JP2667302B2 - Cell synchronization method and packet communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell synchronization method and a packet communication apparatus in a packet communication network for transferring data in fixed-length cells.

[0002]

2. Description of the Related Art In a conventional cell synchronization method in a packet communication network for performing data transfer in fixed-length cells, a first cell synchronization method in which a cell is accommodated in an external frame and a pointer indicating the phase of the cell is placed in the external frame. A method and a second cell synchronization method based on HEC (Header Error Control) using an 8-bit CRC code of a cell header have been proposed.

An example of the above-described conventional cell synchronization method will be described below with reference to the drawings.

FIG. 5 shows a flowchart of a first conventional cell synchronization method. In FIG. 5, reference numeral 37 is an external frame synchronization step, and 38 is a cell phase pointer extraction step from the external frame. FIG. 6 is an explanatory diagram of a first conventional cell synchronization method. In FIG. 6, 39
Is the external frame, 40 is the cell phase pointer, 41 and 4
2 is a cell.

In the first conventional cell synchronization method configured as described above, first, an external frame 39 is synchronized in an external frame synchronization step 37, and then a cell phase pointer extraction step 38 from the external frame is performed. The cell phase pointer 40 is taken out. Cell phase pointer 40 is cell 4
The cell phase pointer 40 indicates the synchronization of the cell 41.

FIG. 7 is an explanatory diagram of a second conventional cell synchronization method. In FIG. 7, reference numeral 43 denotes a temporary cell, reference numeral 44 denotes the first bid of the cell header information portion of the temporary cell 43, reference numeral 45 denotes the last bid of the cell header information portion of the temporary cell 43, and reference numeral 46 denotes H
An EC part 47 is a cell information part. FIG. 8 is an explanatory diagram of the HEC operation in the second conventional cell synchronization method.
In FIG. 8, 48, 49,... 55 are flip-flops, and 56, 57, 58 are exclusive OR operations.

In the second conventional cell synchronization method configured as described above, first, the cell header information portion of the temporary cell 43 is converted into a serial bit string from the first bit 44 to the last bit 45, and the HEC shown in FIG. Perform the operation and calculate the result C
., C7 and the HEC portion 46 of the temporary cell 43 are compared, and if they match, it is determined that a synchronization state is established.

[0008]

However, in the first conventional cell synchronization method, there is a problem that the cell synchronization method depends on an external frame. On the other hand, the second conventional cell synchronization method has a problem. There is a problem that a parallel / serial rearrangement step and a step of performing an HEC operation at a serial data rate are required.

An object of the present invention is to provide a cell synchronization method and a packet communication device which can process at a parallel data rate without depending on the configuration of an external frame.

[0010]

In order to achieve the above object, a cell synchronization method according to the present invention comprises a sequence identifier insertion step of providing a series of identifiers indicating a cell order at a fixed position in each cell; A reading step of reading data at the reading step, a continuity checking step of checking continuity of data sequentially read in the reading step, and a reading step when the data is determined to be discontinuous in the continuity checking step. And a reading position moving step of moving the reading position.

Further, when the data is determined to be discontinuous in the continuity check step, a protection step for detecting that the data is determined to be discontinuous in the continuity check step further continuously for a predetermined number of times. It is preferable that the read position moving step be performed only when it is determined that the data discontinuity has occurred continuously for a predetermined number of times in the protection step.

Further, the packet communication apparatus of the present invention has a cell transmitting section provided with a sequence identifier inserting means for giving a series of identifiers indicating a cell order at a fixed position in each cell, and reads and reads data at a cell length interval. Means, continuity checking means for checking continuity of data sequentially read by the reading means, and moving the reading position of the reading means when the continuity checking means determines that the data is discontinuous And a cell receiving unit having a reading position moving means.

A protection means for detecting, when the continuity check means determines that the data is discontinuous, that the data is determined to be discontinuous by the continuity check means a predetermined number of times more continuously; It is desirable that the protection unit includes the reading position moving unit that is executed only when it is determined that the data discontinuity has occurred continuously for a predetermined number of times.

[0014]

According to the cell synchronization method of the present invention,
Cell synchronization loss state can be detected by reading data at the cell length interval in the reading step, and data continuity is checked in the continuity inspection step, and when cell synchronization loss is detected, cell synchronization is not lost. Since the reading position is moved in the reading position moving step up to this point, it is possible to reach a cell synchronization state, and cell synchronization can be performed by parallel processing without depending on an external frame.

Further, by adopting a configuration having a protection step, it is not determined that an out-of-synchronization state exists until data discontinuity is detected a predetermined number of times in succession. It is possible to protect the user from receiving an incorrect number of times less than the number of times.

Further, in the packet communication device of the present invention, the cell transmitting unit transmits cells having a series of identifiers indicating the order of the cells to a fixed position in the cells by the sequence identifier inserting means. Then, the data is read at the cell length interval by the reading means, and the continuity checking means checks the continuity of the data to enable detection of the cell synchronization loss state.If the cell synchronization loss is detected, the cell synchronization loss state is detected. Since the reading position is moved by the reading position moving means until the cell disappears, it is possible to reach a cell synchronization state, and it is possible to perform cell synchronization by parallel processing and receive cells without depending on an external frame.

