DE4123851C1 - Inter-working unit for coupling asynchronous-to synchronous-transfer mode network - uses multiplexer and demultiplexer for each network, buffer memory and asynchronous-synchronous converters for transmission via exchanges - Google Patents

Abstract

The B-ISDN and VBN networks are interconnected by an interworking unit (IWU) via connections (DV1, DV2) using asynchronous transfer mode (ATM) or and synchronous transfer mode (STM) methods respectively. Operation and maintenance information is passed to the interworking unit via information channels (NK1, NK2), operation, administration and maintenance centres (Z1, Z2) and further information channels (NK3, KN4). The interworking unit comprises a number of channel units, each containing a demultiplexer used to break down multiplexed signals, and buffer stores used to store the decomposed signals. Synchronous to asynchronous and asynchronous to syhnchronous converters are used to convert the signals from asynchronous to synchronous format and vice versa. Code changers convert video or tone information between the two standards. A multiplexer is used to reassemble the decomposed signals for transmission. The interworking unit also features a control unit that uses the operation and maintenance information to control the operation of the interface. USE/ADVANTAGE - Enables interworking between different specification wideband ISDN networks.

Description

The invention relates to an arrangement for connection and Cooperation between different broadband networks (IWU = Interworking Unit), of which the first network with a asynchronous transfer method (ATM = Asynchronous Transfer Mode) and the second network with a synchronous Transfer method (STN = Synchronous Transfer Mode) is working.

If two systems, networks or networks information are supposed to exchange, that is to say to work together from "Interworking". You can choose between "internetworking", the connection of different networks, and "service interaction", the conversion of information from a service into one another service (possibly another network), differentiate. If you want different networks with each other connect, so it is with both cases of interworking to do.

From the generic publication Krautkrämer, Willfried; Sauer, Klaus u. a .: Flexible system concept for Introduction of BK services in the private network area, in ntz Bd. 43 (1990) Issue 12, pp. 880-887 the connection and Collaboration of different  Broadband networks addressed. In particular, the introduction of broadband services in a prescribed ISDN network presented different levels of integration. First, when transitioning to broadband ATM systems, existing ISDN switching equipment and terminals continue to be used and the switching facilities only can be expanded with broadband modules. Here are in one Interface block (IB), which is physically used in ATM switching is housed, the ATM and the STM bit stream put together or separated. In a next one Integration step should ATM and STM services in one integrated broadband switching. A hybrid ATM-STM switching concept is the last Evolution step addressed, where then the system as pure ATM system should work.

EP 3 31 190 A2 discloses a LAN (local area Network) with ISDN (Integrated Services Digital Network) connect. The individual data stations of the LAN to achieve via a common interface. It will indicated how to exchange the necessary Address information between LAN and ISDN can be done.  Since now intensively in the creation of guidelines and Standards for broadband ISDN (B-ISDN) are being worked on, and in some countries already have broadband experimental and operational Networks exist, it is necessary to imagine how the Cooperation of the broadband ISDN with an existing one Broadband network should take place. A lot of information about Broadband ISDN can be found in the recommendations of the CCITT (Recommendations draftet by working party XVIII / 8 by study group XVIII Geneva May 23-25, 1990).

It is an object of the invention to provide an arrangement with a connection and collaboration of different Broadband networks, especially of broadband ISDN and existing broadband networks can be produced.

The problem is solved by an arrangement with the features of claim 1. Advantageous further developments are in specified in the subclaims.

The arrangement according to the invention creates the possibility of Connection and collaboration of different Broadband networks, of which the first network with one asynchronous transmission method and the second network with a synchronous transmission method works. The first The network can be, for example, the broadband ISDN. This is supposed to work according to the ATM procedure. The cell structure of the on the Cells (containers) used for transmission routes look as follows off: A cell has five bytes "header" in the specified which virtual channel a cell belongs to, and 48 Byte information. The destination and the sender address will be in their own virtual signaling or signaling channels transfer.  

