JP2944658B1 - AAL2 cell reception error detection method, AAL2 cell reception error detection device, and recording medium - Google Patents

Abstract

An object of the present invention is to accurately detect missing cells when receiving AAL2 cells. A sequential number of each AAL2 cell is represented by using one bit of an SN field of an STF of an AAL2 cell and upper two bits of, for example, a VPI of an ATM cell header. Cell missing and the number of cell missing are detected based on the number.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AAL2 cell reception error detection method, an AAL2 cell reception error detection device, and a recording medium. 36
In 3.2, ATM (Asynchronous)
AAL2 (ATM Adaptation Layer) using the Transfer Mode (Transfer Mode) signal transmission method.
er 2) in the signal processing (Start F
field) SN (SequenceNumber)
By using the unused fields in the AAL2 cell header as SN in addition to the AAL2
The present invention relates to an AAL2 cell reception error detection method, an AAL2 cell reception error detection device, and a recording medium capable of improving the reliability of cell loss detection.

[0002]

2. Description of the Related Art FIG. 12 shows a conventional AAL2 (ATM A
2 is a block diagram illustrating a configuration of an example of a communication system to which a method of detecting a reception error of a cell is applied. As shown in the figure, a base station or a relay device (base station / relay device) 4 collects cell information from each of the subscriber terminals 1 to n (n is a predetermined natural number) and performs AAL.
The data is transferred to the two-cell verification circuit 5. At this time, for each AAL2 cell to be transferred, the last transferred AA
A value obtained by alternately inverting the value of the SN (Sequence Number) of the L2 cell between 0 and 1 is referred to as STF (Star).
t Field) is substituted into the SN field of a 1-bit area.

As shown in FIG. 13, ATM (Async)
(Hronous TransferMode) cell is
It consists of an ATM header, a start field (STF), a short cell header, and a short cell payload. The AAL2 cell verification circuit 5 verifies the presence or absence of a reception error in the AAL2 cell based on the value of the SN field in the STF of the received AAL2 cell.

[0004] That is, for each received AAL2 cell, the value 0, value 1, value 0, value 1,. . . If value 0 and value 1 are input alternately, AAL2
The cell is regarded as having been normally received, and when the regularity that the value 0 and the value 1 are alternately input is broken, it is regarded that the AAL2 cell is lost at the time of reception.

In the example shown in FIG. 13, since it is not possible to detect that two AAL2 cells have been missed, a reception error occurs, and S indicates that the regularity of SN has been interrupted.
No N error is displayed.

[0006]

However, since the SN field has only one bit, if a cell loss occurs in units of two cells, it is determined that the cell is normal. In addition, when a cell loss occurs in an odd unit, there is a problem that the number of cells lost is unknown.

The present invention has been made in view of such a situation, and uses one or a plurality of unused bits in an AAL2 cell header as an SN to realize an AAL2 cell.
An object of the present invention is to improve reliability in detecting a cell reception error.

[0008]

AAL according to claim 1
The two-cell reception error detection method is an AAL2 cell reception error detection method for detecting an AAL2 cell reception error using an SN field in AAL2 signal processing.
Recognizing the sequential number of the AAL2 cell based on the value of the sequential number field of the start field of the L2 cell and the information of one or more bits in the ATM cell, and detecting a missing cell when the AAL2 cell is received. It is characterized by the following. Further, it is possible to detect a missing cell at the time of reception of an AAL2 cell based on information of one or a plurality of bits of an unused VPI field in an ATM cell. Further, it is possible to detect a missing cell at the time of reception of the AAL2 cell based on information of one or a plurality of bits of an unused VCI field in the ATM cell. Further, it is possible to detect a missing cell at the time of reception of the AAL2 cell based on information of one or a plurality of arbitrary bits of an unused GFC field in the ATM cell. 6. The AAL2 cell reception error detection device according to claim 5, wherein the AAL2 cell reception error detection device detects an AAL2 cell reception error using an SN field in AAL2 signal processing. First extracting means for extracting a value of a number field, second extracting means for extracting information of one or more bits in an ATM cell, and start of AAL2 cell extracted by the first extracting means The sequential number of the AAL2 cell is recognized based on the value of the sequential number field of the field and the information of any one or more bits in the ATM cell extracted by the second extracting means, and when the AAL2 cell is received. Detecting means for detecting cell loss. A recording medium according to a sixth aspect is characterized by recording a program capable of executing the AAL2 cell reception error detecting method according to the first aspect. In the AAL2 cell reception error detection method, AAL2 cell reception error detection device, and recording medium according to the present invention, a value of a sequential number field of a start field of the AAL2 cell, and information of one or more bits in an ATM cell Based on the AAL
Recognize the sequential number of two cells and detect missing cells when receiving AAL2 cells.

