GB2163628A - Facility for transmitting generally accessible information - Google Patents

Abstract

In the centre of a facility for transmitting generally accessible information, the available stereophonic radio broadcasts or other generally accessible information are combined by a programme multiplexer 40 into a time-division-multiplex signal with programme-assigned time slots, and distributed over a first programme bus 44 to a plurality of time stages 45. From this signal, each time stage 45 forms a new time-division-multiplex signal with subscriber-assigned time slots, which is distributed to subscriber facilities via a second programme bus 46 associated with the time stage 45. To control the time stages 45, and thus to select the programmes, each subscriber is connected with the centre via a backward channel 7. <IMAGE>

Description

SPECIFICATION Facility for transmitting generally accessible information This invention relates to a facility for transmitting generally accessible information containing different programmes (such as ster eophonic broadcasts, for example) from a centre to a plurality of attached subscribers and having a multiplex facility in the centre, through which the information is applied to a programme bus in a time-division-multiplex mode, with each programme being assigned a permanent time slot within a time frame on the programme bus.

A facility of this nature was described in 1983 in Vol. 36 of NTZ (No. 7, pages 428 to 433) by K. Kneisel in the article entitled "Bigfon-Vergleich der verschiedenen firmenindividu ellen Systemloesungen". In Table 3, in the column headed "SEL", the data of a system are shown in which two ISDN channels, 15 stereophonic sound programmes and two te levision channels per subscriber can be transmitted from a centre to a plurality of at tached subscribers. The 15 stereophonic sound channels are initially advanced to a pro gramme bus in time-division multiplex, with a permanent time slot within a time frame on the programme bus being assigned to each programme. The resulting data stream is then combined in a multiframe with the data streams coming from the other services (ISDN, television) and transmitted to the subscriber in this manner.

Since no subscriber would listen to 15 ster eophonic sound broadcasts simultaneously, this system undoubtedly transmits more infor mation than necessary. Since, on the one hand, it is impossible to transmit an unlimited volume of information, even with the most modern technologies, and, on the other, there is a very strong desire for introduction of the most varied services, an approach of this na ture is uneconomical. Each subscriber should therefore be provided with only the volume of information he actually needs. in the same ar ticle, a system is presented in the column headed "Siemens", with which the subscriber can use a backward channel to select up to four programmes, which are then provided to him by means of a switching facility.In the case of switching facilities for radio or televi sion programmes, etc., as opposed to tele phone switching facilities, it cannot be as sumed that only a portion of the attached subscribers will be utilising the switching facil ity at any given point in time. On the contrary, the switching facility must be equipped in such a manner that each subscriber can be connected with any programme source at any time. This necessitates a sophisticated switch ing matrix.

According to the invention in its broadest aspect, a facility for transmitting generally accessible information containing different programmes (such as stereophonic broadcasts, for example) from a centre to a plurality of attached subscribers and having a multiplex facility in the centre, through which the information is applied to a programme bus in a timedivision-multiplex mode, with each programme being assigned a permanent time slot within a time frame on the programme bus, is characterised in that a plurality of time stages is connected to the programme bus, a second programme bus is connected to the output of each time stage, a plurality of subscribers is connected to each of the second programme buses, at least one permanent time slot within a time frame on the corresponding second programme bus is assigned to each subscriber, in that each subscriber is connected with the centre via a backward channel, each time stage is connected to a control unit, which assigns the time slots on each of the second programme buses to the time slots on the first programme bus in accordance with the programme wishes of the subscribers transmitted on the backward channels, and only those programmes selected by each subscriber are transmitted to him via a forward channel.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a portion of a broadband integrated-services system having means according to the present invention for transmitting stereophonic broadcasts.

Figure 2 shows a time frame for the system according to Figure 1.

Figure 3 shows the centre for a system according to Figure 1 in greater detail.

Figure 4 shows the temporal sequence of data at three points of the centre according to Figure 3.

Figure 5 shows details of the centre according to Figure 3.

Figures 6 to 8 show modifications of the practical example according to Figures 3 to 5.

On the basis of Figure 1, the entire integrated-services broadband system will now be briefly described. The system comprises a centre 1, a plurality of transmission systems 2 and a plurality of subscribers 3.