The arrangement according to the invention is a Interworking Unit (IWU). This is not only available Local exchanges usually with Transit switching of the networks to be connected in Connection. In addition, it is with those in the two networks existing administration and monitoring centers or OAM centers (OAM = Operation, Administration and Maintenance) in Connection. Instead of an OAM center, the inventive one Arrangement (IWU) in B-ISDN also with a TMN (Telecommunication Management Network).

If the two with the arrangement according to the invention connecting networks only for so-called "Cross Connect" operation are designed, d. H. if connections are not through Electoral processes are made, rather than permanent or semi - permanent connections by means of information about an OAM center will be managed, built and dismantled the necessary to establish a connection Information in addition to the OAM-specific information about OAM channels from the OAM center to the invention Transfer order (IWU). The information on building Connections are then used for control or channel setting the arrangement according to the invention (IWU). There are other cases conceivable for the transmission of information for control or channel setting of the Interworking Unit OAM channels use.

An embodiment of the invention is based on the Drawings explained. Show it:

FIG. 1 shows the arrangement of an interworking unit in the connected networks;

Fig. 2 is a schematic representation of a structure of an interworking unit and

Fig. 3 shows the structure of a single channel unit of an interworking unit.

An arrangement according to the invention, that is to say an interworking unit IWU, connects various broadband networks, for example B-ISDN and VBN, to one another. FIG. 1 is given, that is located the interworking unit between the two networks. The interworking unit IWU is connected to through exchanges DV ₁ , DV _{2 of} both networks. Via the connection, the data to be transmitted are transmitted from a transit exchange via the IWU interworking unit to the second local exchange. On the B-ISDN side, the transfer takes place in the Asynchronous Transfer Mode ATM. On the VBN side, the transfer takes place in synchronous transfer mode STM. With the VBN, the signaling channels are not transported on the connection just described between transit switch DV 2 and interworking unit IWU, but on a separate route, the signaling and identification channel SK. The interworking unit IWU has a separate interface for this channel. The through exchanges DV 1 and DV 2 of both networks are each connected via a message channel NK 1 , NK 2 to an associated OAM center Z 1 , Z 2 . The OAM-specific information is transmitted via these channels. A message channel NK 3 , NK 4 also goes from the OAM centers Z 1 , Z 2 to the interworking unit IWU.

The IWU interworking unit consists of a series of channel units KE. Each channel unit KE establishes a connection between the two networks. Each channel unit KE can be assigned an optical fiber transmission link both on the B-ISDN side and on the VBN side. However, it is also possible for a plurality of channel units KE to be assigned to a transmission link with a high bit rate. It is necessary to provide optical or electrical multiplexers. From Fig. 2, a channel unit KE can be seen, which is connected on each side with a fiber optic transmission link. The channel unit KE has an optoelectric converter OE 1 , OE 4 on each side. In contrast, the other channel units are each equipped with an opto-electrical converter OE 2 , OE 3 on one side, while on the other side they are equipped with an electrical multiplexer or demultiplexer and an opto-electrical converter, which are combined in one unit OEM an optical fiber transmission path are connected. Instead of an electrical multiplexer or demultiplexer, an optical multiplexer or demultiplexer could also be provided. In contrast to the example given here, the multiplexers and optoelectric converters specified here can also be the subject of the transmission system and not of the IWU interworking unit.

The individual channel units KE have multiplexing and demultiplexing devices ATMM 1 to ATMM 3 and STMM 1 to STMM 3 both on the B-ISDN side and on the VBN side. These multiplex and demultiplex devices are necessary because different services or service components in different compositions can be transmitted at different times in a transmission channel (in particular in the case of different networks) and these services or service components may have to be subjected to different code conversions or data rate adaptations . In each channel unit KE, which may not process a transmission channel but a created subchannel, code converters CW 1 to CW 3 are also provided for converting image or sound data between two standards and also for data rate adaptation. These are arranged on the VBN side together with the corresponding multiplex demultiplex devices. A converter for the information W 1 to W 3 is provided in each of the signal units. This is necessary in order to carry out the ATM / STM conversion, which is connected to signal buffering in the buffer memories P 1 to P 3 .

