AU601245B2 - An arrangement for detecting multiframes in time-division multiplexed signals - Google Patents

Description

i-- 601245 ar r r r r r r tr t rr ORIGINAL COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-1969 SThis document cont.in amendments made t,: SSection 49 and is corncc IC: printing.

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COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED "AN ARRANGEMENT FOR DETECTING MULTIFRAMES IN TIME-DIVISION MULTIPLEXED SIGNALS" The following statement is a full description of this invention, including the best method of performing it known to us:t Signature of Applicant Signature of Applicant To: The Commissioner of Patents j- i i i Ir 4 .4 4I, 4 .4I This invention relates to an arrangement having an input for a time-division multiplexed signal with predetermined frame and multiframe structure and an output for a time-division multiplexed signal.

The present description, including the explanation of the problem to be solved, represents the invention by a concrete example. However, the invention can be used wherever a multiframe structure contained in a TDM signal must be recognized in a facility of the above kind.

The Integrated Services Digital Network (ISDN) being installed by the Deutsche Bundespost includes basic-access multiplexers (BAMX) which each connect twelve basic accesses S to an exchange. A basic access makes it possible to connect several terminals and to operate up to two terminals simultaneously via a 64-kb/s customer-information channel (B channel) each. There is also a data channel (D channel) which serves to transfer signalling information but can also 'i be used by the customer to transfer data packages. All these signals, 24 B channels and 12 D channels, are combined in the basic-access multiplexer into a single TDM signal. This TDM signal contains further information (S channels) which serve to control the co-operation between the basic-access multiplexer and the exchange. This additional information is contained in a service channel (S channel) per basic access. Compared with the underlying complete TDM signal, these service channels have a multiframe structure. Every two such multiframes are in synchronism and can thus be regarded as a common multiframe. Thus, there is a total of six independent multiframes which have no fixed phase relationship to each other. This grouping of 2 1, 1 To: The Commissioner of Patents.

F; independent multiframes is herein referred to as a supermultiframe. At the exchange, this TDM signal, which arrives with a predetermined frame and multiframe structure, must be adapted to an internally predetermined frame structure. During this adaptation, it is not necessary to recover the individual channels; only their positions in the TDM signal must be determined. Above all it is necessary to detect the start of a multiframe of each individual I multiframe in the concrete example). At the output of the facility performing the adaptation to the exchange, all signals are present in time-division multiplexed form again.

S In the concrete application, this facility has two outputs which each provide half of the input information as a TDM signal. The same takes place analogously in the opposite direction.

The transparent chanels present hardly any difficulties even if they have to be re-sorted. The necessary identification of the multiframes poses problems, however.

The problem is not to separate the component signal belonging to the multiframe from the TDM signal, but to rec- S ognize the multiframe structure within this component signal, particularly to detect the start of the multiframe, and to immediately evaluate any information contained therein.

The same problem exists wherever TDM input and output signals are permanently associated with one another, but where there is at least one multiframe whose position must be determined. Such other applications include network gateways or repeaters, for example.

3 N -kr This problem is aggrevated if TDM inputs and output signals are not synchronous, so that adarFation must be achieved by stuffing techniques and the like.

The present invention solves this problem by providing a separate processing unit for identifying and, if necessary, processing the information of a multiframe. If there are several dependent multiframes, a separate process ing unit is provided for each independent multiframe, these processing units being independent of each other. Preferably, such a processing unit is program-controlled. The facility given as an example has 6 microprocessor-controlled processing units. It is advantageous to provide an additional processing unit for all channels not contained in the multiframe.

The facility according to the invention makes the synchronizing and control signals contained in a TDM signal in one or more independent multiframes accessible without demultiplexing the TDM signal. For each multiframe, an independent, preferably program-controlled, processing unit is provided. For the component signals not contained in multiframes, for the (basic) frame, an additional processing unit is preferably provided.

The specification describes an adapter to convert an input TDM signal to an output TDM signal, the input TDM signal including supermultiframes made up of a series of multiframes, the multiframes of the series originating from one or more of a plurality of sources of independent multiframes, wherein the independent multiframes are not constrained to occur in a fixed sequence, the supermultiframe pincluding at least one service channel including signals °'4 which control the adapter, the service channel signals having a multiframe structure, the adapter comprising a plurality of processing units. there being at least, one corresponding processing unit for each independent multiframe of a supermultiframe, each corresponding processing unit being adapted to extract from the input TDM signal the corresponding multiframe signals, and to transmit the corresponding multiframe signals in a predetermined sequence in relation to the outputs from the other processing units.

An embodiment of the invention will now be explained with reference to the accompanying drawing.

The single figure of the drawing is a block diagram of the above-mentioned facility for connecting an ISDN remote switching unit (basic-access multiplexer) to an exchange.