Further, by adopting the configuration having the protection means, it is not determined that the cell is out of synchronization until data discontinuity is detected a predetermined number of times in succession. It is possible to protect the user from receiving an incorrect number of times less than the number of times.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cell synchronization method according to an embodiment of the present invention will be described below with reference to the drawings.

1 to 3 are block diagrams showing an embodiment of the cell synchronization method of the present invention. 1 to 3, 1 is a cell assembling step, 2 is an order identifier inserting step, 3 is a cell sending step, 4 is a reading step, 5 is a continuity inspection step, 6 is a protection step, 7 is a cell disassembling step, 8 Is a reading position moving step, 9 is a calculating step of the sequence identifier SN, 10 is a writing step of the sequence identifier SN, 11 is a step of taking data into BUFFER, 12 is a reading step of the temporary sequence identifier D, and 13 is a calculation of continuity R. Step 14, a step of storing the temporary order identifier D, Step 15 of evaluating the continuity R, Step 16 of resetting the protection information H, Step 17 of the cell disassembly processing,
8 is a BUFFER clearing step, 19 is a protection information H calculation step, 20 is a protection information H evaluation step, and 21 is a BUFF
An ER head data discharge step, 22 is a BUFFER shift step, and 23 is a UFFER (L) clear step.

The operation of the cell synchronization method configured as described above will be described below with reference to FIGS.

First, in cell transmission, a cell assembly process 1
The sequence identifier SN is inserted into the K-th data of the cell assembled in the sequence identifier insertion step 2 and the cell transmission step 3
Sent by Therefore, in the transmitted cell stream, the sequence identifier SN increasing by 1 appears at the cell length L intervals. In the cell reception, first, the provisional sequence identifier D is read at a cell length L interval in the reading step 4, and in the continuity inspection step 5, the continuity R is calculated by the calculation step 13 and the provisional sequence identifier D is stored in the storage step 14. The continuity R is evaluated in the continuity R evaluation step 15 to determine whether it is continuous or discontinuous.

If it is determined that the protection information H is continuous, the protection information H is reset in a protection information H reset step 16. If it is determined in the continuity inspection step 5 that the cells are continuous, a cell disassembly step 7 is performed. The cell disassembly process 7 includes a cell disassembly process 17 and a BUFFER clear 18 process. Upon completion of reception of one cell, L data is read into the entire BUFFER cleared in the next read process 4.

On the other hand, if it is determined in the continuity inspection step 5 that there is discontinuity, a protection step 6 is performed. In the protection step 6, since the protection information H is counted in the protection information calculation step 19, it is possible to detect that the discontinuity has occurred a predetermined number of times consecutively in the protection information H evaluation step 20. When it is detected in the protection step 6 that the provisional order identifier D has been discontinued a predetermined number of times, the reading position moving step 8 is performed. In the reading position moving step 8, BUFF
ER head data discharge step 21, BUFFER shift step 22, BUFFER (L) clear step 23
Shifts the position referenced by BUFFER (K) by 1 and clears the BUFF cleared in the next reading step 4.
Only one data is added to FER (L). Even if the sequence identifier SN is continuously received erroneously, if the sequence identifier SN is correctly received within a predetermined number of times, the cell synchronization state is maintained without reaching the reading position moving step 8 by the protection step 6.

As described above, according to the present embodiment, the sequence identifier insertion step, the reading step, the continuity inspection step, the protection step, and the reading position moving step are provided, so that the processing is performed in parallel without depending on the external frame. Thus, cell synchronization can be obtained, and furthermore, the number of consecutive sequence identifier errors less than the predetermined number can be protected. Although the protection step is provided in this embodiment, a simple configuration without the protection step can be adopted.

FIG. 4 is a block diagram of a packet communication device according to an embodiment of the present invention. In FIG. 4, 24 is an information source, 25 is a cell transmitting unit, 26 is a cell assembling unit, 27 is a sequence identifier inserting unit, 28 is a cell transmitting unit, 29 is a packet network, 30 is a cell receiving unit, 31 is a reading unit, 32 Is a continuity inspection unit, 33 is a cell disassembly unit, 34 is a reading position moving unit, 35 is a protection unit, and 36 is a receiver.

The operation of the packet communication device configured as described above will be described below with reference to FIG.

The data sent from the information source 24 to the cell transmitting unit 25 is converted into cells by the cell assembling unit 26, given the sequence identifier SN by the sequence identifier inserting unit 27, and transmitted to the packet network 29 by the cell transmitting unit 28. Can be In the cell receiving unit 30, the reading unit 31 reads the temporary SN from the signal received from the packet network 29, and the continuity checking unit 32 determines the continuity of the temporary SN. The determination result of the continuity inspection unit 32 is sent to the cell disassembly unit, and when it is determined that the cells are continuous, the cells are disassembled. On the other hand, the determination result of the continuity inspection unit 32 is also sent to the protection unit 35, and if the determination result is discontinuous a predetermined number of times continuously, the protection unit 35
Is activated, the reading position moving means 34 is activated. The reading position moving means 34 moves the position at which the reading means 31 reads the temporary sequence identifier SN.

