JPH07336354A - Stm data/atm cell conversion method and device - Google Patents

Abstract

PURPOSE:To shorten the time required for the assembly and disassembly processings of ATM cells. CONSTITUTION:The short cell of the length of 1/N (n is an integer) of the payload length of the ATM cell is used and the new format of the ATM cell for inserting the short cell to the payload of the ATM cell is adopted. In the case of assembling the ATM cell from STM data, the short cells are assembled first, the completely assembled short cells are inserted to the payload of the ATM cell and thus, the ATM cell is assembled. Reversely, in the case of disassembling the ATM cell and converting it to the STM data, the inputted ATM cell is disassembled into the short cells first, distribution is performed corresponding to the opposite party information of the short cells and the STM data stored in the payload of the distributed short cells are sent out to an output line according to the opposite party information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an STM data / ATM cell conversion method and apparatus, for example, continuous fixed time slot data (time division data: T in an ATM switch).
DHW data) and ATM cell data are mutually converted.

[0002]

2. Description of the Prior Art Generally, STM (synchronous transfer mode)
Information transmission of time-division highway data (hereinafter referred to as TDHW data) at 64 Kb / s per channel
Is performed as a basic speed. On the other hand, ATM
In (asynchronous transfer mode), information is sent and received by cells of fixed length. An ATM cell is generally composed of a header of 5 bytes and a data of 48 bytes and a total of 53 bytes.

Therefore, as shown in FIG. 2, periodic TDHW data of 8 kHz sampling (125 μs cycle) (assuming that n channels are accommodated in one cycle) is loaded in the payload of an ATM cell in time slot units. Put it on A
When the TM cell is assembled, the data sampled every 125 μs is stored in the payload for 48 bytes, so that a cell assembling time of 125 μs × 48 = 6 ms is required.

[0004]

However, the ATM
In the exchange, there are various delays in addition to the cell assembly time described above, and the amount of data delay between communication terminals becomes 6 ms or more. If the communication terminal is a terminal that handles data, such a delay causes almost no problem. However, if the communication terminal handles voice data, the larger the delay amount, the worse the call quality due to echo.

Although there is a device other than the ATM switch having a processing unit for converting STM data such as TDHW data into ATM cells or converting ATM cells into STM data, similarly, there is a delay associated with the conversion. It is desired to shorten the time.

[0006]

In order to solve such a problem, in the first aspect of the present invention, in the STM data / ATM cell conversion method for converting STM data into ATM cells, the payload length of the ATM cell is 1 / N (N
Is an integer), STM data is stored in the payload of the short cell, the destination information is added to assemble the short cell, and N short cells that are common to the final point or the middle point Are collected and output as ATM cells at a predetermined cycle.

In the second aspect of the present invention, in the STM data / ATM cell conversion method for converting an ATM cell containing N short cells into STM data, the input ATM cell is decomposed into short cells and short-circuited. It is characterized in that it is distributed according to the destination information of the cell, and the STM data stored in the distributed short cell payload is sent to the output line according to the destination information.

Further, in the third aspect of the present invention, the STM
ST that converts data to ATM cells and outputs it, and also converts input ATM cells to STM data and outputs it
In the M data / ATM cell conversion device, STM data is 1 / N (N
Is stored in the short cell payload of length
A short cell assembling unit that assembles a short cell by adding destination information, and an ATM cell assembling unit that collects N short cells that are common to the final point or an intermediate point and assembles ATM cells and outputs them at a predetermined cycle. , A short cell sorter that splits the input ATM cell into short cells and sorts them according to the destination information of the short cells, and an S stored in the payload of the sorted short cells.
And a short cell disassembling unit for transmitting the TM data to the output line according to the destination information.

[0009]

In each of the first to third aspects of the present invention, a short cell having a length of 1 / N (N is an integer) with respect to the payload length of the ATM cell is used, and the short cell is inserted into the payload of the ATM cell. The AT introduced by the present inventor
It is configured to comply with the new format of M cells.

