DE4031241C2 - - Google Patents

Description

The invention relates to a digital transmission system with at least one operating line for the transmission of Digital signals and with at least one replacement route, one lying above a predefinable error threshold Bit error rate one on an operational link transmitted digital signal or with manual switching an operating route a multi-stage switchover to Replacement route takes place.

The replacement route is used to transmit the digital signals especially in the event of failure and / or malfunction of the Operating route. The transmission lines (operating lines) of transmission systems usually contain each transmitting and receiving line end points and intermediate regenerators. The take over Line end points the adaptation of the digital signals to the Properties of the transmission medium, e.g. B. electrical optical conversion while the regenerators are renewing the digital signals serve to make a required Observe the signal-to-noise ratio of the digital signals. A essential quality feature of digital transmission systems is next to that due to the bit error rate of transmitting digital signal certain transmission quality the availability of the transmission links. To increase this availability can be an operational route or several replacement routes can be assigned. This takes over then in the event of a breakdown or malfunction of the operating line the transmission of digital signals. The Switching can depend on the transmission quality  the operating route also take place automatically. Hereby the availability of the transmission links increases and thus the downtime of digital transmission systems decreased. Since the replacement route with the line terminals and the intermediate regenerators in Malfunction of an operating line after successful switchover on the replacement route only again on the "new" digital signal must synchronize, it can after the switching process to an increased bit error rate during transmission come. Should already be at a relatively low Bit error rate of one transmitted on the operating link Digital signal an equivalent circuit can take place, so it even briefly increases the bit error rate of the digital signal now transmitted on the replacement route come.

From "Textbook of Telecommunications Technology, Volume 2, Berlin, Fachverlag Schiele & Schön GmbH, 1986, pages 1146 to 1150 is a replacement switching device for a directional radio link known with a multi-stage switching an operating route works on the replacement route.

The invention has for its object a digital Specify transmission system of the type mentioned at the outset, which is a reduced increase in the bit error rate when switching has an operating route on the replacement route.

This task is done with a digital transmission system of the type mentioned solved in that as a multi-stage Switching in a first step the first End of the operating line on the transmission side to the replacement line,  in a second step, the second end of the operating route on the sending and receiving side on the replacement route is switched and in a third step the first end the operating route also on the receiving side to the replacement route is switched.

For example, it occurs on an operational route of a faulty regenerator at a bit error rate of Digital signal that is above the predefinable error threshold , there is no abrupt switchover of the on the disturbed operating path transmitted digital signal the replacement route. Switching takes place in several Stages, so that the replacement route on the digital signal can first synchronize before the digital signal is released via the replacement route. Hereby the increase that would otherwise occur during the equivalent switching the bit error rate largely avoided. Even with manual performed equivalent circuits is therefore a "gentle" Switching guaranteed. Only in the event of a total failure in order to react as quickly as possible, switched instantaneously. As a multi-stage switchover in a first step the first end of the disturbed Operating route on the transmission side to the replacement route switched, in a second step the second end of the disrupted operating path on the transmission and reception side switched to the replacement route and in a third Step becomes the first end of the disrupted operating line also switched to the alternative route at the receiving end. In the first step, this already has an effect on the replacement route switched digital signal a synchronization the replacement route without the replacement route already is switched at the receiving end.  

In a further embodiment is for control the multi-stage switchover between the first and the second end of the disrupted operating route and / or the Replacement route at least one control channel provided. This checks the individual stages of the switchover by means of tax data exchange for correctness. This is done a full multi-stage switchover each only after reconfirming the previous step the control channel.

In a further embodiment, also after single-stage or multi-stage switchover disturbed operating line on the replacement line the digital signals sent to the disrupted operating line. In order to enables troubleshooting under operating conditions. It will also switch back after removal  the disruption of the disturbed operating route possible Lich without the previously disturbed operating route again must be synchronized to the data signal.

