AU1223299A

AU1223299A - Communication device for the transmission of message signals

Info

Publication number: AU1223299A
Application number: AU12232/99A
Authority: AU
Inventors: Andreas Klug; Jorg Kopp
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG
Priority date: 1997-09-16
Filing date: 1998-09-15
Publication date: 1999-04-05
Anticipated expiration: 2018-09-15
Also published as: EP1016238A1; ZA988380B; AU739406B2; WO1999014886A1; CA2303538A1; CN1270723A

Description

GR 97 P 2428 - 1 Description Communications device for the transmission of message signals 5 The invention relates to a communications device according to the preamble of Patent Claim 1. Depending on the required fail-safeness of a communications device, different redundancy structures 10 can be provided for the peripheral line assemblies associated with the said device. Examples of this are the "1+1", the "1:1" and the "1:N" line assembly redundancy, as is described in "IEEE Journal on Selected Areas in Communications", VOL. 15, No. 5, June 15 1997, pages 795 to 806. In the case of a "1+1" redundancy structure, two line assemblies are operated in parallel in order to transmit message signal streams in a redundant manner via them. In this case, however, only one of these redundant message signal streams is 20 taken into account for further handling. In the case of "1:1" line assembly redundancy, only one of two line assemblies is used as active line assembly, a changeover being made to the remaining line assembly, serving as backup assembly, only in the case 25 of an error in the active line assembly. Finally, in the case of "l:N" line assembly redundancy, a single backup line assembly is provided in addition to a plurality N of line assemblies. When an error occurs on one of the N line assemblies, then 30 the backup line assembly is used instead of this line assembly. The communications device according to the preamble of Patent Claim 1 relates to such "1:N" line assembly redundancy. A communications device having 35 such "l:N" line assembly redundancy is described in the German Patent Application GR 97 P 2428 - 2 mentioned above. The communications device is in this case connected to a plurality N of transmission lines. The interface to these N transmission lines is formed by N line terminals of selection means of the 5 communications device. These selection means are connected via further N+1 line terminals to N+l line assemblies which form a "1:N" redundancy group. In this case, in the normal mode, that is to say during error free operation of the line assemblies, these selection 10 means are used to connect for example the first N line assemblies as active line assemblies to N transmission lines. On the other hand, the remaining line assembly N+1 serves as backup line assembly. In the event of an error occurring in one of the active line assemblies, 15 the selection means are then changed over in such a way that the transmission path that previously ran between the defective line assembly and the associated transmission line now runs via the backup line assembly N+1. 20 The communications device that has been explained has the disadvantage that in the event of failure of such a selector arrangement and in the event of a resulting replacement of this selector arrangement, all of the transmission lines connected 25 thereto and hence the connections running via the said lines are interrupted. The abovementioned German Patent Application furthermore claims a design of a communications device according to the preamble of Patent Claim 1. This 30 design provides for the selection means of a "l:N" redundancy group to be provided with N signal terminals on a first connection side and, on the other hand, only with one individual signal terminal, connected to the backup line assembly, on a second connection side. 35 Line-specific switching means are inserted into each of the transmission lines, which switching means connect the respective transmission line optionally via a first switching path to the active line assembly assigned to the said transmission line GR 97 P 2428 - 3 or via a second switching path to one of the N signal terminals of the selection means. In this case, the selection means and the N switching means can be controlled in such a way that, in the normal mode, the 5 N transmission lines are connected to the N active line assemblies directly via the first switching paths of the line-specific switching means, whereas, in the backup mode of one of the N active line assemblies, the assigned transmission line thereof is connected to the 10 backup line assembly via the second switching path of the associated switching means and the selection means. The object of the present invention, then, is to show a way of being able to design a communications device according to the preamble of Patent Claim 1 so 15 that the use of separate selection means can be dispensed with in the case of "1:N" line assembly redundancy. In the case of a communications device according to the preamble of Patent Claim 1, this 20 object is achieved by means of the circuitry features specified in this patent claim. The invention affords the advantage of utilizing structures which are necessary for the realization of "1+1" line assembly redundancy for "1:N" 25 line assembly redundancy as well. An arrangement of line assemblies in pairs is provided for the "1+1" line assembly redundancy, the transmission lines associated with such a pair of line assemblies each being routed to both line assemblies. In this case, the structure of 30 the "1+1" line assembly redundancy can be utilized in such a way that the transmission lines of a line assembly, as in the case of "1+1" line assembly redundancy, are each routed to the line assembly assigned pairwise. As a result, one line assembly is 35 able, in the event of failure of the other line assembly, to connect the transmission lines thereof to a backup switching bus.

