MULTISTAGE DIGITAL SWITCHING NETWORK

Abstract: A multistage network according to the invention, which is particularly useful for telecommunication systems, is characterized by increased reliability at a reasonable complication of the system. Each of the subnetworks (1, 2) of a multistage digital switching network consists of modules (3, 4, 5 and 6, 7, 8, respectively) connected in series, wherein each of the said modules constitutes a single digital time-space switch, namely either a sing­ le- or a multi-stage switching network. The subnetworks (1, 2) are so interconnected to each other that the inputs of the middle module (4) of the first subnetwork (1) are indirectly connected, through the connecting module (10), with the outputs of the mid­ dle module (7) of the second subnetwork (2), whereas the inputs of this module (7) are indirectly connected, through the second connecting module (9), with the out­ puts of the middle module (4) of the first subnetwork (1); besides, the connecting modules (9, 10) are identi­ cal with the middle modules (4, 7) of both subnetworks. According to an alternative solution each subnetwork (15, 16) consists of three modules (17, 18, 19 and 20, 21, 22, respectively) connected in series; they are so interconnected to each other, that unused outputs of the middle modules (18, 21) are reversibly connected to inter-stage links of the said subnetworks. The above solution is applicable only if quantity of un­ used links in the middle modules is at least equal to quantity of links used for the connection with the mo­ dules of the external stage.

Description: Subject of the invention is a multistage digital switch­ ing network, particularly useful for the construction of a telecommunication system and especially for telephone exchanges. In well-known solutions of multistage switching networks as described in the publications: K. Neufang "Das Digi­ talkoppelnetz im System EWSD", Telcom Report, 1981, 4, pages 28 to 32, and H. Inose "An Introduction To Digi­ tal Integrated Communications Systems", Peter Peregrimus Ltd., 1979, pages 141 to 145 there have been used two identical and independent subnetworks, from which in case of emergency, each one can work individually. The line concentrating unit of an exchange is connected with the switching network by a pair of PCM links, from which each one is connected to one of the subnetworks, whereas connections between the respective subnetworks are made by means of a specialized switching equipment. In another solution, as described in a publication of K. Kurahasi, T. Egawa, J. Shimizu and M. Itoh "DTS-1 Speech Path System", Rev. Electr. Commun. Lab., 1979, 27, pages 728 to 739, there was used a duplication of a middle spacestage of the switching network and in each external timestage an additional switch has been provi­ ded. In another approach as described in a publication of J. M. Cotton, K. Giesken, A. Lawrence and D. C. UPP. "ITT-1240 Digital Exchange Digital Switching Network", Electr. Commun., 1981, 56, pages 148 to 160, the connect­ ing units are connected to the switching network indi­ rectly, through two access switches; besides, each of the said switches is connected to the connecting unit by the separate PCM link. In the proposed solutions, in order to increase the re­ liability of operation, a duplication of the complete switching network or only some part of it has been used. Moreover, there is additionally engaged a specialized switching equipment or is increased the quantity of the applied digital time-space switches. These undertakings, whereas effective, are very expensive and material-consuming, while due to them the systems of the switching networks are characterized by a consider­ able degree of complication. A purpose of the invention was the elaboration of such a multistage switching network, which is characterized by a high reliability and should be produced from standard switching elements, at lower complication of the system and at lower cost of production. A multistage network according to the invention consti­ tutes a system of two sub-networks, from which each one consists of three modules connected in series, but each of the said modules constitutes a single digital time-­ space switch either a single- or multi-stage switching network. Both subnetworks are so interconnected to each other that the inputs of the middle module of the first subnetwork are indirectly connected through the connect­ ing module with the outputs of the middle module of the second subnetwork, but the inputs of this middle module are connected indirectly through the second connecting module with the outputs of the middle module of the first subnetwork. Two connecting modules which are intercon­ necting the subnetworks are identical with the middle modules of both subnetworks. The above solution enables the structure of switching net­ works in any range of capacity, characterized by a high reliability. For switching a traffic between both basic parts of a network, the standard switching elements are used. Utilization of non-standard elements of presently applied technology of a large scale of integration should cause a cost rise of a switching network. In comparison with the solutions based on the duplication of a complete switching network, the network according to the invention is characterized by a smaller number of the utilized switching elements. According to an alternative solution, both subnetworks are so connected to each other, that the unused outputs of middle modules of the respective subnetworks are re­ versibly connected to inter-stage links of the said sub­ networks. The solution presented above is characterized by a smal­ ler number of applied switching elements in comparison with the solutions described in the prior art. The solution according to the invention enables a struc­ ture of switching networks characterized by high re­ liability, however its application is only possible if the quantity of unused links of middle modules will be at least equal to the quantity of links used for the connection with modules of an external stage. The invention will be explained in greater detail by way of an embodiment as shown in the drawings in which Fig. 1 shows a block diagram of a general multistage network having a capacity of N PCM links, Fig. 2 shows a diagram of three-stage network having a capacity of 128 links, Fig. 3 shows an alternative block diagram of a general multistage network and Fig. 4 shows an alternative diagram of a three-stage network having a capacity of 64 PCM links. The switching network of Fig. 1 having a capacity of "N × N" PCM links consists of two subnetworks 1 and 2 each of which has a capacity of " × " links. Each of the said networks consists of three modules 3, 4, 5 and 6, 7, 8, respectively, which are connected in series, respectively. These modules constitute single switching elements or either a single- or multistage switching network. The subnetworks 1 and 2 are so con­ nected to each other that the inputs and outputs of the middle module 4 of the first subnetwork 1 are reversibly connected with the inputs and outputs of middle module 7 of the second subnetwork 2, and the connections between the said elements are intermediate, through pairs of two connecting modules 9 and 10, which are identical with the middle modules 4 and 7 of both subnetworks 1 and 2. The switching network having a capacity of 128 PCM links is constructed from time-space switches having a capa­ city of 8 × 8 links. The subnetworks are connected through the connecting modules 11 and 12, which are identical to the middle stages 13 and 14 of the subnet­ works. Analogously, as the network shown in Fig. 1, a switching network having a capacity of "N × N" PCM links shown in Fig. 3 consists of two identical subnetworks 15 and 16 each of which having a capacity of " × " links and consists of three modules 17, 18 and 19 and 20, 21, and 22, respectively, which are connected in series, respect­ ively. The said modules constitute single switching ele­ ments and are either single- or multi-stage switching networks. The subnetworks 15 and 16 are so interconnected to each other, that the unused outputs of the middle modules 18 and 21 are reversibly or cross-connected to the inter­ stage links in the respective sub-networks. The switching network having a capacity of 64 PCM links is constructed from time-space switches having a capaci­ ty of 8 × 8 links. The subnetworks 23 and 24 are connected by means of unused links in the middle stage denoted by numbers from 5 to 8, which are reversibly connected to inter-stage links in the respective sub-networks.