Therefore, for example, S such as TDHW data
When assembling an ATM cell from TM data, first, a short cell is assembled, and the completed short cell is inserted into the payload of the ATM cell to assemble the ATM cell. On the contrary, disassemble ATM cells to STM
When converting to data, first, the input ATM cells are decomposed into short cells and sorted according to the destination information of the short cells, and the STM data stored in the payload of the sorted short cells is sorted according to the destination information. Output to the output line.

As described above, the assembly and disassembly of the ATM cell are performed in a clear unit called a short cell, so that even before the ATM cell is completely assembled,
The transmission of the ATM cell can be started when one or more short cells are inserted in the payload. Therefore,
The time required for assembling and disassembling ATM cells can be shortened as compared with the conventional case, and the overall communication delay time can also be shortened.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to a time division multiplexing highway (T
An embodiment applied to an ATM exchange that accommodates a DHW) will be described in detail with reference to the drawings.

FIG. 3 shows an ATM according to this embodiment.
It is a block diagram which shows the structure of an exchange.

In FIG. 3, the ATM switch 10 is an AT.
M self-routing switch 1 and a plurality (6 in FIG. 3).
Individual subscriber circuits 21 to 26.

Each subscriber circuit 21, ..., 26 is respectively
A plurality (maximum n) of subscriber terminals A1 to An, B1 to Bn,
It contains C1 to Cn, D1 to Dn, E1 to En, and F1 to Fn. Each subscriber circuit 2i (i is 1 to 6) contains a plurality of subscriber terminals Xj (X is A to F, j is 1 to 1).
n) data (which is STM data) is multiplexed and T
After converting to DHW data (also STM data), ATM cells are assembled and output to the ATM highway 4i. In addition, each subscriber circuit 2k (k is 1 to
In 6), when an ATM cell is given from the ATM highway 4k, the ATM cell is decomposed and converted into TDHW data.
Further, this TDHW data is demultiplexed and output to the destination subscriber terminal Yk (Y is A to F).

In FIG. 3, a connection configuration with other ATM exchanges is not shown for simplification of description, but other A-switches are connected via a line processing unit or an ATM line not shown.
It is also connected to a TM exchange, and ATM cells are used for other ATMs.
It can also be exchanged with exchanges. ATM in this case
The cell must also have the format described below.

Here, the mutual conversion between the TDHW data and the ATM cell is performed by the TDH built in the subscriber circuit 2i.
It is executed by the W data / ATM cell conversion circuit 3i.

The ATM self-routing switch 1 is
Based on the destination inserted in the header of the ATM cell given from the TM highway 4i, switching is performed for each route and output to the ATM highway 4k related to the destination.

In the case of this embodiment, TDHW data / AT
TDHW data and ATM performed by the M cell conversion circuit 3i
It is characterized by conversion between cells. That is, T
It is characterized in that DHW data is converted into an ATM cell into which the concept of a short cell is introduced and vice versa.

FIG. 1 is an explanatory diagram showing the relationship between ATM cells and short cells. ATM cells have a header of 5 bytes
e and payload (information section) 48 bytes, 53 bytes in total
te. In the case of this embodiment, the payload is further divided into short cells. Here, the format of the short cell is 2 bytes for the header and 4 bytes for the payload.
When defined as e, eight short cells can be inserted in the payload of the 53-byte ATM cell. As described above, each short cell has a header, and by storing channel information (VPI, VCI), time stamp information (TSP), etc. in this header, one A
TM cells may transfer data on multiple different channels. Here, in one ATM cell, a short cell whose destination is completely or partially in common (for example, route unit or VP) is used.
Short cells that are common in I units are aggregated. for that reason,
If there is little channel data with a common destination, ATM
Short cells in an empty state may occur in the cells.

FIG. 4 is a block diagram showing the internal structure of the TDHW data / ATM cell conversion circuit 3i. In FIG. 4, the TDHW data / ATM cell conversion circuit 3i is
First conversion unit 20 for converting DHW data into ATM cells
And second conversion of ATM cell data into TDHW data
The conversion unit 30 of FIG.