A control unit ST is provided to control the individual channel units. The channel unit ST is connected via bus A and bus S to the modules of the channel units KE. Bus A controls the B-ISDN side and the converters for the information W 1 to W 3 , while bus S serves the modules on the VBN side. The controller sets its modules to the desired operating state via bus systems A and S. The control unit ST receives and sends the information from the virtual signaling channel or channels from the B-ISDN network via bus system A. These are central signaling channels e.g. B. in the form of the ZKK system No. extended by broadband signaling 7 or follow system. The control unit ST receives and sends the signaling information of the VBN network via the bus system S. Optionally, this can also be done via the separate signaling channels SK 1 and SK 2 . The signaling channels can be a ZZK system no. 7 as well as a network-specific central channel signaling system. When signaling via bus system S, channel-accompanying signaling can also be implemented. The control unit ST converts the signaling information, which are each intended for the other network. The control unit ST is connected to the OAM centers Z 1 and Z 2 via the message channels NK 3 and NK 4 . Messages are exchanged between the control unit ST and the control centers Z 1 and Z 2 via the message channels NK 3 and NK 4 . One of the control centers can be declared responsible for setting the operating states. Both centers are informed about the actual operating status of the IWU. In addition, failures or malfunctions are reported to the two central offices in the interworking unit. However, only one of the OAM headquarters, namely the privileged, is authorized to carry out interventions. This can be done, for example, by blocking channels in advance or by initiating maintenance. The control unit ST can have operating and display devices for on-site interventions and in particular an interface A-LMT for a local maintenance terminal. However, this can also connect to the OAM central units Z 1 , Z 2 via the OAM channels NK 3 , NK 4 .

The control unit ST therefore fulfills the following functions:

• - Conversion of the signaling information
• - Evaluation of signaling information for Setting the operating states of the channel units at the connection of switchable networks
• - OAM processes including the setting of the operating states of the channel units, if these are specified by an OAM center, as is possible with cross-connect operation of the networks involved. If the signaling systems in both networks are different, the protocols must be resolved up to layer 7 of the OSI model.

A detailed structuring of a channel unit is shown in FIG. 3. In particular, the resolution is carried out in the two transmission directions. The designation Downlink (with the index D) is used for the transmission direction from B-ISDN to the VBN and the designation Uplink (with the index U) is used for the reverse direction.

In the downlink direction, the serial, digital broadband signals arrive at the ATM demultiplexer ATMD after the optoelectric conversion in the optoelectric converter OE. This is a controlled ATM demultiplexer ATMD, ie the resolution of the virtual ATM channels to be carried out on the subchannels according to transmitted services or service components is specified to the ATM demultiplexer ATMD via the bus system A. The ATM demultiplexer ATMD examines the "headers" of the incoming ATM cells and forwards cells with the same header to the output specified for this header information from the setting information transmitted via the bus system A. Depending on the services that need to be converted for a connection, not all outputs may be used. Repetitive parts of the header information are routed to the control unit ST via bus system A. Consistent parts of the header information, e.g. B. the information about the virtual "Path" or "Channel" are only transmitted at the beginning of the transmission or when prompted by the control unit ST. The header is suppressed before the information is passed on to a buffer memory P _D 1 to P _D n of the corresponding subchannel.

