JPH0946355A - Method and device for cellulating frame data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the influence of cell destruction in a network upon the reproduction of frame data at the receiving side. SOLUTION: In the case of transmitting frame data Fj by a cell Ci having an information field longer than the frame length Fsp (j) of the data Fj, the data Fj are stored in the information field of the cell Ci when the free data length Cemp (i) of the cell Ci is more than the frame length Fsp (j). When the length Cemp (i) is less than the length Fsp (j), dummy data are stored in a free area in the information field of the cell Ci. The frame data Fj which are not stored at the time are stored in a fixed length cell Ci+1 transmitted following the cell Ci. One frame data are stored in one fixed length cell without fail and fixed length cells including no free area in their information fields are successively assembled and transmitted to the network. When only one frame data is stored in a cell, the influence of cell destruction is exerted upon only one frame data.

Description

Detailed Description of the Invention

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a system for converting transmission data into cells, and more particularly to a cell generation method and apparatus for generating fixed-length cells from frame data.

[0002]

2. Description of the Related Art Generally, when data is transmitted through an ATM (asynchronous transfer mode) network, the transmission data is decomposed into cells, and the decomposed data is assembled as payload data into fixed-length cells.

However, if the transmission data is composed of a frame shorter than the information part of the fixed-length cell, the frame data is sequentially packed into the fixed-length cell payload, and the last overflowing frame data is stored in the payload of the payload. Decompose only the free space and store it. Therefore, there is a case where one frame data is transmitted while being divided into two fixed-length cells.

[0004]

As described above, even when one frame data is divided into two cells and transmitted, if the received cell is decomposed on the receiving side and the original frame data is restored. No problem arises. However, if any one cell is discarded in the network, the frame data cannot be restored even if the other cell is transmitted normally. In other words, only one of the two cells is discarded,
Since the entire frame data becomes unreproducible, the probability that the frame data becomes unreproducible is higher than the cell discard probability. In particular, when transmitting an encoded voice signal having a frame configuration, the voice of a frame related to a discarded cell cannot be reproduced, so that the communication quality is further deteriorated than the deterioration caused by cell discard.

An object of the present invention is to provide a method and apparatus for converting frame data into cells, which minimizes the effect of discarding cells in a network on frame data reproduction on the receiving side.

[0006]

According to the present invention, when transmitting frame data having a predetermined frame length by a fixed length cell having an information field longer than the frame length, an empty data length of the fixed length cell is transmitted. And the frame length are compared, and if the empty data length is equal to or longer than the frame length, the frame data is stored in the data field of the fixed length cell, and if the empty data length is less than the frame length, the data field of the fixed length cell Store the dummy data in the empty area of. The frame data that has not been stored at that time is stored in a fixed length cell that is transmitted subsequent to the fixed length cell.

In this way, one frame data is always stored in one fixed-length cell, and fixed-length cells having no free area in the information field are sequentially assembled and transmitted to the network. In particular, when only one frame data is stored in one cell, even if one cell is discarded, only one frame data is affected.

[0008]

FIG. 1 is a block diagram showing one embodiment of a cell generation device according to the present invention. The voice input data is LD-CELP (low delay-code excited lin).
Ear prediction) is encoded by the audio encoder 101 and stored in the frame memory 102. Also,
The payload data to be carried in the information section of the fixed-length cell is adjusted in the cell memory 103. The cell assembling unit 104 assembles a fixed-length cell by adding a header to the predetermined amount of payload data in the cell memory 103, and outputs the fixed-length cell to a transmitting unit (not shown). Data input / output of the frame memory 102 and the cell memory 103 is controlled by the processor 106 via the memory controller 105. The dummy data generator 107 generates dummy data under the control of the processor 106, and the dummy data is transmitted to the cell memory 103 by the memory controller 105.
Is written to the specified cell in

The processor 106 monitors the free data length of the cell being assembled stored in the cell memory 103 and compares the free data length with the frame length of the frame memory 102, as described later. If the empty data length of the cell is equal to or longer than the frame length, the frame data of the frame memory 102 is written to the information section of the cell of the cell memory 103 via the memory controller 105. vice versa,
If the free data length is smaller, the dummy data corresponding to the free data length is written from the dummy data generator 107 to the information section of the cell, and the information section of one cell is filled.

FIG. 2 illustrates a signal format in the present embodiment. As shown in FIG. 2A, the fixed-length cell Ci in the cell memory 103 includes a header H and an information field of 48 bytes, and the information field has a free data length Cemp (i). Shall be. Also,
The speech coded signal stored in the frame memory 102 is
As shown in FIG. 2B, the frame data Fj, Fj +
LD-CEL with a frame structure consisting of 1, ...
In the case of the P system, the data length Fsp of each frame is 40 bytes. As shown in FIG. 2C, in the cell generated by the present embodiment shown in FIG. 1, the information field of the fixed-length cell Ci stores frame data Fi and dummy data in the remaining area. Similarly, fixed-length cell Ci
The +1 information field stores frame data Fi + 1 and dummy data in the remaining area.

