WO2000002410A2

WO2000002410A2 - Hybrid communication system with an hdlc control line

Info

Publication number: WO2000002410A2
Application number: PCT/DE1999/001976
Authority: WO
Inventors: Josef Wahler; Reinhard Deml
Original assignee: Siemens Aktiengesellschaft
Priority date: 1998-07-03
Filing date: 1999-07-01
Publication date: 2000-01-13
Also published as: DE19829822A1; WO2000002410A3; WO2000002410B1

Abstract

The communication system (PBX) has a cell based coupling field module (BB-KN) and at least one time-slot based connection device (SB-AE1, ..., SB-AE3) for the connection of time-slot based communication devices. In order to switch data received by the time-slot based connection device (SB-AE1, ..., SB-AE3) using the cell based coupling field module (BB-NN), bi-directional conversion occurs between the data format of the time-slot based connection device (SB-AE1, ..., SB-AE3) and the data format of the cell-based coupling field module (BB-KN).

Description

description

Communication systems

From the product brochure "Special edition telcom report and Siemens magazine Com: ISDN in the office - HICOM", Siemens AG, Berlin and Munich, 1985, in particular pages 58 to 75, a communication system designed for time slot-based information transfer, in particular voice data transfer, is known The time slot-based communication system-internal data transmission, for example between a switching network arranged in the communication system and a network or subscriber line unit arranged in the communication system, takes place via so-called multiplex channels - often referred to in the literature as PCM highways (pulse code modulation). according to the TDM procedure (Time Division Multiplex).

In most cases, a so-called ^Λ PCM Highway to 'comprises a 30 user data channels which s are at a transfer rate of 64 kbit / configured as an ISDN-oriented B-channels (Integrated Services Digital Network) and on the other hand a signaling channel which serves as ISDN -oriented D channel is designed with a transmission rate of 64 kbit / s. A data transmission rate of 2 Mbit / s is thus available for a time slot-based data transmission in accordance with the TDM method.

The known communication system has a time slot-based switching network to which a maximum of 64 bidirectional PCM highways can be connected. By this time slot based switching network are from the 64 connectable ^λ PCM Highways 'any two of ^X in a PCM Highway' combined 32 channels connected to one another. This results in a switching capacity of a maximum of 128 Mbit / s for the time slot-based switching network. Due to the increasing need for transmission of video information in modern communication technology, such as still and moving pictures in videophone applications, the importance of transmission and switching techniques for high and variable data transmission rates greater than 100 Mbit / s is increasing.

As a data transmission method for high data speeds, e.g. the so-called Asynchronous Transfer Mode (ATM) is known. Data transmission based on the asynchronous transfer mode currently enables a variable transmission bit rate of up to 622 Mbit / s.

The present invention is based on the object of specifying a communication system by means of which the switching capacity can be increased.

This object is achieved according to the invention with the features of patent claim 1.

For a better understanding of the functioning of a cell-based switching technology, in particular a switching technology based on the asynchronous transfer mode, it seems necessary to first go into known principles again.

In the cell-based data transmission method known as asynchronous transfer mode (ATM), data packets of fixed length, so-called ATM cells, are used for the data transport. An ATM cell is composed of a five-byte long cell header containing the switching data relevant for the transport of an ATM cell, the so-called ^λ header, and a 48-byte user data field, the so-called ^Λ payload.

In the switching technology designed according to the asynchronous transfer mode, when a connection is established before the start of the user data transmission in an ATM communication network by exchanging signaling information, connection tables with switching information consisting of a virtual channel identification and a virtual path identification are set up in the respective ATM switching device. In the connection tables, the virtual channel identification is assigned a VCI value and the virtual path identification is assigned a VPI value. The switching information entered in the connection tables specifies how the virtual paths or virtual transmission channels contained in the virtual paths of the connections incoming and outgoing at the ATM switching device are assigned to one another by the signaling, ie which input is linked with which output in terms of switching technology . ATM cells transmitted via these virtual connections essentially have switching data consisting of a VPI and a VCI value in the cell header. At the input of an ATM switching device, the ATM cell header data are processed, ie the switching data arranged therein are recorded and evaluated. The ATM cells are then switched to an output representing a specific destination on the basis of the switching information stored in the connection table by a switching matrix module arranged in the ATM switching device.