[0009]

FIG. 1 is a block diagram showing a configuration example of an embodiment of a communication system to which an AAL2 cell reception error detection method of the present invention is applied. As shown in the figure, the communication system accommodates subscriber terminals 1 to n (n is a predetermined natural number) and performs multiplexing on a base station / relay device 4.
And an AAL2 cell verification circuit 15 for verifying AAL2 cells transmitted from the base station / relay device 4, and an ATM (Asynchr) having an output of the AAL2 cell verification circuit 15 as an input.
on Transfer Mode) switch 6
It is composed of

FIG. 2 shows an example of the configuration of an AAL2 cell. As shown in the figure, the ATM cell has an ATM header,
Start field (STF), short cell header,
And a short cell payload. FIG.
Shows an example of the format of the ATM cell header. As shown in FIG.
lPath Identifier (hereinafter abbreviated as VPI) field, Virtual Channel I
a denifier (hereinafter abbreviated as VCI) field,
Payload Type (PT), Cell Los
s Priority (CLP), Header Er
rr Control (HEC). FIG. 4 shows an example of the STF format. As shown in the figure, the STF is a 6-bit OS
F, 1-bit SN (Sequence Number)
r) field and 1-bit parity. The SN is composed of one bit of the SN field in the STF and an arbitrary predetermined number m of bits (mbit) of the VPI field in the ATM cell header.

FIG. 5 shows an ATM cell header format inside the network. In the case of the example shown in FIG. 5, one bit of the SN in the STF and two bits of the VPI field in the ATM cell header constitute the SN.

In this case, as shown in FIG. 6, two bits (VPI-1 and VPI-2) of the VPI field and SN
A value of 0 to 7 is represented by one bit of the field, that is, the SN of the AAL2 cell.

In the case of the example shown in FIG. 7, one bit of the SN in the STF and two bits of the VCI field in the ATM cell header constitute the SN.

In this case, as shown in FIG. 8, two bits (VCI-1 and VCI-2) of the VCI field and SN
A value of 0 to 7 is represented by one bit of the field, that is, the SN of the AAL2 cell.

FIG. 9 shows an AT for a user network interface.
It shows the M cell header format. In the case of the example shown in FIG. 9, one bit of the SN field in the STF and A
Generic Flow Con in TM cell header
The SN is constituted by two bits of a trol (hereinafter abbreviated as GFC) field.

In this case, as shown in FIG.
2 bits of field (GFC-1 and GFC-2) and S
0 to 7 by 3 bits of 1 bit of N field
Is represented as the SN of the AAL2 cell.

Next, the operation will be described. When multiplexing AAL2 cells transmitted from a plurality of subscriber terminals 1 to n, the base station / relay device 4 of the communication system shown in FIG. STF in AAL2 cell for each cell
Based on the SN in ITU-T Recommendation I. The cell discarding process according to 363.2 is performed, and only normal cells are transmitted to the ATM switch 6.

In FIG. 5, in addition to the SN in the STF in the AAL2 cell, the VPI field 2 in the ATM cell header is used only in a section where the VPI field is unused.
Use bit as SN. Thus, the unused V
By effectively using the PI field as the SN, compared to the case of the SN where conventionally only a 1-bit area was used,
Counting is performed based on the number of bits used (3 bits in this example), and it is possible to verify missing cells, display an error indicating missing cells, display the count number, and the like.

Therefore, in addition to one bit of the SN field in the STF of the AAL2 cell, the VP in the ATM cell header
By using an arbitrary number of bits of the VPI as the SN only in a section where I is not used, it is possible to improve the reliability of detecting missing cells.

As a result, as shown in FIG. 11, for example, when two AAL2 cells are missing, AAL2
The cell verification circuit 15 can detect that two AAL2 cells have been missed, and can display an SN error on a display device (not shown).

In FIGS. 7 and 9, the reliability of the detection of a missing cell can be improved basically in the same manner as in FIG.

