GB2166025A - Arrangement for wideband network termination - Google Patents

Abstract

In an arrangement for connecting a subscriber's narrowband terminals (64 kb/s) and wideband terminals (2 x 64 kb/s to 30 x 64 kb/s) to an exchange, all of the subscriber's terminals are connected to a subscriber line unit (5) via standardised S0 interfaces (11, 11'). The wideband terminals are also connected to the line unit via wideband interfaces (10). Via the wideband interfaces, bidirectional data traffic is handled at a rate of 2,048 kb/s. Communication with the exchange is bidirectional at 2,048 kb/s. Signalling, in particular the assignment of the required number of channels for each connection, is performed via the D channel of the S0 interface, utilising the known D-channel protocol. Access to the D channel by narrowband and wideband terminals is controlled via layer 1 of the S0 interface. <IMAGE>

Description

SPECIFICATION Arrangement for wideband network termination This invention relates to arrangements for wideband network termination and in particular to an arrangement for connecting a subscriber's terminals to an exchange via a bidirectional time-division multiplex link containing at least one voice channel, which can also be employed for data transmission, and a control channel.

In unpublished Guideline 1R230, issued by the Fernmeldetechnisches Zentralamt of Deutsche Bundespost, an interface (SO interface) is described, via which a plurality of terminals can be connected to an exchange. A bidirectional time-multiplex link, via which one signalling channel (called the D channel) and two channels termed base channels (B channels) are used for transmission runs via this interface. 64 kb/s can be handled in each base channel. A plurality of terminals, each operating at 64 kb/s, can be connected. Each of these terminals can be a telephone instrument or a data terminal. 16 kb/s can be transmitted in the signalling channel. The signalling channel is incorporated in a further 64 kb/s channel.

In addition to other functions, selection of the terminals and assignment of a base channel to a selected terminal for the duration of a connection is performed via the signalling channel.

Data exchange via the signalling channel is subject to stipulated rules (D-channel protocol).

Under CCITT Recommendation 0.503, connections necessitating an exchange of information at a rate in excess of 64 kb/s must be established via a plurality of 64 kb/s channels.

This applies to connections for high-speed data communication up to approx. 2 Mb/s.

Connections of this nature are generally termed "wideband connections", and this designation will be employed below. Differentiation must be made between these connections and the connections via which video signals are also exchanged and which are operated at a speed of approx. 14 Mb/s. Connections of this nature are customarily terms "broadband connections".

At present, it is intended that a link operating at 2.048 Mb/s be created between the subscriber and the exchange for each of a subscriber's existing wideband terminals, with signalling being performed within the usable data range in accordance with X.21. On the other hand, 2.048 Mb/s connections are used in a PCM 30 system for transmitting 30 base channels, termed narrowband channels, as opposed to wideband and broadband channels, with signalling for all 30 channels being performed together via a 64 kb/s data channel.

There is also a further 64 kb/s data channel for synchronisation. For this planned system, an interface (S2 interface) is currently being standardised.

It is an object of the present invention to provide an arrangement for connecting terminals to an exchange and a method of assigning channels to the terminals.

According to the invention in its broadest aspect there is provided an arrangement for connecting a subscriber's terminals to an exchange via a bidirectional time-division multiplex link containing at least one voice channel, which can also be employed for data transmission, and a control channel, characterised in that the content of the voice channel and the content of the control channel are transmitted in a time-division multiplex frame over the time-division multiplex link, the timedivision multiplex frame also being able to transmit the contents of a plurality of further voice channels; in that there is a line unit at the subscriber, in that the line unit has a first interface unit on the side facing the exchange, via which the entire contents of the time-division multiplex frame are transmitted, in that the line unit has a second interface unit and a third interface unit on the side facing the terminals, in that the control channel and at least one voice channel are transferred via the second interface unit and at least the remaining voice channels are transferred via the third interface unit, in that a portion of the terminals is connected only with the second interface unit, and in that each of the remaining terminals is connected both with the second interface unit and with the third interface unit.