Centre 1 contains n stereophonic sound sources 1 1a to 1 in, which can output, for example, radio broadcasts, broadcasts from a local studio or stereophonic broadcasts received via cable, as well as monophonic broadcasts. Those stereophonic sound sources 11 a to 11 m which output an analogue output signal are followed by an analogue-digital converter 12a to 12m. In the case of stereophonic sound sources which already output digitalised output signals, it might be necessary to substitute a code converter for an analogue-digital converter. The digital or digitalised information streams coming from stereophonic sound sources 11 a to 11 n are advanced to a stereophonic sound distribution and switching facility 4.In addition, supplementary information, e.g. transmitter and station identification for broadcasts coming from stereophonic sound sources 1 11, is also provided to stereophonic sound distribution and switching facility 4 via supplementary inputs 41. Moreover, stereophonic sound distribution and switching facility 4 also has a control input 42, which is connected with the output of a control unit 13. A services multiplexer 5 is provided in centre 1 for each subscriber 3 attached to centre 1. A separate output of stereophonic sound distribution and switching facility 4 is assigned to each services multiplexer 5. Further inputs of each services multiplexer 5 are connected with outputs of further facilities 51, via which the respective subscriber is attached to other services.

Via a control line 131, further facilities 51 are connected with a backward channel 7 coming from subscriber 3 via control unit 13.

Transmission system 2 provides a forward channel 6 and the above-mentioned backward channel 7 for each subscriber 3.

Each subscriber 3 has a services demultiplexer 31. Services demultiplexer 31 re-separates one from the other the signals belonging to the various services, which were combined one with the other in corresponding services multiplexer 5 in centre 1. Attached to the outputs of services demultiplexer 31 are two digital-analogue converters 32a and 32b, as well as further facilities 34 for the further services.

The outputs of digital-analogue converters 32a and 32b are connected with inputs of stereophonic sound reproduction units 33a and 33b.

The stereophonic sound programme to be reproduced are selected by means of signalisation via backward channel 7. Further facilities 34 are also connected with backward channel 7.

The time frame which is formed in each services multiplexer 5 from the information streams appearing at its inputs will now be briefly explained on the basis of Figure 2.

However reference should first be made to the fact that the term "multiplexer" can have both a narrowly defined, as well as a broadly defined, meaning. The narrowly defined meaning refers to a component which permits any input selected from a plurality of inputs to be switched through to the single output. A multiplexer in its broadly defined meaning refers, in addition, to components which, for example, are employed for buffering the input data, for re-ordering this data and for control purposes. The same also applies analogously with respect to the term "demultiplexer",.

Multiplexers and demultiplexers which generate and further process, respectively, time frames of the type shown in Figure 2 are units of more complex design. As an example of the different employment of these two terms, reference is made to an article appearing on pages 251 to 258 of "Elektrisches Nachrichtenwesen" in 1983 (Vol. 57, No. 3).

The time frame in accordance with Figure 2 comprises 16 identical periods of time, shown in the form of lines in Figure 2. Every 4 sequential periods of time form a subframe.

Each period of time contains 68 sequential data words. In the figure, these words are illustrated in the form of columns, and will be called by this name hereinafter. Columns 3 to 17, 20 to 34, 37 to 51 and 54 to 68 are reserved for transmission of a television channel. Columns 18 and 19 contain 2 audio programmes belonging thereto, each in stereo.

Columns 35 and 36 are reserved for transmission of the stereophonic sound programmes coming from stereophonic sound distribution and switching facility 4. Columns 52 and 53 are reserved for transmission of an information stream coming from a PCM 30 system.

Transmission of 8 ISDN channels ISDN 1 to ISDN 8 is possible in columns 1 and 2. Moreover, data words for frame synchronisation, S1, for subframe synchronisation, S2, for a service channel, SC, as well as for additional information pertaining to picture transmission, AIP, and for additional information pertaining to stereophonic sound transmission, AR1 and AR2, are transmitted here as well.