Claims: 1. Multistage digital switching network composed of a system of two identical subnetworks intercon­ nected to each other, each of which having a capa­ city of " × " PCM links, characterized in that each of the subnetworks (1, 2) consists of three modules (3, 4, 5 and 6, 7, 8, respectively), which are connected in series, respectively, where­ in each of the said modules constitutes a single digital time-space switch, either a single- or a multi-stage switching network, and that simulta­ neously the subnetworks (1, 2) are so interconnect­ ed to each other, that the inputs of the middle mo­ dule (4) of the first subnetwork (1) are indirect­ ly connected through the connecting module (10) with the outputs of the middle module (7) of the second subnetwork (2) and the inputs of this mid­ dle module (7) are indirectly connected through the second connecting module (9) with the outputs of the middle module (4) of the first subnetwork (1), while the connecting modules (9, 10) are identical with the middle modules (4, 7) of both subnetworks (1, 2). 2. Multistage digital switching network comprising a system of two identical subnetworks interconnected to each other, from which each one has a capacity of " × " PCM links, characterized in that each of the subnetworks (15, 16) consists of three mo­ dules (17, 18, 19 and 20, 21, 22, respectively), which are connected in series, respectively, wherein each of the said modules constitutes a single digital time-space switch, either a single-­ or multistage switching network and that the sub­ networks (15, 16) are so interconnected to each other, that the unused outputs of the middle mo­ dules (18, 21) are reversibly connected to inter­ stage links of the said subnetworks.

Inventors: JAJSZCZYK, ANDRZEJ, KABACINSKI, WOJCIECH
Applicants: POLITECHNIKA POZNANSKA
Application year: 1986
Main classification: H04Q11
IPC codes: H04Q3