Through the solution according to the present invention, it is possible to connect a plurality of a subscriber's terminals to the exchange via a single link. Both narrowband and wideband terminals can be connected. Signalling and channel assignment to the individual terminals is performed in accordance with uniform aspects; signalling coincides largely with the signalling required for narrowband terminals and is based thereupon.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows the basic equipment configuration of an arrangement according to the invention, Figure 2 shows the basic internal design of a line unit in an arrangement according to the invention, and Figures 3 to 7 show connection alternatives for a subscriber's terminals to a line unit of an arrangement according to the invention.

The heart of the arrangement shown in Figure 1 is a line unit 5. A line termination unit (interface unit) 6 contained therein forms the subscriber-side termination of a time-division multiplex link, which links this subscriber with an exchange 8. The exchange side termination of this time-division multiplex link is formed by a line termination unit 7, whose design corre sponds to that of line termination unit 6. Line termination units 6 and 7 permit time-division multiplex connections at a data rate of 2,048 kb/s (32 64 kb/s channels) in each direction.

One of these channels is employed for synchronisation, a further channel contains a control channel, and the other 30 channels (base channels) are employed for the exchange of useful information.

Connected to line unit 5 is a narrowband terminal 1 for 64 kb/s, a wideband terminal 2 for 128 kb/s, a wideband terminal 3 for 578 kb/s and a wideband terminal 4 for 1,920 kb/s. It is also possible to connect further terminals, as well as terminals for other data rates. Each connected terminal, as well as line unit 5, has an ISDN terminal interface (So interface) and is equipped with an So-interface unit 11 or 11' for this purpose. Interface units 11 in the terminals and 11' in line unit 5 differ, on the one hand, in the nature in which the signalling channel data is processed and, on the other, in the data rates at their outputs to the respective device interiors (144 kb/s or 2,048 kb/s, respectively). Moreover, the wideband terminals and line unit 5 are each equipped with a terminal interface 10 ("Sw interface").So-interface units 11 and 11', as well as Sw interface units 10, are mutually interconnected one with the other by means of suitable connection lines. In addition, Figure 1 also shows a connection module 9, which permits connection, within exchange 8, of the channels coming from line termination unit 7 to the coupling facilities of the exchange.

Figure 2 shows further details of line unit 5 shown in Figure 1. Line unit 5 consists primarily of two branches designed, in principle, in an identical manner. The branch shown at the top in Figure 2 is responsible for processing the information received (from exchange 8), the bottom branch for processing the information to be sent to exchange 8. Line terminal 6 thus comprises a receiving portion 16 and a sending portion 20. So-interface unit 11' also comprises a sending portion 13 and a receiving portion 14. In the same manner, Sw-interface unit 10 comprises a sending portion 17 and a receiving portion 18. It should be noted that in both the So- and the Sw-interface units, the sending portion is located in the receiving branch of line unit 5 and the receiving portion in the sending branch of line unit 5 in each case.Located between receiving portion 16 of termination unit 6 and sending portions 13 and 17 of the So- or Sw-interface units is a branching unit 15. Similarly, a combining unit 19 is located between receiving portions 14 and 18 of the So- and Sw-interface units and sending portion 20 of line termination unit 6.

Line termination unit 6, with its receiving portions 16 and its sending portion 20, satisfies all of the other transmission functions, such as amplification, equalisation, code conversion and signal recovery. like identical line termination unit 7 of exchange 8, it can be designed in the manner that is customary for PCM 30 systems. Terminal interface unit 10 for wideband links, with its sending portion 17 and its receiving portion 18 has, in principle, the same tasks as line termination unit 6.