GR 97 P 2428 - 4 Advantageous refinements of the invention emerge from the subclaims. The present invention is explained in more detail below by way of example with reference to 5 drawings. Figure 1 shows, in the form of an extract, the schematic structure of a communications device according to the present invention, using the example of a normal mode, and 10 Figure 2 shows the communications device illustrated in Figure 1 for the case of a backup mode. A communications device according to the present invention will now be explained in more detail below with reference to Figures 1 and 2. In this case, 15 Fig. 1 illustrates the normal mode and Fig. 2, on the other hand, the backup mode of the communications device. In this case, only those elements of the communications device which are necessary for an understanding of the present invention are illustrated 20 in these figures. The communications device KE illustrated in Fig. 1 may be an ATM communications device which operates according to the asynchronous transfer mode and enables transmission of message signals in the form 25 of message cells in the course of virtual circuits. Since an ATM transmission principle of this type is sufficiently known, it will not be discussed in more detail below. As an example, the communications device KE has 30 a central switching network ASN which is assigned, for control thereof, a central control device MPU. In the case of this communications device, what may be involved is a so-called "cross connect" for setting up permanent virtual circuits or switching equipment \'

LLN

GR 97 P 2428 - 5 ("switching node") for setting up switched virtual circuits. In both cases, the connections are set up from the central control device MPU. However, since this setting up of connections is not the subject 5 matter of the present invention, it is not discussed in further detail below. A plurality of line assemblies are connected to the central switching network ASN via for example bidirectional electrical terminals. A number N+l of 10 these line assemblies are indicated which, as will be explained in more detail below, form a "l:N" redundancy group and are designated by BG 1 to BG N+1. In this case, the line assemblies are each provided for the connection of at least one peripheral transmission 15 line. The transmission lines are in this case designated by LTG 1 to LTG N in accordance with their assignment to the line assemblies. The remaining line assembly BG N+l, on the other hand, serves as backup line assembly. 20 Each two of the abovementioned line assemblies BG 1 to BG N form partner line assemblies of an assembly pair. Two of these assembly pairs are designated by BGP 1 and BGP M in Figures 1 and 2. The assembly pair BGP 1 in this case comprises the partner 25 line assemblies BG 1 and BG 2, while the assembly pair BGP M is formed from the partner line assemblies BG N-1 and BG N. The transmission lines associated with the two partner line assemblies of an assembly pair, these are the transmission lines LTG 1 and LTG 2 in the case 30 of the assembly pair BGP 1, for example, are routed to the two partner line assemblies after the manner of "1+1" line assembly redundancy. The line assemblies BG 1 to BG N each have, at the interface to the associated transmission line 35 (LTG 1 to LTG N), a line-specific switch which is designated by Sl and is designed as a relay in the exemplary embodiment.

GR 97 P 2428 - 6 The respective line assembly is connected to the associated transmission line via the closed switching path of the respective switch, which is indicated for the individual line assemblies in Fig. 1. 5 In addition, the line assemblies BG 1 to BG N each have, at the interface to the transmission line of the associated partner line assembly, a switching contact of a line-specific switch which is designated by S2 and is again designed as a relay, for example. A 10 backup switching bus EBUS is connected to the remaining switching contact of the respective switch S2; the backup line assembly BG N+1 already mentioned is also connected, by one side, to the said backup switching bus EBUS. The other side of this backup line assembly 15 is connected to the central switching network ASN via a switch Sl which corresponds to the abovementioned switches S1. Furthermore, the two partner line assemblies belonging to an assembly pair are each connected via a 20 bidirectional control line SL, the function of which will be discussed in more detail below. The switches Sl and S2 are initially controlled, for example in the course of a connection set-up, from the central control device MPU. For this 25 purpose, the requisite control signals are transmitted in the form of message cells in the course of permanently set-up virtual circuits towards the individual line assemblies BG 1 to BG N, an internal transport protocol (ITP) being used for this. 30 Moreover, in the present exemplary embodiment, the line assemblies BGi to BG N+1 specified in Figures 1 and 2 each have an arrangement for signal conversion, which is designated by S4 using the example of the line assembly BGl, on the connection path between the line 35 assembly and the switching network ASN.

