GB2086191A - Controlling space-time continuity in dynamic connections of buffer networks for time-division - Google Patents

Abstract

A device is associated with a buffer network controlled by a central control 2. The buffer network comprises two transit control units 5a, 5b and a plurality of line and respective interface units 3 for communication with the central control and a plurality of PCM systems, a space-time switching network 4 having two synchronous sections 4a, 4b identical to one another, each section including a plurality of input time switching groups and the same number of output time switching groups with interposition of a space switching stage, and control circuits 6 for controlling the identity of the output information from two corresponding output groups. For the input and output groups, the device includes respective units for transmitting and receiving digital diagnosis samples. Thus, it is possible to control a given connection imposed by the central control which receives, as a response, information on relevant channels and their identification or not, as well as information on the continuity, or not, of the connection. <IMAGE>

Description

SPECIFICATION Improvements in or relating to devices for controlling space-time continuity in dynamic connections of buffer networks for timedivision The present invention relates to a device for controlling space-time continuity in dynamic connections of a buffer network for time-division telecommunication system leading to a single switching node comprising a central control and the said buffer network.

Such a buffer network referred to above (see for instance Italian patent No. 1037256 filed on April 14, 1975 in the name of Societa Italiana Telecomunicazioni SIEMENS S.p.A.) may comprise: a plurality of line units equal in number to the number of PCM systems, each line unit being an interface between the buffer network and a respective one of the PCM systems; a communication network connected to the line unit, controlled by the central control, and arranged to effect space-time switching of each PCM channel, the switching network comprising two synchronous sections identical to one another and having full access to the PCM systems by way of respective line units; a group identifying circuit connected to the outputs of the switching networks and arranged to detect possible differences in the signals processed by the switching sections; and two transit control units identical to one another and forming an interface between the central control and the switching sections. Each of the space-time switching sections is of TST-type and comprises a first time switching stage arranged to transfer each PCM sample from the input PCM channel phase to a working phase each time assigned by the central control, a space switching stage and a second time switching stage arranged to transfer the PCM samples from the working phase to the output PCM channel phase. The first time switching stage comprises a predetermined number of time switching groups each of which has its input connected to a predetermined number of PCM systems.Similarly, the second time switching stage comprises a number of output time switching groups (equal in number to the number of input time switching groups) each of which is connected to a predetermined number of PCM systems (equal in number to the PCM systems connected to any input time switching group).

The switching network, while effecting the space-time switching mentioned above, connects (upon control of the central control) an input channel of any one of the input time switching groups to an output channel of any one of the output time switching groups. Such connection is to be understood as being "dynamic" since it is made by the controls from the central control.

For optimum operation of the buffer network it is very important to control the space-time continuity of such dynamic connections. Such controls may be thought of as being made either cyclically or statistically or as a consequence of diagnosis programmes following from processing interrupt requests sent to the central control.

According to one aspect of the invention, there is provided a device for controlling space-time continuity in dynamic connections of a buffer network for time-division PCM telecommunication systems of bidirectional type connected to a switching node comprising a central control and the buffer network, the buffer network being of the type comprising: a plurality of line units equal in number to the number of PCM systems, each line unit forming an interface between the buffer network and a respective one of the PCM systems; a switching network connected to the line unit and arranged to be controlled by the central control and to effect space-time switching of each PCM channel, the switching network comprising two synchronous sections identical to one another, each section comprising a first time switching stage arranged to transfer each PCM sample from the phase of its respective input PCM channel to a working phase imposed by the central control, a space switching stage of the PCM sample and a second time switching stage arranged to transfer each PCM sample from the working phase to the phase of its respective output channel, the said first and second time switching stages comprising a predetermined number of input and output time switching groups each of which is connected to a predetermined number of line units; a plurality of group identifying circuits equal in number to the number of output time switching groups in one switching section, each identifying circuit being connected between at least two output time switching groups respectively belonging to both space-time switching sections and being arranged to sense and signal to the central control possible differences in the output signals from the two groups; and at least two transit control units identical to one another and forming an interface between the central control and the buffer network, the transit control units being arranged to pre-process the alarm signals from the members of the buffer network before transmitting them to the central control, the device comprising: at least one transmitting unit arranged to transmit diagnosis digital samples for each of the input time switching groups and to replace, upon control of the central control, at least one PCM sample passing through an input channel of the group with a diagnosis digital sample, the transmitting unit also being arranged to send an answer message to the central control, the message being parity corrected and containing information identifying the input channel as well as identification and non-identification information for the input channel; and at least one receiving unit arranged to receive the diagnosis digital samples for each one of the output time switching groups, and to receive the diagnosis digital sample from the output channel dynamically corresponding, upon control of the central control, to the input channel, the receiving unit also being arranged to send to the central control a paritycorrected message containing identification or non-identification information for the diagnosis digital sample, identification information of the output channel and identification or nonidentification information of the output channel.

