Digital satellite exchange for subscriber connections

Digital satellite center Digital satellite center

The invention relates to the connection of analogue and digital subscribers near or far from a digital local exchange, and more particularly to a digital connection unit of telephone network subscribers.

In the case of analogue subscribers, analog-to-digital conversion of speech signals must be performed at the digital local exchange. This conversion is performed by the subscriber interface10 in a unit located either in the exchange itself or in the satellite exchange closest to the subscriber.

FR-A 2 144 109 discloses an interface unit which can be either local, i.e. installed in a telephone exchange, or which is remote, i.e. forms a satellite exchange, 15 which is connected to the exchange by means of 2 Mbit / s multiplex lines.

In digital exchanges, the centralization of local loops is performed either before or after the analog-to-digital conversion, and the connections are always the same, with analogue local loops on one side and 2 Mbit / s digital connections on the other.

Interfaces of this type, which have only analogue subscriber connections, mean that a certain number of subscribers cannot participate in the digitalisation of the telephone network. Geographically dispersed groups of subscribers, usually located far away, are connected to the exchange by common lines, analog hubs, or analog multiplexers. All of these devices are independent of the switching system and are installed and maintained by personnel other than the switching system.

On the one hand, the current trend is to install integrated digital service networks that cover the entire range of telecommunications requirements: telephone, data, image and voice. The integration of services must therefore start from the distribution network, whereby a terminal installation is placed next to the subscriber, which controls a number of terminals, such as a telephone, a fax machine, data terminal equipment, etc., and which is connected to a digital local exchange, e.g. 144 kbit / s via a digital cable, simultaneously transmitting speech, image and signaling coding to the subscriber.

The object of the invention is to connect local and remote analog and digital subscribers in a way that offers all subscribers the advantages of a digital network.

It is also an object of the invention, in the case of subscribers located in an area remote from the digital local exchange, to group these subscribers into groups in a subscriber satellite unit and to connect the satellite unit to the exchange so that these subscribers are no longer special in terms of services or operation and maintenance.

The invention relates to a digital satellite exchange for connecting analogue and digital subscribers and for connecting local and remote subscribers, comprising a digital control unit and digital subscriber hubs of at least one of the following types: local type of analogue subscribers, remote type of analogue subscribers, local type of digital subscribers, remote type of digital subscribers, remote mixed type of analogue and digital subscribers, each hub comprising terminal units and connected by a multiplex connection to a digital control unit and a digital control unit comprising a switch field connected to said control units; and causing said multiplex connections to be centralized, and that said switch field is connected to the digital switch center by a multiplex connection.

The invention will be explained in more detail below by means of exemplary embodiments shown in the accompanying drawings, in which: Figure 1 shows the general architecture of a digital satellite exchange according to the invention.

Fig. 2 shows a digital local concentrator for analog subscribers included in the exchange of Fig. 1, Fig. 3 shows a digital remote concentrator for analog subscribers included in the exchange for Fig. 1, Fig. 4 shows a digital local concentrator for digital subscribers included in the exchange for Fig. 1, Fig. 5 shows a digital remote concentrator for digital subscribers shows the digital control unit included in the center of Fig. 1.

Figure 1 shows the general architecture of a digital satellite exchange CSN according to the invention, which includes a digital control unit UCN, analog local subscribers CNLA, analog subscriber digital remote hubs CNEA, digital subscriber digital local hubs CNLN, digital subscriber digital remote hubs CNEN and analog or digital subscriber digital subscribers. The digital local hubs CNLA and CNLN are located in the immediate vicinity of the digital control unit UCN in the same premises as the latter.

The digital remote hubs CNEA, CNEN and CNEM are at varying distances from the digital control unit UCN to which they are connected by multiplex connections. It is clear that a digital satellite center can have all types or only some type of digital hubs. The UCN digital control unit, on the one hand, connects and accesses the digital local and remote hubs to the digital local exchange and, on the other hand, monitors the digital satellite exchange.

