Asynchronous time division multiplex communication system.

The invention relates to an asynchronous time-division multiplex transmission system, the incoming cells in a comparator transmits to feeder lines by means of a temporary storage of the cells in the buffers, and an evaluation of the path identification contained in the cells on a trunk line, with at least one coupling element.

In the asynchronous time-division multiplex transmission system, payload, eg, telephone, picture or sound signals sent in fixed length blocks. As a fixed length block, a cell is referred to, having a predetermined number of bits in serial order. Each cell consists of a header and an information field. In the header field, the path identification of the cell is, among other things housed. Under a path identification is a connection identifier or a routing information to understand. In the call reference the indication of the target or sub-target of the useful information is contained. The routing information is added within the system in certain transmission assemblies and includes an indication of a partial goal within the transmission assembly. The payload is housed in the information field.

Cells are assigned sequentially certain time intervals (time frame). The duration of such period of time depends on the underlying clock frequency of the transmission component. If no payload is present, empty cells are transmitted in such a time frame, that is, cells without payload information. Cells that contain a payload are referred to as useful cells.

During the transfer of cells between the cells participants switching networks in which paths are made by evaluating the path identification through. Such a switching network can be composed of a plurality of switching matrix blocks. Such a switching matrix block with several feeder and trunk lines consists of several coupling elements. A coupling member includes a plurality of feeder lines and trunk line. In a coupling element while cells are transferred from a feeder line to a trunk line. Upon arrival of cells on multiple input lines during a time frame that want to access a trunk line, specific strategies for coupling are necessary.

From DE-OS 37 14 385, the coupling element above is known. Here, the incoming feeder lines on cells are stored in one input buffer. After evaluation of the path identification in each feeder line associated comparator is released in accordance the path identification with the address of a trunk line the trunk line for the cell in the input buffer. Are simultaneously different cells, the assigned in the feeder lines, input buffers are stored, is provided for a trunk line, as is cyclically each released an input buffer or an incoming trunk associated comparator for outputting the cells from the respective input buffer of a decision circuit. Intricately in this coupling element is that each feeder line is associated with a comparator.

The invention is therefore based on the object to provide a coupling element for an asynchronous time-division multiplex transmission system, which is implemented with a smaller circuit scale.

This object is achieved with a coupling element of the aforementioned type in that in the coupling element in a reordering the cells are transformed into intermediate blocks so that at least in an intermediate block the path identification of the supplied to the feeder lines cells is that determination of the assignment of the path identification data contained in the various intermediate blocks associated with the cell in which each intermediate line buffers are read to a trunk line in the coupled with at least one intermediate line comparator and that a multiplexer connecting the outputs of the buffer to read out a cell with the trunk line.

In this coupling element, the cells, which are supplied to various feeder lines are, in a reordering prepared so that at least the path identification of the different cells of a time frame to be placed in an intermediate block. It is also possible to form another intermediate blocks with the directional identifications. Furthermore, can be added to the intermediate blocks with the path identification and payload of the cells. The remaining payload of the cells are organized in other intermediate blocks, which are given to more intermediate pipes. This redistribution must only the intermediate lines on which the intermediate blocks are transported with the way identifiers are each connected to a comparator. Due to this measure, the number of comparators is reduced in such a coupling element. It is no longer necessary to provide a comparator for each feeder line, whereby the expenditure for the realization over the prior art coupling element is reduced. In the coupling element of the invention, for example, only one comparator is required if the path identification is provided on an intermediate line between blocks. If the comparator been found that the path identification to the trunk line is associated with, ie that the corresponding cell of the serving line is to be fed, the path identification of the cell and the remaining data is read into buffers that are associated with the various intermediate lines. The data stored in the buffers data is provided by means of a multiplexer to the trunk line. In this case, the cell is again composed so as it is fed on a feeder line. A blank cell which has been detected by the comparator is not read into the buffer. Furthermore, the cells are switched through to their time arrives, that it be given all the cells of a time frame on a trunk line, before the cells of the next time frame will be directed to a trunk line.

In one development of the invention provides that in the reordering of the supplied to the feeder lines cells, which are each divided into words of equal length time slots and their respective word count of the number of feeder lines corresponding to intermediate blocks are formed, which are composed of the words which are present in the respective cells at the same time intervals. In this development, intermediate blocks are formed on the intermediate lines which are composed of the words of the various cells and corresponds to the word count the number of words a cell. The prerequisite is that the number of intermediate lines to the number of feeder lines corresponds. By this measure, the buffers are evenly covered and thus optimally utilized. The intermediate blocks can hereby be mutually given simultaneously or with a certain delay to the intermediate lines. Because the buffers are not housed as in the known coupling element to the feeder lines, a smaller dimensioning of the buffer is possible. The cells are in fact evenly distributed to the buffer in the invention and it can not occur as in the known coupling element that in a buffer more cells are stored as in another, because on a feeder line for a period arrive more cells than on another feeder line.

