d communicate (including a call) by relay exchange of the communication station 40b.

Between the cell assembling / disassembling apparatuses 10b and 10c and the digital PBX 20b, the TTC standard recommendation JJ-20.
Digital interfaces 11 to 12 are provided. First, the operation of the cell assembling / disassembling apparatus 10b when the voice terminal 40a of the communication station 40a communicates with the voice terminal 30b of the communication station 30b will be described with reference to FIG. In the cell assembling / disassembling apparatus 10b of the communication station 40b, PCM audio data at a speed of 64 kbps from the digital PBX 20b is compressed by the compression unit 12b.
1 compresses to a low bit rate. Here, ITU-
T. Recommendation G. 728 compliant LD-CELP 16
Compressed to kbps. Then, the compressed voice data is converted into cells by the cell assembling section 123 and transmitted to the ATM network.

Conversely, cells received from within the ATM network are accumulated in the fluctuation absorbing buffer 111, and are transmitted from the buffer 111 after the fluctuation time delay guaranteed by the fluctuation absorption control unit 112 to absorb the delay fluctuation generated in the ATM network. Control is performed to read cells at regular time intervals. The cells read from the buffer 111 have a speed of 16 kbp in the cell decomposing unit 113.
The compressed audio data is reproduced as s compressed audio data, and is expanded by the expansion unit 114 into audio data at a speed of 64 kbps. The synchronization signal insertion unit 132 and the synchronization signal detection unit 133
FIG. 5 shows an example of the synchronous signal insertion unit 132 shown in FIG.
As shown in (2) of FIG. 5, once every eight samples, the synchronization signal S for detecting the relay exchange is inserted into one LSB bit so as not to affect the 64 kbps voice data as in (1). I do.

The synchronizing signal detecting unit 133 is a synchronizing signal inserting unit 1
32 has a control function of switching the selector 115 to the A side and the selector 123 to the C side when detecting the relay switching detection synchronization signal S by 32. In the case of FIG. 3, the digital PBX
Since the 64 kbps PCM signal from 20b is not a relay-switched signal, it is a signal as shown in (1) of FIG. 5, and the relay-switching detection synchronization signal S is not detected. The selector 123 is on the D side.
Note that the same operation is performed in the communication station 40a in FIG.

Next, in FIG. 2, the voice terminal 30a of the communication station 40a and the voice terminal 30d of the communication station 40d are
The operation of the communication station 40b in the case of performing communication (including a call) by the relay exchange of 0b will be described with reference to FIG. When the digital PBX 20b relays and exchanges, the synchronization signal detector 133 of the cell assembling / disassembling apparatuses 10b and 10c changes the input data into a format as shown in FIG. Upon detecting S, the selector 115 of the cell assembling / disassembling apparatuses 10b and 10c is switched to the A side, and the selector 123 is switched to the C side. As a result, in the cell assembling / disassembling apparatus 10b, the cell received from the communication station 40a of FIG. 2 via the ATM network side is not absorbed by the fluctuation, and is relayed and exchanged as it is by the digital PBX 20b.
It is transmitted from the cell assembling / disassembling device 10c to the ATM network, and is subjected to fluctuation absorption control by the cell assembling / disassembling device 10d of the communication station 40d in FIG.

Similarly, the cells received by the cell assembling / disassembling apparatus 10c from the communication station 40d via the ATM network from the communication station 40d in FIG.
Is subjected to fluctuation absorption control by the cell / assembly / disassembly apparatus 10a. The signal between the digital PBX 20b and the cell assembling / disassembling apparatuses 10b and 10c when the selector 115 is switched to the A side and the selector 123 is switched to the D side is (3) in FIG.
The cell flows in a format as shown in FIG. 7, but in this case, the synchronization signal S for detecting the relay exchange is always inserted to constantly monitor whether or not the relay exchange is being performed.

When the communication between the voice terminal 30a and the voice terminal 30d is completed, the relay exchange of the digital PBX 20b is released, and the cell assembling / disassembling apparatus 10 is released from the digital PBX 20b.
The signals sent to b and 10c again change from the format shown in (3) of FIG. 5 to the format shown in (1) of FIG. 5. Since the synchronization signal detecting unit does not detect the synchronization signal S, the selector 115 to B side, selector 123
To the D side.

