JP2000295241A - Voice signal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit voice signals of a plurality of channels employing a voice compression technology efficiently without causing degradation in a primary group digital hierarchy interface (T1 interface) and to provide an on- demand transmission system in an ATM network adopting a specified signaling bit. SOLUTION: A plurality of channels of compressed voice signals are multiplexed on one time slot and a stolen bit for signaling bit is assigned to a specific time slot and data are transmitted efficiently without degradation. Furthermore, the signaling information of the multiplexed voice channels is degenerated and assigned to the signaling bit for each time slot so as to attain on-demand transmission in an ATM network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal transmission system, in particular, a digital audio signal compressed by using the TTC-G. 704 relates to a transmission system using a primary group digital hierarchy interface (T1 interface).

[0002]

2. Description of the Related Art Conventionally, when a voice signal in a telephone band is transmitted through a T1 interface, a voice signal converted into a 64 Kbps digital signal is ignored ignoring bits that are bit stealed for signaling bits as individual line signals. 1
Allocate to time slots and transmit. In the case of a voice signal compressed to a digital signal of 32 Kbps or 16 Kbps by using the voice compression technology, voice degradation due to bit stealing of the signaling bit is avoided, and the transmission bandwidth of the signaling bit for each channel is limited to one time slot. Only one channel of audio signal could be transmitted, and the transmission band could not be used effectively. In addition, as a method of using the invalid band, a signal or the like for communication between the data terminal devices is used.
Effective utilization is achieved by restricting and transmitting according to the invalid band.

[0003] In addition, the "audio signal multiplexing apparatus" disclosed in Japanese Patent Application Laid-Open No. 4-47725 is designed to reduce the quality degradation of an audio signal by allocating a specific time slot other than a time slot to which an audio signal is allocated to a single signal. An audio signal multiplexing device for multiplexing without occurrence is disclosed.

[0004]

The above-mentioned prior art has several problems. First, there is a problem that the transmission band of the T1 interface cannot be used sufficiently effectively. The reason is that the signaling bits defined in the frame configuration of the T1 interface are bit stolen, one bit every six frames, and especially in the transmission of a compressed audio signal, if this bit is missing, the audio quality is severely degraded. Therefore, audio signals that do not use this band must be allocated.

A second problem is that when a compressed voice signal is multiplexed into one time slot in order to effectively use the transmission band of the T1 interface, signaling of each channel cannot be transmitted. is there. The reason is that only a signaling band up to 1,333 bps per time slot is allocated to the T1 interface.

It is an object of the present invention to provide an audio signal transmission system for efficiently transmitting compression-converted audio signals of a plurality of channels through a T1 interface.

[0007] Another object of the present invention is to provide an A-VTOA-0085.000 specified by the ATM Forum for transmission via an ATM (Asynchronous Transfer Mode) network.
TM-CES (ATM Circuit Emulation Servic
e) To provide a method for realizing the transmission of signaling information required for on-demand transmission, which is an effective use method of an ATM network using the method described above, even when a low bit rate voice signal is multiplexed on a T1 interface. It is.

[0008]

Means for Solving the Problems To solve the above-mentioned problems, the audio signal transmission system according to the present invention employs the following characteristic configuration.

(1) A voice signal in a telephone band compressed to a low bit rate is converted to a TTC-G. The compressed bit rate XN multiplexing is multiplexed in the time slot of the primary digital hierarchy interface (T1 interface) specified in 704 so that the compressed bit rate XN multiplexing becomes 64 Kbps or less, and the bit stealed for the signaling bit is transmitted to the specific time slot. The audio signal transmission method to be assigned.

(2) The audio signal transmission method according to the above (1), wherein the bits of the audio signal bit-stealed for the control signal on the interface definition in the multiplexing are also transmitted.

(3) The transmission side includes a transmission side to the transmission network and a reception side from the transmission network. The transmission side multiplexes the CODEC unit for compressing the audio signal and the compressed audio signal for each channel. A time slot allocating unit, a bit stealing control unit for transmitting a bit of an audio signal bit stealed for a signaling bit, and a frame generating unit for generating a claim of a T1 interface and transmitting the claim to a network terminating device. The side receives data from the network terminating device, and performs frame synchronization, a frame synchronization unit, a bit extraction channel for each of the stolen voice channels, a voice signal extraction unit for extracting a voice signal in channel units, and a voice signal expansion unit. An audio signal transmission system having a CODEC unit.

(4) The transmitting side further includes a signaling extractor for extracting signaling information for each channel, a signaling extractor for extracting, a signaling allocator for allocating the extracted signaling information to a specific time slot, and a multiplexed signal. The audio signal transmission method according to the above (3), further comprising a DM bit generation unit that aggregates signaling information for each time slot of the audio signal and allocates the information to signaling bits of a T1 interface.