To reduce the processing clock in the multiplexers or demultiplexers and the following components, a serial / parallel conversion z. B. made in byte structure. The instructed via the bus system A converter W ' 1 to W'n call the cell information (without header) in the cycle specific to the service or the service component from the assigned buffer memory P _D 1 to P _D n, to keep it in a continuous bit stream pass on. The converters W ' 1 to W'n still have to perform the function of clock adaptation between the two networks with the associated buffer memories P _D 1 to P _D n. While the read-in process into the buffer memory still takes place with the clock T _A from the B-ISDN network, the retrieval process is already carried out with the clock T _{S of} the existing VBN. If the two networks have different cycle tolerances, compensation processes are necessary. From time to time either an empty cell is inserted or a cell with information has to be suppressed.

For services or service components that require subsequent code conversion, the code converter CW _D can send a signal, e.g. B. in the form of a time window to the associated transducer W ' 1 to W'n. This signal indicates when it is possible to adapt the clocks with the least disruptive influence on the information to be converted.

If a virtual central signaling channel SK is also transmitted in a connection, the information of this channel is passed on to the control unit ST after the conversion, adapting to the transmission properties of the bus system A. In this case, no clock adjustment is relative to the clock T _S performed. Rather, it is an ATM / ATM conversion to bus system A.

As already noted in the clock adaptation, the signals leave the converters W ' 1 to W'n in a continuous byte cycle. If code conversion or clock rate adaptation is necessary for certain services or service components, the signals first reach the code converters CW _D 1 to CW _D m. Otherwise, they are fed directly to the associated STM multiplexer.

There are two types of code converters in particular consider:

• 1. Code converter for image signals and
• 2. Code converter for audio signals.

In code conversion for image signals, there are a variety of Parameters to be considered when converting are taken into account and reflected in the data structure and Reflect data rate. They are e.g. B. picture or Field changes per second, number of lines per image, Number of pixels per line, display of intensity and color, with or without audio signal, already a data reduction image signals to name just a few of the parameters. Depending on these parameters, which in the Signaling procedure directly or in the form of "Standard representations of the coded image" must be specified the code converter to the requirements via bus system S can be set. Are code conversions for certain Combinations not possible or only on certain Channel units, so the connections are already from the involved networks rejected or on the for appropriate channels.

The code conversion for audio signals is the number of Parameters not as extensive as for image conversion, for in principle, however, the procedure for setting the converter applies the same as above.

Although only two converter types are specified here, is to assume that in the future also converters for further services or service component are required. Data rate adapter  are z. B. for the "narrowband" data rates from 300 bit / s to 9.4 kbit / s to 64 kbit / s in various CCITT recommendations specified. For higher data rates, especially broadband data rates in the Mbit / s range, the data rates are based on the Bit rates of the hierarchy of digital transmission systems aligned, with the net bit rate being around that for this Synchronous tamping processes lower bit rate than required hierarchical bit rate.

If the signaling for the existing broadband network, VBN, in a central or channel-accompanying Signaling channel transmitted with the signals of other services are carried, so the Signaling information via the bus system S to one Data rate adapter are delivered, which they in the for STM multiplexer reformatted necessary data stream.

Like the ATM demultiplexer ATMD, the STM multiplexer STMM is a controlled multiplexer. It is instructed via the bus system S in which way it has to summarize the individual bit streams from the code converters, data rate adapters or directly from the converter W ' 1 to W'n with the addition of the necessary synchronous message words to the outgoing total bit stream. It is converted from parallel to serial transmission.

In the uplink direction, the processes are comparable in terms of direction. In the STM demultiplexer STDM, the total bit stream is divided into the sub-bit streams, whereby the synchronous and message words are not passed on. Only the operating status messages of the message words are sent to the control unit ST via the bus system S. The information is e.g. B. passed in parallel byte by byte. In the code converters CW _U 1 to CW _U m and data rate adapters, the conversions or data rate adjustments that are necessary for the uplink direction are to be carried out. Signaling channels carried along are routed via bus system S to the control unit ST.

The converters W ″ 1 to W ″ n, which convert from STM to ATM, first convert the information in cell form without a header. The signaling information for B-ISDN is fed to the channel part provided for this purpose via bus system A. The converters also receive their setting information via bus system A.