As described above, in each of the above embodiments, the following effects can be obtained. The first effect is that the number of missing cells can be recognized. That is, whether the number of missing cells is one or three,
Alternatively, it is possible to distinguish between 5 cells and 7 cells, and the number of missing cells can be accurately determined. Second
The effect of AAL2 cell is that even number (2,4, ...)
That is, the SN error can be detected even when the error occurs.
Thereby, detection omission of the SN error can be suppressed.

The reason is that in both the first effect and the second effect, in addition to one bit of the SN field in the STF of the AAL2 cell, any unused VPI, VCI, or GFC in the ATM header is used. SN of bit number
This is because the reliability of the verification of the missing cell by the SN can be improved by using it effectively.

In the above-described embodiment, a missing cell is detected by using unused 2-bit information of VPI, VCI, or GFC in addition to 1-bit SN. However, it is also possible to use information of three bits or more.

It is also possible to use information of any two or more unused bits in the ATM cell header.

[0026]

As described above, according to the AAL2 cell reception error detection method, AAL2 cell reception error detection device, and recording medium of the present invention, the value of the sequential number field of the start field of the AAL2 cell,
Recognizing the sequential number of the AAL2 cell based on information of any one or more bits in the ATM cell,
Since the missing cell at the time of receiving the AAL2 cell is detected, the accuracy of detecting the missing cell of the received AAL2 cell can be improved, and the number of missing cells can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a communication system to which an AAL2 cell reception error detection method of the present invention is applied.

FIG. 2 is a diagram showing an AAL2 cell format.

FIG. 3 is a diagram showing an ATM cell header format.

FIG. 4 is a diagram showing an STF format.

FIG. 5 shows upper 2 bits of VPI of an ATM cell header as S
It is a figure showing the example used as N.

FIG. 6 is a diagram illustrating an example in which counting is performed for each cell using the upper two bits of the VPI.

FIG. 7 shows upper 2 bits of VCI of an ATM cell header as S
It is a figure showing the example used as N.

FIG. 8 is a diagram illustrating an example of counting for each cell by using upper two bits of a VCI.

FIG. 9 shows the upper two bits of GFC in the ATM cell header as S
It is a figure showing the example used as N.

FIG. 10 is a diagram illustrating an example of counting for each cell using upper two bits of GFC.

FIG. 11 is a diagram illustrating a method of counting the number of cells using the upper two bits of the VPI of the ATM cell header as an SN and determining a cell loss.

FIG. 12 is a block diagram illustrating a configuration example of a system to which a conventional AAL2 cell reception error detection method is applied.

FIG. 13 is a diagram illustrating a conventional AAL cell reception error detection method.

[Explanation of symbols]

 1 to 3 subscriber terminal 4 base station / relay device 5, 15 AAL2 cell verification circuit 6 ATM switch

Claims (6)

(57) [Claims] An AA for detecting a reception error of an AAL2 cell using an SN field in AAL2 signal processing.
An L2 cell reception error detection method, comprising: recognizing a sequential number of an AAL2 cell based on a value of a sequential number field of a start field of the AAL2 cell and information of one or more bits in an ATM cell; A method for detecting an AAL2 cell reception error, comprising detecting a missing cell at the time of receiving a cell. 2. The system according to claim 1, wherein a missing cell at the time of reception of an AAL2 cell is detected based on information of one or more bits of an unused VPI field in the ATM cell. AAL2 cell reception error detection method. 3. The method according to claim 1, wherein a missing cell at the time of reception of an AAL2 cell is detected based on information of one or more bits of an unused VCI field in the ATM cell. AAL2 cell reception error detection method. 4. The method according to claim 1, wherein a missing cell at the time of reception of an AAL2 cell is detected based on information of one or more bits of an unused GFC field in the ATM cell. AAL2 cell reception error detection method. 5. An AA for detecting a reception error of an AAL2 cell using an SN field in AAL2 signal processing.
An L2 cell reception error detection device, comprising: first extraction means for extracting a value of a sequential number field of a start field of an AAL2 cell; and second extraction means for extracting information of any one or a plurality of bits in an ATM cell. Extracting means; a value of a sequential number field of a start field of the AAL2 cell extracted by the first extracting means; and one or more bits in the ATM cell extracted by the second extracting means Detecting means for recognizing the sequential number of the AAL2 cell based on the information of the AAL2 cell, and detecting a missing cell when the AAL2 cell is received. 6. A recording medium on which a program capable of executing the AAL2 cell reception error detection method according to claim 1 is recorded.