Method and devices for establishing point-to-multipoint connections and multipoint-to-point connections

The present invention relates to a method for setting up point-to-multipoint connections and multipoint-to-point connections in a Switching network according to the preamble of claim 1, a switching network for this purpose according to the preamble of claim 2, a control device for this purpose according to the preamble of claim 3 and a switching center thereof according to the preamble of claim 4

Splitting an incoming trunk in a switching matrix several secondary interconnections, and the Coupling together of several incoming interconnections in a further switching matrix to a common secondary Connecting line from the ITU-T Recommendation G.841 (DRAFT) "Types and Characteristics of SDH Network Protection Architectures", version April 1995 Figure 5-7 (page 51) in the field of SDH technology (<u>S</u>ynchrone<u>D</u>igital <u>H</u>ierarchie) known. In the switching networks shown there is ever a switching input with multiple switching matrix outputs by a point-to-multipoint connection and a plurality of coupling field inputs with a Switching matrix output connected by a multipoint-to-point connection. The use of two different and represented at least independent, ie redundant communication paths increases Transmission integrity thereof in telecommunication networks or parts. A, indicated by arrows first pair of data source and data sink via a first switching matrix ( "Matrix Connection"), two redundant Transmission pairs and a second switching matrix ( "Matrix Connection") with a second pair of data source and data sink connected. The said switching networks are part of SDH network nodes, so-called "Cross-connect". The paired arrangement of the transmission paths is here needed for transmission in full duplex mode. For a transfer in Half duplex or unidirectional transmission would only ever a Channel of transmission pairs required. The data transmission active transmission pair is called SNCw connection (<u>S</u>ub<u>n</u>etwork<u>C</u>onnection <u>w</u>orking) denotes the redundant transmission path pair as SNCP connection (<u>S</u>ub<u>n</u>etwork <u>C</u>onnection <u>p</u>rotection). The transmission in one direction on one channel of the duplicated transmission pairs is presented below. In the opposite direction is, mutatis mutandis vice versa.

A first of the data source to said second data sink, to be transmitted Data stream is duplicated by the first switching matrix and the data stream and its duplicate in parallel on one channel of the redundant transmission paths SNCP and SNCw sent to the data sink. Immediately prior to data sink be the data stream and its duplicate of the second switching matrix on received the redundant transmission paths and coupled together. In this data stream and duplicate are checked for their quality, so that thereof, if it is possible, an error-free received data stream may be selected and forwarded to the data sink. If both redundant transmission paths fail simultaneously and or malfunction, , the data stream in the manner described above with high Transmission quality and transmission reliability of the data source Data sink are transmitted.

With reference to FIG 1, a situation is first described as without can arise using the inventive method. Figure 1 shows a switching network in three stages from five switching modules with currently shared connections between the switching modules of the three stages. The Switching network consists of an input stage (I) with five switching modules 11, 12, 13, 14, and 15, an intermediate (II) with five switching modules 21, 22, 23, 24 and 25 and an output stage (III) with five switching modules 31, 32, 33, 34 and 35. Each of the five switching modules of the input (I) and the Output stage (III) is associated with each of the five switching modules of the intermediate (II) connected via intermediate lines, not shown in the figure. shown However, compounds that run over this intermediate lines so that characterized some intermediate lines are seen indirectly. The Between lines thus lie between input stage (I) and intermediate (II) and between intermediate (II) and the output stage (III). An intermediate line always exists between one output of a switching module and a stage one input of an adjacent stage switching module. Such Intermediate line in Figure 1, for example between the switching modules 11 and 21 used.

The switching modules have five inputs in the example shown and five outputs. An input of a switching module can within the the same switching module in a selectable manner with at least one output Switching Modules are connected. can An output of the switching module also be selected with at least one input of the same switching module get connected. A switching module can in each case up to five independent Connections between each one of its inputs and each one of his Outputs switch simultaneously. The switching modules 11 and 31 have a such a switching state. In these as well as most other Switching modules of the switching matrix is ​​a direct through-connection of the inputs and Outputs by horizontal lines between the inputs and outputs shown. This is intended to serve only a simple illustration.

When a connection through the switching network through only one input only one switching module of the input stage (I) to one output only a Switching module of the output stage (III) results, so this is reversible unique connection called a "unicast connection". In the Figure 1 connected "unicast connections" are by thin solid lines shown.

however, are also possible, the compounds described at the outset, wherein which received from the switching network on one of its inputs data are duplicated and sent in parallel on several of its outputs. Here Such constellations are as point-to-multipoint connections or "Multicast connections" means. "Multicast connections" are in the Figures with thick, dashed lines running. Such "multicast connection" for example, in the circuit module 24 is connected on the input side to Switching module 11 and the output side leads to the switching modules 31 and 32nd Another "multicast connection" leads from the entrance of the A14 Switching module 14 via the switching module 24 to the output of the A33 Switching module 33 and the output A34 of the switching module 34th

Similarly, a plurality of inputs of a switching matrix can one of its outputs to herein as a multipoint-to-point connection or "merge connection" designated compound are coupled together. "Merge connections" are in the figures shown with thick solid lines. coupled The switch module 25 such a "merge connection" between its inputs together to the switching modules 11 and 12 back and its output to switching module 31 out. Another "merge connection" exists between the inputs B14 and B15 of the switching modules 14 and 15 via the switching module 25 to Output B35 of the switching module 35. In the case of a "merge connection" the data stream and its duplicate, the input side of the switching matrix have been received in parallel, by coupling together switching module their quality checked. If the data stream or its duplicate as have been detected without error, is a single error-free data stream selected and routed to a single output. If neither Duplicate data stream are still errors, could also be a faulty, possibly also because of its defectiveness specially labeled, Data stream are supplied to the output.

