DE2843088A1 - Time-multiplexed communications system - has subscriber stations connected via interfaces to two ring lines and has central exchange - Google Patents

Abstract

The time-multiplexed communications system has a ring network, head station, subscriber stations and parallel ring lines with opposite directions of transmission. The same TDMA frame is used for all messages sent and received. The stations are connected to both ring lines via interfaces. The head station and the subscriber-station interfaces contain devices to allow the messages sent via the system to be switched centrally. Each interface has a frequency-stable phase locked loop and two time frame generators. Several subscriber stations can be connected to one interface.

Description

System for a time division multiplex messaging system with a

Line network in ring structure (addition to P 28 20 428.6) The main patent (Application P 28 20 428.6) relates to an installation for a time division multiplex messaging system with a line network in a ring structure, a headend, connection points with subscriber stations and parallel ring lines with opposite transmission devices and is intended in particular for systems with decentralized switching.

In the case of double ring networks that have become known to date (see e.g.

DE-AS 24 09 471, also 1978 International Zurich Seminar on Digital Communications F5 "A Proposal for the Introduction of Digital Techniques into Local Distribution "; 1974 International Zurich Seminar D2" Reliability - a Key Element in loop systems ") should be parallel to the loop with the connected Subscriber stations a second ring line are laid, which is provided as a reserve is. Overhead control devices (switching units) are located at several points on the ring, in which the interconnected ends of the other ring main in the event of damage separated and connected to the ends of the other ring line. Kick a Unpredictable, sudden malfunction, e.g. a cable break in the main line, after the error has been identified and its location until it has been rectified - as well as in foreseeable cases - the one between two overhead control systems Section of the ring network to be switched off. The remaining parts of the network remain while the repair work is functional by being switched off Part of the main ring, a diversion via the overhead control systems adjacent to the damage site and the reserve line is switched.

Because cable breaks occur in most cases as a result of external influences (e.g. dredging), not only the main ring line, but also the reserve ring line be destroyed at the same point in the network. Therefore, the redirection is made via the Reserve line between the relevant overhead control systems does not have the short one Route in the same direction of transmission as on the main line, but over the long route with the opposite direction of transmission.

Without going into further details, it can be seen from this that in the known prior art in the headend (ring control unit) depending on Length of the diversion for appropriate time compensation between the frame starts must be taken care of on the main line and on the secondary line and the number of in one In the event of damage, the less overhead control systems, the greater the number of participants who are switched off available. Of course there are ways to detect a bug in the pipeline network, the location and disconnection of the affected section from the Make headend from remote control. In any case, such a network is included unforeseen occurrence of an error in the main line for all connected Subscriber off until the diversion is activated. The between the the Participants located in the vicinity of the overhead control system at the point of damage remain in addition, for the duration of the damage, i.e. until the repair is completed and the cancellation of the diversion circuit, out of order.

Although with such a structure a double ring network with overhead control devices at opposite directions of transmission even with a cable If both ring lines break at the same point, most of the unaffected power supply units remain functional, it is considered unsatisfactory for the participants in the known ring networks the mean time between two errors (MTBF) is very high strongly of an effective technique for fault detection and location as well depends on the number of overhead control systems. Compared to other network structures, in which e.g. the participants in a star configuration to an exchange or to a Headend and from there connected to an exchange using multiplex technology are, however, result in known ring structures and less effective ones Techniques for fault detection and location and a small number of overhead control systems very quickly lower and even worse for the mean time between two errors Values than those of the other structures compared (see 1978 International Zurich Seminar, F5. 3, Fig. 4 and associated explanations, right column on the same page). From the perspective of a participant, it must therefore be required that recognition, switchover and repair times go to zero. In practice this means that a cable break should be imperceptible to the participant.

According to the main patent (application P 28 20 428.6) it is proposed that both ring lines as independent, but with a uniform time division multiplex frame Transmission paths operated for all messages sent and received to switch and to connect the connection points with both ring lines. Transfer devices, as they are trained in the known with a main and a reserve line Double ring networks are required, are omitted in the embodiments according to the main patent (Registration P 28 20 428.6) or are remotely comparable with the connection of the subscriber stations to both ring lines, in which there is no between a main and a reserve line A distinction can be made, since both are equal and independent of each other anytime the too the transmitted messages. This double Keeping the messages in a double ring network can certainly not be compared to a disadvantage such double ring networks, in which only in the event of damage, parts of the second5 of the reserve ring, to be switched on and that normally completely remains unused. (Incidentally, an unused reserve line must be used from time to time be checked for functionality). These double-transmitted messages are of course only required once for reception. But that means for The reception are normally two ways of receiving and in the event of damage (Cable break) still one of the two available because the double transmitted Messages arrive from opposite directions to each subscriber station.

