JPH1065677A - Method for converting cells of plural data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate an addition of new CODEC (coder-decorder) and a change of existed CODEC. SOLUTION: Compressed sound whose burst periods and burst lengths are Ta, Tb, Bb, Tc and Bc are outputted from the CODEC12a1 , 12a2 12b1 and 12c1 of respective channels. The greatest common measure of Ta, Tb and Tc is set to be a basic period TR, and TR is equally divided by the largest one among Ba, Bb and Bc so as to comprise time slots TS1 , TS2 ,.... The respective channels are sequentially allocated to TS1 , TS2 ,.... When the transmission burst exits, the burst is inserted into the slot, and is multiplexed. Then, the respective bursts of multiplexed/compressed sound are sequentially made into sound packets and the packets are put into ATM cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data generated in bursts such as voice data compressed to a low bit rate and having a plurality of burst cycles and burst lengths different from each other, such as IP packets and ATM cells. The present invention relates to a method of converting data into a cell composed of a group of data.

[0002]

2. Description of the Related Art ATM (Asynchronous Transfer Mode) which is positioned as a basic network technology for multimedia communication
, Regardless of the nature of the transfer data, such as the type of transfer speed,
One of its features is that it can process all information such as images, sentences, and voices on the same physical line. Accordingly, it is considered that an ATM network currently used mainly for data communication is transformed into a data + voice network which also inevitably serves real-time voice information processing together with the price reduction of ATM-related devices. Against this background, there is an urgent need to develop voice communication technology on ATMs.

In particular, in a dedicated line for a specific use between private networks or between a base station and an exchange in mobile communication, etc., the limited network capacity is efficiently used,
In order to reduce the cost per line, low bit rate compression of audio information and silence compression that does not transmit silence are essential. The bit rates of the currently widely used compression techniques are in the range of 32-4 kb / s.
When cellifying voice information of a bit rate lower than kb / s into cells, the delay (cell delay) for accumulating one channel of voice information of one channel generally increases as the bit rate decreases, so that one cell is used. It is necessary to consider a method of storing a plurality of channels of audio information packets having a short user information length therein to reduce cell transfer delay without reducing cell transfer efficiency.

In the recent audio compression algorithm of 8 kb / s or less, the compression processing is performed in units of frames of a plurality of audio samples, so that the output compressed audio is obtained in bursts in units of tens to hundreds of bits per frame. Can be Therefore, by packing the compressed voice for each frame into a standard cell as a voice information packet, unnecessary cell delay is suppressed, and high-efficiency voice information can be transmitted.
However, in order to maintain a high data transfer efficiency, a certain number of line multiplexing is required, so that it is necessary to realize low bit rate voice cell conversion and multiplexing processing in one set.

That is, in a low bit rate audio coding system of 8 kb / s or less, as shown in FIG. 6, data is output in bursts in units of tens to hundreds of bits for each frame rate. For example, as shown in FIG.
h-3 low-bit-rate audio data is packetized by attaching a header h to each frame, for example, and the audio packets are AT
A cell is composed of multiplexed voice information by sequentially filling the payload of the M standard cell. In the case of silent compression, no audio packet is output in a silent frame. Thus, cell information delay can be suppressed and highly efficient voice information can be obtained.

[0006] Such low bit rate audio information is multiplexed.
Figure 8 shows a possible configuration for
Can be C corresponding to various encoding systems in the audio compression unit 11
ODEC (codec) 12a ₁~ 12a_m, 12b₁
~ 12b_n, 12c₁~ 12c_pIs provided, and CODE
C12a₁~ 12a_m, 12b₁~ 12b_n, 12c₁
~ 12c_pEach has a frame cycle of Ta, Tb, Tc
The number of bits in one frame is also represented by the pulse width in the figure.
Are different from each other as shown.

The same kind of CODECs 12a _{1 to} 12a _m , 1
2b ₁ ~12b _n, 12c ₁ per ~12c _p, voice input and output portion 14a of the multiplexing process CLAD unit 13, 14b, 1
4c, the audio input / output unit multiplexes bursts (compressed audio information) of a plurality of channels (lines) input from a plurality of CODECs, that is, associates each multiplexed time slot with a channel. To multiplex.