The digital local hub CNLA for analog subscribers is connected to analog subscribers by subscriber lines such as subscriber line 1 and / or at least one multiplexer 2, each of the multiplexers being connected to a hub on medium speed (640 or 704 kbit / s) multiplex line 3. The multiplexer is connected to speed and ten 704 kbit / s. The digital local hub CNLA is connected to the digital control unit UCN by a multiplex connection L1, which consists of four 2 Mbit / s multiplex lines, whereby the multiplex connection provides 120 communication channels in each direction.

The digital remote concentrator CNEA for analog subscribers is connected to analog subscribers by subscriber lines such as subscriber line 5 and / or at least one multiplexer 6, each of the multiplexers being connected to a hub by medium speed multiplex line 7. The multiplexer is connected to subscriber lines speed. The digital remote hub CNEA is connected to the digital control unit UCN by a multiplex connection 9 consisting of one to four 2 Mbit / s or medium-speed multiplex lines, the number of multiplex lines depending on the number of subscriber lines connected to the remote hub.

The digital local hub CNEN of the digital subscribers is connected to the subscriber terminals 10, each terminal being connected to a hub 144 kbit / s on a digital subscriber line 11 and / or to at least one multiplexer 12, each multiplexer being connected to a hub on a medium speed multiplexer. s with digital subscriber line 15. The digital local hub CNLN of the digital subscribers may also be connected to at least one automatic multiservice subscriber exchange 16, each subscriber exchange being connected to the hub by at least one 2 Mbit / s or medium speed 640 or 704 kbit / s multiplex line 17. The digital local hub CNLN is connected to a digital control unit four 2 Mbit / s multiplex cables.

The digital remote hub CNEN for digital subscribers is connected to the digital control unit UCN by a multiplex connection 18 consisting of four to four 2 Mbit / s or medium-speed multiplex lines. The digital remote hub CNEN is connected to at least one multiplexer 19, each multiplexer being connected to the hub on a medium speed multiplex line 20. The multiplexer is connected to the subscriber terminals 21, each terminal being connected to the multiplexer 144 kbit / s on a digital subscriber line 22. The digital remote hub may also be connected to at least one multiservice subscriber exchange 23, each subscriber exchange being connected to the hub with at least one 2 Mbit / s or medium speed multiplexer. The digital remote hub may also be connected to the subscriber terminals 25, each terminal being connected to a 144 kbit / s digital subscriber line 26.

The digital remote hub CNEM for analog and digital subscribers is connected to the digital control unit UCN by a multiplex connection 28 consisting of one to four 2 Mbit / s or medium speed multiplex lines. The digital remote hub for analog and digital subscribers includes a digital local hub CNLA for analog subscribers, a digital hub CNLN for digital subscribers6, and an interface circuit 27 connected to each local hub on the one hand and a multiplex connection 28 on the other. The digital local hub CNLA of the analog subscribers is connected to the subscribers 5 on the subscriber lines and to the multiplexers on the multiplex lines as in the case of the hub CNLA described above. Correspondingly, the digital local hub CNLN of the digital subscribers is connected, as in the case of the hub CNLN described above, to the subscriber terminals mul10 multiplexers and multi-service subscriber exchanges.

The digital control unit UCN is connected to the digital local exchange by a multiplex connection 29 consisting of 2-16 bidirectional 2 Mbit / s multiplex lines.

It is obvious that for each type of hub CNLA,

CNEA, CNLN, and CNEN may include all or some of the interfaces of the above types, and the same applies to the CNLA and CNLN hubs of the digital remote hub for analog and digital subscribers.

The digital satellite exchange CSN may be embedded in the digital local exchange or it may be located far from the exchange to group subscribers in a remote area.

In the case of the CNLA of a digital local hub for analog subscribers, it should be noted that the subscriber line may include both private subscribers and subscriber exchanges connected to the hub by at least one subscriber line. The local hub CNLA sees subscriber exchanges as similar to private subscribers.

144 The kbit / s digital subscriber lines comprise, according to CCITT recommendations, two 64 kbit / s B channels for voice and data and one 16 kbit / s D channel for signaling, packet switched data, remote alarm and telemetry data. The combination of two B-channels and D-channels provides a basic interface level for the subscriber, such an interface being particularly suitable for transmitting signaling information required for data terminals to operate in an integrated digital service network, CCITT recommendations also define an extended interface comprising n 64 kbit / s B channels and one 64 kbit / s D channel, where n is less than or equal to 30. Signals corresponding to such an extended connection are transmitted on a medium-speed or 2 Mbit / s multiplex cable.