As long as only one place according to the main patent (application P 28 20 428.6) formed double ring network a malfunction, e.g. a cable break - also both ring lines - occurs, the minimum requirements still remain for undisturbed operation and damage so narrowly limited to one point that the damage effect for all subscriber stations connected to the ring network is irrelevant for receiving and sending messages. Of special The advantage is the fact that the main patent (application P 28 20 428.6) In accordance with the solution, in the event of damage, there are no frame times for transmission routes changed cable length must be compensated, since both ring lines not only operated independently in the event of damage and in the event of a cable break each independent ring is opened. So maturities are in this context meaningless. In the event of interruptions - according to the probability calculation - a maximum of half of the currently existing connections are received by one the alternative reception options can be switched to the other. There in the subscriber stations but both transmission paths can be continuously observed the decision for one of the two alternatives to receive the messages at any time be revised. Once an error occurs, it is corrected before the next occurs, which should be true in practice, goes to one in this way for all structured system connected participants the mean time between two mistakes towards infinity.

The invention aims at a further development of the subject matter of Main patent (registration P 28 20 428.6) and is characterized by facilities in the headend and in the subscriber stations for the central switching of the messages transmitted on the network. This is done by each participant for both sending out as well as for receiving the messages fixed time slots of the time division multiplex frame for signaling and exchanging narrowband messages with the control center assigned. The number of participants is thus determined by the number of time slots within of a time division multiplexed frame. The broadband channels, on the other hand, are optional assign, so that a similarly good channel utilization of the transmission medium as can result from decentralized switching.

Although in the event of an unexpected, sudden malfunction, e.g. with a cable break, the function in the network in a system with a structure according to the invention is not yet impaired, the detection and localization of the fault is also here important in order to ensure the operational safety that normally exists by eliminating it immediately restore. The detection of an error is based on the concept at the invention on which the main patent (application P 28 20 428.6) is based, by itself, since then the one behind the fault location in the direction of transmission Connection point no longer receives messages from the relevant line. That is recognized by the affected connection point and also in the head end.

Preferred embodiments of the invention can as well as in the main patent (Registration P 28 20 428.6) for problem-free fault location with facilities in the Connection points or in the headend for sending or receiving alarm signals be equipped in the event of an interruption in a transmission path. By a - expedient Priority alarm signal, from which the connection point can be recognized, can be set in the headend immediately recognizes whether the error is one of the two transmission lines or affects both. If only one line is broken, the headend receives alarm signals from the connection point, which is behind the broken line in the direction of transmission where the error lies.

If both lines are broken, the ones next to the break point get Connect the alarm signals in the same way on the broken lines with the opposite transmission directions to the headend. That connection point those on the broken line have neither messages nor synchronization information receives is immediately adjacent to the point of failure and this fact can be independent related to their operating status through corresponding additional information notify the headend with the alarm signal. So that the error is also within In the shortest possible time, it can always be precisely located in the area between two connection points. To this end, it is advantageous to equip all connection points with two time frame generators each and to equip a frequency-stable phase-locked loop. These facilities serve for transmission security in the event of a cable break or such a fault in which receive no information about the time frame structure from the transmission medium will.

As with the known systems with double ring networks, there is also Embodiments of the invention the possibility of several at one connection point Connect participants (concentrator). Here is the distance between the individual participants of crucial importance. With several subscriber lines Such a measure makes sense in e.g. a building. In sparsely populated areas, Especially in rural areas, participants will be given their own connection points assign.

For the operation of communication systems, various Reasons requires that the power supply of the subscriber equipment from the transmission network takes place here. In optoelectronic systems with fiber optic cables for transmission the Messages can power supply over such lines not done. Accordingly, as with the main patent (application P 28 20 428.6) in embodiments of the invention, a separate pair of lines is provided for this purpose, that - e.g. also for the energy supply of the repeaters - in parallel with the fiber optic cables is relocated. For the energy supply of the subscriber stations remains in this way of course, an interruption of the supply cable at one point without Influence. However, to a second or any other simultaneous and similar To prevent errors, the subscriber stations can be equipped with circuits, those parts of the subscriber station in the event of failure of the network's own power supply line supply from a stationary power supply unit that is connected to the subscriber's supply network connected. If e.g.

the voltage in the power supply line below a predetermined one Threshold value, is automatically switched to the other location-based energy supply. Such an energy supply, which is independent of the transmission network, is everywhere anyway required where the participants have other devices besides a telephone, e.g.