According to another aspect of the invention, there is provided a circuit arrangement for diagnosing faults in a connection path of a PCM telecommunication switching exchange comprising a central processing unit and a buffer network connected to a plurality of lines via respective line units, the buffer network comprising a plurality of groups of input and output time switching stages, the circuit arrangement comprising at least one transmitting unit for each input group and at least one receiving unit for each output group, each transmitting unit being arranged, under control of the central processing unit, to replace a PCM sample with a diagnostic digital sample and to send a message to the central processing unit identifying the channel containing the diagnosis sample, each receiving unit being arranged to receive the diagnosis digital samples for each of the output time switching groups, under control of the central processing unit, and to send to the central processing unit a message concerning identification of the diagnostic sample and the channel containing the sample.

It is thus possible to provide a device for controlling the space-time continuity in dynamic connections of a buffer network for time-division telecommunication systems without causing service interruption in the connection, as well as for forming messages to be sent to the central control containing all information inherent in such a control.

It is also possible to provide a device which is self-controllable, i.e. it is arranged to sense possible malfunctionings in its own members.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a buffer network to which a device constituting a preferred embodiment of the present invention is connected; and Figure 2 is a block diagram of the device and the member to which it is connected.

With reference to Figure 1, a buffer network is generally indicated at 1 and is controlled by a central control 2. The buffer network 1 and the central control 2 form a buffer exchange.

The buffer exchange 1 comprises: line units 3 (only one is shown in Figure 1) wich act as an interface with the bidirectional PCM systems connecting the buffer network to each peripheral unit, detect line alarms and transfer PCM samples from exchange timing to line timing and vice versa; a switching network 4 arranged to effect spacetime switching of the PCM signals. The network 4 comprises two sections 4a and 4b identical to one another and arranged to switch in synchronism; a group identifying circuit 6 arranged to compare channel by channel the switching results to signal in real time possible malfunctioning in the buffer exchange; two transit control units 5a and 5b, one for each respective switching section 4a and 4b.The transit control units form an interface between the buffer network 1 and the central control 2; and distribute orders from the central control to subordinate members in the switching network 4 and receive, filter and pre-process the alarms before sending them to the central control 2.

The central control 2 is of the type comprising two processors A and B identical to one another and operating in parallel according to a masterslave scheme.

The two transit control units 5a and Sb are connected to both processors and dialogue with the one which each time acts as master. Also the two switching sections 4a and 4b operate in parallel in accordance with the master-slave scheme. The master network is chosen each time by the central control 2 and such a selection is communicated to the line units 3 so that only the channels processed by the master network are transmitted on line.

Figure 1 indicates the paths of PCM channels with solid lines, whereas the paths physically distinct therefrom for the controls and the alarms are indicated by broken lines.

Each switching section 4a and 4b operates a double space and time switching on groups of bits forming each PCM channel. Space switching transfers the groups of bits from one of the PCM systems connected to the buffer network to another, whereas time switching transfers the groups of bits from the input PCM system phase to the output PCM system phase.