Another embodiment is at the beginning and at the end of each operating route and the replacement route each because a channel unit can be switched on, the channel being on units at the beginning of the operating lines and the replacement stretch a first control unit and the channel units at the end of the operating lines and the replacement route is assigned a second control unit, and where in the channel unit from the first and second control Have unit controllable switching means with which an operating route over one over the channel units connecting cable to the replacement line is switchable. The assigned to the channel units common connecting line enables the digital Transmission system by simply "attaching" from wide ren channel units to the common connecting line to expand easily in operation or disarm or wait. This also ver Availability of the operating routes increased.

In an advantageous embodiment, the Ver connection line between the channel units as symmetri cal line trained. Due to the symmetrical training The connection line will influence the transmitting digital signals minimized.

In another embodiment, there is no interference a digital track of an operating line on the replacement channel low priority signal. Since the replacement ka can only be used in the event of a fault during trouble-free operation of the digital transmission system the replacement route for the transmission of data  be used with low priority.

In another embodiment, the operating stretch priorities assignable. These are priorities according to the requirements of digital transmission system freely definable. This will make the access right on the replacement route for the unlikely Case regulated that two or more operating routes to have a fault at the same time and are switched over Need to become. This priority assignment will Operating route with the lower priority only then replacement switched after the operating route with the higher priority automatically switched back or ma has been excluded from the equivalent circuit.

In one embodiment, the control unit especially the functions: change of error rates, Change of priorities, switch to a second Control channel, manual switching of an operating route with or without taking into account the priorities, locks of routes, do not save the settings in one volatile memory and output of a log feasible. With the help of this, for example via a Ta stature with assigned microprocessor, enterable radio the digital transmission system is simple In different configurations and operating modes adaptable to conditions.

The invention is described below with reference to the figures illustrated embodiments explained in more detail.

Fig. 1 shows a block diagram of a digital transmission system.

FIGS. 2a to 2d show a further embodiment of a digital transmission system.

Fig. 3 is a block diagram showing a channel unit of an equivalent circuit device.

Fig. 4 shows a block diagram of an equivalent Schaltge device for a digital transmission system.

The digital transmission system shown in FIG. 1 has multiplexing devices MI 1 . . . MIn, MIe in the beginning as well as multiplexing devices MII 1 . . . MIIn, MIIe at the end of a pipeline system with operating routes B 1 . . . Bn and with a replacement route E. The multiplexing devices form MI 1 . . . MIn, MIe at the beginning of the line system, a first transmission location I and the multiplexing devices MII 1 . . . MIIn, MIIe at the end of the piping system a second transmission location II. On the operating route B 1 . . . Bn and the replacement route E are digital signals D 1 . . . Dn, LP transferable. At each end of each line section, that is, at the end of each operational route ke B 1 . . . Bn and at both ends of the substitute route E, line end points L are arranged. Regenerators R are switched on between the line end points L at the ends of the operating lines and the replacement line. Each end of the operating lines B 1 . . . Bn and the replacement line E are each connected to an identically constructed channel unit K. The channel units K at one end of the operating sections B 1 . . . Bn and a respective assigned control unit StI, StII each formed an equivalent switching device EI, EII. The control units StI, StII are connected to one another via a control channel St. In the equivalent switching devices EI, EII, the channel units K are also each assigned a connecting line V that can be connected to the alternative route E.

In trouble-free operation, the n operating channels B 1 . . . Bn that in the multiplexing devices MI 1 . . . MIn, MII 1 . . . MIIn summarized digital signals D 1 . . . Dn transferred. On the replacement channel E, the operating sections B 1 . . . A digital signal LP with a lower priority (low priority) can be transmitted. The operating channels B 1 . . . Bn and the replacement channel E can be realized by coaxial cable connections, by fiber optic cables or, for example, by radio links. The line end points L take on the adaptation of the digital signals D 1 . . . Dn, LP to the properties of the respective operating line, for. B. electrical-optical conversion. The re generators R serve to renew the digital signals D 1 . . . Dn, LP to maintain a required signal-to-noise ratio.