The digital satellite center in Figure 1 is thus suitable for all types of connections and to economically connect sparsely populated areas, such as rural areas, as well as areas where the population is grouped into clusters, such as apartment buildings in an urban area. It is advantageous to connect the analogue and digital lines as close as possible to the subscribers, either to obtain savings in the number of cables in the distribution network or to increase the connection capacity of the existing network. In the case of analogue subscribers, the digital satellite exchange CSN enables the connection of up to about ten ascending distant subscribers via a multiplexer and up to 256 subscribers via a digital remote concentrator. Multiplexers and digital remote hubs are usually connected by one or more multiplex lines, but a microwave link can also be used depending on the geographical location of the unit to be connected (multiplexer or remote hub). The use of medium speed allows the use of cables in the existing distribution network, which does not incur additional costs for connecting the unit to be connected (multiplexer or remote hub). The digital satellite center provides a great deal of flexibility in terms of connections, as it allows the multiplexers to be connected either directly to the local type.

CNLA or CNLN hub or via a remote type CNEA or CNEN hub. The CNEM digital remote hub for analogue and digital subscribers facilitates the connection of subscribers because it allows the connection of analogue and digital subscribers in the same geographical area. An arbitrary combination of analogue subscriber lines and digital subscriber lines and also multi-service subscriber exchanges can be connected to the digital satellite center at the same time. In order to enable the growth of the distribution network, its use must be facilitated by enabling a simple change in the configuration of the interface units. To this end, the multiplexer connection is achieved simply by replacing the subscriber interface card in the local or remote hub with a multiplexer interface card, and the remote hub connection is achieved by adding the interface cards to the transmission lines operating at the appropriate speed in the local hub and the digital control unit UC. This modular design of the digital satellite center equipment allows the connection to be made at minimal cost with few devices in terms of number and types of cards, thus minimizing the number of spare parts for the operating facility. These features and advantages of the digital satellite center according to the invention schematically shown in Figure 1 are schematically shown in Figures 2-6.

Fig. 2 shows by way of example the digital local concentrator CNLA of the analog subscribers of Fig. 1 and the multiplexer 2 of the analog subscribers. The local concentrator CNLA is of the type disclosed in FR-A 2 513 470. The digital hub CNLA of Figure 2 comprises an interface circuit 40, subscriber line terminal units UT and a multiplexer terminal unit UTM. The subscriber line terminal unit includes a number (e.g., 16) of subscriber line terminals T each connected to subscriber line 1, a first digital hub stage 41, and an auxiliary control unit 42 connected to each terminal and the first hub stage 41. Each subscriber line terminal T includes an SLIC interface and an encoder, decoder and filter circuit and performs all the functions referred to in the term BORSCHT, including input, overload protection, ring signal, monitoring, coding / decoding and filtering, two-wire / four-wire conversion and testing. The definition of the term BORSCHT is in the journal IEEE-Spectrum, February 1977, page 46. Each subscriber line terminal T is connected to a first digital hub stage 41, which in turn is connected to an interface circuit 40. The multiplexer terminal unit UTM includes a multiplexer terminal 44, which is an interface circuit, a first digital hub stage 41 and an auxiliary control unit 42 connected to the interface circuit 44 and the first digital stage. to the interface circuit 40. The interface circuit 44 is connected by a multiplex line 3 to an analog subscriber multiplexer 2, which includes subscriber line terminals T similar to the terminals of the terminal unit UT and an interface circuit 46 which establishes a connection between the terminals T and the interface circuit 44 via a multiplex connection 3. Each subscriber line terminal T of the multiplexer 2 is connected to the subscriber line 4. The interface circuit 46 performs multiplexing and demultiplexing of signals coming to and from the subscriber line terminals. The interface circuit 40 is connected to a multiplex connection L1, which connects the digital local hub CNLA to the digital control unit UCN (Fig. 1). This interface circuit 40 is a duplicate clock synchronization circuit, which is also described in the above-mentioned publication FR-A 2 513 470. This circuit generates the synchronization and clock signals required by the terminal units UT and UTM and includes the synchronization circuits in series with the four multiplex lines of the multiplex connection L1. The terminal units UT and UTM each comprise one circuit board.