The same applies to the buffer memories P _U 1 to P _U n with regard to the compensation of the network clocks as for the buffer memories of the downlink path. The cell information (without header) is retrieved by the ATM multiplexer ATMM from the buffer memories P _U 1 to P _U n. The ATM multiplexer ATMM is instructed via bus system A which of its inputs it activates, ie from which buffer memories it has to call up information. Likewise, it receives the information via bus system A via the "header" to be added for each active input. It assembles the outgoing information in the cell sequence as it is given to it via bus system A. It is also possible for the ATM multiplexer ATMM to compile the outgoing information in the sequence arriving at the ATM demultiplexer ATMD, if so specified. The information is then transferred serially to the optoelectric converter OE.

This is an example of an existing broadband network mediating broadband network VBN of the Deutsche Bundespost been used. With a line signal of 140 Mbit / s can transmit the following services or combinations of services will:

A video signal at 135 Mbit / s (FBAS sampled at 13.5 MHz and linearly coded with 10 bits), an audio signal with 512 Kbit / s  or an audio signal with 135 Mbit / s, or a video signal with 135 Mbit / s, two audio signals with 512 Kbit / s each, two 64 Kbit / s Data channels, once 2048 K / bit with a net bit rate of 1920 Kbit / s data or a broadband data signal with 138.24 Mbit / s Net bit rate. According to these combinations make the settings in the channel units. For the VBN provides central signaling channels for signaling, which are duplicated for security reasons and between the Switching centers are run on separate routes.

Claims (8)

1. Arrangement for connection and cooperation of different broadband networks, of which the first network (B-ISDN) works with an asynchronous transmission method (ATM) and the second network (VBN) with a synchronous transmission method (STM), with the following features:

• - The arrangement (IWU) is connected to local exchanges or transit exchanges (DV 1 , DV 2 ) of both networks (B-ISDN, VBN),
• the arrangement (IWU) is connected to administration and monitoring centers (Z 1 , Z 2 ) of both networks (B-ISDN, VBN),
• the arrangement (IWU) has at least one channel unit (KE),
• a control unit (ST) is provided which controls the channel unit (KE),
• - Each channel unit (KE) has a multiplexer and a demultiplexer (STMM 1 to STMM 3 , ATMM 1 to ATMM 3 ) for each network, a buffer memory (P 1 to P 3 ) and a synchronous / asynchronous and asynchronous / synchronous Converter (W 1 , W 2 , W 3 ).

2. Arrangement according to claim 1, characterized in that each Channel unit (KE) consists of two branches, one of which the connection from the asynchronous network (B-ISDN) to the synchronous one Network (VBN) and the other makes the reverse connection. 3. Arrangement according to claim 2, characterized in that each branch of the channel units (KE) a demultiplexer (ATMD, STMD) for the one network, a buffer memory (P _D 1 to P _D n, P _U 1 to P _U n) one Has synchronous / asynchronous converter (W ″ 1 to W ″ n) or an asynchronous / synchronous converter (W ′ 1 to W′n) and a multiplexer (STMM, ATMM) for the other network. 4. Arrangement according to one of claims 1 to 3, characterized characterized in that at least one arrangement (IWU) Interface is provided for processing on separate signaling channels (SK) transmitted Signaling information. 5. Arrangement according to one of claims 1 to 4, characterized in that the arrangement (IWU) have optoelectric converters (OE 1 to OE 4 ). 6. Arrangement according to claim 4, characterized in that a channel unit (KE) on the network side is assigned an optoelectric converter (OE 1 to OE 4 ). 7. Arrangement according to claim 4, characterized in that several channel units (KE) one optical or electrical Multiplexer and one or more optoelectric converters (OEM) are assigned. 8. Claim according to one of claims 1 to 7, characterized in that code converters (CW 1 to CW 3 ), in particular for image and / or audio signals, are provided.