As described above, according to the present embodiment, by providing the sequence identifier inserting means, the reading means, the continuity checking means, the protecting means, and the reading position moving means, the parallel processing can be performed without depending on the external frame. In this way, cell synchronization can be obtained, and it is possible to protect a consecutive sequence identifier error that is less than a predetermined number. Although the protection means is provided in this embodiment, a simple configuration without the protection means can be adopted.

[0029]

Since the cell synchronization method of the present invention is configured as described above, data is read at a cell length interval in the reading step, the continuity of the data is checked in the continuity check step, and the cell synchronization is lost. The state can be detected, and when the cell synchronization loss is detected, the reading position can be moved in the reading position moving step until the cell synchronization loss state is not reached, and the cell synchronization state can be reached, without depending on the external frame. Cell synchronization is enabled by low-speed parallel processing.

Further, the protection step enables protection in the case where a series of identifiers indicating the order of cells are erroneously received consecutively less than a predetermined number of times.

Further, since the packet communication apparatus of the present invention is configured as described above, the cell receiving unit reads data by the reading means and checks the continuity of the data by the continuity checking means, thereby achieving cell synchronization. The out-of-sync state can be detected, and when the out-of-synchronization is detected,
Since the reading position can be moved to the cell synchronization state by the reading position moving means until the cell synchronization is not lost, cell synchronization can be performed by low-speed parallel processing without depending on external frames, and cells can be received. Is possible.

Further, the protection means enables protection in the case where a series of identifiers indicating the order of cells are erroneously received consecutively less than a predetermined number of times.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a cell synchronization method according to an embodiment of the present invention.

FIG. 2 is the same configuration diagram

FIG. 3 is the same configuration diagram

FIG. 4 is a configuration diagram of a packet communication device according to an embodiment of the present invention.

FIG. 5 is a flowchart of a first conventional cell synchronization method;

FIG. 6 is an explanatory diagram of a first conventional cell synchronization method.

FIG. 7 is an explanatory diagram of a second conventional cell synchronization method.

FIG. 8 is an explanatory diagram of an HEC operation in the second conventional cell synchronization method.

[Explanation of symbols]

 Reference Signs List 1 cell assembling process 2 sequence identifier inserting process 3 cell sending process 4 reading process 5 continuity checking process 6 protection process 7 cell disassembling process 8 reading position moving process 9 calculating process of sequence identifier SN 10 writing process of sequence identifier SN 11 to buffer 12 Tentative order identifier D reading step 13 Continuity R calculation step 14 Temporary order identifier D storage step 15 Continuity R evaluation step 16 Protection information H reset step 17 Cell disassembly processing step 18 BUFFER Clearing step 19 Computation step of protection information H 20 Evaluation step of protection information H 21 Ejection step of BUFFER head data 22 BUFFER shift step 23 BUFFER (L) clearing step 24 Information source 25 Cell transmission unit 26 Cell assembling means 27 Order Identifier insertion means 28 Cell transmission means 29 Packet network 30 cell receiving unit 31 reading means 32 continuously checking means 33 cell separation means 34 reads position moving means 35 protection 36 recipients

Continuing on the front page (72) Inventor Yasuyuki Okumura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Ryozo Kishimoto 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone (56) References JP-A-3-220839 (JP, A) JP-A-2-137432 (JP, A) JP-A-1-136439 (JP, A) JP-A-4-229743 (JP, A A)

Claims (4)

(57) [Claims] 1. In a packet communication network for performing data transfer in fixed-length cells, an order identifier inserting step of giving a series of identifiers indicating the order of cells at fixed positions in each cell, and reading and reading data at intervals of the cell length. And a continuity check step of checking continuity of data sequentially read in the reading step; and moving the reading position in the reading step when it is determined in the continuity checking step that the data is discontinuous. A cell synchronization method, comprising: a reading position moving step. And a protection step for detecting, when the data is determined to be discontinuous in the continuity check step, further determining that the data is determined to be discontinuous in the continuity check step a predetermined number of times. 2. The cell synchronization method according to claim 1, further comprising the step of performing the read position moving step which is executed only when it is determined in the protection step that data discontinuity has occurred continuously for a predetermined number of times. 3. In a packet communication network for performing data transfer in a fixed-length cell, a cell transmission unit including an order identifier insertion means for giving a series of identifiers indicating a cell order to a fixed position in each cell; Reading means for reading data at intervals, continuity checking means for checking continuity of data sequentially read by the reading means, and said reading means when the continuity checking means determines that the data is discontinuous And a cell receiving unit having a reading position moving means for moving the reading position of the packet communication device. 4. A protection means for detecting, when the continuity checking means determines that the data is discontinuous, further detecting that the data is determined to be discontinuous by the continuity checking means continuously for a predetermined number of times. 4. The packet communication apparatus according to claim 3, further comprising: the reading position moving unit that is executed only when the protection unit determines that the discontinuity of the data has occurred continuously for a predetermined number of times.