According to a preferred embodiment (see Itaiian patent No. 1037256), time switching takes place at two successive times passing through an intermediate working phase in which space switching occurs. Thus, each of the switching sections 4a and 4b comprises a first time switching stage comprising n input time switching groups (only one of them being indicated by 9 in Figure 2), a space switching stage including a space network 1 6 (see Figure 2), and a second time switching stage comprising n output time switching groups (only one of them being shown in Figure 2 and indicated by 10). Each input and output time switching group 9 and 10 is connected to a predetermined number of PCM systems (e.g. 8 line units) by way of the same number of line units 3.

The two input and output time switching stages of each switching section comprise a plurality of input groups 9 and output groups 10 identical to each other and all connected to a plurality of line units 3.

Each PCM system connected to the buffer network 1 has a respective line unit 3 which is rigidly connected to an input time switching group 9 and an output time switching group 10.

By gathering in a single assembly the units 3 and the groups 9 and 10 designed to serve a number of PCM systems, it is possible to give each switching section 4a and 4b a modular structure, which makes it possible to underequip initially and to adapt its capacity subsequently to the number of PCM systems to be controlled.

By way of example, each module comprises 32 line units 3, 8 input time switching groups (4 for each switching section), 8 output time switching groups 10 (4 for each switching section) and 4 group identifying circuits 6.

The input time switching group illustrated in Figure 2 and the output time switching group 10 also shown in Figure 2 may be thought of as belonging to different modules. Each input time switching group 9 is connected to terminals (indicated by 3a, 3b, . . .... .) of a predetermined number of line units 3. The octects of the input PCM channels are consecutively written in an input word memory 12 after series-parallel conversion (effected by a converter 11). A writing control (indicated by w) is generated phase by phase by a logic timing group 13 and the addresses (indicated by g) written in memory 1 2 are partly provided by the line units 3 (in so far as the relevant channel is concerned) and partly by the group 13 itself (in so far as the group to which the same channel belongs, is concerned).The reading control (indicated by r) for the memory 12 is generated by the group 1 3 and is in phase with writing of the addresses imposed by the same group 1 3. The reading addresses (indicated by h) are written in the cells of a recirculating memory 14 stepped forward by the group 13.

Thus, each PCM sample is written in the input word memory 12 at the cell corresponding to the channel to which it belongs and read in the working phase allocated by the central control to the relevant connection. Once the octects have been subjected to the required time switching, they are supplied to a converter 15 which effects a parallel-series conversion of the octects which are then sent to a space switching network 1 6 (see for instance Italian patent No. 1037256).

The output octects from the space network 1 6 are subjected to series-parallel conversion effected by a converter 1 7 and are written, by a signal 2, in the cell of an output work memory 18 which is each time identified by the addresses (indicated by s) written by the central control 2 in a recirculating memory 1 9 which is stepped forward by a logic timing group 20 which also generates the control rand the addresses c for reading the output memory 1 8.

The octects provided by the word memory 19 are sent to a parallel-series converter 21 before being distributed to the electrical terminations 3a, 3b,3c, . . . of the line units 3.

Each input time switching group 9 is associated with a unit 100 arranged to transmit diagnosis digital samples as well as to form the message inherent in such a transmission (as better explained below). Each output time switching group 10 is associated with a unit 200 arranged to receive the said diagnosis digital samples as well as to form a message inherent in such reception (this message is also explained in detail below). The transmitting unit 100 comprises a block 22 whose output is connected to the input of the input work memory 12 and whose input is connected to the output of a comparator 23.The function of the block 22 is to form one or more test octects (diagnosis digital samples) each of which, upon energization of the block 22 (following energization of the comparator 23), prevents the PCM sample, which is about to be stored in the memory 12 at that moment, from being stored therein. This results in the PCM sample being annulled and replaced by a diagnosis digital sample. The comparator 23 receives the writing address (signal g) and the controls from the central control 2 (with the interposition of the transit control units 5a and 5b) on its first and second inputs, respectively. When space-time continuity in a given connection is to be checked, the central control 2 sends, as mentioned above, controls identifying a predetermined input channel to the second input of the comparator 23.