Stereophonic sound distribution and switching facility 4 will now be described in more detail on the basis of Figure 3, in which stereophonic sound distribution and switching facility 4 is illustrated together with above-described analogue digital converters 12a to 12m, control unit 13, services multiplexer 5, further facilities 51, forward channel 6 and backward channel 7. Each analogue-digital converter 12a to 12m, as well as (unillustrated) stereophonic sound sources 11 m + 1 to 11 n with digital output, is followed by a multiplexer 43a to 43n, thereby permitting additional supplementary information to be added via above-mentioned supplementary inputs 41.

The outputs of multiplexers 43a to 43n lead to inputs of a programme multiplexer 40.

Moreover, the outputs of multiplexers 43a to 43n are also connected with inputs of a first synchroniser 471. This first synchroniser identifies the beginnings of the data words at the outputs of individual multiplexers 43a to 43n and can thus influence programme multiplexer 40 via a frame generator 472 and a programme control unit 401 contained in the programme multiplexer. The output of programme multiplexer 40 is connected with a first programme bus 44. All programmes coming from stereophonic sound sources 1 1a to 1 1n are transmitted on first programme bus 44 in time-division multiplex, with one time slot being permanently assigned to each stereophonic sound sources 1 1a to 1 1n, and thus to each programme.

Multiplexers 43a to 43n, programme multiplexer 40 with its programme control unit 401, first synchroniser 471 and frame generator 472 are each shown here as individual units; these units co-operate very closely, so that different distribution is readily possible.

A plurality of time stages 45 is attached to first programme bus 44. In Figure 3, only one of these time stages 45a is shown, with its connections. A further time stage 45b is indicated by means of dashed lines. Reference to further time stages is indicated by means of further outgoing lines from first programme bus 44. In addition, a second synchroniser 473 is attached to first programme bus 44.

Control unit 13 is now synchronised by means of second synchroniser 473 and controls attached time stages 45 as a function of the programme requests actuated by means of the attached subscribers via their backward channels 7. A second programme bus 46 is attached at the output of each time stage 45. A plurality of subscribers is attached to each of the second programme buses 46 by means of the above-described, subscriber-assigned services multiplexers 5.

Two time slots are permanently assigned to each subscriber attached to each second programme bus 46. Each time stage 45 therefore converts the programme-assigned time slots on first programme bus 44 to subscriber-assigned time slots arranged on corresponding second programme bus 46. The number of time slots on first programme bus 44 is entirely independent of the number of time slots on second programme bus 46, as a plurality of subscribers can hear the same programme simultaneously, on the one hand, and individual programmes might not be selected by any of the attached subscribers, on the other.

Thus, a very high degree of flexibility is ensured. It is also possible to assign to each time stage 45 its own second synchroniser 473 and its own control unit 13 or to combine the time stages into groups. Thus, it is also possible to provide relatively distant spatial separation one from the other between individual time stages 45 and between time stages 45 and programme multiplexer 40, and thus stereophonic sound sources 11, as well.

Time stages 45, for example, can be arranged on the lower network level of an integratedservices public network, while programme multiplexer 40 is arranged on a higher network level. Because of the subscriber-assigned re-ordering of the time slots in time stage 45 between first programme bus 44 and subscriber-assigned services multiplexer 5, only a minimum of sophistication is necessary in services multiplexer 5 for selection of the desired programmes. To accomplish this, a permanent subscriber-assigned address is stipulated for each services multiplexer 5 via address inputs 52, with the address representing the location of the corresponding time slots of second programme bus 46. As a result of interposed time stage 45, the facilities required for programme selection need not be provided individually for each subscriber.

The data flow to various locations within centre 1 will now be described on the basis of Figure 4. The first line shows the data flow to an input of programme multiplexer 40. The data flows to the other inputs are, in principle, identical. In addition to having different contents, the data flows differ in that there is mutual time displacement between them. Each of these data flows comprises a sequence of stereophonic sound data words 81. The root of each stereophonic sound data word 81 is the actual stereophonic sound data portion 811, which originates in corresponding analogue-digital converter 1 2a to 1 2m or in stereophonic sound source 11m+1 to 11n.In the case of the present invention, the manner in which the content of the two stereophonic sound channels is contained in the respective stereophonic sound data portion is irrelevant.