An essential quality feature of digital transmission systems is in addition to the bit error rate of the digital signals to be transmitted D 1 . . . Dn, LP also determine the transmission quality of the transmission paths. For this reason, in the embodiment of a digital transmission system shown in FIG. 1, the n operating paths B 1 . . . Bn assigned to the replacement line E. This takes over the transmission of the digital signal transmitted on the disrupted operating line in the event of failure or a malfunction of an operating line. The transmission system is therefore of the type n + 1. When using a system of the type n + 1, it is assumed that due to the relatively low probability of failure of currently available, in particular conductor-based, transmission systems, the probability of the simultaneous failure of two operating lines is very low. Although only one replacement channel is actually available for n-operation routes, due to the low probability of the simultaneous failure of two operating routes of each operating route, an alternative route seems to be available alone. A priority assignment that can be defined in the equivalent switching devices EI, EII regulates the right of access of the individual operating lines B 1 . . . Bn on the spare channel E in the unlikely event that two or more operating channels would have to be switched ersatzge at the same time. The operating route with the lower priority is only switched after the operating route with the higher priority has been automatically switched back or manually excluded from the equivalent circuit.

The equivalent switching devices EI, EII are modular from those for the operating routes B 1 . . . Bn as well as for the equivalent route E built channel units K on. This ensures that, for example, in the case of channel units K designed as inserts, no change between a channel unit K for an operating route and the replacement route is possible. The bus system implemented by the connecting line V for the equivalent circuit of the digital signals D 1 . . . Dn makes it possible to add additional operating lines or to take already switched channel units out of operation even when the equivalent switching devices EI, EII are in operation. Due to the symmetrical design of the bus system of the connecting line V, minimal influence on the digital signals is achieved.

In order that, on the one hand, equivalent switching operations are carried out as quickly as possible and, on the other hand, faults caused by replacement switching operations are avoided, a distinction is made between two equivalent switching types depending on the equivalent switching criterion: single-stage and multi-stage equivalent circuits. carried out. The multi-stage equivalent circuit (slow equivalent circuit) enables the alternative route E to first synchronize with the digital signal of the disrupted operating route before the data is passed on. The control units StI, StII monitor the triggering or blocking of replacement circuits. In addition, in the control units StI, StII of the equivalent switching devices EI, EII, the criteria for triggering equivalent circuits are also defined. Thus, in the event of a total failure of an operating route, that is, when data transmission of a digital signal D 1 occurs over an operating route. . . Dn, for example, by interrupting a fiber optic connection is not possible, an alerting of the equivalent switching devices EI, EII via the respective line end point L. Via control inputs S, the equivalent switching devices EI, EII can detect this alarm. The affected operating route is then immediately replaced. If the urgent alarm is cleared again, the equivalent circuit is canceled.

The equivalent switching criterion for a multi-stage equivalent circuit is determined by the transmission quality of an operating path determined by the bit error rate of the digital signal to be transmitted. In this case, code errors are determined by evaluating a so-called line code of the digital signal transmitted over an operating path and are used to identify a faulty regenerator or a faulty operating path. These so-called basic line telegrams are evaluated by the respective equivalent switching device. The bit error rate of the respective operating path can be determined from this. If the bit error rate of an operating route rises above a predefinable error threshold and thus the transmission quality of the operating route drops, a multi-stage switchover to the replacement route takes place. This largely avoids the increase in the bit error rate that otherwise occurs during equivalent switching. In this way, an almost undisturbed transmission of the respective digital signal can be guaranteed even with manual equivalent switching. In the embodiment shown in FIG. 1, for the sake of clarity, only one switch was shown in the channel units for simplicity.