From the data sheet "MOS INTEGRATED CIRCUIT μPD98410 ^λ \ NEC

Corporation, 1997, Document No. S12624EJ1V0DS00 (l ^st edition), for example, a highly integrated ATM Durchschaltebau- stone with an exchange capacity of 1.2 Gbit / s known, which realizes the operation of an ATM intermediary above-described averaging means.

A major advantage of the arrangement according to the invention is that an implementation of a cell-based switching matrix module in an existing communication system and the associated increase in the switching performance of the

Communication system in a simple manner and without intervention in the central control of the communication system can be carried out.

Advantageous developments of the invention are specified in the subclaims.

By implementing cell-based connection devices that can be connected directly to the cell-based switching matrix module, both time slot-based and cell-based data can be conveyed by the same communication system.

By integrating a time slot-based as well as a cell-based switching matrix module into the communication systems, whereby switching-related control of the cell-based switching matrix module takes place by converting the switching-technical control information of the time slot-based switching matrix module by a further control unit, a data switching is carried out possible both via the time slot-based and the cell-based switching matrix module. Thus, a conversion of an exclusively time slot-based communication system into an exclusively cell-based communication system can take place in several, easier to implement steps.

An embodiment of the invention is explained below with reference to the drawing.

Show:

1: a structural diagram for the schematic representation of the essential functional units of a communication system according to the invention;

2 shows a structural diagram for the schematic representation of the essential functional units of a broadband functional unit arranged in the communication system; 3: conversion from a time slot-based data format into a cell-based data format according to a first operating mode of a conversion unit;

4: Conversion from a time slot-based data format into a cell-based data format according to a second operating mode of the conversion unit.

1 shows a schematic representation of the essential functional units of a communication system PBX according to the invention. The communication system PBX has a time slot-based narrowband functional unit SB-FE and a cell-based broadband functional unit BB-FE. Time slot-based data transmission takes place on the basis of the PCM data format (Pulse Code Modulation) in accordance with the TDM method (Time Division Multiplex). Cell-based data transmission is based on the ATM data format (asynchronous transfer mode).

Furthermore, the communication system PBX has time slot-based narrowband connection units, three time slot-based narrowband connection units SB-AE1,..., SB-AE3 are shown and cell-based broadband connection units, for example, two cell-based broadband connection units are shown. Connection units BB-AE1, BB-AE2 shown on. The time slot-based narrowband connection units SB-AE1, ...,

SB-AE3 have, for example, U _P0 -, S ₀ - or a / b interfaces for connecting communication terminals KE1, ..., KE4 to the PBX communication system or an S _2M interface - often referred to in the literature as a primary multiplex connection - for one Connection to another PBX2 communication system.

Analog communication terminals KE3, KE4 are connected to the communication system PBX via an a / b interface. A U _P0 or an S ₀ interface is used to connect digital communication terminals KE1, KE2 to the communication system PBX and each comprises 2 user data channels, which are designed as ISDN-oriented B channels with a transmission rate of 64 kbit / s and a signaling channel which is designed as an ISDN-oriented D channel with a transmission rate of 16 kbit / s. An S _2M interface comprises 30 ISDN-oriented B channels with a transmission rate of 64 kbit / s and one ISDN-oriented D channel with a transmission rate of 64 kbit / s.

The cell-based broadband connection units BB-AE1, BB-AE2 have, for example, an STMl interface (Synchronous Transfer Mode) with a transmission capacity of 155 Mbit / s for connection to an ATM communication network ATM or a UTP25 interface (Unshielded Twisted Pair) with a respective transmission capacity of 25 Mbit / s for connecting so-called multimedia terminals' MT to the communication system PBX.

The narrow-band functional unit SB-FE has a time slot-based switching matrix module KN, a central control unit CPU and a signaling unit SIG. The central control unit CPU realizes the switching control of the time slot-based switching matrix module KN. In the course of a data transfer realized via a time slot-based narrowband connection unit SB-AE1, ..., SB-AE3, the signaling information received via a signaling line HDLC (High Level Data Link) from the central control unit CPU into switching-related control information converted for the time slot-based switching matrix module KN. User data assigned to the signaling information are switched through from any time slot of an input line to any time slot of any output line of the time slot-based switching matrix module KN on the basis of the switching control information.