To keep the cost of the coupling element as low as possible, it is provided that the reordering is the first word of a cell with the path identification and that the comparator, coupled to the first word of the cells transmitting intermediate line. Since the path identification is present only in the first word of a cell and the first words are only given on an intermediate line, only one comparator for a coupling element is also required.

If the comparator determined the allocation of the path identification for trunk line, is an output control circuit, the buffer to read the words of a cell in the chronological order of their occurrence dates. Here, if the words of a cell are not displaced in time, this simultaneously read into the buffer, while the words are read to each other sequentially in a temporal displacement of the intermediate blocks. The read-out operation from the buffers is also controlled by the output control circuit. This connects the trunk line to the outputs of buffer by cyclic control of the multiplexer in the order of reading of the words of a cell in the buffer. then the cell will appear in the form in which it has been fed on a feeder line to the trunk line.

The shuffling circuit can be realized in a simple way, if this mutually respectively displaced the intermediate blocks to the period of a word, that the chronological order of the intermediate blocks of the chronological order of words in a cell corresponds. For this purpose, the rearranging circuit contains a synchronization circuit which mutually offset the supplied to the feeder lines cells each case by the time interval of a word, and further controlled by an input control circuit multiplexer, which forms the intermediate blocks from the cells in each case the time period of a word offset from one another. The synchronization circuit must thereby first synchronize the arriving during a time frame cells together and then perform the skew.

The reorganization of the cells in between blocks is implemented in the multiplexer. This leads the reorganization by means Einzelmultiplexern whose outputs are connected to a respective intermediate line and whose inputs are connected by controlling the input control circuit cyclically to a respective output of the synchronization circuit.

An embodiment of the invention is explained below with reference to the drawings. Show it:<ul><li>Fig. 1 is a block diagram of an asynchronous time-division multiplex transmission system,</li><li>FIG. 2 is a simplified illustration and coupling element</li><li>FIG. 3 shows an example of the timing relationship of the lines of FIG. 2 transported words and cells.</li></ul>

The block diagram shown in FIG. 1 the principle of an asynchronous time-division multiplex transmission system can be explained. The signals of a terminal, for example, telephone, picture or sound signals are segmented into a packetizer and, provided with a head box where a path identification is available. The path identification includes an indication about the destination of the signals. Such a terminal and the packetizer form a subscriber terminal 1. The data of such a terminal are transmitted within a defined time (time frame) in the form of cells. The duration of such a time frame depends on the underlying clock frequency of a transmission component. Such cells are made of the already above-mentioned header and the payload. If within a time frame no data to be transmitted, an empty cell is formed, ie, a cell is indicated in the header field, that no further information follows. Such empty cells are used to synchronize the system. The cells carrying a payload are referenced payload.

In the block diagram shown in FIG. 1, the data as of 64 subscriber terminals 1 through 64 lines, each with a capacity of 150 Mbit / s are transmitted to a terminal Group 2. In the group 2, the terminal data are combined and transmitted over a smaller number of lines with a higher capacity. For example, these data can be 16 lines with a capacity of 600 Mbit / s are guided. In a subsequent switching matrix 3, which is composed of multiple switching matrix blocks and those of several coupling elements, found by evaluating the path identification instead of an exchange of data by being added to a particular trunk line. A coupling element in this case consists of a circuit arrangement that is connected to multiple input lines and a trunk line. The circuit arrangement or the coupling element, data that should be forwarded to the connected to the coupling element serving line, determine and the necessary paths within the circuit provide for it. The switching network 3 is again a multi-line, for example, 16 lines with a capacity of 600 Mbit / s connected to a terminal group. 4 The terminal group 4 forwards the received data via lines to subscriber terminals 5 on. For example, in this case 64 lines each with a capacity of 150 Mbit / s are provided. Such a system still transmits data of the subscriber terminal 5 on the subscriber terminal. 1

In FIG. 2 is a coupling element which is part of a switching network is illustrated. The coupling element includes a re-arraying circuit 25 having a synchronization circuit 6, which is connected to four feed lines 7a to d. On the four feeder lines 7 a to d in the form of data cells of the synchronization circuit 6 are supplied. Within a certain time frame, such cells are transported to the feeder lines 7a to d. These cells are not synchronized to each other, as shown in Fig. 3a. FIG. 3a shows four cells, might be supplied, for example on one of the feed lines 7a to d of the synchronizing circuit 6. These cells are divided into four words 1 to 4. FIG. The words have the same time spacing (same number of bits) in each case. Since the individual cells are not time synchronized with each other, they are synchronized in the synchronization circuit 6 and to one another in each case offset by one word, as shown in Fig. 3b. The cell on the line 7a is offset in time by a word to the cell on the line 7b. Further, the cell on the line 7b with respect to the cell on the conduit 7c by one word, and the cell on the line 7c to the cell on line 7d also shifted by one word. In this case, the cell is read out on the line 7a to the time interval of three words rather from the synchronization circuit 6 as the cell on line 7d.