When the addresses (addresses identifying the same input channel of the input time switching group 9) available at the two inputs of the comparator 23 are equal to one another, the comparator 23 is energized and its output 23a then assumes a well defined electrical state (e.g.

high level), which corresponds to the identification of the selected channel. The output 23a is connected to the input of a block 24 (e.g.

comprising a flip-flop) whose output 24a takes two distinct electrical configurations (high level, low level) respectively corresponding to energization or non-energization of the comparator 23. Energization of the comparator 23 results in the energization of the block 22 (sending of the diagnosis digital sample to a predetermined input channel) and in the energization of the block 24 (which corresponds to the identification of the channel predetermined by the central control 2).

The second input of the comparator 23 and the output 24a of the block 24 are connected to a logic processing network 25 whose function is to form a message generally indicated by H and containing information about sending of a diagnosis digital sample to a predetermined channel. The message H contains information about the selected input channel (CAN. INC.), and information about the identification or nonidentification of the input channel (RCI in the message H) comprising for instance the bit "1" or "O" corresponding to identification or nonidentification. The message H is parity-connected (P in the message H) by a parity generator 26 and is then sent by way of a channel 25a to one of the transit control units 5a and 5b which is arranged to forward the message to the central control 2.

With reference to the receiving unit 200 (Figure 2), a first comparator has been indicated by 27 and one of its inputs is connected to the output of the output word memory 18, whereas its other input is connected to the output of a block 122 arranged to provide diagnosis digital samples identical to those provided by the block 22 in the transmitting unit 100.

Still with reference to the receiving unit 200. a second comparator is indicated by 28 and its first input receives the reading address (the said signal c) of the output channels of the said output time switching group 10, whereas its second input receives the controls (also containing the addresses of the selected output channel) from the central control 2. The output 28a of the comparator 28 is energized upon coincidence of the addresses available at the inputs (coincidence between the output channel selected by the central control 2 and the channel identified by the signal c). The output 28a is connected to the input of a block 29 (usually comprising a flip-flop) and to one input of a logic gate 30 whose other input is connected to the output 27a of the first comparator 27.The block 29 provides at its output two distinct electrical configurations (high or low ievel) respectively identified by the energization or non-energization of the output 28a of the second comparator 28. The high-level signal at the output of the block 29 indicates identification of the output channel identified by the comparator 28, whereas the low level indicates lack of identification of the same output channel by the comparator 28.

The logic gate 30 energizes its output 30a when its two inputs are at a high level, which respectively corresponds to identification of the output channel corresponding, according to the dynamic connection imposed to the central control 2, to the said input channel referred to above in connection with the transmitting unit 100, and to recognition of the diagnosis digital sample in the same output channel (energization of the output 27a of the first comparator 27). The output 30a of the logic gate 30 is connected to the input of a block 31 (usually comprising a flipflop) whose output has two characteristic electrical states (high or low level) respectively corresponding to the identification or nonidentification of the diagnosis digital sample in the output channel in question.The second input of the comparator 28 and the outputs of the blocks 29 and 31 are connected to a logic processing network 1 25 which is arranged to form a message K to be sent to one of the two transit control units 5a and 5b which is arranged to send the same meassge K to the central control 2. The initial part of the message comprises the identification bit of the diagnosis digital sample (indicated by RO in the message K), the information identifying the selected output channel (indicated by CAN.US. in the message K), the identification or nonidentification of the output channel (indicated by RCU in the message K) and a parity bit (indicated by P in the message K) inserted by a parity generator 126 of known type.

A given dynamic connection is each time imposed by the central control by way of the buffer network 1 (more precisely from a line unit to the switching network and from the latter again to the line unit). Such a connection comprises an input channel in an input time switching group 9 and an output channel in an output time switching group 10. The groups 9 and 10 can belong to different modules. The space-time continuity control of such a connection comprises sending a diagnosis digital sample to the input channel (which is done by the transmitting unit 100) and sensing the same diagnosis digital sample in its respective output channel (which is done by the receiving unit 200).