Data transmission devices, video telephones, etc. are operated.

Apart from the fact that in the embodiments of the invention in a sudden, unexpected malfunction, e.g. in the event of a line break due to mechanical Action or failure of circuit parts in a connection point, which affect the transmission of the messages sent and received If there could be no interruptions even in the short term, this is all the more true for planned repair and expansion work, e.g. when inserting new connection points for which it - in contrast to the well-known double ring networks - It is not necessary to temporarily switch the ring sections off and on again. Faults of this kind are of course to be rectified immediately, if possible several places are not affected at the same time, and do not represent a malfunction represent.

Another major advantage of the invention is that at their embodiments in particular the imponderables of damage that lead to malfunctions in hard-to-reach places, e.g. cables laid in the ground are low. Other sensitive parts, such as the connection points, are easily accessible and easily manageable. Disturbances that occur there are accordingly easy to fix. Since inventively structured systems even in the case of a Disturbances of the type mentioned do not fail, do not need any planning measures to be hit (see DT-AS 24 09 471, Col. 10, Z.7 off.) that of an acceleration serve to identify and locate a fault and isolate it, by e.g. endangered components or those where there is an opportunity to intervene must exist for such cases, be centralized at one point in the network. The one advantage of ring networks, namely their short average cable length per participant, would not only be abandoned by such measures, but in a considerable, the disadvantage that is detrimental to the general assessment of ring networks are reversed, if all these components, which are centralized in one place, have their own ring section to provide a wide spatial expansion, i.e. the pipeline network to several to deform large loops.

Embodiments of the invention are shown schematically in the drawing shown. They show: FIG. 1: a double ring network with a head and a determination point and connection point for a subscriber station or concentrator, FIG. 2: a block diagram with the circuit parts of a subscriber station used for transmission security, Fig. 3: an illustration of the clock supply with an interruption of both rings, Fig. 4: an illustration of the message flow when both rings are interrupted, Fig. 5: an illustration of the message flow in the event of failure of a ring, Fig. 6: a representation of the message flow in the event of multiple interruptions in both rings, 7: a block diagram for the energy supply to the subscriber stations.

The line-based communication network shown in FIG. 1 exists from two parallel-laid ring lines Ri and Ra with antidirectional transmission direction. Both ring lines begin and end in a headend in which, on the one hand, is controlled from a highly stable clock generator, the time frame for a time division multiplex transmission generated and fed into the rings Ri and Ra and on the other hand the switching function is carried out. The subscriber stations are located at the connection points of the rings, either as concentrators for several connected participants or for individual participants are provided. There messages are fed into the two rings Ri and Ra or taken from these (see the enlarged, highlighted principle illustration of Coupling point). These messages are in the form of individual time slots in the same Way in both rings Ri and Ra led.

The block diagram shown in Fig. 2 shows the circuit parts which are used for transmission security as well as for error detection and location. Every Connection point is provided with a time frame generator per ring. Both time frame generators are supplied with a clock by a phase locked loop; the necessary The reference is derived from the edge changes in the message stream of both rings. A clock indicator per ring line and connection point allows one to be recognized Cable break. Such a disorder triggers in the associated Timeframe Generator an alarm, which is picked up especially in the headend.

The time division multiplex transmission system with central switching and a ring network for the connected subscriber stations must have at least two places have, at which the sent messages from the message stream again can be removed. It has been found appropriate to use the received messages at the destination or destination, namely at the relevant connection point, from the Remove message stream. With the specified transmission direction on the Lines and the double transmission of the messages sent on the two anti parallel transmission paths are therefore used for a connection between two Participants need two time slots on each line. In the detail display In Fig. 1 it can be seen that according to the principle of a relay station for one connected participants set time slots from the receiving direction the same time slots occupied by him with his messages to be sent are exchanged will. The same functional scheme is also available at the exchange.

Establishing and clearing connections One participant occupies the establishment of the connection at the same time via the connection point assigned to it its channels (time slots) in the rings Ra and Ri by writing identical signaling information.