The audio input / output units 14a, 14b and 14c are connected to the cellular deceleration units 15a, 15b and 15c, respectively, and the audio information multiplexed by the audio input / output unit 14a is converted into audio packets for each channel. The voice packets are packed into cells in the order in which they were generated, and ATM cells are created. Similarly, the multiplexed audio information of the audio input / output units 14b and 14c is similarly transmitted to the cellular deceleration units 15b and 15c, respectively.
Is an ATM cell. These cellularized decelerating units 15
The ATM cells generated in a, 15b and 15c are sent to the ATM network 16.

A input from the ATM network 16
The TM cell is supplied to a corresponding one of the cellularized decellularizing units 15a, 15b, and 15c according to a coding method of voice information in the cell, and is decellularized, that is, separated into compressed voice for each frame of each channel. Multiplexed audio,
It is supplied to the corresponding one of the audio input / output units 14a, 14b, and 14c, separated by the audio input / output unit for each channel, and supplied to the corresponding CODEC of the audio compression unit 11. Each CODEC of the audio compression unit 11 is connected to one of the 64 kb / s audio lines 18 via the selection connection unit 17. In other words, the same type of CODEC as the other party's CODEC
Are selectively connected by the selection connection unit 17.

[0010]

Since the frame period and the number of bits (burst length) of the compressed information (burst) are different depending on the coding system, multiplexing is performed for each channel sound of the same coding system. . In other words, in the conventional multiplexing technique, the time length of the time slot corresponding to the channel is the same, and the time slot and the burst length of the compressed voice to be allocated to the time slot are matched, so that channels having different burst lengths are multiplexed. Can not. Also, when the frame periods are different, the correspondence between each channel and the time slot number is not constant, and multiplexing cannot be performed. That is, conventionally, it was necessary to provide a voice input / output unit for each encoding method.

Also, in the cell-forming decellularization unit, since the cells are packed without gaps, if the length of the voice packet is different, the packing process becomes complicated, and the celling of voice packets of the same length is performed. Since decellularization is performed, it is necessary to provide a cellular decelerating unit for each encoding method.
As described above, since the voice input / output unit and the cell decelerating unit are provided for each encoding method, the apparatus scale is increased and the price is increased. When a new CODEC is introduced, or the CODEC to be used is changed. However, it is necessary to newly introduce a voice input / output unit and a cellized / decellularized unit to cope with the CODEC, and the voice multiplexing CLAD unit 13 itself needs to be changed, which is costly. there were.

These problems occur not only when the compressed voice is converted into ATM cells but also when the voice is converted into IP packets (packets in a packet transmission network). Further, the present invention is not limited to the case where compressed voice is multiplexed and converted into cells (ATM cells, IP packets, etc.). In general, when a plurality of bursts of data are converted into cells, the burst cycle and burst length are different. Causes a similar problem.

[0013]

According to the present invention, the greatest common divisor of a burst period of a plurality of input data is selected as a basic period, and the basic period is divided into a plurality of time slots.
For each input data, time slots are sequentially allocated as long as the burst length is satisfied, and if there is transmission data in the allocated input data in the time slot order, at least one
Pack cells in bursts.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the present invention is applied to a case where a plurality of compressed voices are multiplexed and converted into cells, and portions corresponding to those in FIG.
In this embodiment, all CODECs 12a ₁ , 12a ₂ , 12b ₁ , 12
c _1, ... is connected to the multiplexing demultiplexing unit 21 is connected to one voice input and output portion 14 of the multiplexing demultiplexing unit 21 and the multiplexing process CLAD unit 13. The audio input / output unit 14 is connected to one cellized decellularization unit 15.