A supplementary data portion 812 is attached to each stereophonic sound data portion 811, and each stereophonic sound data portion 811 is preceded by a word synchronisation portion 813. Assembly of a stereophonic sound data word 81 from stereophonic sound data portion 811, supplementary data portion 812 and word synchronisation portion 813 is performed in corresponding multiplexer 43a to 43n. The second line in Figure 4 shows the data flow on first programme bus 44. Here, stereophonic sound data words 81 assigned to the various stereophonic sound programmes are grouped together in frames. The beginning of a frame is denoted by means of a frame synchronisation word 821, followed by stereophonic sound data words 822a to 822n, whose contents coincide with sterophonic sound data words 81. Thus, a permanent temporal location within the frame is assigned to each programme.The third line shows the data flow on second programme bus 46. Here, too, each frame again begins with a frame synchronisation word 831, whose contents coincide with frame synchronisation word 821. This is followed by a number of stereophonic data word pairs 832, whose quantity k coincides with the quantity of subscribers connected or connectable to second programme bus 46. Shown here is first data word pair 832,1a and 832,1b, which contains the data of the second programme and the fifth programme, a further data word pair 832,ia and 832,ib, which contains the data of the nth programme and the twenty-fifth programme, and last data word pair 832,ka and 832,kb, which contains the data of the fifth programme and the third programme. The two stereo data words of a data word pair are assigned to stereophonic sound reproduction units 33a and 33b of respective subscriber 3.In accordance with the wishes of the attached subscribers, it is possible for individual data words to be present several times on second programme bus 46.

The design and function of the stereophonic sound input unit of a services multiplexer 5 will now be described on the basis of Figure 5. The input of a third synchroniser 53, which, like first synchroniser 471, responds to word synchronisation portion 813 contained in the stereophonic data word, is connected to second programme bus 46. Third synchroniser 53 is followed by a frequency divider 54, which divides by a number that is equal to the number of sterophonic sound programmes that can be received by a subscriber; i.e. by two in this example. The output of frequency divider 54 is connected with the clock input of a counter 55. The reset inputs of counter 55 and frequency divider 54 are connected with the output of a fourth synchroniser 56, which provides an output pulse at the beginning of a frame on second programme bus 46. Counter 55 thus counts stereophonic data word pairs 832.A comparator 57 compares the count of counter 55 with the permanent subscriber address assigned to respective services multiplexer 5 that is present at its address inputs 52. Frequency divider 54 can be viewed as being the last portion of counter 55, which is not included in the comparison. If there is coincidence between the count in counter 55 and the address at address inputs 52, the output signal from comparator 57 opens a gate 58, thereby connecting second programme bus 46 with the data input of a memory 59 having two memory locations 59a and 59b. The output signal from comparator 57 simultaneously enables memory 59 via an enable input EN, so that the precise stereophonic data word pair 832 intended for the attached subscriber is written into memory 59. The write-in procedure, itself, is initiated by means of the system clock pulse T.

Changeover between memory locations 59a and 59b is initiated by means of the output pulse from third synchroniser 53, while memory 59 is returned to its home position by means of the output signal from fourth synchroniser 56, thereby making the stereophonic sound data available for further processing in services multiplexer 5. The word synchronisation portion contained in each stereophonic data word is not stored in memory 59.

Figures 6 to 8 show a modification of the practical example described on the basis of Figures 3 to 5. This practical example differs from that already described in the nature in which the individual stages are synchronised one with the other. in the above-described example, the required clock pulses are generated from the data flow, itself, where they are needed. For this purpose, the data flow contains word synchronisation portions 813, frame synchronisation words 821 and frame synchronisation words 831. In the present example, on the contrary, the required clock pulse signals are advanced via different paths.

Figure 6, which corresponds largely to Figure 3, first shows analogue-digital converters 1 2a to 1 2m, multiplexers 43'a to 43'n with supplementary inputs 41', a programme multiplexer 40' with a programme control unit 401', a first programme bus 44', a time stage 45'a, a control unit 13', a second programme bus 46', a services multiplexer 5' with further facilities 51 and address inputs 52, as well as forward channel 6 and backward channel 7.