FIG. 3 is a flow chart showing an embodiment of the cell generation method according to the present invention. Processor 106
First, after initializing variables i and j (S201),
Empty data length Cemp (i) of cell Ci and frame data length F
Compare with sp (j) (S202). Free data length Cemp
If (i) ≧ frame data length Fsp (j) (N in S202)
o), the processor 106 includes the memory controller 105
To read the frame Fj from the frame memory 102 and write it to the information field of the cell Ci in the cell memory 103 (S203).

If an empty area remains in the information field of the cell Ci even after the frame Fj is written (No in S204), the variable j is incremented to process the next frame data (S205). , And return to step 202. When the information field of the cell Ci is filled with the data (Yes in S204), a header is added to the cell Ci and the cell Ci is output from the cell assembling unit 104 to the transmitting unit (S206). And the variables i and j
Are incremented respectively (S207), and step S is performed to process the next frame Fj + 1 and cell Ci + 1.
Return to 202.

If the free data length Cemp (i) <the frame data length Fsp (j) (Yes in S202), the processor 1
06 controls the dummy data generator 107 to generate dummy data for the empty data length Cemp (i). However, in the present embodiment, the information field of the cell Ci is 4
Since the frame data length Fsp (j) is 8 bytes and the frame data length Fsp (j) is 40 bytes, the empty data length Cemp (i) is always 8 bytes, and therefore the dummy data is also 8 bytes. The dummy data is written into the information field of the cell Ci in the cell memory 103 by the memory controller 105 (S208). Then, a header is added to the cell Ci, and the cell Ci is output from the cell assembling unit 104 to the transmitting unit (S2).
09). When the processing for the cell Ci is completed in this way, the processor 106 increments the variable i in order to write the remaining frame Fi to the next cell Ci + 1 (S210), and returns to step S202.

[0014]

As described in detail above, the cell generation method and apparatus according to the present invention always store one frame data in one fixed-length cell. The influence on the reproduction of the frame data can be suppressed. In particular, 1 per cell
In the case where only one frame data is stored, even if one cell is discarded, only one frame data is affected, and the influence of cell discard can be minimized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a cell generation device according to the present invention.

2A is a diagram illustrating a format of a fixed-length cell according to the embodiment, FIG. 2B is a diagram illustrating a voice-encoded signal format according to the embodiment, and FIG. 2C is a payload of a transmission cell according to the embodiment; FIG. 3 is a schematic diagram illustrating a configuration of data.

FIG. 3 is a flowchart illustrating an embodiment of a cell generation method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Speech encoder 102 Frame memory 103 Cell memory 104 Cell assembling part 105 Memory controller 106 Processor 107 Dummy data generator

Claims (8)

[Claims] 1. A method of transmitting frame data having a predetermined frame length by a fixed length cell having an information field longer than the frame length, wherein empty data length of the fixed length cell and the frame length are compared. If the empty data length is greater than or equal to the frame length, the frame data is stored in the empty area of the information field of the fixed length cell, and if the empty data length is less than the frame length, the fixed length cell A cell generation method comprising storing dummy data in an empty area of an information field and adding a header to the information field having no empty area to generate the fixed length cell. 2. The method according to claim 1, wherein when the free data length is less than the frame length, the frame data is stored in an information field of a fixed length cell transmitted subsequent to the fixed length cell. 2. The cell generation method according to 1. 3. The cell generation method according to claim 1, wherein the frame data is composed of a speech coded signal. 4. The one fixed-length cell stores only the one frame data.
4. The cell generation method according to any one of claims 3 to 3. 5. An apparatus for transmitting frame data having a predetermined frame length by a fixed length cell having an information field longer than the frame length, a first memory means for storing the frame data, and the fixed length cell. Second memory means for storing data corresponding to the information field, dummy data generating means for generating dummy data according to the empty data length of the fixed length cell, empty data length of the fixed length cell and frame length Comparing means for comparing the fixed data length and the frame length with the empty data length is stored in the information field of the fixed length cell, and if the empty data length is less than the frame length, the fixed length By storing the dummy data in the information field of the cell, there is a free area in the information field. Cell generating device comprising a cell generating means for generating a no fixed-length cells, in that it consists of. 6. The method according to claim 6, wherein the cell generation unit stores the frame data in an information field of a fixed-length cell transmitted subsequent to the fixed-length cell when the free data length is less than the frame length. The cell generation device according to claim 5, wherein 7. The cell generation device according to claim 5, wherein the frame data is composed of a speech coded signal. 8. The single fixed-length cell stores only the one frame data.
8. The cell generator according to any one of claims 7 to 7.