The SIG signaling unit takes care of the character supply of the PBX communication system with audible tones and if with announcements, as well as the reception of DTMF clock dialing signs (multi-frequency dialing method) and external dialing tones. The signaling unit SIG is connected to the time slot-based switching matrix module KN via a time slot-based connection.

The broadband functional unit BB-FE has a cell-based switching matrix module BB-KN - for example the highly integrated switch-through module μPD98410 - with a switching performance of 1.2 GBit / s, a further control unit BB-CPU and several conversion units UE. The further control unit BB-CPU realizes the switching control of the cell-based switching matrix module BB-KN. For this purpose, the central control unit CPU and the further control unit BB-CPU are connected to one another via a separate control line ST. In the course of switching data received via a time slot-based narrowband connection unit SB-AE1, ..., SB-AE3 through the cell-based switching matrix module BB-KN, the data received via the signaling line HDLC by the central control unit CPU and in switching-related control data for the time slot-based switching matrix module KN transmitted switching-related control data transmitted via the separate control line ST to the further control unit BB-CPU and converted into switching-related control data for the cell-based switching matrix module BB-KN.

In order to convert the switching control data of the time slot-based switching matrix module KN to the switching control data of the cell-based switching matrix module BB-KN, the time slot-based switching information from input line / time slot and output line / time slot necessary for establishing a connection is assigned to cell-based switching information input VCI value and output VCI value (Virtual Channel Identifier). The conversion units UE are on the one hand via a cell-based connection with the cell-based switching matrix module BB-KN and on the other hand via time slot-based subscriber lines TAL with the time slot-based narrowband connection units SB-AE1, ..., SB-AE3 or alternatively connected to the time slot-based switching matrix module KN via a time slot-based connection DL. As part of a data transmission via a time slot-based narrowband connection unit SB-AE1, ..., SB-AE3, the conversion units UE perform a bidirectional conversion between the data format of the cell-based connection and the data format of the time slot-based connections TAL , DL. In particular, there is a bidirectional conversion between the TDM data format and the ATM data format.

A switching line of approx. 200 Mbit / s of the cell-based switching network module BB-KN is reserved for data transmission via time slot-based narrowband connection units SB-AE1, ..., SB-AE3. A switching line of approximately 1 GBit / s is thus available for data transmission via cell-based broadband connection units BB-AE1, BB-AE2. Alternatively, the switching capacity of the cell-based switching matrix module BB-KN can be allocated for data transmission via time slot-based narrowband connection units SB-AE1, ..., SB-AE3 or via cell-based

Broadband line units BB-AE1, BB-AE2 dynamic, i.e. adapted to the respective need.

2 shows a schematic representation of the essential functional units of the broadband functional unit BB-FE. To control cell-based data exchange in the PBX communication system, the further control unit BB-CPU is connected via a control bus CPU-BUS with the cell-based switching matrix module BB-KN arranged in the broadband function unit BB-FE and the conversion units UE1, ... , UE3 and additionally connected to the cell-based broadband connection units BB-AE1, BB-AE2. The cell-based switching matrix module BB-KN has a coupling unit module-specific storage unit SPE that is subdivided into two partial memories. A switching table HTT — often referred to in the literature as ^x header translation table — is stored in the first partial memory of the switching unit module-specific storage unit SPE. This switching table HTT contains the switching information necessary for switching ATM cells in the form of a pair of values consisting of input VCI value and output VCI value, on the basis of which an ATM cell arriving at the cell-based switching matrix module BB-KN transmits Input VCI value is identified and converted and transmitted based on the assigned output VCI value.

The second partial memory of the coupling unit module-specific storage unit SPE serves for the temporary storage of the user data transmitted in the ^x payload area of an ATM cell during the switching of the ATM cell in the cell-based coupling unit module BB-KN.

Furthermore, the cell-based switching matrix module BB-KN has two high-frequency UTOPIA interfaces (Universal Test & Operations PHY Interface for ATM). Via the UTOPIA interfaces, the cell-based switching matrix module BB-KN is connected to two multiplexer devices MUX1, ..., MUX4 via a 16-bit wide cell-based UTOPIA data bus DB. A bidirectional data transfer rate of 622 Mbit / s can be achieved via the 16-bit wide cell-based UTOPIA data bus DB. The multiplexer devices MUX1, ..., MUX4 - which are configured, for example, as described in the German patent application with the official identification number 197 515 60.6 - convert the data format of the 16-bit wide cell-based UTOPIA data bus DB to the data format of an 8-bit wide cell-based UTOPIA data bus. The multiplexer devices MUX1, ..., MUX4 each have a maximum of four 8-bit widths Cell-based UTOPIA data buses can be connected, via which a maximum bidirectional data transfer rate of 310 Mbit / s can be achieved.