(5) The audio signal transmission method according to the above (4), wherein the receiving side further has a signaling extractor for extracting signaling information for each channel from the synchronized frame and transmitting the signaling information to an audio interface.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the audio signal transmission system according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a preferred embodiment of an audio signal transmission system according to the present invention, wherein (A) shows a transmitting side to a transmission line and (B) shows a receiving side from the transmission line. First,
The configuration on the transmitting side in FIG. 1A will be described. The transmitting side of the embodiment of the audio signal transmission system includes a switching unit (PBX) 1,
Voice interface (I / F) unit 2, CODEC (coding / decoding) unit 3, time slot allocation unit 4, signaling extraction unit 5, bit steal control unit 6, signaling allocation unit 7, time slot signal (DM bit) It comprises a generation unit 8, a frame generation timing generation unit 9, and a network terminal (NT) 10.

The audio I / F 2 is for an analog or digital audio signal. The CODEC unit 3 compresses and expands the audio signal in channel units. The time slot allocating unit 4 performs multiplex allocation of the compressed audio signal to a time slot having a data rate of 64 Kbps. The bit stealing control unit 5 assigns bits of the audio signal to be bit stealed for signaling bits to a specific time slot.

The signaling extraction unit 5 includes a voice I / F unit 2
More signaling information for each channel is extracted. The signaling allocator 7 allocates signaling information of all voice signal channels to specific time slots. DM
The bit generation unit 8 aggregates the signaling of the multiplexed audio signal in units of time slots and allocates the signaling to the original signaling bits of the T1 interface. The frame generation timing generator 9 generates a frame together with the F bit for error monitoring for the frame synchronization of the T1 interface, and sends the frame to the network terminating device 10.

Next, the receiving section of FIG. 1B will be described. The receiving unit includes a frame synchronizing unit 11, a bit steal control unit 12, a signaling extracting unit 13, an audio signal extracting unit 14, a CODEC unit 3 ', an audio I
/ F section 2 'and exchange 1'. The frame synchronizer 11 synchronizes the frame of the T1 interface received from the NT 10.

The bit stealing control unit 12 extracts bit stealed audio signal bits allocated to a specific time slot. Signaling extraction unit 13
Extracts the signaling information of each audio signal channel and sends it to the audio I / F 2 'for each channel. The audio signal extraction unit 14 extracts an audio signal for each channel together with the bits from the bit steal control unit 12. CODEC
The unit 3 'extends the extracted voice signal to an interface with the exchange 1'.

Next, the frame structure of the T1 interface which is an interface with the network terminating device (NT) 10 generated by the voice signal transmission system of FIG. 1 will be described. Normally, when transmitting a voice signal using the T1 interface, a voice signal of 64 Kbps per channel is allocated to each time slot. Also, signaling information is allocated according to a defined frame format.

Referring to FIG. 2, a frame of the T1 interface (1.544 Mbps) has a total of 193 bits of 24 time slots and frame bits 22 for a time slot 21 composed of 8 bits.
The transmission is performed in a frame 23 having a period of z (125 μS). Here, a multi-frame configuration 24 of frames 1 to 24 including transmission such as frame synchronization and transmission line code error characteristic monitoring.
Is as shown in FIG. The signaling information 25 is 6
Each frame is bit stealed from one bit in each time slot of one frame. Here, in the case of a 32 Kbps audio signal that has been subjected to adaptive differential pulse code modulation (ADPCM) as an audio compression technique, two channels are allocated to one 64 Kbps time slot.

Referring to FIG. 3, for example, a 2 MDTI (Digital Trunk In) in which 30 channels of 64 Kbps voice signals are multiplexed as a voice interface with the exchange 1.
terface) signal will be described. in this case,
32 Kbps ADPC for each channel in CODEC unit 3
M conversion is performed. In the 32 Kbps audio signal, two channels are allocated to four bits of one time slot 21. The time slot for transmitting the audio signal is allocated to time slots 2 to 24 in one frame 23 (see 35 in FIG. 3). Here, when 30 channels of 32 Kbps are sequentially allocated by two channels from TS2, bits 1 to 4 of 1TS are allocated to odd-numbered channels 501, and bits 5 to 8 are allocated to even-numbered channels 502. Will be.