FIGS. 2a to 2d show the different steps of a multi-stage switching of a working link B 1 on ei ne standby link E. In FIGS. 2a to 2d is Darge represents that over the operating range B 1 is a Digitalsi gnal D 1 and via the protection link a Digital signal LP is transmitted with low priority. The operating route B 1 and the replacement route E each have a line terminal LI 1 , LII 1 , L 1 E, LIIE and intermediate regenerators R 1 , RE at each end. The replacement switching devices EI, EII are connected to one another via a control channel S. In Fig. 2a is indicated with the help of a drawn in the operating section B 1 Hochspannungspfei les that there is a fault in the operating section B 1 . If this disturbance lies above the bit error rate lying through the predeterminable error threshold, the equivalent switching devices EI, EII initiate a multi-stage switchover. For this purpose, as shown in FIG. 2b, in a first step in the set-up switching device E 1, the digital signal D 1 is switched over to the substitute line E. This enables the substitute line E to be synchronized with the digital signal D 1 . The equivalent switching command is given to the equivalent switching device EII via the control channel St. FIG. 2c shows how in the second step the digital signals D 1 of the operating path B 1 in the equivalent switching device EII are switched over to the equivalent route E on both the transmitting and receiving sides. This changeover is confirmed via the control channel St to the first replacement switching device EI. This confirmation is received and evaluated by the first equivalent switching device EI via the control channel St. Thereupon, who at the first equivalent switching device EI the digital signal D 1 of the operating route B 1 also switched on the receiving side to the alternative route E. This largely avoids the increase in the bit error rate that occurs during single-stage switching. In FIGS. 2a-2d it is shown that also during the entire order switching process or even after switching of the faulty operation range B 1 to the substitute link E the digital signals D 1 to the malfunctioning working link B 1 ge sends. This enables troubleshooting under operating conditions and thus makes troubleshooting easier. In addition, it is possible to switch back after eliminating the fault in the disturbed operating path without the previously disturbed operating path, such as that, having to be synchronized with the digital signal D 1 .

The block diagram shown in Fig. 3 of a channel unit K shows a possible structure for an equivalent switching device for a multi-stage equivalent circuit. The channel unit is constructed symmetrically in both transmission directions. In this way, the digital signals D 11 arrive, D 12 are first fed to an equalizer En, the output of which is used for evaluation for signal failure detection D. The signal at the output of the signal failure detection D is supplied as a control signal Lo to the external control unit and to a logic circuit L of the channel unit K. If a signal failure is detected, an alarm signal (AIS = Alarm Indication Signal) is generated with the help of an oscillator O and fed in via switches 3 , 4 in the outgoing direction. The signal at the output of the equalizer En is passed via the switch 3 or via switches 2 , 4 to a decision-maker flip-flop F and a module T for clock recovery, the output of the flip-flop F via a transmitter Se Sends digital signals D 11 off, D 12 off again. The connecting line to the connection of further channel units takes place via the inputs V 1 from, V 1 to, V 2 to, V 2 from. In this case, in the trouble-free state via the switches 1 , 2, the connecting lines are switched so that the digital signals passed through the channel unit K are not routed to the connecting lines V 1 from, V 1 to, V 2 to, V 2 from. Only in the event of a fault, in particular can a multi-stage switchover of the digital signals to the connecting lines and thus to the replacement link take place. In a first step, the incoming Digi talsignal D 11 is switched to the transmitter side on the replacement link, ie on the connecting line V 1 , via the switch 1 . In a second step, the standby link is in cooperation with the Kanalein standardize the second end of the disturbed Be operating trackside send and receive sides to the substitute link is switched, that is, via the switch 2 is in cooperation with the switches of the channel unit of He set range, the signal V 2 switched on as signal D 12 . In a third step, the first end of the disrupted operating route is finally switched to the alternative route on the receiving side in the channel unit of the alternative route.