Upon reading of the messages H and K reaching it, the central control 2 senses the continuity or lack of continuity in the connection on which the control has been effected. The first case occurs when the input and the output channels (whose identification is respectively stored in the blocks 24 and 29) are actually those inherent in the connection under control and when the diagnosis digital sample has been identified in the output channel (by the said block 31). In the case where any information associated with the messages H and K does not correspond to that expected from a positive result of such a control, the central control realizes that space-time continuity of the connection does not exist.

The preferred device which comprises two respective units, i.e. a transmitting unit 100 and a receiving unit 200, besides, fulfilling the above explained function (which comprises controlling the space-time continuity in a connection), is structured so as to be able to effect self-control. In the case where the central control 2 selects a predetermined input channel and the control reaching the second input of the comparator 23 is activated for a different one, the block 24 is energized for a "wrong" input channel but the central control 2 upon reading the message H "sees" non-identity between the selected input channel and the input channel to which the diagnosis digital sample is to be sent.This may be due either to malfunctioning of the transit control unit which has transmitted the message to the transmitting unit 100 or to malfunctioning in the connection between the transit control unit and the comparator 23. Similar considerations obviously apply to the output channel selected by the central control and the output channel recognized by the comparator 28 and identified by its respective message K.

In the case where the block 24 is to be selfcontrolled, it is sufficient to send to the second input of the comparator 23 a control to which no input channel corresponds. In this case, the block 24, if operating correctly, must not store the identification of any channel and its respective bit in the message H (position KCI in the same message H) is equal to "zero". In the case of malfunctioning of the biock 24, the said bit becomes instead equal to "one". Similar considerations apply to self-control on the block 29 in the receiving unit 200.

Thus, the preferred device, upon control by the central control, controls the continuity of a given space-time dynamic conneciion affecting the transit network and sends messages containing information inherent in such control to the central control without interrupting the service in the same connection (in fact only one PCM sample in transit is replaced by a diagnosis digital sample).

Moreover, by reading the said messages as a result of actual continuity checking controls in a connection or of deliberately erroneous controls, the central control senses malfunctioning in some members of the preferred device which can control itself owing to its specific configuration.

Claims (6)

1. A device for controlling space-time continuity in dynamic connections of a buffer network for time-division PCM telecommunication systems of bidirectional type connected to a switching node comprising a central control and the buffer network, the buffer network being of the type comprising: a plurality of line units equal in number to the number of PCM systems, each line unit forming an interface between the buffer network and a respective one of the PCM systems; a switching network connected to the line units and arranged to be controlled by the central control and to effect space-time switching of each PCM channel, the switching network comprising two synchronous sections identical to one another, each section comprising a first time switching stage arranged to transfer each PCM sample from the phase of its respective input PCM channel to a working phase imposed by the central control, a space switching stage of the PCM sample and a second time switching stage arranged to transfer each PCM sample from the working phase to the phase of its respective output channel, the said first and second time switching stages comprising a predetermined number of input and output time switching groups each of which is connected to a predetermined number of line units; a plurality of group identifying circuits equal in number to-the number of output time switching groups in one switching section, each identifying circuit being connected between at least two output time switching groups respectively belonging to both space-time switching sections and being arranged to sense and signal to the central control possible differences in the output signals from the two groups; and at least two transit control units identical to one another and forming an interface between the central control and the buffer network, the transit control units being arranged to pre-process the alarm signals from the members of the buffer network before transmitting them to the central control, the device comprising: at least one transmitting unit arranged to transmit diagnosis digital samples for each of the input time switching groups and to replace, upon control of the central control, at least one PCM sample passing through an input channel of the group with a diagnosis digital sample, the transmitting unit also being arranged to send an answer message to the central control, the message being parity corrected and containing information identifying the input channel as well as identification and non-identification information for the input channel; and at least one receiving unit arranged to receive the diagnosis digital samples for each one of the output time switching groups and to receive the diagnosis digital sample from the output channel dynamically corresponding, upon control of the central control, to the input channel, the receiving unit also being arranged to send to the central control a paritycorrected message containing identification or non-identification information for the diagnosis digital sample, identification information of the output channel and identification or non identifcation information of the output channel.