Such synchronization and skew can be realized for example by means of synchronous detection circuits 8a-d, four memories 9a-d and a synchronous control circuit 10th The synchronous detection circuits 8a-d detect a cell early and enter the synchronous control circuit 10 corresponding information. The synchronous control circuit 10 are then free memory 9a to d so that a cell can be read into the memory. After all cells have been read into the memory 9a to d, the first cell is read in the memory 9d by a corresponding command of the synchronous control circuit 10th Subsequently, the remaining cells from the memories 9c to a read out with a time shift, as shown in FIG. 3b.

It should be noted that the lines for the sake of clarity, shown in Fig. 2 are drawn in the form of a line, even though they partially consist of several parallel lines. Also required for the control of the individual digital circuit elements clock lines and the clock generators are not shown.

The four outgoing from the synchronizing circuit 6 lines are connected to a multiplexer 11 which is also a circuit of the re-arraying circuit 25th This multiplexer 11 includes four individual multiplexers 12a-d and an input control circuit 13 connected the individual multiplexers 12a-d are connected at their respective output of a respective intermediate line 14a to 14d. By means of the multiplexer, the one word staggered cells are rearranged to intermediate blocks. In an intermediate block, the words of a cell, which occur in the cells at the same time segments appear, that appears at the output of the multiplexer 12d, an intermediate block with the first word of each cell. then appear the second through fourth words of the cells to the outputs of the single multiplexer 12c to a. The intermediate blocks, which appear on lines 14a-d are plotted in Fig. 3c.

The control of the individual multiplexers 12a-d is realized by means of the input control circuit 13 may consist of a counter, for example. The input control circuit 13 includes the synchronization circuit 6, an enable signal, if the cells are read out from the memories 9a to 9d. In this case, certain inputs 13 of the single multiplexer 12a are released through d for each of the duration of the time interval of a word from the input control circuit. These inputs of the multiplexer are designated in Fig. 2 with numerals 1 to 4. First, the input 3 of the multiplexer 12a, the input 2 of the multiplexer 12b, the input 1 of the multiplexer 12c and the input 4 of the multiplexer 12d is released. then the first word of the cell from the memory 9d appears on the intermediate line 14d. For the next words of the input 2 of the individual multiplexer 12a, the input 1 of the individual multiplexer 12b, the input 4 of the individual multiplexer 12c and the input 3 of the individual multiplexer 12d is released. then the first word of the cell from the memory 9c and on line 14c the second word of the cell from the memory 9d appears on the line 14d. On the next shift of the input 1 of the individual multiplexer 12a, the input 4 of the individual multiplexer 12b, the input 3 of the individual multiplexer 12c and the input 2 of the individual multiplexer 12d is released. The switching process ends with the release of the input 4 of the individual multiplexer 12a, the input 3 of the individual multiplexer 12b, the input 2 of the individual multiplexer 2 and the input 1 of the individual multiplexer 12d. Subsequently, this cycle again until all of the words stored in the memories 9a to d cells on the lines 14a are repeatedly read out to d.

Such redistribution of the words of a cell is possible only when the cell has the same number of words as feeder lines are available.

At the feeder line 14d, a register 15 is connected, in which the first words of a cell is read. In the first word must be present in any case, the path identification. In a comparator 16 which is connected to the register 15, the path identification is evaluated, which is present in the first word of a cell. If it is determined by the comparator 16 by evaluating the stored in the memory 18 information that the cell of the trunk line is assigned to 17, in an output control circuit 19, a detector 20 will cause an enable circuit 21, buffer 22a vacated by d for good read the words of a cell. The enable circuit 21 are thereby released the buffers 22a-d corresponding to the occurrence of words on lines 14a-d. It is thus first of the buffer 22d is enabled to read the first word of a cell from the register 15th After the duration of the time interval of a word of the buffer 22c is enabled to read in the second word of the cell. Simultaneously, the first word of the next cell can be read into the buffer 22d already. Similarly record with the release of the buffer 22b and a. The buffers 22a-d are FIFOs. The FIFO should be dimensioned so that an overflow practically can not take place. The memory size of the FIFO can be determined by traffic simulations of the coupling element. The detector 20, the output control circuit 19 releases one point 23 which controls a multiplexer 24th The multiplexer 24 connects one of its four inputs with the trunk line 17. The multiplexer 24 is controlled so that a cell is added beginning with the first word and ending with the fourth word to the trunk line 17th

If an empty cell occurs, the comparator 16 will determine that the path identification of the dummy cell is not assigned to the trunk line 18 and a release of the buffer 22a to 22 d will not take place. No empty cell but only a useful cell is thus given to the trunk line 17th

When the coupling element for simplicity shown with four feeder lines, the number of feeder lines may be much larger. Here, however, the number of words the number of feeder lines must be selected a cell the same.