However the distances to the connected terminals are generally significantly shorter than the distance to the exchange. Moreover, it is necessary for terminal interface unit 10 to be designed in such a manner as to permit a plurality of terminals to be connected simultaneously. This not only influences the signal and power levels at the output, but also the code that is employed, for example. Preferably, an AMI code is employed, which permits simple superimposition of the signals coming from the various terminals. The data received by receiving portion 16 of line termination unit 6 is advanced without alteration to sending portion 17 of Sw-interface unit 10 via branching unit 15.In branching unit 15, the data of those two base channels which should also be available for the narrowband terminals and the signalling data of the 64 kb/s channel containing the control channel is simultaneously advanced to sending portion 13 of So-interface unit 11'. This data is advanced to sending portion 13 of So-interface unit 11' in temporal coincidence with data advance to sending portion 1 7 of Sw-interface unit 10, with the data not intended for sending portion 13 of Sointerface unit 11' being deleted. In sending portion 13 of So-interface unit 11', a 192 kb/s data stream is gated out of the incoming 2,048 kb/s data stream and converted in accordance with Guideline IR230, which was referred to at the outset.

In the opposite direction, i.e. in the direction from the terminals to the exchange, this procedure is, for the most part, reversed. The data arriving at receiving portion 14 of Sointerface unit 11' at a rate of 1 92 kb/s (2 base channels, 1 control channel) is converted to a 2,048 kb/sdata stream, with the data in excess of 144 kb/s having no contents (zeroes). The content and temporal sequence of the data arriving at the input of receiving portion 18 of Sw-interface unit 10 at a rate of 2,048 kb/s are advanced without alteration to combining unit 19. As already mentioned above, receiving portion 18 is part of the transmission path. Thus, there are 2 data streams, each having a rate of 2,048 kb/s, at the two inputs of combining unit 19, which are to be provided to sending portion 20 of line termination unit 6 in the form of one single data stream, also having a rate of 2,048 kb/s. For this purpose, it is first necessary to synchronise the two data streams one relative to the other in combining unit 19. Each of the two data streams comprises 32 channels, each having a rate of 64 kb/s. Of these 32 channels, the channel employed cylinder 30 that receives a brake piston (not shown). The limb 28 is succeeded by a bridge portion 34 extending substantially in axial and circumferential directions which bridge portion 34 straddles the brake disc 8. On the other side the bridge portion 34 merges into a further (second) radially-extending limb 36.Beside the brake cylinder 30 in the limb 28, there is provided an axially extending bore 38 in which the guide bolt 22 is fixed which also extends axially. As already outlined above, the guide bolt 22, with its free end pojecting from the bore 38, engages the bore 14 of the brake carrier arm 10 and is axially slidable therein.

The diameters of the guide bolt 22 and of the bore 14 are harmonised with each other in such a manner that the guide bolt 22 forms a fixed bearing with the bore 14. The free end of the guide pin 24 secured in the brake carrier arm 10 penetrates through a bore 26 which is provided in the brake caliper 20 on the other side of the brake cylinder 30. In this context, the guide pin 24 is of smaller diameter than the bore 16 so that a circular ringshaped gap 42 is formed between the guide pin 24 and the bore 26 and the guide pin 24 is radially and tangentially movable in the said gap. For damping of these movements, an elastic sleeve 44 which may, for example, be made of rubber is inserted in the bore 26 located in the brke caliper 20.The elastic sleeve 44 has substantially cylindrical shape and is formed at its external circumfernece with an annular protuberance 46 which engages a correspondingly shaped annular groove 48 in the bore 26 so that the elastic sleeve 44 is retained in the bore 26.

Thanks to the arrangement described of the device, there are particular transmission requirements in the case of the 2,048 kb/s data rate between Sw-interface units 10. The propagation delay problems between Sw-interface units 10 can be mitigated if they are not interconnected by means of busses, but by means of radial lines of equidistant length. An alternative of this nature is illustrated in Figure 4.

In the special case in which, as illustrated in Figure 5, only one single wideband terminal 2 is connected, there are no problems with re spect to different propagation delays. In the alternative according to Figure 6, Sw-interface units 10 of wideband terminals 2, 3 and 4 and of line unit 5 are interconnected by means of a loop. This alternative largely avoids transmission difficulties. In the case of this alternative, combining unit 19 in line unit 5 is, as explained above, designed in such a man ner as to permit it to switch between chan nels from So-interface unit 11' and the corre sponding channels from Sw-interface unit 10.

