JPH06232911A - Communication equipment - Google Patents

Abstract

PURPOSE:To use an ATM relay network by executing ATM cell processing in the unit of line groups between exchanges and sending the cell to an ATM relay network thereby keeping communication quality of N-ISDN. CONSTITUTION:An STM-ATM converter 701 adds 5-octat header to 48-time slots A, B to convert the cell into ATM cells E, F. The cell E is converted into an STM by an STM-ATM converter 702 via ATM exchanges 401, 402 and it is inputted to an STM converter 302. Furthermore, the cell F is converted into an STM at an STM-ATM exchange 703 via the exchanges 401, 402 similarly and the STM is inputted to the STM exchange 303. Number of slots of the time slots A, B is a required line number for a traffic between the exchanges 301, 302 and between the exchanges 301, 303. Then a delay caused by processing one voice information set into a cell is not caused by notifying a line group set between the STM exchanges, processing the information into cells in the unit of groups and connecting the cells to the ATM exchange.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a wide band communication network in a communication network in which narrow band communication and wide band communication coexist by suppressing an increase in delay, which is an important communication quality parameter in narrow band communication. The present invention relates to a communication method capable of realizing a narrow band relay network. The present invention relates to an STM-ATM conversion technique in a communication network in which an STM communication network and an ATM communication network coexist.

[0002]

2. Description of the Related Art Since voice is the main information in the current digital communication network, the line has a voice information bit rate of 6
It is made based on 4 kb / s. That is, 64 kb /
It is based on transmitting s voice information by octet multiplexing. This will be described with reference to FIGS. 6 and 7.

In FIG. 6, a highway 51 for voice information,
The data of 52 and 53 is the STM multiplexing circuit (STMMU).
X) 201, and the highway 60 outputs the multiplexed data of these three pieces of audio information.

The multiplexing of this voice information data will be described with reference to FIG. A1 and A2 of the highway 51 indicate audio information coded in 8 bits, and the time between A1 and A2 is equal to the audio sampling rate of 8 kHz.
It is 5 μsec. The same applies to B1, B2, C1 and C2. Reference numeral 60 indicates information obtained by multiplexing these three pieces of audio information, and 8 bits (1 octet) is 125 μs.
It is multiplexed for each ec. Therefore, this communication network is 64
It is called a kb / s communication network. In addition, all information is synchronously multiplexed, so the synchronous transfer mode (Synchronuos Tra
nsfer Mode (hereinafter abbreviated as STM).

The current Narrowband Integrated Services Digital Network (N-ISDN) is composed of STM. N-IS
In DN, if the speed information is up to about 1.5 Mb / s or 2 Mb / s, 24 or 30 64 kb
Transfer is possible by using the / s path at the same time.

On the other hand, with information of 1.5 to 2 Mb / s or more, an asynchronous transfer mode (Asynchronous Transfer Mode) is used as a transfer network for image information or high-speed data information.
Wideband ISDN using ATM) has been studied and studied for its introduction.

A multiplexing method in this ATM will be described with reference to FIGS. 8 and 9.

In FIG. 8, reference numeral 50 is voice information,
The ATM conversion circuit 500 converts the voice into 48 octets, that is, 6 msec of burst data 70. ATM multiplexing circuit (ATM) for performing cell formation and cell multiplexing
The MUX 200 includes burst data 70 in which the voice information is converted into cells, and burst data 71, 7 other than voice.
2 is asynchronously multiplexed and output as an ATM cell.

As shown in FIG. 9, the voice information 50 is converted into burst data 70 of 48 octets, which is A
A header is added on the TM highway 80 and output as an ATM cell composed of 53 octets.

As described above, in ATM, all information is divided into 48 octets and treated as cells of 53 octets to which header information is added, so that a communication network that does not depend on the bit rate of information can be constructed. That is, for low-speed data, the transmission interval between cells is set to be relatively long, and for high-speed data, the transmission interval of cells is shortened so that arbitrary information can be handled in a unified unit called a cell. it can.

A communication network using this ATM is a broadband ISD
M (B-ISDN). In the future, it is considered that N-ISDN will be evolved into B-ISDN. But S
N-ISDN using TM and B-ISD using ATM
In N, since the multiplexing method is different, if they are mixed in the communication network, there arises a problem that the STM and ATM lines must be used separately.