Fig. 4 shows the block diagram of an equivalent switching device E. This contains n + 1 channel units K for n operating routes B 1 . . . Bn and a replacement link E a control unit StI, a power supply device U and a signaling device SIG. The channel units K are connected to a replacement link E and n operating links B 1 . . . Bn connectable. The power supply device U supplies the channel units K, the signaling device SIG and the control unit StI. The channel units K are connected to each other via a connecting line V. For this purpose, a connecting line consisting of a forward and return line runs as a connecting line V from the channel unit K of the replacement line E via the channel units of the n-1 operating lines to the channel unit K of the nth operating line Bn. In addition, three control lines Lo, In, Sw are connected to the channel units and to the control unit StI. The control line Lo is used for signal loss monitoring (loss of input), the control line In is used to identify a channel unit K (insertion information). The control line Sw transmits the changeover signal (switch) from the control unit StI to the respective channel unit K. The control lines Lo for signal failure monitoring and the control line Sw are also connected to the signaling device SIG. The control device StI can be connected via an input S for a control line to a second control unit (not shown in FIG. 2) arranged at the other end of a transmission system. Basic line telegrams, for example from line end devices of the operating lines, are fed in via the connection G of the control unit StI.

Claims (10)

1. Digital transmission system with at least one operating link (B 1 ... Bn) for the transmission of digital signals (D 1 ... Dn) and with at least one replacement link (E), with one on an operating link if the bit error rate is above a predefinable error threshold (B 1 ... Bn) transmitted digital signal (D 1 ... Dn) or in the case of manual switching of an operating section (B 1 ... Bn), a multi-stage switchover to the replacement link (E) takes place, characterized in that as a multi-stage switchover in a first step, the first end (EI) of the operating line (B 1 ... Bn) on the transmission side to the replacement line (E), in a second step the second end (EII) of the operating line (B 1 ... Bn) send- and is switched on the receiving side to the alternative route (E) and in a third step the first end (EI) of the operating route (B 1 ... Bn) is also switched on the receiving side to the alternative route (E). 2. Transmission system according to claim 1, characterized in that a channel unit (K) is provided at the beginning and at the end of each operating section (B 1 ... Bn) and the replacement section (E), each channel unit (K) for multi-stage switching provided switching means ( 1, 2, 3, 4 ). 3. Transmission system according to one of claims 1 or 2, characterized in that for controlling the multi-stage switchover between the first (EI) and second (EII) end of the operating section (B 1 ... Bn) and / or the replacement section (E) at least one control channel (S) is provided. 4. Transmission system according to one of claims 1 to 3, characterized in that even after a single-stage or multi-stage switchover of an operating route (B 1 ... Bn) to the replacement route (E), the digital signals (D 1 ... Dn) to the Operating route (B 1 ... Bn) are sent. 5. Transmission system according to one of claims 1 to 4, characterized in that the channel units at the beginning of the operating lines (B 1 ... Bn) and the replacement line (E) each have a first control unit (StI) and the channel units (K) at the end a second control unit (StII) is assigned to the operating lines (B 1 ... Bn) and the replacement line (E), the channel unit (K) being able to be controlled by the first and second control units (StI, StII) switching means ( 1, 2, 3 , 4 ) with which an operating route (B 1 ... Bn) can be switched over to the replacement route (E) via a connecting line (V) running over the channel units (K). 6. Transmission system according to one of claims 1 to 5, characterized, that the connecting line (V) as a symmetrical line is trained. 7. Transmission system according to one of claims 1 to 6, characterized in that a digital signal with low priority is transmitted on the replacement link (E) without disturbing an operating link (B 1 ... Bn). 8. Transmission system according to one of claims 1 to 7, characterized in that priorities can be assigned to the operating lines (B 1 ... Bn). 9. Transmission system according to one of claims 1 to 8, characterized, that by the control unit (StI, StII) in particular the Features: change error rates, change priorities a route, switching to a second control channel, manual switching of an operating route with or regardless of priorities, blocking of Stretch, save the settings in a non-volatile Storage and output of a log can be executed are. 10. Channel unit (K) for a digital transmission system according to one of claims 1 to 9.