GR 97 P 2428 - 7 As already specified above, Fig. 1 illustrates the case where the communications device KE is operating in the normal mode, that is to say where in particular the line assemblies BG 1 to BG N are 5 functioning free from errors. In this normal mode, closure of the line-specific switches Sl means that the transmission lines LTG 1 to LTG N are connected via the line assemblies BG 1 to BG N to the switching network ASN in order to perform normal transmission of message 10 signals (message cells) within the communications device KE. As already mentioned previously, the partner line assemblies of the assembly pairs (BGP1 to BGP M) are in each case connected directly via a bidirectional 15 control line SL. In the event of an error occurring in one of the partner line assemblies, on the one hand the switch Sl present in this assembly is opened and hence the connection to the switching network ASN is interrupted. On the other hand, a control signal is 20 transmitted via the relevant control line SL towards the partner line assembly. In response to the reception of such a control signal, the switch S2 of this partner line assembly is then closed and, as a result, the backup mode is activated for the defective partner line 25 assembly. Such a backup mode is explained below with reference to Figure 2, where the partner line assembly BG 1 shall represent a defective line assembly, as an example. 30 According to Figure 2, the switch Si assigned to the partner line assembly BG 1 is controlled such that its switching path is open and, consequently, the connection path between the transmission line LTG 1 and the switching network ASN is interrupted. Furthermore, 35 the switch S 2 within the partner line assembly BG 2 is controlled in such a way that a closed connection path now exists from the transmission line LTG 1 via the backup switching bus EBUS towards the backup line Aq GR 97 P 2428 - 8 assembly BG N+1, the associated switch Sl of which is in the closed state in this backup mode. As a result, message signals (message cells) can then be transmitted via this backup line assembly BG N+l as a backup for 5 the defective partner line assembly BG 1 assumed as an example. Such a backup mechanism also applies to any other of the partner line assemblies BG 2 to BG N. A modification of the communications device KE may consist in forming a plurality of independent 10 redundancy groups from the line assemblies in the manner described above when there are a multiplicity of line assemblies present, which redundancy groups are each provided with a specific number of active line assemblies and a backup line assembly assigned thereto. 15 In the text above it was assumed only as an example that each of the line assemblies is assigned only one transmission line. The line assemblies and the backup switching bus mentioned may alternatively be designed such that a plurality of transmission lines 20 are connected to the individual line assemblies and the backup switching bus, for the transmission of message signals, has a bus width corresponding to this plurality of transmission lines. Finally, it may also be pointed out that 25 although the present invention was explained using the example of an ATM communications device in the text above, the invention is not restricted to that. Rather, this invention can also be applied in communications devices that differ from the ATM principle, if a "1:N" 30 redundancy structure for the line assemblies is to be provided in the said devices. 71)

Claims

1. Communications device (KE) for the transmission of message signals via transmission lines (LTG 1, 5 ......, LTG N) with a central switching network (ASN) and line assemblies (BG 1, ... BG N), which are associated with the said switching network, are each connected to at least one of the transmission lines and form at least one "l:N" redundancy group comprising a 10 number N of active line assemblies and an additional backup line assembly (IB N+1), each of the N active line assemblies within such an "l+N" redundancy group being able to be substituted by the associated backup line assembly, 15 characterized in that two neighbouring line assemblies (BG 1 and BG 2; ... ;BG N and BG N+1) from the N line assemblies (BG 1 to BG N) of the respective "l:N" redundancy group in each case form partner line assemblies of an 20 assembly pair (BGP 1, ... , BGP M), in that the transmission lines (for example LTG 1 and LTG 2) which are individually assigned to the partner line assemblies of an assembly pair are in each case routed to the other partner line assembly as well, 25 after the manner of "1+1" line assembly redundancy, in that the partner line assemblies of an assembly pair are each designed in such a way that the transmission line (LTG 1) which is individually assigned to the respective partner line assembly (for example BG 1) can 30 be connected via first switching means (Si) to the switching network (ASN), and the transmission line (LTG 2) which is individually assigned to the other partner line assembly (BG 2) can, on the other hand, be connected via second switching means (S2) to a backup 35 switching bus, and in that the first and second switching means (Si and S2) of the partner line assemblies (for example BGP1) of an assembly pair (for example BGP1) can be controlled in such a way that, in the normal mode, the GR 97 P 2,428 1 * - 9a individually assigned transmission lines are connected via the first switching means (Sl) to the switching network (ASN), GR 97 P 2428 . - - 10 whereas in the backup mode of one of the partner line assemblies (for example BG 1), the individually assigned transmission line (LTG 1) thereof can be connected to the switching network (ASN) via the second 5 switching means (S2) of the other partner line assembly, the backup switching bus (EBUS) and the backup line assembly (BG N+1).

2. Communications device according to Claim 1, characterized 10 in that the said device is designed as an ATM communications device which operates according to an asynchronous transfer mode and enables the transmission of message signals in the course of virtual circuits, and in that the switching network (ASN) is assigned a 15 central control device (MPU) which controls the setting up and clearing down of virtual circuits.

3. Communications device according to Claim 2, characterized in that the central control device (MPU) is furthermore 20 designed in such a way that the first andit-second switching means (S1, S2) of the individual partner line assemblies can initially be set to the normal mode from the said central control device in the course of fixedly set virtual circuits. 25

4. Communications device according to one of Claims 1 to 3, characterized in that the partner line assemblies (for example BG1 and BG2) of an assembly pair (for example BGP1) are 30 connected to one another via a control line (SL) for the outputting of an error message, and the partner line assemblies are designed in such a way 'that, in response to such an error message, on the receiving partner line assembly the closing of the second 35 switching means (S2) and hence the activation of the backup mode for the defective partner line assembly are effected. GR 97 P 2428 . - 11

5. Communications device according to one of Claims 1 to 4, characterized in that the first and second switching means (Sl, S2) 5 of the individual partner line assemblies are designed as relays.