FIG. 6 is a block diagram showing a third embodiment of the cell assembling / disassembling apparatus 10. As shown in FIG. 6 is another specific example of the relay exchange detection unit 131 in FIG. In this example, the digital PBX 20 transmits a control signal for identifying execution / non-execution of the transit exchange, and the transit exchange control signal detection unit 134 determines the control signal, and the selectors 115 and 123
Is to switch. As an example of the control signal, TT
In the C standard recommendation JJ-20.11-12, there is an example in which a control signal for 30 channels is defined in a time slot number 16 in which a signal is undefined, and this control signal is used.

As described above, the compressed voice data of the cell received from the ATM network is relayed and exchanged by the digital PBX, and
In the case of cell transmission to the TM network, it is possible to detect that the relay exchange has been performed by the digital PBX, and to relay the cell as it is without absorbing fluctuations. As a result, even at the time of multi-stage connection by the relay exchange, the fluctuation absorption processing may be performed only at the station connected to the voice terminal, and it is possible to reduce the propagation delay time of the voice due to the fluctuation absorption.

[0020]

As described above, according to the present invention, the presence / absence of inter-station relay of a digital PBX is detected, and when the presence of inter-station relay is detected, digital compressed voice data is sent to the digital PBX as it is. Since the relay is performed, the fluctuation absorption processing including the buffer accumulation of the cell need only be performed by the station connected to the corresponding voice terminal, and the fluctuation fluctuation absorption processing of the cell at the station performing the relay exchange can be omitted. There is an effect that the transmission delay time can be reduced. Further, since the digitally compressed audio data from the digital PBX when the detection means detects the presence of inter-station relay is transferred to the ATM network as it is, the transmission delay of the audio data can be further reduced.

[Brief description of the drawings]

FIG. 1 is a first view of a cell assembling / disassembling apparatus to which the present invention is applied.
It is a block diagram showing an embodiment.

FIG. 2 is a diagram showing a second embodiment of the device.

FIG. 3 is a block diagram illustrating a first operation example of the device.

FIG. 4 is a block diagram for explaining a second operation example of the device.

FIG. 5 is a diagram showing a format of data audio data transmitted by the device.

FIG. 6 is a block diagram showing a third embodiment of the device.

[Explanation of symbols]

10, 10a, 10b, 10c, 10d: Cell assembling / disassembling device, 20, 20a, 20b, 20d: Digital PB
X, 30, 30a, 30b, 30d: voice terminal, 111
... fluctuation absorption buffer, 112 ... fluctuation absorption control unit, 1
13: Cell disassembly unit, 114: Extension unit, 115, 123 ...
Selector, 121: compression unit, 122: cell assembly unit, 13
1 ... Relay exchange detector, 132 ... Synchronous signal inserter, 133
... Synchronous signal detecting unit, 134 ... Relay switching control signal detecting unit.

Claims (3)

[Claims] 1. A network for relaying and switching digital compressed voice data from an asynchronous transfer mode network, comprising: a buffer for storing cells received from the asynchronous transfer mode network; and a fluctuation for reading out cells in the buffer after a guaranteed cell fluctuation time has elapsed. A cell processing device including an absorption control unit, a cell decomposing unit that decomposes the read cells into the digital compressed audio data, a decompression unit that decompresses the digital compressed audio data, and a digital audio data from the cell processing device. A digital exchange for performing intra-station exchange and relaying the digital compressed voice data between the stations, and the cell processing device has a detection unit for detecting the presence or absence of the inter-station relay of the digital exchange, and a detection unit. When the presence of inter-station relay is detected, the digital compressed voice data is sent to the digital exchange. Fluctuation absorption method in an asynchronous transfer mode compressed audio communication, characterized in that a speech data sending means that. 2. The compression unit according to claim 1, wherein the cell processing device compresses the digital audio data from the digital exchange when the detection means detects that there is no inter-station relay, and converts the digital audio data into digital compressed audio data. And a cell assembling unit for assembling the digital compressed voice data into cells and transmitting the digital compressed voice data to the asynchronous transfer mode network. 3. The voice data transfer according to claim 1, wherein when the detection means detects the presence of inter-station relay, the cell processing device transfers digital compressed voice data from the digital exchange to an asynchronous transfer mode network. Means for absorbing fluctuations in the asynchronous transfer mode compressed voice communication.