The structure of the CNLA of the digital local hub is thus easily changed by replacing the UT card of the subscriber line terminal unit with the UTM card of the multiplexer terminal unit and vice versa.

Fig. 3 shows by way of example the digital remote concentrator CNEA of the analog subscribers of Fig. 1 and the analog subscriber multiplexer 6. The digital remote concentrator CNEA of Fig. 3 includes the digital local concentrator CNLA of Fig. 2 and an interface circuit 50 connected by a multiplex connection L3 to the digital local concentrator CNLA. This multiplex connection L3 is similar to the multiplex connection L1 in Figure 2 and has four 2 Mbit / s multiplex lines. The interface circuit 50 is connected to the digital control unit UCN by a multiplex connection and includes a code conversion and resynchronization 15 circuit 51 and one or two oscillators 52, 53 synchronized to the clock frequency obtained by the multiplex connection 9. The oscillators control a digital remote hub CNEA, where one oscillator is used when the multiplex connection consists of one multiplex line20 and two oscillators when it consists of at least two multiplex lines. There is a code conversion and resynchronization card for each 2 Mbit / s or medium speed multiplex line forming the multiplex connection 9. Code conversion and resynchronization operations are well known to those skilled in the art. In the digital local hub CNLA, each terminal T is connected to the subscriber line 5 and the UTM interface 44 of the multiplexer terminal unit is connected by a multiplex line 7 to an analog subscriber multiplexer 6 similar to the multiplexer 2 of Fig. 2 and connected to the subscriber lines 8. As mentioned in connection with the description of Figure 1, the multiplexers 6 of the analog subscribers are connected to nine or ten subscriber lines and thus contain nine or ten terminals T, whereby the multiplex line 7 operates at a medium speed of 640 kbit / s in the case of nine subscriber lines.

Figure 4 shows the digital local hub CNLN and multiplexer 12 of the digital subscribers of Figure 1. In Figure 4, the hub CNLN includes, for example, a digital terminal UTN 5 connected to subscriber terminals, e.g., device 10, a subscriber exchange terminal unit UTC connected to a multi-service subscriber terminal 16, and 16 digital subscriber exchanges. A UTMN connected to a digital subscriber multiplexer 12. The terminal units are connected to an interface circuit 40 similar to the interface circuits CNLA and CNEA of the hubs of Figures 2 and 3.

The digital terminal unit UTN includes digital subscriber line terminals TLN connected to the first 15 digital hub stages 41, and an auxiliary control unit

42, which is connected to each terminal TLN and the first digital hub stage 41. Each digital subscriber line terminal TLN is connected by a 144 kbit / s digital subscriber line 11 to a subscriber terminal 20 10 and acts as an interface for various 144 kbit / s transmission systems: forward link, quad-line or four-wire. The subscriber line terminal also distinguishes between 64 kbit / s channels and 16 kbit / s D channels, which transmit signaling and packet-switched data.

For example, the UTC includes two interface circuits 60 connected to the first digital hub stage 41 and an auxiliary control unit 42 connected to each interface circuit and the first digital hub stage 41. Each interface circuit

60 is connected to the multi-service subscriber exchange 16a, 16b by a multiplex line 17a, 17b.

The digital multiplexer terminal unit UTMN includes an interface circuit 47, a first hub stage 41 and an auxiliary control unit 42 connected to the interface circuit 47 and the first hub stage 41. The interface circuit 47 is connected on a multiplex line 13 to a digital subscriber multiplexer 12 including a digital subscriber line 5 UTN subscriber line terminals. The terminals TLN are connected to an interface circuit 61, which performs multiplexing and demultiplexing of signals to and from the digital multiplexer terminal unit UTMN via the multiplex line 13. Each digital subscriber line terminal TLN is connected by a digital subscriber line 15 to subscriber terminal equipment. The first digital hub stage 41 of each terminal unit UTN, UTC, UTM is connected to an interface circuit 40, which in turn is connected by a multiplex connection L2 to the digital control unit UCN.