Duplicated data streams are preferably at different transfer line bundles. This trunk group then open for incoming data streams to different switching modules Input stage (I) or to start for outgoing data streams on different switching modules of the output stage (III). "Merge connections" advantageously already in the switch modules Intermediate (II) connected together to only intermediate lines between Input (I) and intermediate (II) and not between intermediate (II) and Output stage (III) to be burdened with duplicate data streams. It is also useful, the "multicast connections" only in the switching modules to split between step (II), since only the intermediate lines between Intermediate (II) and the output stage must lead (III) duplicated data streams. Coupled together by "Merge connections" and splitting up ,, Multicast connections "can also switch modules other stages of Switching matrix take place, especially in switching networks with more stages as shown in the switching network of Figure 1. In any event, a possible Early coupled together and as late as possible splitting advantageous.

From the arrangement of the connections in Figure 1 reveals that the Switching module 24, that by the lower utilization of the Number of Inputs compared to the number of outputs only the output for remains switching module 35 usable. Thus, the connection between a Switching module 12 and 24 only on the switching module 35 and its Outputs will be continued, for example, but not to the outputs of the other Switching modules of the output stage (III). The the intermediate (II) leading part this "unicast connection" is by a chain, thin line Figure 1 shown. There occurs a blockage within the switching matrix, when the dot-dashed lines in Figure 1 because of a connection request a compound represented led to an output of the circuit modules 31- 34 shall be.

A similar problem arises not only for the finished Output line b out of the switching module 32nd This line can with reaches the switching arrangement shown in Figure 1 on the switch module 25 will. The switch module 25, however, has only one in Figure 1 Entrance free, namely to switching module 13. In a connection request of one of the free inputs of the other switching modules of the input stage (I) to free output line b towards occurs another blockage.

Object of the invention is, in a switching network of the type mentioned point-to-multipoint connections and multipoint-to-point connections among Considering the respective blocking probability build.

This object is achieved by the technical teaching of claim 1, Claim 2 of claim 3 and claim 4 dissolved. Further advantageous Embodiments of the invention are dependent claim and the refer description.

The invention and its advantages with reference to a be illustrated embodiment with the aid of drawings.<dl tsize="7"><dt>figure 1</dt><dd>shows an example of a switching matrix with one of the possible Switching states, as it is of no use can yield method.</dd><dt>figure 2</dt><dd>shows an example of the known from Figure 1 switching matrix with a over 1 changed switching state as before have passed the switching state shown in Figure 1 could.</dd><dt>figure 3</dt><dd>shows an example of the known from Figure 1 switching matrix with a over 1 changed switching state in which The inventive method advantageously applied has been.</dd></dl>

In "multicast connections" are more outputs than inputs of Switching Modules used. Other hand, in "Merge connections" more Inputs required as outputs of a switching module. "Merge" and "multicast connections" charge a switching module so as to the number of its unused inputs and outputs unbalanced in the opposite way. in the following the terms "symmetry" and "asymmetry" in Associated with the Number of used inputs and outputs of a Switching Modules used. It is now proposed according to the invention, a as equal as possible, symmetrical number of inputs and to use outputs of a switching module for connections by a "Merge connection" a switching module with an asymmetrical higher Loading of the outputs and a "multicast connection" a switching module is selected with an asymmetrically higher load inputs. To is advantageously a Unsymmetrieparameter for each switch module out, to which the "merge" and ,, multicast connections "reversed proportional effect. It could be at the Unsymmetrieparameter eg be a number that the respectively to the to the difference between Numbers unused inputs and outputs in "Merge connections" increases or reduced in "multicast connections". A symmetric Load of a switching module is reached when this held Unsymmetrieparameter its amount as small as possible. Other approaches to the formation of Unsymmetrieparameters are possible but not covered here. It could, for example, the number to slip forming inputs and outputs and is already programmed on the inputs and outputs of a Switching Modules are represented each by a two-dimensional vector, to produce their difference vector of two equally possible major elements should.

In the following, first, the application of the invention Method illustrated with reference to a further development of the switching state of Figure 2 in the switching state in Figure 3. Both figures show the example of known from Figure 1 switching matrix with each modified switching states. The switching state in Figure 2 represents a possible precursor of the switching states of Figure 1 or Figure 3 represents and can without any special effort, both in the unfavorable switching state of Figure 1 open than also beneficial Application of the method according to the switching state of Figure 3 will be further developed.