In general, a multiplexer device MUX1, ..., MUX4 is either with an 8-bit wide cell-based UTOPIA data bus either with a cell-based broadband connection unit BB-AE1, BB-AE2 or with a conversion unit UE1, ... , UE3 connectable. Thus, the first multiplexer device MUX1 via a first 8-bit wide cell-based UTOPIA data bus with the first cell-based broadband connection unit BB-AEl and the second multiplexer device MUX2 via a second 8-bit wide cell-based UTOPIA Data bus connected to the second cell-based broadband connection unit BB-AE2. The fourth multiplexer device MUX is connected to the conversion units UE1,..., UE3 via an 8-bit wide UTOPIA data bus.

On the other hand, a maximum of eight bidirectional time slot-based ^λ PCM highways with a data transmission rate of 2 Mbit / s can be connected to the conversion units UE1,... UE3.

The first conversion unit UE1 is connected via a first time slot-based subscriber line TAL1 to the first time slot-based narrowband line unit SB-AE1 and via a second time slot-based subscriber line TAL2 to the second time slot-based narrow band line unit SB-AE2. The second U conversion unit UE2 is connected via the time slot-based data line DL to the time slot based switching matrix module KN and the third conversion unit UE3 is connected via a third time slot based subscriber line TAL3 to the third time slot based narrowband connection unit SB-AE3. A conversion unit UE1,..., UE3 carries out a bidirectional conversion between the TDM data format of an ^X PCM highway and the ATM data format of the 8-bit-wide cell-based UTOPIA data bus. For this it is necessary that each time slot - 'often referred to with canal - one at a conversion unit UE 1, ..., UE3 connected PCM highways' in the literature in connection with a ^Λ PCM highway clearly a VCI value, and vice versa is assignable. Since up to eight ^λ PCM highways can be connected to each conversion unit UE1, ..., UE3, 256 different VCI values must be adjustable for each conversion unit UE1, ..., UE3.

To store the conversion information necessary for a bidirectional conversion between the TDM data format and the ATM data format, by means of which ^λ PCM highway / time slot is assigned to VCI value and vice versa, each conversion unit UE1,... ., UE3 a conversion unit-specific storage unit SPE.

A bidirectional conversion between the TDM data format of a PCM highway and the ATM data format by a conversion unit UE takes place in accordance with two different operating modes of the conversion units UE1, ..., UE3, which are described in more detail below.

3 shows a schematic illustration of the conversion of the TDM data format into the ATM data format according to a first operating mode of the conversion units UE1, UE2.

A 125μs long TDM frame R1, R2 comprises a total of 32 channels, via which data transmission in the context of 30 connections - with an assignment of 30 channels for the transmission of useful data information and 2 channels for the transmission of signaling information - is possible. When converting a continuous data stream based on the TDM method to the cell-ba- Based on the ATM format, all 32 channels successive in time in a TDM frame - each with 1 byte of user data information - are converted to the ATM cell data format in the manner described below.

Starting with the first byte of the user data area of an ATM cell ATM-Zl, ATM-Z2, the transmission of the user data information contained in a TDM frame R1, R2 takes place. In the user data area of an ATM cell ATM-Zl, ATM-Z2, the user data information of a channel 0, ..., 31 of a ^λ PCM highway is summarized. For example, in the first ATM cell ATM-Zl a maximum of 48 user data bytes of channel 0 of the PCM highway 'and in the second ATM cell ATM-Z2 a maximum of 48 user data bytes of channel 1 of the ^Λ PCM highway', etc. summarized.

4 shows a schematic representation of the conversion of the TDM data format into the ATM data format according to a second operating mode of the third conversion unit UE3.