The above-indicated facilities coincide either entirely (identical reference numerals)or largely (primed reference numerals)with the corresponding facilities in Figure 3. In addition, there are also word clock lines 121a to 121 m, which lead from analogue-digital converters 1 2a to 1 2m to programme control unit 401' and word clock lines 121 m + 1 to 121n, which lead from digital stereophonic sound sources 1 1m+ 1 to 1 1n to programme control unit 401' and which advance the word clock pulses belonging to the individual stereophonic sound programmes to programme control unit 401'. A first word clock bus 44a and a first frame clock bus 44b are assigned to first programme bus 44'.A second word clock bus 46a and a second frame clock bus 46b are assigned to second programme buses 46'.

Figure 7 shows the data flows that are different from those shown in Figure 4. Each stereophonic data word 81' now comprises only a stereophonic sound data portion 811 and a supplementary data portion 812. Instead of word synchronisation portion 813, a separate word clock signal 814 is now transmitted on corresponding word clock line 121. Instead of frame synchronisation word 821, a frame clock signal 823 is now transmitted on first frame clock bus 44b, in addition to first programme bus 44'. The word clock signal distributed on first word clock bus 44a is not shown here. Correspondingly, a frame clock signal 833 is distributed on second frame clock bus 46b instead of frame synchronisation word 831. While frame clock signals 823 and 833 have the same temporal sequence, they can be phase-shifted one relative to the other.

When word clock pulse and frame clock pulse are advanced via the corresponding buses, it is obvious, as shown by Figure 8, that services multiplexers 5 do not require any third synchronisers 53 or fourth synchronisers 56. Otherwise, their design is identical to the services multiplexers described above on the basis of Figure 5.

It is also possible to provide mixed application of the two types of synchronisation described on the basis of Figures 3 to 5, on the one hand, and 6 to 8, on the other. For example, synchronisation of time stages 45 with programme multiplexer 40, especially if they are spatially distant one from the other, can be performed in accordance with the first practical example. Synchronisation between a time stage 45'a and services multiplexers 5' attached thereto can be performed independently therefrom, in accordance with the second practical example.

Claims (6)

1. A facility for transmitting generally accessible information containing different programmes (such as stereophonic broadcasts, for example) from a centre to a plurality of attached subscribers and having a multiplex facility in the centre, through which the information is applied to a programme bus in a timedivision-multiplex mode, with each programme being assigned a permanent time slot within a time frame on the programme bus, characterised in that a plurality of time stages (45a, b) is connected to the programme bus (44), a second programme bus (46) is connected to the output of each time stage (45,a b), a plurality of subscribers (3) is connected to each of the second programme buses (46), at least one permanent time slot within a time frame (46) on the corresponding second programme bus is assigned to each subscriber (3), each subscriber (3) is connected with the centre via a backward channel (7), each time stage (45a, b) is connected to a control unit (13), which assigns the time slots on each of the second programme buses (46) to the time slots on the first programme bus (44) in accordance with the programme wishes of the subscribers (3) transmitted on the backward channels (7), and only those programmes selected by each subscriber (3) are transmitted to him via a forward channel (6).

2. A facility according to claim 1, characterised in that there is one services multiplexer (5) in the centre (1) for each subscriber (3), which combines the generally accessible information selected by the subscriber (3) together with other information (e.g. telephone, television) intended for this subscriber (3) for timedivision-multiplex transmission, and there is a services demultiplexer (31) at each subscriber (3), which re-separates one from the other the information intended for this subscriber (3) again.

3. A facility according to claim 2, characterised in that the services multiplexer (5) contains a counter (54, 55), which counts the time slots within the time frames distributed on the second programme bus (46), and the services multiplexer (5) further contains a comparator (57), which identifies the counts assigned to the subscriber (3) and causes a memory (59) to accept the contents of the respective time slot (stereophonic data word 832).

4. A facility according to any one of claims 1 to 3, characterised in that there are units (43, 471, 472, 473, 53, 56) which add synchronisation characters (813, 821, 831) to the individual information and the time frames or which identify them.

5. A facility according to any one of claims 1 to 4, characterised in that the centre (1) contains additional transmission paths (121, 44a, 44b, 46a, 46b) which serve to transmit synchronisation characters (814, 823, 833).

6. A transmitting facility substantially as described with reference to the accompanying drawings.