It satisfies the additional function of suppress ing undesired information contained in the channels that are not used by the wideband terminals at the input of line unit 5. The alter native according to Figure 7 corresponds largely to the alternative according to Figure 3.

However, in this case, the synchronisation characters sent by a frame synchronisation generator 21 arranged at the end of the bus are employed for synchronisation of the data to be sent from the wideband terminals, instead of the synchronisation characters sent by line unit 5.

When a call attempt is made from one of the subscriber's wideband terminals, the centre first checks whether the number of base channels required therefor is free. The call attempt, itself, is handled via the control channel. If a sufficient number of base channels is free, the required channels are assigned to the requesting wideband terminal via the control channel. In the case of a call attempt coming from another subscriber, the centre first checks whether a suitable terminal and the required number of base channels are free. The connection is then also established via the control channel. During the subsequent connection, the selected wideband terminal receives and sends on the assigned channels.

The narrowband terminal connections are handled exclusively via ISDN terminal interface units 11 and 11', in a known manner.

The standardised "D-channel protocol" is utilised for signalling purposes. Access to the control channel by narrowband and wideband terminals is controlled via layer 1 of the SO interface.

Claims (10)

1. An arrangement for connecting a subscriber's terminals to an exchange via a bidirectional time-division multiplex link containing at least one voice channel, which can also be employed for data transmission, and a control channel, characterised in that the content of the voice channel and the content of the control channel are transmitted in a time-division multiplex frame over the time-division multiplex link, the time-division multiplex frame also being able to transmit the contents of a plurality of further voice channels; in that there is a line unit (5) at the subscriber, in that the line unit (5) has a first interface unit (6) on the side facing the exchange (8), via which the entire contents of the time-division multiplex frame are transmitted, in that the line unit (5) has a second interface unit (11') and a third interface unit (10) on the side facing the terminals (1, 2, 3, 4), in that the control channel and at least one voice channel are transferred via the second interface unit (11') and at least the remaining voice channels are transferred via the third interface unit (10), in that a portion of the terminals (1) is connected only with the second interface unit (11'), and in that each of the remaining terminals (2, 3, 4) is connected both with the second interface unit (11') and with the third interface unit (10).

2. An arrangement according to claim 1, characterised in that the output of the second interface unit (11') is a standardised SO interface having two base channels (B channels), which can be employed as voice or data channels, and one signalling channel (D channel), which is employed as a control channel.

3. An arrangement according to claim 1 or 2, characterised in that 32 identical channels are transferred in each direction via the first interface unit (6), in that one channel thereof is employed for synchronisation, in that a further channel contains the control channel, and in that the other 30 channels are used for the transmission of voice and data.

4. An arrangement according to any one of claims 1 to 3, characterised in that the third interface unit (10) is designed in such a manner that it can handle the same information as the first interface unit (6).

5. An arrangement according to claim 4, characterised in that in the line unit (5), the information coming from the second interface unit (11') and the information coming from the third interface unit (10) are combined in the correct temporal sequence.

6. An arrangement according to claim 4, characterised in that the line unit (5) contains changeover switches which permit either the content of the voice channels arriving via the second interface unit (11') or the content of an equal number of voice channels arriving via the third interface (10) to be routed through the first interface unit (6) together with the remainder of the voice channels arriving via the third interface unit (10).

7. A method of temporarily assigning channels to a subscriber's terminals which are connected to an arrangement according to any one of claims 1 to v6, characterised in that the assignment of the channels is performed from the exchange (8) via the control channel and the second interface unit (11'), and in that each of those terminals (2, 3, 4) which are also connected with the third interface unit (10) can be assigned a plurality or all of the voice channels.

8. A method according to claim 7, characterised in that the standardised D-channel protocol is utilised for assignment of the channels, and in that access to the D channel is controlled via layer 1 of the SO interface.

9. A method according to claim 7 or 8, characterised in that further control and monitoring information is transferred via the channel containing the control channel.

10. An arrangement for connecting a subscriber's terminals to an exchange substantially as described with reference to the accompanying drawings.