2. A device as claimed in claim 1, wherein each input time switching group comprises a seriesparallel converter, an input word memory connected to the converter, a parallel-series converter connected to the word memory, a recirculating address memory, and a logic timing group arranged, by means of a periodic signal, to provide an address writing control for writing the address provided by the line units in connection with the input channel and by the logic group itself in connection with the input time switching group to which the channel itself belongs, the addresses concerning the PCM channels leading to the said input word memory which is controlled by a read control for the addresses written by the central control in the cells of the address memory, the transmitting unit comprising: a first block whose output is connected to the input of the input word memory, the block being arranged to provide on its output a diagnosis digital sample, when energized; a comparator whose first input is arranged to receive the addresses of the input channels of the input word memory and whose second input is arranged to receive controls from the central control which identify the address of a predetermined input channel of the group, the comparator being arranged, when energized, to activate the first block; a second block connected to the output of the comparator and arranged to provide on its output two distinct electrical states corresponding to identification or nonidentification of the input channel recognized by the central control; a logic processing network comprising a parity generator for the output messages from the network, the generator having inputs connected to the second input of the comparator and to the output of the second block, the logic processing network being arranged to form the answer message of the transmitting unit.

3. A device as claimed in claim 2, wherein each output time switching group comprises a seriesparallel converter, an output word memory connected to the converter, a parallel-series converter connected to the output word memory, a recirculating address memory, a logic timing group arranged to provide the writing control of the addresses for the output channels of the switching groups, the addresses being provided by the recirculating memory and written in the output word memory, the reading control of the PCM samples in the output word memory being provided by the logic group which also provide the reading addresses of the output word memory, the receiving unit comprising. a first comparator one input of which is connected to the output of the output word memory and another input of which is connected to the output of a third block arranged to provide at least one diagnosis digital sample identical to the diagnosis digital sample provided by the first block 22 of the transmitting unit the comparator being arranged to energize its output in response to equality of the diagnosis digital samples available at its inputs; a second comparator whose first input is arranged to receive the addresses of the output channels of the group and whose second input is arranged to receive controls from the central control identifying the address of the output channel of the group corresponding to the input channel of the group in the transmitting unit, the comparator being arranged to energize its output in response to equality of the addresses available at its inputs; a logic gate whose two inputs are respectively connected to the outputs of the comparators; a fourth block having its input connected to the output of the logic gate and providing on its output two distinct electrical states corresponding to identification or non-identification of the diagnosis digital sample in the output channel; a fifth block having its input connected to the output of the second comparator and being arranged to provide on its output two distinct electrical states corresponding to identification or nonidentification of the output channel; a logic processing network including a parity generator for the output messages from the network, the logic network being connected to the second input of the second comparator and to the output of the fourth and fifth blocks and being arranged to form the answer message of the receiving unit.

4. A circuit arrangement for diagnosing faults in a connection path of a PCM telecommunications switching exchange comprising a central processing unit and a buffer network connected to a plurality of lines via respective line units, the buffer network comprising a plurality of groups of input and output time switching stages, the circuit arrangement comprising at least one transmitting unit for each input group and at least one receiving unit for each output group, each transmitting unit being arranged, under control of the central processing unit, to replace a PCM sample with a diagnostic digital sample and to send a message to the central processing unit identifying the channel containing the diagnostic sample, each receiving unit being arranged to receive the diagnosis digital samples for each of the output time switching groups. under control of the central processing unit, and to send to the central processing unit a message concerning identification of the diagnostic sample and the channel containing the sample.

5. A circuit arrangement for diagnosing faults in a connection path of a PCM telecommunications switching exchange, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A switching exchange including a circuit arrangement as claimed in claim 4 or 5.