Considering that the present STM network centering on voice develops into an ATM network including moving images, the STM network and the ATM network as shown in FIG. It is possible to interface with.

FIG. 10 (a) shows a system in which an ATM cell conversion circuit is installed for each subscriber in the case where the ATM conversion is performed for each subscriber. That is, cellizing circuits 501, 502, and 503 are provided for the terminals 101, 102, and 103, respectively, and the cellized information is input to the ATM switch 410 for the subscriber line exchange, and the other party is connected via the ATM line 600. This is a method of connecting to the ATM switch 411 for the trunk line exchange.

FIG. 10 (b) shows a system in which only calls in progress are converted into ATM. That is, the terminals 101, 102, 103
Is accommodated in the STM switch 310 for the subscriber line exchange, and only the call during the call is converted into an ATM cell by the cell conversion circuit 504.
This is a method of connecting to the ATM switch 411 for the partner trunk line exchange via the TM line 600.

[0015]

However, in both of these methods, since the conversion to cells is performed collectively, the voice information is 6 msec at the stage of cell conversion, from the cell to the STM, as shown in FIG. When returning to 6msec, total 12mse
There is a problem that the delay of c occurs. This delay affects echo quality as echo. There is also a problem that an echo canceller circuit is required due to the influence of this delay.

It is an object of the present invention to provide a communication system which suppresses the increase of the above-mentioned voice delay, enables the STM network and the ATM network to coexist, and promotes the ATM conversion of the relay network.

[0017]

A first aspect of the present invention relates to a communication system in which a synchronous transfer mode switch having a period of time T and an asynchronous transfer mode switch having Q octets as one transfer unit are mutually operated. In a communication system composed of a communication network connected to the P.T., for the n number of synchronous transfer mode lines set up between the synchronous transfer mode switch and the other side synchronous transfer mode switch, P × T cycles, where P is P ≦ It is characterized in that a conversion means for converting into an integer cell of Q / n is provided.

A second aspect of the present invention relates to an STM-ATM converter, which is provided between a synchronous transfer mode switch and an asynchronous transfer mode switch, and which transfers time division data input from a synchronous transfer mode line to an asynchronous transfer mode. In the STM-ATM conversion device, which includes means for converting and outputting to cells of the asynchronous transfer mode, and means for converting cells input from the asynchronous transfer mode line into time division data in the synchronous transfer mode. For a line group set up with a transfer mode switch, a means for gathering the line groups with the number of octets or less that can be accommodated in one cell and generating one cell, and the above-mentioned line number group from one cell that arrived And means for separating time-division data corresponding to.

[0019]

In general, the number of lines between exchanges is set according to the traffic volume. In Japan's digital communication network, 6 channels are adopted as the line operation unit,
A line group having an integral multiple of 6 channels is set between the exchanges according to the traffic volume. The present invention focuses on this line group,
A line group set between the exchanges is divided into, for example, 48 channels or 47 channels, and cells are formed in units of 48 channels or 47 channels. The cellized information is transferred between the STM switches through the ATM relay network. As a result, it is not necessary to make ATM cells in subscriber line units, and it is possible to reduce the delay that occurs when making ATM cells or cell decoding in channel units.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing the configuration of a communication network according to the first embodiment of the present invention.

In this first embodiment, the terminals 101, 102,
N-ISDN exchange that accommodates 103 (64 kb / s
STM switch, hereinafter abbreviated as STM switch) 301
And N-ISD accommodating terminals 104, 105, 106
The N exchange 302 and the N-ISDN exchange 303 accommodating the terminals 107, 108 and 109 are respectively B-
This is a communication network connected through an ISDN ATM switch (hereinafter, referred to as ATM switch) 401, 402, 403. As a feature of the present invention, STM-ATM converters 701, 702, 703 are provided. -AT
The M converters 701 to 703 convert the n ATM lines set mutually among the N-ISDN STM switches 301 to 303 into cells of P × T cycle (where P is an integer of P ≦ Q / n). Equipped with means.

Here, reference numerals 601, 602, 603 and 901, 902, 903 are ATM lines, 801, 8
02 and 803 are STM lines.