In the present invention, all input data (channels), that is, all CODECs 12a ₁ , 12a ₂ , 12b
_1, 12c _1, ... compressed audio output data Da ₁₁ of, D
_{a 12, ..., Da 21,} Da 22, ..., Db 11, Db 12, ...,
The burst periods Ta, Tb, Tc, of Dc ₁₁ , Dc ₁₂ ,.
The greatest common divisor of ... is a basic period T _R. Figure 2A as shown in the burst length of the entire input data in this embodiment (channel) (number of bits) Ba, Bb, Bc, ... equally dividing the fundamental period T _R with a value close to the large than the largest of time slot T _S1, T _S2, T _S3 Te, ..., constitute a T _Sn. FIG.
In the case of the example shown in the above, the frame period is 10 ms, 20 ms, 3
Since they are 0 ms and 40 ms, the basic period T _R may be set to 10 ms, and the time slot length may be set to 189 bits or more that can accommodate the maximum burst length.

Bursts of input data (channels) are sequentially allocated to the time slots T _{S1 to} T _Sn . Input data (channel) is first channel Da _11, Da _12, ..., the second channel Db _11, Db _12, ..., the third channel Dc _11,
Dc _12, ... and the three, burst period Ta of the three input data, Tb, Tc is Ta = T _R, Tb = 3T
FIG. 2B shows the state of allocation to each time slot when a, Tc = 4Ta, and the burst length is Ba, Bb, Bc bits (all of Ba, Bb, Bc are smaller than the bit length Bt of the time slot). That is, the first channel is set to the first time slot T _S1 and the second channel is set to the second time slot T _S2.
, The third channel is allocated to the third time slot T _S3 . In each of the time slots T _S1 , T _S2 ,..., If there is transmission data in the assigned input data (channel), the burst is inserted. First basic period T
A burst Da ₁₁ of the first channel is provided in a first slot T _S1 of _R1 .
Is inserted, the burst Db ₁₁ of the second channel is inserted into the second slot T _S2, and the burst Dc ₁₁ of the third channel is inserted into the third slot T _S3 . The second in the basic period T _R2 of the first slot T _S1 is to insert a burst Da ₁₂ of the first channel, second channel, not in the third channel was inserted because there is no delivery bursts. Since the burst period Ta of the first channel is equal to the fundamental period T _R, the fundamental period T _R1, T
The burst D of the first channel is placed in the first slot T _S1 of _R2 ,.
_{a 11, Da 12, Da 13} , ... but are inserted respectively, from burst period Ta of the second channel is a 3T _R, since the transmission data is not generated only every 3T _R, 4 th fundamental period T _R4 burst Db ₁₂ to the second slot T _S2 is inserted in the burst Dc ₁₂ of the third channel is inserted into the third slot T _S3 of the fifth basic period T _R5. In the same manner, the burst of each channel is inserted into the assigned time slot. As shown in FIG. 2B, each burst is inserted such that the beginning of the time slot coincides with the beginning of the burst.

As described above, in the multiplexing / demultiplexing unit 21, the input data is time-division multiplexed by inserting a transmission burst into a predetermined time slot having a basic period as a frame. The multiplexed compressed audio information is input to the audio input / output unit 14 for the correspondence between the basic period and the time slot position,
It recognizes the relationship between each time slot and the number of bits of the compressed audio information (burst) inserted therein, and outputs each burst and its time slot identifier ID as a set to the cellular decelerator 15.