All 32 channels 0, ..., 31 of an ^X PCM highway are transmitted successively within one or in two successive ATM cells. Starting with the first byte of the user data area of an ATM cell ATM-Zl, ATM-Z2, the user data bytes assigned to the individual channels 0, ..., 31 of the TDM frame Rl, R2 are transmitted in sequence. Immediately after the last byte (the byte assigned to channel 31) of the first TDM frame R1 has been transmitted, the first byte (the byte assigned to channel 0) of the second TDM frame R2 is transmitted. An assignment of the payload data bytes of an ATM cell ATM-Zl, ATM-Z2 to a channel 0, ..., 31 of a TDM frame Rl, R2 thus takes place via the position of the byte in the payload area of the ATM cell ATM-Zl , ATM-Z2.

On a data transfer starting from a first, at the first time slot-based narrowband connection unit SB-AE1 connected communication terminal KE1 to a third communication terminal KE3 connected to the second time slot-based narrowband connection unit SB-AE2, the functional units described below are involved.

The time slot-based data to be transmitted are transmitted from the first time slot-based narrowband connection unit SB-AE1 via the first time slot-based subscriber line TAL1 e.g. transmitted via channel 0 to the first conversion unit UE1. In the first conversion unit UE1, the time slot-based data are converted into cell-based data in accordance with the first operating mode. On the basis of the conversion information stored in the conversion unit SPE, the time slot-based switching information (first time slot-based subscriber line TAL1 / channel 0) is converted into the associated cell-based switching information (VCI value).

The signaling data belonging to the user data and containing the origin and destination addresses are transmitted to the central control unit CPU via the signaling line HDLC. In the central control unit CPU, the signaling data are converted into switching control data for the time slot-based switching matrix module KN.

These switching-related control data for the time slot-based switching matrix module KN are transmitted to the further control unit BB-CPU via the separate control line ST, and are converted by the latter into switching-technical control data for the cell-based switching matrix module BB-KN.

Starting from the first conversion unit UE1, the cell-based data are sent to the fourth multiplexer device MUX4 via an 8-bit-wide cell-based UTOPIA data bus and from there via the 16-bit-wide cell-based UTOPIA data bus DB to the cell -based switching network module BB-KN forwarded. On the basis of the cell-based switching information (VCI value) stored in the cell header of the cell-based data and on the basis of the switching table HTT stored in the first partial memory of the coupling unit module-specific storage unit SPE, the cell-based data is transmitted within the cell-based switching matrix module BB-KN.

Starting from the cell-based switching network module BB-KN, the cell-based data is sent via the 16-bit wide cell-based UTOPIA data bus DB to the fourth multiplexer device MUX4 and from there via the 8-bit wide cell-based UTOPIA data bus transmitted to the first conversion unit UE1. In the first conversion unit UE1, the cell-based data are converted into time slot-based data in accordance with the first operating mode. The conversion information stored in the conversion unit-specific storage unit SPE is used to convert the cell-based switching information (VCI value) into the associated time slot-based switching information (second time slot-based subscriber line TAL2 / channel 4). The time slot-based data to be transmitted are transmitted from the first conversion unit UE1 via the second time slot-based subscriber line TAL2 e.g. Transmitted via channel 4 to the second time-slot-based narrowband connection unit SB-AE2, from which the time-slot-based data are forwarded to the third communication terminal KE3.

A data transfer from the third communication terminal KE3 to the first communication terminal KE1 takes place in an analogous manner in the opposite direction.

On a data transfer starting from the further communication system PBX2 connected to the third time slot-based narrowband connection unit SB-AE3 via the ATM Communication network ATM, the functional units described below are involved.

The time slot-based data to be transmitted are transmitted from the third time slot-based narrowband connection unit SB-AE3 via the third time slot-based subscriber line TAL3 to all channels 0, ..., 32 to the third conversion unit UE3. In the third conversion unit UE3, the time slot-based data are converted into cell-based data in accordance with the second operating mode. Using the conversion information stored in the conversion unit-specific storage unit SPE, the time slot-based switching information (third time slot-based subscriber line TAL3) is converted into the associated cell-based switching information (VCI value).

The signaling data belonging to the user data and containing the origin and destination address are transmitted via the signaling line HDLC to the central control unit CPU and to the further control unit BB-CPU. In the central control unit CPU, the signaling data are converted into switching control data for the time slot-based switching matrix module KN. These switching-related control data for the time slot-based switching matrix module KN are transmitted via the separate control line ST to the further control unit BB-CPU and are converted by the latter into switching-technical control data for the cell-based switching matrix module BB-KN.