Focusing on the STM-ATM converter 701 in FIG. 2, its operation will be described by showing a time chart.

It is assumed that the 48 time slots shown in A of FIG. 2 are connected to the STM switch 302 and the 48 time slots shown in B are connected to the STM switch 303.

The STM-ATM converter 701 has four
A header C of 5 octets is added to 8 time slots and converted into an ATM cell E. The time slot of B is also converted into the ATM cell F by adding the header D of 5 octets. The converted cell E is converted into STM by the STM-ATM converter 702 via the ATM switches 401 and 402, and is input to the STM switch 302. Similarly, the cell F is converted into STM by the STM-ATM converter 703 via the ATM switches 401 and 402, and is input to the STM switch 303.

Here, the number of time slots of A is the number of lines required for traffic between the STM switches 301 and 302, and is set to n times the normal line operation unit. Similarly, the number of B time slots is also the number of lines required for traffic between the STM switches 301 and 303.

Here, the embodiment of the present invention is characterized by focusing on the line group set between the STM exchanges and connecting them to the ATM exchange by forming cells into groups and connecting them. Since there is no delay as in the case of converting information into cells, there is an effect that there is almost no effect on the call quality even when passing through an ATM communication network.

In the ATM network, cells are transferred asynchronously,
There is a delay in the memory in the ATM speech path, and STM-ATM
When the cell arrives at the converter, it is always 125 μse
The cell does not always arrive every c. Therefore, AT
When converting from M to STM, a buffer memory for several cells is provided and 125 μsec for an STM switch.
Allow time slots to arrive on a periodic basis. The delay due to this buffer memory is several times 125 μsec,
It is not a delay that affects call quality.

When cell information 901 shown in FIG. 2 is transmitted together with the information indicating the cell order, it is used to indicate the cell number in one octet within 48 octets, and the remaining 47. Octets can be used as lines.

The structure of the STM-ATM converter used in this embodiment is shown in FIG.

Here, the STM-ATM conversion device is
Converts TM to ATM and ATM to STM. Reference numerals 1 and 3 denote STM lines, and reference numeral 2
Reference numerals 4 indicate ATM lines. Reference numeral 5 is a control circuit for controlling the operation of the present converter. The STM line 1 is led to FIFO memories 6, 7 and 8 for converting from STM to ATM, and the outputs of these FIFO memories 6 to 8 are led to an ATM line 2 via a multiplexer 11. Further, the ATM line 4 is provided with a FIFO processing delay memory 20 for header processing, and FIFO memories 16, 17, 18 for converting ATM to STM.
And the outputs of the FIFO memories 16, 17, and 18 are led to the STM line 3 via the multiplexer 25. Further, holding memories 9 and 10 for controlling the writing and reading of the FIFO memories 6 to 8 are provided, and the output of the holding memory 10 is also input to the multiplexer 11. ATM line 4 is ATM header holding memory 1
9, the writing of the FIFO memories 16 to 18 is controlled by the output of the holding memory 19. In addition, the FIFO memories 16 to 18 and the multiplexer 2
The reading is controlled by the holding memory 22 for controlling No. 5.

Next, the operation of this STM-ATM converter will be described.

First, the conversion operation from STM to ATM will be described. STM information is input from the STM line 1 in the form of 801 in FIG. 2A and 2B are input to separate FIFO memories 6 and 7 for each line group. The holding memory 9 stores information on which FIFO memory to input,
The output 12 writes STM information in the FIFO memories 6 to 8. The holding memory 9 is controlled by the control circuit 5 through the control line 26. Reading from the FIFO memories 6 to 8 is controlled by the holding memory 10. FI
The read timing from the FO memories 6 to 8 is controlled by the control line 13. A cell header is also stored in the holding memory 10, and as shown by 901 in FIG. 2, before reading the header C and the header D from the FIFO memories 6 to 8, via the multiplexer via the control line 14 and A.
It is output to the TM line. The control of the multiplexer 11 is controlled via the control line 15. When the header C is output to the control line 14, the FIFO memory 6 outputs A, and then the control line 14 outputs the header D, and then the FIFO memory. The cells 7 and B are output to the ATM line 2 as cells E and F, respectively. This holding memory 1
0 is controlled by the control circuit 5 through the control line 29.