The TDM signal coming from an input V2 is applied to a bus BUS2. Connected to this bus BUS2 are the inputs of 6 processing units DS1,2 The outputs of the processing units DS1,2, DS5,6 and DS9,10 are connected to a bus BUSI, which leads to an output VI. The outputs of the processing units DS3,4 DS7,8, and DS11,12 are connected to a bus BUSII, which leads to an output VII. An additional processing unit B has its input connected to the bus BUS2, while its two i outputs are connected to the bus BUSI and the bus BUSII, respectively. The processing unit B contains two sub-units BI and BII, whose inputs are connected in parallel and to the bus BUS2, and whose outputs lead to the bus BUSI and the bus BUSII, respectively.

The drawing shows only those parts of the facility 30 -according to the invention which are necessary to understand

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the invention. Not shown are, among other things, transmission modules, power supply, clock generators at the input and output ends, controllers, and all modules for the opposite direction. Modules serving to detect and signal operating states or errors are not included in the drawing, either. All those modules, with the exception of those necessary for the opposite direction, are present at a centralized location. However, the may also be decentralized, distributed among the individual processing units DS1,2 DS11,12 and B.

Under control of the clock generator at the input end, each processing unit DS1,2 DS11,12 and B extracts from the TDM signal coming from the input V2 the component signal destined for it. This component signal is brought to the correct format and, under control of the clock generator at the output end, passed to the output at the correct instant, where it is combined with further component signals from other processing units to form a new TDM signal which has a correct frame and multiframe structure even in the ab- 0 sence of synchronization. In the example, two new TDM signals are obtained, which are delivered at the outputs VI and VII.

The D and S channels for two subscribers are inserted into the TDM signal in one multiframe each. In this example, the individual multiframes are of the same length but have no fixed phase relationship to each other. Each processing unit DS1,2 DS11,12 assigned to such a multiframe must first separate from the TDM signal the component signals belonging to the respective multiframe; to this end, X^W41-the frame structure of the TDM signal must be known. Within :i 1 i the component signal belonging to the separated multiframe, the structure and particularly the start of this multiframe must then be determined. The contents of the multiframe can then be evaluated or changed, as required. At the output of the respective processing unit DS1,2 DS11,12, the, possibly changed, contents of this multiframe are placed on the bus BUSI or BUSI in such a way as to form, together with the output signals from the other processing units connected to the same bus, the desired TDM signal for the output VI or VII. Each processing unit DS1,2 DS11,12 contains essentially a microcomputer and an output buffer. The identification, processing, and transfer of the contents of a multiframe are performed in a manner familiar to those skilled in the art.

The processing unit B, which is divided into the subunits BI and BII, transfers the B channels from the input V2 to the outputs VI and VII. The B channels are not tied into a multiframe structure, nor must their contents be recognized. They must only be passed on at the correct instant. Therefore, the subunits BI and BII of this processing unit B are essentially buffers which are caused to write and read by counters at the input end and the output end, respectively. The processing unit B can also be called upon to synchronize the clock generators and counters at the input end and those at the output end in the opposite direction.

In the present embodiment, a facility with an input and two outputs for TDM signals is described, so that the frame and multiframe structures at the input necessarily .differ from those at the output. In the opposite direction, OW O a corresponding facility with two inputs and one output is necessary. The invention is also applicable to a facility which converts a TDM signal with a first frame and multiframe structure into a TDM signal with another frame and multiframe structure, such as a facility at a network gateway, and to a repeater which is synchronized, monitored or remotely controlled by a signal contained in a multiframe.

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Claims (7)

1. An adapter to convert an input TDM signal to an out put TDM signal, the input TDM signal including supermultiframes made up of a series of multiframes, the multifr.mes of the series originating from one or more of a plurality of sources of independent multiframes, wherein the independent multiframes are not constrained to occur in a fixed sequence, the supermultiffame including at least one S service channel including signals which control the adapter, the service channel signals having a multiframe structure, S the adapter comprising a plurality of processing units, there being, at least, one corresponding processing unit for each independent multiframe of a supermultiframe, each cor- responding processing unit being adapted to extract from the input TDM signal the corresponding multiframe signals, and to transmit the corresponding multiframe signals in a prede- termined sequence in relation to the outputs from the other processing units.

2. An adapter as claimed in claim 1 wherein each proc- essing unit is adapted to reformat the corresponding multi- frame.

3. An adapter as claimed in claim 1 or claim 2 wherein each processing unit is processor controlled.

4. An adapter as claimed in any one of claims 1 to 3 wherein one or more additional processing units are provided to process signals in the input TDM signal which are not part of the independent multiframes.

An adapter as claimed in any one of claims 1 to 4 including an output clock generator to control the outputs B. of the processing units.

6. An adapter as claimed in any one of claims 1 to adapted for duplex transmission.

7. A TDM signal adapter as herein described with refer- ence to the accompanying drawing. DATED THIS TWENTY-SECOND DAY OF JUNE, 1990. ALCATEL N.V. l