Starting from the third conversion unit UE3, the cell-based data is sent via an 8-bit wide cell-based UTOPIA data bus to the fourth multiplexer device MUX4 and from there via the 16-bit wide cell-based UTOPIA data bus DB the cell-based switching network module BB-KN is forwarded. On the basis of the cell-based switching information (VCI value) stored in the cell header of the cell-based data and on the basis of the switching table HTT stored in the first partial memory of the switching unit module-specific storage unit SPE, the cell-based data is transmitted within the cell-based switching module BB- CN. The signaling data received via the signaling line HDLC are converted by the further control unit BB-CPU (according to the ATM adaptation layer AAL5) into a cell-based data format and forwarded analogously to the user data.

Starting from the cell-based switching matrix module BB-KN, the cell-based user and signaling data are sent to the second multiplexer device MUX2 via the 16-bit wide cell-based UTOPIA data bus DB and from there via the second 8-bit wide one cell-based UTOPIA data bus is transmitted to the second cell-based broadband connection unit BB-AE2, from which the cell-based user and signaling data are forwarded via the ATM communication network ATM.

Claims

claims

1. Communication systems (PBX),

with at least one time slot-based connection device (SB-AE1, ..., SB-AE3) as an interface for time slot-based communication devices,

- with a cell-based switching matrix module (BB-KN),

- With one, via a time slot-based connection line (TAL) to the time slot-based connection device (SB-AE1, ..., SB-AE3) and via a cell-based connection line to the cell-based switching matrix module (BB-KN) connected conversion unit (UE), for bidirectional conversion between a time slot-based data format and a cell-based data format, and - with a control unit (BB-CPU) for switching control of the cell-based switching matrix module (BB-KN).

2. Communication system according to claim 1, characterized by a cell-based connection device (BB-AEl, BB-AE2) connected via a further cell-based connecting line to the cell-based switching matrix module (BB-KN) as an interface for cell-based communication devices .

3. Communication system according to one of the preceding claims, characterized by a time slot-based switching matrix module (KN) connected to the conversion unit (UE) via a further time slot-based connecting line (DL), and a central control unit (CPU) for switching control of the time slot-based switching matrix module (KN).

4. Communication system according to claim 3, characterized in that the central control unit (CPU) and the control unit (BB-CPU) are connected to one another via a control line (ST), that for switching from, via the time slot-based connection device (SB-AE1 , ..., SB-AE3) received time slot-based data through the cell-based switching matrix module (BB-KN), a transmission of switching control information from the central control unit (CPU) via the control line (ST) to the control unit (BB- CPU) is provided, and that the control unit (BB-CPU) is set up to convert this switching-related control information into switching-technical control information for the cell-based switching matrix module (BB-KN).

5. Communication system according to claim 3 or 4, characterized in that the central control unit (CPU), the time slot-based connection device (SB-AE1, ..., SB-AE3) and the control unit (BB-CPU) via a further control line ( HDLC) are connected to each other, and that the further control line (HDLC) is provided for the transmission of signaling information received or to be transmitted via the time slot-based connection device (SB-AE1, ..., SB-AE3).

6. Communication system according to claim 3 to 5, characterized by, with the time slot-based switching module (KN) connected signaling unit (SIG).

7. Communication system according to one of the preceding claims, characterized by a multiplexer device (MUX1, ..., MUX4), on the one hand via a bidirectional, cell-based data bus (DB) with the cell-based switching matrix module (BB-KN) and on the other hand with the conversion unit (UE) is connected via a bidirectional, cell-based connection unit — individual data bus.

8. Communication system according to claim 2 and 7, so that the multiplexer device (MUX1, ..., MUX4) is connected to the cell-based connection device (BB-AEl, BB-AE2) via a further connection unit-individual data bus.

9. Communication system according to one of the preceding claims, that a plurality of timeslot-based connecting lines (TAL, DL) are connected to the conversion unit (UE).

10. Communication system according to one of the preceding claims, ie that a data transmission via the cell-based connecting lines is set up on the basis of the ATM data format (asynchronous transfer mode).

11. Communication system according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that data transmission over the time slot-based connecting lines based on the PCM data format (Pulse Code Modulation) according to the TDM method (Time Devision Multiplex) is set up.