Conversely, conversion from ATM to STM is
This is done in the circuit from line 4 to STM line 3. Cells are input to the ATM line 4 as indicated by 902 in FIG. The header included in the cell is input to the ATM header holding memory 19, and one is selected from the FIFO memories 16, 17 and 18 based on the routing information written in the header, and the information is written there. . This control is performed by the control line 21. The delay circuit 20 is for temporarily storing cell information until the cell header is input to the ATM header holding memory 19. FIFO
The information written in the memories 16 to 18 is stored in the holding memory 2
It is output under the control of No. 2 and is output as STM information to the STM line 3 through the multiplexer 25. Here, the control line 23 is for performing read control from the FIFO memories 16 to 18, and the control line 24 is for the multiplexer 25.
Is a line that selects the input of. Holding memory 22 and AT
The M header holding memory 19 is controlled by the control circuit 5 via the control lines 27 and 28.

As described above, this STM-ATM converter has a structure in which one cell is generated for a plurality of lines and a plurality of time slots are transmitted. The average generation time interval of the cell is 125 μsec, and even if the cell is delayed by the FIFO memory, it is 2 to 3 cells, and the delay is about 125 μsec × (2 to 3). Therefore, as an effect thereof, there is an advantage that the communication quality is not affected and the communication network can be unified into the ATM including the broadband information, as compared with the case where the ATM is adapted to the line.

(Second Embodiment) Next, a second embodiment will be described with reference to the communication network configuration shown in FIG.

In the second embodiment shown in FIG. 4, ATM trunk line exchanges 405 and 406 are connected in a long distance line section 605, and the ATM trunk line exchange 405 is connected to an ATM subscriber line exchange 404. The ATM subscriber line exchange 404 receives the STM via the STM-ATM converter 704.
The subscriber line exchange 304 is connected to the ATM trunk line exchange 406 via the STM-ATM converter 705.
The M trunk line exchange 305 is connected to the ATM trunk line exchange 406 via the STM-ATM converters 706 and 707.
The subscriber line exchanges 306 and 307 are connected to each other.

In the second embodiment, the traffic of 24 lines between the STM subscriber line exchange 304 and the STM subscriber line exchange 306 is the STM subscriber line exchange 304 and S.
In this example, there is 24 lines of traffic with the TM subscriber line exchange 307. At this time, the STM-ATM converter 705 collectively assembles the 48 lines into cells, and the ATM subscriber line switch 404 and ATM trunk line switches 405 and 406, and the STM-ATM converter 7
A path is set to the STM trunk line exchange 305 via 05. In the STM trunk line exchange 305, ST for 48 lines
M subscriber line exchange 306 and STM subscriber line exchange 307
To 24 cells to each cell. In this way, 48 lines are provided between the STM subscriber line exchange 304 and the STM trunk line exchange 305, 24 lines are provided between the STM trunk line exchange 305 and the STM subscriber line exchange 306, and the STM is provided.
24 lines can be set between the trunk line exchange 305 and the STM subscriber line exchange 307. Where STM
Between the trunk line exchange 305 and the STM subscriber line exchange 306 and between the STM trunk line exchange 305 and the STM subscriber line exchange 307, the STM-ATM converter 705 converts the ATM into ATM, and the STM-ATM converter 706. , 70
Convert to STM at 7.

In the case of the second embodiment, the ATM line 605, which is a long-distance line section, can be efficiently converted to ATM, and all the lines in the network can be converted to ATM. It is possible to construct a communication network having a good affinity with the broadband communication network. Moreover, it is possible to realize ATM conversion while maintaining the communication quality in N-ISDN.

(Third Embodiment) Next, FIG. 5 shows a time chart of the third embodiment to explain a multiplexing method different from that of FIG. 2 which is the time chart of the first embodiment.

This FIG. 5 corresponds to FIG. 2 and is denoted by reference numerals 101 and 9
01, 902 and 104 are the same as those in FIG.
1, STM-ATM converter 701, ATM switch 40
2, output to the terminal 104.