Here, from the rules of the T1 interface,
One bit every six frames and bit 8 of the even-numbered channel are bit stealed for a control signal (503 in FIG. 3).
Therefore, this bit is assigned to TS1 (see 402 in FIG. 3). Also, signaling information for each channel required for communication between terminal devices is allocated to TS1 (see 401 in FIG. 3). Further, voice signals are transmitted through the ATM network, and the ATM-CE of the ATM network terminating device (NT) 10 is used.
When on-demand transmission using S is performed, OR (logical OR) of signaling information of two channels of audio signals assigned to the time slots is assigned to the original control signal bits (FIG. 9). 5 of 3
03). Here, the signaling bits 403 assigned to the TS1 are always valid when at least one voice channel is transmitted, and signaling information is transmitted in channel units. However, these signaling bits need not be used in the case of constant bit rate (CBR) transmission. Naturally, the assignment of TS1 is repeated every six frames from the viewpoint of the rules.

[0024]

Next, another embodiment of the audio signal transmission system according to the present invention will be described with reference to FIG. In this example, 16 Kbps converted using low-delay code-driven linear prediction coding (LD-CELP) as a sound compression technique
Are allocated to one time slot of 64 Kbps by four channels.

For example, when receiving a 2MDTI signal in which 30 channels of 64 Kbps audio signals are multiplexed as the audio interface 2 with the exchange 1, the CODEC unit 3
Is subjected to 16 Kbps LD-CELP conversion for each channel. In the 16 Kbps audio signal, four channels are allocated to two bits of one time slot 42 of TS2 to TS24. Here, 30 channels of 16 Kbps are set to T
Assuming that four channels are allocated in order from S2, 1
Bits 1 and 2 of the TS are the N-th channel (N = 1, 5,
9, 13, 17, 21, 25, 29) and 46. Bits 3 and 4 are allocated to the (N + 1) th channel 47, and bits 5 and 6 are allocated to the (N + 2) th channel 48.
, Bits 7 and 8 are allocated to the (N + 3) th channel.

Here, from the rules of the T1 interface,
One bit every six frames, bit 8 of the (N + 3) th channel is bit stealed for a control signal (5 in FIG. 4).
Therefore, this bit is assigned to TS1 (see 44 in FIG. 4). Also, signaling information for each channel required for communication between terminal devices is allocated to TS1 (see 43 in FIG. 4). Further, when voice signals are transmitted through the ATM network and on-demand transmission is performed using ATM-CES of the ATM network terminating device (NT), the original control signal bits are assigned to the time slots, respectively. The signaling information of the audio signal of the channel
The result is assigned (see 503 in FIG. 4). Here, the signaling bit 45 assigned to the TS1 is always valid when at least one voice channel is transmitted, and signaling information is transmitted in channel units. However, these signaling bits need not be used in the case of constant bit rate (CBR) transmission. Also, the assignment of TS1 is naturally repeated every six frames from the rules.

Next, another embodiment of the audio signal transmission system according to the present invention will be described with reference to FIG. Here, 8 is converted using a joint structure type algebraic code driven linear predictive coding (CS-ACELP) as a voice compression technique.
A Kbps audio signal is allocated to one time slot of 64 Kbps by eight channels. For example, a 64 Kbps audio signal is 30 audio interfaces 2 with the exchange 1.
A case where a channel-multiplexed 2MDTI signal is received will be described. In this case, the CODEC unit 3 performs 8 Kbps CS-ACELP conversion for each channel. This 8Kb
The ps audio signal is assigned to one channel for each bit of one time slot 52 of TS2 to TS24.

Here, from the T1 interface rules, 6
The bit of the channel which is a multiple of 1 bit 8 is hit stealed for the control signal for each frame (refer to 503 in FIG. 5), and thus this bit is assigned to TS1 (5 in FIG. 5).
4). Also, signaling information for each channel required for communication between terminal devices is allocated to TS1 (see 53 in FIG. 5). Further, voice signals are transmitted through an ATM network,
When performing on-demand transmission using the ATM-CES of the ATM network terminator, the original control signal bits are assigned the OR of the signaling information of the audio signals of the eight channels assigned to the respective time slots. (See 503 in FIG. 5). Here, the signaling bit 55 assigned to TS1 is always valid when transmitting even one voice channel,
Transmits signaling information for each channel. However, these signaling bits have a fixed bit rate (CB
R) It does not need to be used for transmission. Also, naturally, the assignment of TS1 is repeated every six frames from the rules.

The embodiment of the audio signal transmission system according to the present invention has been described above in detail. In the present invention, the audio signal compressed for each channel is multiplexed / separated into frames of the T1 interface for a plurality of channels. More specifically, audio signal compression means (CODE
C section), means for multiplexing the compressed audio signal in channel units according to the bit rate (time slot allocating section), and for transmitting the bit of the audio signal bit stealed for the signaling bit. Means to assign to a specific time slot (bit stealing control unit)
And a means (frame generation timing generation unit) for generating a frame of the T1 interface and transmitting it to the network terminating device (switch).