The first conversion section 20 stores the TDHW data in the payload of the short cell in time slot units, adds destination information (header) and assembles the short cell, and the short cell assembly section 21. And an ATM cell assembling section 22 which sends the data to the ATM self-routing switch 1 at the short cell assembling cycle while collecting the cells to form an ATM cell.

On the other hand, the second conversion unit 30 decomposes the ATM cells received from the ATM self-routing switch 1 into short cells and distributes the short cells to each time slot according to the destination information (header) of the short cells. And a short cell disassembling unit 32 for transmitting the time division data stored in the distributed short cell payload to the time division highway.

TDHW data / ATM cell conversion circuit 3i
Each of the conversion units 20 and 30 is mainly composed of a memory for buffering the data before and after the conversion. For example, the hardware logic executes the transfer between the memories based on the destination of the data before the conversion. Then, the data format is converted.

The ATM switch 10 according to this embodiment will be described below.
Will be described in the order of an operation related to conversion of TDHW data to ATM cells and an operation related to conversion of ATM cells to TDHW data.

The subscriber circuit 2i multiplexes the data from the accommodated subscriber terminals Xj by 125 .mu.s sampling and converts it into TDHW data. This TD
The HW data is the TDHW data / ATM cell conversion circuit 3
First, 4 bytes are loaded in the payload of the short cell on a time slot basis by i. Further, the destination information is inserted into the header of the short cell to complete the short cell. Each short cell is collected in each destination route (every 4 k of ATM highway) at a cycle of 500 μs (125 μs × 4), which is the short cell period, and ATs are collected.
It is loaded in the payload of the M cell, and the route number is inserted in the header of the ATM cell before this loading. In this way, the ATM cell is transmitted while assembling the 53-byte ATM cell.

FIG. 5 is a conceptual diagram when assembling an ATM cell from TDHW data according to this embodiment. Since the short cells are aggregated for each route to assemble the ATM cells, the header HEA of the ATM cells can be immediately formed, and then the short cells can be sequentially inserted. Therefore, even before inserting all the short cells into the payload PAY,
That is, the transmission of ATM cells can be started.

An ATM self-routing switch 1 in which such an ATM cell is input from the ATM highway 4i.
Performs switching for each route according to the header information.

On the other hand, ATM self-routing switch 1
In the subscriber circuit 2k to which the ATM cell switched by the above is provided from the ATM highway 4k, the ATM cell received by the TDHW data / ATM cell conversion circuit 3k is decomposed into short cells and the header information (that is, channel information VPI and VCI)
Allocate to a predetermined time slot on TDHW. Then, the subscriber circuit 2k receives each time stamp information (TSP).
Information), TDH by 1 byte every 125 μs
Output on W. This restores the TDHW data.

FIG. 6 shows an example of an ATM cell assembled in the subscriber circuit 2i of the ATM switch 10 of this embodiment.

The ATM cell shown in FIG. 6A is an ATM cell in the direction from the subscriber circuit 21 to the subscriber circuit 24 in the connection between the subscriber terminals A1-D1, A3-D3, ..., A7-D7. It is a cell. The ATM cell header contains AT
Route information indicating the M highway 44 is inserted. Information defining the subscriber terminal D1 is inserted in the header of the short cell between the subscriber terminals A1 and D1, and the data to be transmitted to the subscriber terminal D1 is 4 bytes in the payload.
Has been inserted. The other short cells have the same configuration.

The ATM cell shown in FIG. 6B is an ATM cell in the direction from the subscriber circuit 22 to the subscriber circuit 24 in the connection between the subscriber terminals B1-D2, B3-D4, ..., B7-D8. It is a cell. The ATM cells shown in FIG. 6C are subscriber terminals A2-E1, A4-E3, ..., A8-E.
Subscriber circuit 21 to subscriber circuit 2 in connection between 7
5 is an ATM cell in the direction to 5. The ATM cells shown in FIG. 6D are subscriber terminals C1 -E2, C3 -E4,
..., ATM cells in the direction from the subscriber circuit 23 to the subscriber circuit 25 in the connection between C7 and E8.