In this third embodiment, the STM switch 301
The number of lines between the STM switch 302 and the STM switch 302 is 24, and time slots for 2 frames are multiplexed for each line, and a total of 48 octets are multiplexed into 1 cell, and 250 cells are combined.
The feature is that it is sent every μsec. In this case, the delay of each line increases to 250 μsec, but the transmission of 1 cell / 250 μsec will result in 24 lines of STM.
It is set between the exchanges 301 and 302. Also in this case, the delay amount can be significantly reduced as compared with the delay of 6 msec in the case where cells are formed for each line.

As described above, the present invention generally provides two N
-Multiple P time slots for each circuit for a line group consisting of n lines of the ISDN exchange, and 1 ATM.
The feature is that it is a cell. That is, 1 ATM
When the number of octets in a cell is Q, ATM cells are formed under the condition of n × P ≦ Q. Note that Q is 48 or 47 when the cell number is added.

For example, in the first embodiment, P = 1, n = 4
8. In the third embodiment, P = 2 and n = 24. When a cell is configured in units of 6 channels as a line operation unit, n = 6 and P = 8 may be set. The delay in this case is 8 × 125 at the time of cell formation.
μsec = 1 msec, 1 when converting from cell to STM
msec, which results in a total delay of 2 msec. Even in this case, the delay amount when converting cells into line units, 6 mse
The delay amount can be greatly reduced from c × 2 = 12 msec.

[0046]

As described above, according to the present invention, ATM cells are formed in units of a line group between exchanges, and the ATM relay network is transmitted, so that the ATM relay network is maintained while maintaining the communication quality of N-ISDN. Can be used. Therefore, it is possible to quickly realize the ATM of the relay system including the broadband communication network.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention.

FIG. 2 is a time chart explaining the operation of the first embodiment.

FIG. 3 is a diagram showing a configuration example of an STM-ATM conversion device.

FIG. 4 is a diagram showing the configuration of a second embodiment of the present invention.

FIG. 5 is a time chart explaining the operation of the third embodiment of the present invention.

FIG. 6 is a diagram illustrating a configuration of conventional octet multiplexing.

FIG. 7 is a time chart explaining conventional octet multiplexing.

FIG. 8 is a diagram illustrating a configuration of conventional cell multiplexing.

FIG. 9 is a time chart explaining conventional cell multiplexing.

FIG. 10 is a diagram showing an arrangement example of a circuit for converting conventional audio information into cells. (A) is an example in which ATM conversion is performed for subscribers, and (b) is an example in which ATM conversion is performed for a call in progress.

[Explanation of symbols]

 1, 3 STM line 2, 4 ATM line 5 Control circuit 6-8, 16-18 FIFO memory 11, 25 Multiplexer 9, 19, 22 FIFO control holding memory 19 ATM header holding memory 20 Delay circuit 12, 21 FIFO memory Write control line 13, 23 FIFO memory read control line 14 Control line for outputting header 15, 24 Multiplexer control line 26, 27, 28, 29 Control line 101-109 Terminal 200 ATM multiplexing circuit 201 STM multiplexing circuit 301-303 N-ISDN STM switch 310 Subscriber line switch STM switch 401-403 B-ISDN ATM switch 410 Subscriber line switch ATM switch 411 Trunk switch ATM switch 500 ATM conversion circuit 501-504 Cell conversion circuit 601 6 03,901-903 ATM line 701-707 STM-ATM converter 801-803 STM line

Claims (2)

[Claims] 1. A communication system comprising a communication network in which a synchronous transfer mode switch having a cycle of time T and an asynchronous transfer mode switch having Q octet as one transfer unit are connected to each other. , For the n number of synchronous transfer mode lines set up with the other side synchronous transfer mode switch, P × T cycle, where P is provided with a converting means for converting into an integer cell of P ≦ Q / n. Characteristic communication method. 2. A means, provided between the synchronous transfer mode switch and the asynchronous transfer mode switch, for converting and outputting time division data input from the synchronous transfer mode line to a cell in the asynchronous transfer mode, and from the asynchronous transfer mode line. STM having means for converting input cells into time division data in synchronous transfer mode
In the ATM conversion device, for a line group set between the synchronous transfer mode switch and the other party's synchronous transfer mode switch, the line group is grouped into one cell with the number of octets or less that can be accommodated in one cell. An STM-ATM conversion device comprising: a means for generating and a means for separating time division data corresponding to the number of lines from one cell that has arrived.