The exchange in the head-end station monitors both lines Alternating in time frames and searches for signaling information. You pursued after the first detection of a signaling only the call on the relevant one Ring line, generates a second signal after a processing time (e.g. Audible tones) and sets them to the assigned time slots of the target participant both rings. The calling subscriber follows a timeframe alternating both rings - Ri and Ra - and searches its return channel for acknowledgment information from the exchange. Acknowledgment information is sent to one of the ring lines recognized, the calling subscriber station only observes the one assigned to it Channel on this line. The connection is thus established in the signaling phase came. The transition to data transmission occurs when the called subscriber due to the signaling of the exchange, the data transmission (lift the handset at the part fon) begins. The control of the exchange recognizes the beginning the data transmission and switches off their signaling as well as via the Koppe7feld the subscriber-assigned channels for data exchange together.

The calling subscriber in turn recognizes the beginning of the data transmission by suspending the acknowledgment signaling from the exchange.

The connection is cleared down by terminating the data transfer (Hang up the handset) of a participant. The data will be replaced by end information. The end information is acknowledged by the other participant. If both participants send out the end criterion, the switching triggers the channel switching in the switching matrix. After a time of sending determined by a time criterion, the sending of the End information replaced by sending a free time slot and finally all set. The channels are now free.

Interferences Figs. 3 to 6 show that the presented with the invention Double ring communication network also for systems with central switching against disturbances is largely insensitive, as this also occurs during the establishment and termination of the connection as well as can be neutralized in the conversation phase.

a) Missing call or call acknowledgment Remains correct after initially recognized call or correctly recognized call acknowledgment, the signaling off, i.e. it if an empty time slot is received, the exchange resp.

the participants concerned use the alternative ring with the assigned Time slots. If no signaling is recognized there either (time slot is empty), then so the connection is released: The sending subscriber or the exchange replaces the call transmission due to missing call acknowledgments for a limited time by sending out end information and free time slots and then provides sending quite a.

The receiving subscriber or the exchange replaces the Call acknowledgment signaling by sending out end information and free time slots due to a missing call and then completely stops sending.

b) Ring system with a cable break (both cables are connected to the same Position interrupted).

Since the central clock generator in the headend is a highly stable one When the time frame is sent in both rings, the synchronism can occur on both sides of the The break point can still be derived from one ring each (see Fig. 3).

From the sending party A in both rings in the party A signaling information sent to assigned channels reaches the exchange because of the cable break only on one ring conductor.

The exchange calls the destination subscriber B on his channel turn on with rings. The subscriber B is only on the second ring achieved.

The called subscriber acknowledges with replacement of the call on both rings. The flow of information therefore remains undisturbed.

c) Ring system with failure of a ring line Only one of the two falls Ring lines off (Fig. 5), the transmitted call reaches the exchange in the head station on the other ring.

The called subscriber acknowledges. This acknowledgment reaches the exchange also on the intact ring.

The partial failure of a connection point is equivalent to that Failure of a loop and has no effect on the functionality of the Network.

d) Multiple cable breaks / total failure of connection bells Cable defects lead to the failure of participant groups.

A partial maintenance of the operation in the emerging In contrast to operation with decentralized switching, network sections are not possible.

The circuit shown in FIG. 7 for supplying power to the connection points enables the ineffectiveness when using the double ring principle described a cable break that usually occurs simultaneously in the message and supply double ring will occur for the supply double ring.

If there are further cable breaks in the supply double ring at the same time potential-free sections are created there. This criterion is used to get out the power supply unit usually available for each connection point (connection points with only have a telephone subscriber no own power supply unit) energy to be fed into the potential-free piece. Connection points that do not have their own Power supply units are also supplied by the other connection points of the section.

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Claims (6)

PA T E N-T.A N S P R.O C H E System for a time division multiplex messaging system with a line network in a ring structure, a head end, connection points with partial Nejimer stations and parallel ring lines with opposite transmission directions, at the beidelZing lines as independent, but with uniform Time division multiplex frames for all messages sent and received Switched transmission paths and connected the connection points to both ring lines are, according to patent (P 28 20 428.6), characterized by facilities in the head end and in the subscriber stations for the central switching of those transmitted in the network News. 2. Plant according to claim 1, characterized by devices in the Connection points and in the headend for sending or receiving alarm signals when the transmission path is interrupted. 3. Plant according to claim 1 or 2, characterized by two each Time frame generators and a frequency-stable phase-locked loop for each connection point. 4. Plant according to one of claims 1 to 3, characterized in that that several participants are connected to one connection point. 5. Plant according to one of claims 1 to 4, characterized by a Line pair for at least partial power supply of connection points, the is laid in a ring and parallel to the message transmission lines. 6. Plant according to claim 5, characterized by a voltage-dependent Circuit for supplying energy from the network devices of the subscriber stations' own in the event of failure of the power supply line of the network.