On the other hand, on the receiving side from the transmission network, there are means for receiving data from the network terminating device (exchange) and performing frame synchronization (frame synchronization timing generation section), and a bit stealing bit of each voice channel. (Bit stealing control unit) for extracting an audio signal for each channel (audio signal extracting unit), and for expanding the audio signal (CODEC unit) 3 '.

Another feature is that signaling information is transmitted for every voice channel. Specifically, as a transmitting side to the transmission network, means for extracting signaling information for each channel (signaling extraction unit) and means for assigning the extracted signaling information to a specific time slot (signaling assignment unit) are multiplexed. Means (DM bit generation unit) for aggregating signaling information for each time slot of the generated audio signal and assigning it to signaling bits of a T1 interface. On the other hand, the receiving side from the transmission network includes a means (signaling extracting unit) for extracting signaling information for each channel from the synchronized frame and transmitting the signaling information to the voice interface.

However, the present invention should not be limited to only the specific examples described herein, and those skilled in the art can easily understand that various modifications can be made without departing from the gist of the present invention. Like.

[0033]

As apparent from the above description, according to the audio signal transmission system of the present invention, the following various effects can be obtained. First, the audio signal compressed and converted in the T1 interface can be efficiently transmitted without deterioration. The reason is that a plurality of channels are allocated to one time slot of the T1 interface, and bits that have been bit stealed for transmission of control signals are also allocated without truncation.

Second, on-demand transmission when transmitting voice signals using an ATM network is also possible. The reason is that the signaling information for each multiplexed voice signal is allocated to a specific time slot, and the control signal bit for each time slot defined in the T1 interface is also used for signaling of the voice signal channel allocated to the time slot. Is assigned as degenerated information and transmitted.

[Brief description of the drawings]

FIG. 1 is a block diagram of a preferred embodiment of an audio signal transmission system according to the present invention, wherein (A) is a transmitting side and (B) is a receiving side.

FIG. 2 is a frame configuration diagram of a T1 interface.

FIG. 3 is an operation explanatory diagram of the audio signal transmission system in FIG. 1;

FIG. 4 is a diagram illustrating another operation of the audio signal transmission system in FIG. 1;

FIG. 5 is a diagram illustrating still another operation of the audio signal transmission system in FIG. 1;

[Explanation of symbols]

 1, 1 'exchange 2, 2' voice interface unit 3, 3 'CODEC unit 4, time slot assignment unit 5, 13 signaling extraction unit 6, 12 bit stealing control unit 7, signaling assignment unit 8 DM bit generation unit 9 frame generation unit 10 Network terminator 11 Frame synchronization unit 14 Audio signal extraction unit 24 T1 interface 503 Signaling bit

Claims (5)

[Claims] An audio signal of a telephone band compressed to a low bit rate is transmitted to a TTC-G. The compressed bit rate XN is set in the time slot of the primary group digital hierarchy interface (T1 interface) specified in 704.
A voice signal transmission system characterized in that multiplexing is performed so that the multiplexing is 64 Kbps or less, and bits to be bit stealed for signaling bits are allocated to a specific time slot. 2. The audio signal transmission system according to claim 1, wherein bits of an audio signal bit stealed for a control signal on an interface definition in said multiplexing are also transmitted. 3. A transmitting side to a transmission network, and a receiving side from the transmission network, wherein the transmitting side multiplexes the compressed audio signal of a channel unit and a CODEC unit for compressing an audio signal. A time slot allocating unit, a bit stealing control unit for transmitting a bit of an audio signal bit stealed for a signaling bit, and a frame generating unit for generating a claim of a T1 interface and sending the claim to a network terminating device; Is a frame synchronization unit for receiving data from the network terminating device and performing frame synchronization, an audio signal extraction unit for extracting an audio signal for each bit extraction channel unit of each of the stolen audio channels, and a CODEC for expanding the audio signal. An audio signal transmission system, comprising: 4. The transmitting side further comprises a signaling extractor for extracting signaling information for each channel, a signaling extractor for extracting, a signaling allocator for allocating the extracted signaling information to a specific time slot, and a multiplexed voice. The voice signal transmission system according to claim 3, further comprising a DM bit generation unit that aggregates signaling information for each time slot of the signal and allocates the information to signaling bits of a T1 interface. 5. The voice according to claim 4, wherein the receiving side further comprises a signaling extraction unit for extracting signaling information for each channel from the synchronized frame and transmitting the signaling information to a voice interface. Signal transmission method.