FIG. 3 shows an example of a specific functional configuration of the audio input / output unit 14. As shown in FIG. The multiplexed compressed audio information is sequentially input to the input buffer 23, and the transfer clock is counted by a transfer bit number counter 24. This counter 24 is reset every basic period T _R (basic frame synchronization signal), thereby Is recognized, the data transfer clock of each channel is counted by the counter 24, and the counted value is compared with the number of time slot bits B _S stored in advance in the definition information storage unit 25 to obtain the basic period T. The time slot between _R is identified. Also, the frame synchronization signal of each CODEC is input,
For example, when the multiplexed audio information of the first basic period T _R1 in FIG. 2B is shown in FIG. 2C, this frame synchronization signal has a high level during the burst length in each slot and a low level during other periods. . The number of output bits per frame of CODECa is 1 for each of Ba, CODECb, and c.
If the number of output bits per frame is Bb and Bc, respectively, the burst length is equal to the number of bits.
When there is no CODEC output (silence), the level is low. Since such a frame synchronization signal of each CODEC is input, a difference between the count value of the transfer bit number counter 24 at the time of rising and falling of the frame synchronization signal of this CODEC is detected, and thus, the time synchronization in each time slot is detected. The number of valid bits is detected (recognized). Therefore, it is possible to take out only the number of effective bits for each time slot from the input buffer 23 and output this audio data (burst) and the number ID of the time slot as a set to the cellular decelerating unit 15. The various types of recognition are performed by the recognition unit 26. In addition, it is possible to confirm whether or not the audio data of the corresponding channel exists by the frame synchronization signal of each CODEC, and to perform the soundless / silent discrimination in the case of the silent compression control.

With such processing, an interface for transmitting and receiving a set of audio data in units of bits and a time slot number ID to / from the cellular decelerator 15 by asynchronous transfer can be provided. Cellular decelerating unit 1
5, it is possible to limit the difference between the channels to only the packet length (burst length), to operate at a high speed at a unique clock speed, and to absorb the complexity of the processing associated with multiplex processing.

FIG. 4 shows a specific example of the functional configuration of the cellularized decellularizing section 15, and its operation will be described. Since the CODEC used for each voice signal is selected for each call process, information corresponding to each time slot number and the type of CODEC used, that is, the burst length, is stored in the storage unit 31, and the voice input / output unit 14 Is written into the cell assembling memory 32 under the control of the packet write controller 33. Time slot number ID corresponding to the audio data
Is input from the audio input / output unit 14, and the burst length selection unit 3
4, the corresponding burst length in the storage unit 31 is selected, and the selected burst length is given to the packet write control unit 33, and the voice data is written into the cell assembly memory 32 by the burst length. Thus, the audio data of each time slot is written into the cell assembly memory 32.

When the cells are filled in the order in which they are written in the memory 32, that is, in the case where they are performed for each burst (frame) of each channel, the standard cell read control unit 35 controls the order in which the cells are written in the memory 32. Each burst is read, and a header h such as the channel ID and burst length generated by the packet header generator 36 is added to the burst, and the cells are packed as cells as shown in FIG. Upon completion of the embedding, the standard cell header H generated by the standard cell header generator 37 is added to the ATM cell to make it an ATM cell, which is written into the ATM output FIFO 38. Each time the writing of the audio data corresponding to each time slot into the memory 32 is completed, the data transfer control unit 39 sends a transfer control signal to the audio input / output unit 14 to request the transfer of the next audio data.

When the frame period of the voice data (channel) is small, a plurality of continuous bursts may be assembled into one voice packet within a range where voice delay does not matter. The cell disassembly in the cellular decelerator 15 is performed by analyzing the header H of the ATM cell input to the ATM input FIFO 41 by the standard cell header analyzer 42, and further analyzing the header h of each voice packet by the packet header analyzer 43. , Each time slot is identified, written into the cell decomposition memory 44 for each burst under the control of the write control unit 45, and read from the cell decomposition memory 44 under the control of the multiplexed compressed voice. The data is read out and transferred to the voice input / output unit 14. The audio input / output unit 14 temporarily stores the audio data from the cellularized decellularizing unit 15 in the output buffer 47 (FIG. 3), and then supplies it to the multiplexing / demultiplexing unit 21.

It is conceivable that the FAX signal and other types of information are converted into cells and decells on the voice line by the same multiplex processing CLAD unit. In this case, for example, as shown in FIG.
A 4 kb / s audio input / output port 52 and an input / output port 53 for other purposes are provided, and the same as the audio input / output unit shown in FIG.
For AX signals, 32 kb / s for G3 and 6 kb for G4
Since a band of 4 kb / s is required, after detecting the presence or absence of a facsimile signal, if the facsimile is used, a 64 kb / s voice having an interface with the cellularized decellularization unit 15 at a frame period of 125 μs based on 64 kb / s. Input / output port 52, and input / output port 53 for other uses having an interface with cellular decelerating unit 15 through data input / output port 53 for data.
Is used. These three input / output ports 51, 52, 53
Is selected by the priority control and data transfer control unit 54. In this way, different types of information can be handled without changing the interface between the voice input / output unit 14 and the cellularized decellularizing unit 15.