In Figure 2, the switching module 24 splits the multicast connection of Switching module 11 to switch module 31 and 32nd This results output side an asymmetrically higher load and the difference of an occupied input and two occupied outputs a Unsymmetrieparameter with the value minus one. The switching module 25 is input side asymmetric loads higher and has a Unsymmetrieparameter with the value plus one, formed from the difference of two occupied inputs and one occupied output.

Now is of the switching network a "merge connection" between Inputs B14 and B15 and the B35 output, hereinafter referred to as "merge connection B "are produced. According to the invention for a symmetrical loading of the circuit modules provided. Said input side higher onerous "merge connection" to a switching module are merged, the output side by "multicast connections" is imbalanced loaded higher. Therefore, according to the invention Process the "merge connection B" via the switching module 24th Of the Unsymmetrieparameter of switching module 24 then assumes the value zero since because of the newly established "merge connection B" to the previous value minus one of the value is added plus one, namely the difference between two occupied Inputs and one occupied output.

Furthermore, the switching network is in Figure 2 the input A14 with the Outputs A33 and A34 by a "multicast connection", hereinafter referred to as "Multicast connection A" connecting. The "multicast connection A" debits the aufsplittende switching module on the output side and unbalanced influences its Unsymmetrieparameter by the addition of the value plus 1, the difference between an occupied input and two occupied Outputs. According to the "multicast connection A" from a be split switching module that "Merge connections" is loaded on the input side unbalanced higher. Therefore, the "multicast connection A "via the switching module 25, so that there the same Numbers of inputs and outputs are load-guiding and Unsymmetrieparameter of switching module 25 by adding the value plus one to zero.

The inventively prepared and described above "multicast connection A "and" merge connection B "are shown in FIG. 3 After outside, the switching matrix in Figure 3 compared with Figure 1 unchanged relationship between the input interface of the Input stage (I) and the output interface to the output stage (III), ie it is in Figure 1 and in Figure 3, the same inputs of switching modules the input stage (I) via switching network internal connections with the same Outputs of switching modules of the output stage (III), respectively.

The aforementioned in connection with Figure 1 a connection that there of switching module 12 through switching module 24 may result in switching module 35 and is only at its four outputs switchable, is also in Figure 3 again shown. There, however, the compound a could both on the free continued outputs of the switching module 33 and the switching module 34 will. In total there is then for the receipt of a connection eight Outputs of the switching network reach. The blocking probability is so compared to the switching state in Figure 1 halved.

The introduction of said connection switching module 25 to the output b is taken up again in FIG. 3 By the switching state in Figure 3, the Output b now of the five inputs of the switching module 13 and additionally achieved by the four free inputs of the switching module 15 will. Here, the blocking probability is the ratio of five to nine reduced, thus also almost halved.

Besides the described development of the switching state as in Figure 2 in the switching state as shown in Figure 3, it is according to the invention with the The method also possible to the switching state of Figure 1 in the switching state the figure 3 to transfer under a so-called ,, rearrangements ". In such a "rearrangement" is used for a umzugruppierende Connection first within the switching matrix, a parallel Communication path established via other switching modules, according to the Check its ability to function is switched. Then, the previous connection path released. A ,, rearrangement "of in Figure 1 Switching state shown will be described below.

In the case of a "rearrangement" by the novel process first network the asymmetrically loaded switching modules in a coupling determined, these are in Figure 1, the switching modules 24 and 25. Then, determined whether the asymmetry be reduced in these switching modules can by unbalanced incriminating connections to other switching modules outsourced and continue its own unbalance balancing Connections can be taken over by the other switching modules. This analysis shows for the switching state in Figure 1, in that the switching module 24 a "multicast" by a "merge connection" and in switching module 25 a "Merge" must be replaced by a "multicast connection". The Asymmetry in switching module 24 is by flipping the "multicast connection A "is reduced to the switching module 23 and at the same time the possibility created to carry out a "merge connection" via the switching module 24, the which then can compensate for existing asymmetry. For this purpose, the "merge connection B" in a further step of switching module 25 to Switching module 24 rearranged. In a final step, the Asymmetries eliminated in the switching modules 23 and 25 by the ,, Multicast connection A "of switching module 23 shifts to switching module 25 becomes. This then results in a switching state, as shown in Figure 3, with its Advantages already described.

As pointed out above, is a "rearrangement" consuming and in particular in Cross-connects in the SDH technology very time-consuming. Therefore, it is particularly advantageous from the outset the switching state by the above based on to make 2 and 3 described inventive method so that so that the blocking probability and hence the probability is kept low for a "rearrangement".

The inventive method can be applied to any switching networks apply. For the representation of the embodiments and the Figures is schematic diagrams.

For the inventive process it is also irrelevant that all Switching modules of one stage building "merge" and "multicast connections" allow, because even when two such switching modules in a Stage can proceed in the manner of the invention.

If a further increase of more than two transmission reliability redundant transmission paths requires, the inventive Method can be applied also for the construction of such compounds.

The splitting or coupling together of transmission paths in Switching matrices in connection with an increase in the Transmission security is also only an exemplary application of the Inventive method. Also for example, in the construction of Conference calls could be challenged in the inventive manner will.