The first digital hub stage 41 and the auxiliary control unit 42 are similar to those in Figs. 2 and 3, and it is clear that the digital local hub CNLN of the digital subscribers may include one or more terminal units UTN, UTC and UTMN shown in Fig. 4 or only some of them.

Fig. 5 shows a digital remote hub CNEN of the digital subscribers of Fig. 1 with a digital local hub CNLN of digital subscribers as shown in Fig. 4 25 and an interface circuit 50 similar to Fig. 3. Each digital subscriber line terminal TLN of the digital terminal UTN is connected to a digital subscriber line 30 . Each interface circuit of the subscriber exchange terminal unit UTC is connected by a multiplex line 24a, 24b to a multi-service subscriber exchange 23. The UTMN interface circuit 47 of the digital multiplexer terminal unit is connected by a multiplex line 20 to a multiplexer 19 L4, which is similar to the multiplex connection L2 of Figure 4. The interface circuit 50 is connected to the control unit UCN of Fig. 1, these connections consisting of one to four 2 Mbit / s or medium-speed multiplex lines.

As noted in connection with the description of Figure 1, the digital remote hub CNEM for analog and digital subscribers includes a digital local hub CNLA for analog subscribers and a digital local hub CNLN for digital subscribers. These hubs are thus similar to those shown in Figs.

Fig. 6 schematically shows the digital control unit UCN of Fig. 1 with a time division switch field RCX, a main control unit UC and digital hub connection circuits 62,63,64. These interface circuits are of the first type when the multiplex connections 9,18,28 connecting them to the remote hub are 2 Mbit / s connections, and of the second type when these are medium speed multiplex connections. The circuits are thus similar to each other and thus interchangeable, as long as all or some of the multiplex connections 9,18,28 are equally fast.

The digital remote hub CNEA for analog subscribers is connected via a multiplex connection 9 to an interface circuit 62, which in turn is connected to the RCX 2 Mbit / s multiplex connection 65. The digital remote hub CNEN for digital subscribers is

The digital remote hub CNEM for analogue and digital subscribers is connected via a multiplex connection 28 to a circuit 64 of the interface 14, which in turn is connected to a time division switch field RCX with a 2 Mbit / s multiplex connection 67. Digital local hub CNLA for analog subscribers L1 and L2. The time division switch field is connected by a 2 Mbit / s multiplex connection 29 of the digital local exchange multiplex connection interface module, this multiplexed connection consisting of 2-16 bidirectional 2 Mbit / s multiplex lines. Time-division switch Field

The RCX forms the second hub stage of the digital satellite exchange CSN of the invention and thus provides a two-way connection of analog and digital subscribers to the digital local exchange. The time division switch field RCX 15 is controlled by the main control unit UC, which is connected to the switch field.

This main control unit handles the traffic with the digital local exchange using the CCITT No. 7 common channel signaling system when the traffic with the digital hubs uses the channel specific transmission policy using one time slot of the frames of the multiplexed connections L1, L2, 65, 66, 67, e.g. 32 term.

As noted above, the digital satellite exchange 25 may include various types of digital hubs: local, remote, or analog and digital. The time division switch field RCX connects the digital satellite exchange to the local exchange 16 on a 2Mbit / s multiplexed line forming a multiplex connection 29. On the subscriber line side, the switching field may be connected to digital hubs representing up to

2 Mbit / s multiplexed cable. This allows up to 2048 subscribers distributed in about 20 different locations to be connected to digital remote hubs, which in turn are expanded with multiplexers. The digital satellite exchange according to the invention is thus ideally suited as equipment for high-density areas such as urban and industrial areas, as well as for low-density areas such as rural areas with sparsely populated areas. The digital satellite center can also connect up to 120 local calls that do not have to go through the digital local center.

This ability to handle local calls is a significant advantage in building a telephone network.

In addition, the ability to equip a particular type of digital hub with subscriber line terminals, subscriber exchange terminal cards, or multiplexer terminals provides high interface flexibility, complementing the use of any type of digital hub.