In the example shown in FIG. 2, if T _R = 10 ms and the data transfer rate t _r = 2 (Mb / s), the number of multiplexing (number of time slots) n is 32 to 64, The number B _S can secure 640 to 320 bits, and the frame rate is a multiple of 10 ms and the compression rate is 8 kb / s or more.
It is applicable to various CODECs of about 4 kb / s. Figure 2B in the basic period T _R, the maximum burst length above, have been constructed with equally divided to time slots with a value close thereto, it is not limited to this, for the long burst length than the time slot length B _S , A plurality of consecutive time slots may be allocated.

In the above description, the voice compression multiplexing of the present invention is converted into ATM cells. However, the present invention is applicable not only to ATM cells but also to packetization into IP packets. Further, the present invention can be applied to a case where a plurality of data having different burst periods and different burst lengths are multiplexed and converted into cells.

[0026]

As described above, according to the present invention, the basic period is selected, divided into time slots, and these are allocated to each channel (input data), whereby the burst period and burst length of the input data are obtained. Is changed,
Even if a new one is added, it is possible to perform multiplex cell conversion by a common cell deceleration unit without providing a cell deceleration unit for each burst period, thereby simplifying the entire hardware configuration. It can be made at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a cell conversion device to which an embodiment of the present invention is applied.

FIG. 2A is a diagram illustrating a relationship between a basic cycle and a time slot, B is a diagram illustrating an example of a basic cycle and an example of data allocation of each time slot, and C is a diagram illustrating an example of a CODEC frame synchronization signal.

FIG. 3 is a block diagram showing a specific functional configuration example of a voice input / output unit 14 in FIG. 1;

FIG. 4 is a block diagram showing a specific example of a functional configuration of a cellular decelerator 15 in FIG. 1;

FIG. 5 is a diagram illustrating a cell unit and a cell unit for a plurality of types of information;
FIG. 6 is a block diagram showing an example of a functional configuration of a voice input / output unit 14 for using the device 5;

FIG. 6 is a diagram showing a bit rate, a frame rate, and the number of bits in one frame of various encoding schemes.

FIG. 7 is a diagram for explaining a proposed method for assembling a multiplexed cell of compressed audio of a plurality of channels.

FIG. 8 is a block diagram showing a configuration for implementing a proposed method of assembling and disassembling a multiplexed cell of compressed voice.

Claims (5)

[Claims] 1. A plurality of burst-like data are input,
These data are different in at least one of burst periods and / or burst lengths. In a cell conversion method for converting these data into cells consisting of a predetermined group of data, the greatest common divisor of the burst period of each input data is provided. Is divided into a plurality of time slots, and time slots are sequentially allocated to each input data as long as the burst length is satisfied. A cell conversion method for a plurality of data, characterized in that cells to be transmitted are packed at least one burst at a time if there is data to be transmitted. 2. The method according to claim 1, wherein the length of the time slot is longer than a maximum burst length in the input data. 3. The plurality of cells according to claim 1 or 2, wherein the filling of the input data into the cells is performed without any gap by adding an identifier of the data and a filling length for each filling. Data cell conversion method. 4. The allocation is performed for each burst of the input data to multiplex a plurality of input data, and each time slot is identified for each of the basic periods in synchronization with the multiplexed burst sequence. 4. The method according to claim 3, wherein the identifier and the burst are used as a set in the cell stuffing process. 5. A packing length corresponding to the identifier is detected.
5. The cell conversion method according to claim 4, wherein the cell is packed every time the added value of the burst of the corresponding time slot in the multiplexed burst sequence becomes equal to the packed length.