As shown in FIG. 6, since the ATM cells are assembled in short cell units instead of in time slot units, it is easier to assemble ATM cells associated with the same route in parallel as compared with the prior art.

As described above, according to the above embodiment, the TD
Conversion from HW data to ATM cells and conversion from ATM cells to TDHW data are performed by intermediating a clear unit called a short cell, so even before the ATM cells are completely assembled, they are transferred to the payload. 1
Or, when two or more short cells are inserted, the A
Transmission of TM cells can be started, and the time required for assembling and disassembling ATM cells can be shortened as compared with the conventional case. As a result, the overall communication delay time can be shortened. For example, the overall communication delay time is considered to be about 2 ms.

In the above embodiment, the present invention is applied to the ATM switch, but other devices (eg, STM data and ATM cells) which require mutual conversion are used.
It can be applied to ATM video conferencing devices, etc.).

The number of short cell bytes is ATM.
Any fraction of the cell payload length is optional,
Further, information other than the destination may be inserted in the header of the short cell.

Further, the STM data is not limited to the time division multiplexed data (TDHW data).
For example, the data from a plurality of subscriber terminals Xj may be immediately loaded on the payload of the short cell without being multiplexed.

[0038]

As described above, according to the present invention, the ATM
A new format of the ATM cell is adopted in which a short cell having a length of 1 / N (N is an integer) with respect to the payload length of the cell is used and the short cell is inserted into the payload of the ATM cell. Since the disassembly is performed in a clear unit called short cell, that is, different time slot data is inserted into one ATM cell for transmission and reception.
The time required for assembling and disassembling ATM cells can be shortened as compared with the prior art, such as the arrival time of each time slot data required to be inserted into a cell can be shortened, and the overall communication delay time can also be shortened.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an ATM cell format according to an embodiment.

FIG. 2 is an explanatory view showing a state of assembling a conventional ATM cell.

FIG. 3 is a block diagram showing a configuration of an ATM exchange according to an embodiment.

FIG. 4 is a block diagram showing a configuration of the TDHW data / ATM cell conversion circuit.

FIG. 5 is an explanatory diagram showing a state of assembling the ATM cell of the embodiment.

FIG. 6 is an explanatory diagram showing an example of assembling the ATM cell of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... ATM self-routing switch, 21-26 ... Subscriber circuit, 31-36 ... TDHW data / ATM cell conversion circuit, 10 ... ATM switch, 20 ... 1st conversion part, 2
1 ... Short cell assembly section, 22 ... ATM cell assembly section, 3
0 ... Second conversion unit, 31 ... Short cell distribution unit, 32 ...
Short cell disassembly unit.

Claims (3)

[Claims] 1. S for converting STM data into ATM cells
In the TM data / ATM cell conversion method, a short cell whose length is 1 / N (N is an integer) is used for the payload length of the ATM cell, the STM data is stored in the payload of the short cell, and the destination information is stored. STM data / A characterized in that short cells are added and assembled, N short cells common to the destination or the middle point are collected and output as ATM cells at a predetermined cycle.
TM cell conversion method. 2. A STM data / ATM cell conversion method for converting an ATM cell containing N short cells into STM data, wherein an input ATM cell is decomposed into short cells and distributed according to destination information of the short cells, An STM data / ATM cell conversion method, characterized in that the STM data stored in the distributed short cell payload is sent to an output line according to destination information. 3. The input STM data is converted into an ATM cell and output, and the input ATM cell is converted into an ST cell.
In the STM data / ATM cell conversion device for converting and outputting to M data, the STM data is stored in the payload of the short cell having a length of 1 / N (N is an integer) of the payload length of the ATM cell, A short cell assembling unit that assembles short cells by adding destination information, and an ATM cell assembling unit that collects N short cells that are common to the destination to the final point or an intermediate point and assembles ATM cells to output at a predetermined cycle. , The short cell distribution unit that decomposes the input ATM cells into short cells and distributes them according to the destination information of the short cells, and the STM data stored in the payload of the distributed short cells, the output line according to the destination information An STM data / ATM cell conversion device, comprising: