DE4428606A1 - Encoded signal radio transmission method e.g. for local television signal - Google Patents

Abstract

The method involves modulating a carrier with signals of a number of digital channels. The modulated signals are received by intermediate stations which decode the signals and feed them to receivers. Signals are transmitted in at least one of the channels to the intermediate stations. These signals are not tuned to the receiver of at least one of the intermediate stations. The untuned signals are replaced in the station(s) in question by signals which are tuned to the receiver of this station. The untuned signals may be test card-type signals. The digital channels which contain the untuned signals have transmission capacity for one or more video signals and/or audio signals and/or data signals.

Description

The invention relates to a method and an arrangement for Broadcast transmission of coded signals, one Carrier modulated with signals from several logical channels and is received by intermediate stations which receive the signals forward to recipients after recoding.

TV and radio broadcasting are currently mainly analog transmission methods in use, such as the PAL method with residual sideband amplitude modulation or stereo FM method. Digital transmissions form in this area an exception. Especially the extremely high one So far, bandwidth requirements for digital video signals have existed a general introduction of digital Transmission method in television broadcasting prevented.

Through modern procedures to reduce the data rate of Video signals are prerequisites for a digital one Given television broadcasting, which then also digital radio and includes digital data transmission. Especially a multiplex method for the transmission of  data-reduced signals as part of international Standardization organization ISO from a working group MPEG (Motion picture experts group) created with which depending on the data reduction rate between four high-quality up to more than 20 lower quality television programs on one Carrier, that is, via a conventional Transmission channel, can be transmitted. The Multiplexing is MPEG-2 Packet multiplex method in which a transport package is a Has a length of 188 bytes, of which 184 bytes are user data. Detailed information on the MPEG-2 process can be found in the Publications ISO / IEC 13818 - 1 to 3.

An initially intended application of the multiplex method MPEG-2 consists of transmission via satellite or Cables to so-called cable head stations, of which the received signals are fed into broadband cable networks and be distributed to the recipients. A terrestrial However, transmission to the cable head-ends is included not excluded. In the cable head-end stations a transparent implementation of the MPEG-2 multiplex signal from used up to the cable head-end station Modulation methods, for example QPSK modulation, into the modulation method provided for the cable network, for example a 64-stage Quadrature amplitude modulation (64-QAM).

This requires considerable technical effort, if local programs are inserted in the multiplex signal should be. This considerable effort exists mainly in the implementation at one Re-multiplex function. Problems also arise when in that received from a cable headend MPEG-2 multiplex signals a program contains what For example, not for reasons of copyright Receivers of this cable headend are forwarded  should.

The object of the invention is to provide a method which in a simple way, in intermediate stations, especially cable head stations, one or more in one Hide multiplexed logic channels and / or a received multiplex signal further signals to add.

This object is achieved in that in at least one of the logical channels up to the Intermediate signals are transmitted that are not for the receivers of at least one of the intermediate stations are determined and that these signals in the at least one Intermediate station to be replaced by signals for the Receivers of this intermediate station are intended.

With the method according to the invention, locally generated Signals for services such as local television in the multiplex signal, especially in the MPEG-2 multiplex signal, with little technical effort be inserted. The MPEG-2 multiplex signal does not need divided into its multiplex components and then to be remultiplexed. Hiding one of the logical channels is possible in a simple manner, whereby instead of the logical channel to be hidden Placeholders or signals are to be used, which for the present useful information to each recipient.

To a temporal correlation of the different logical Channels within the MPEG-2 multiplex signal too ensure, so-called '' time stamping '' is provided Compared to a full demultiplexing function and subsequent complete remultiplex function are with the The method according to the invention does not interfere with the method time stamping is required. In addition, the  Monitoring compliance with maximum limits of the Total data stream completely.

The transmission capacity of the service to be inserted later is already in one with the method according to the invention Multiplex signal forming center occupied and at the Multiplexing included. These channels can with useful information for other intermediate stations will. According to a development of the invention However, it can also be provided that the method is not for the receivers of the at least one intermediate station certain signals are placeholder signals.

Another development of the method according to the invention is that those logical channels that are not intended for the recipient of at least one intermediate station Signals contain the transmission capacity for one or multiple video signals and / or one or more audio signals and / or have data signals.

As such, the method according to the invention is for different types of multiplex signals suitable. A special one favorable application, however, is that the transfer to the intermediate stations by QPSK modulation of the Carrier with a multiplex signal and that Multiplex signal encoded video, audio and data signals contains, the video signals according to the MPEG standard are encoded.

Already with a central multiplex unit Data channels occupied by placeholders can be in the intermediate station a description of the respective local service in the sense service information. Furthermore, with the method of the invention a replacement signal for the Case to be inserted that a service within the received MPEG-2 multiplex signals fails.  

In principle, in the method according to the invention Transmission to the intermediate station by radio, in particular Satellite, but also via cable. Also for them Forwarding of the signals from the intermediate stations to the Various transmission media are possible for recipients. An advantageous embodiment of the invention However, the procedure is that the intermediate stations Cable head-ends are. The cable head stations can Multiplex signals, in particular MPEG-2 multiplex signals from Satellite or supplied via terrestrial radio networks will.

With the currently planned digital cable channels provided that cable transmission through Quadrature amplitude modulation of the digitally available transcoded signals preferably with 64 stages. in the However, the method according to the invention can also other modulation methods for forwarding the Signals to the receivers can be used via cable.

An advantageous arrangement in an intermediate station, preferably in a cable head-end, to carry out of the method according to one of the preceding claims characterized in that the received signals over a QPSK demodulator can be fed to a channel decoder, that the output signals of the channel decoder of a device for replacing data packets that can be fed from the Channel decoder a bit clock signal and a packet clock signal are generated with which coder for local signal sources are controllable, their output signals via a multiplexer can be fed to the device for replacing data packets are, and that to the output of the device for replacement of data packets, a channel encoder and a QAM modulator for the transmission to the receivers are connected.

Embodiments of the invention are in the drawing represented with several figures and in the following Description explained in more detail. It shows:

Fig. 1 is a block diagram of an arrangement in a head station and

Fig. 2 also as a block diagram an arrangement for forming an MPEG-2 multiplex signal.

The arrangement shown in FIG. 2 is known per se and is described, for example, in the conference proceedings of the 16th annual conference of the FKTG, Nuremberg, 16th to May 20, 1994, pp. 67 ff. A so-called transport multiplexer 11 combines all the signals to be transmitted to form an MPEG-2 multiplex signal. Only two of the n inputs of the transport multiplexer 11 are shown in FIG. 2, each occupied by the output of a further multiplexer 12 , 13 . The further multiplexers 12 , 13 combine the signals belonging to a program, usually video, audio and data signals. In the case of the multiplexer 12, these are fed from inputs 14 , 15 , 16 via coders 17 , 18 , 19 and in the case of the multiplexer 13 from inputs 20 , 21 , 22 via coders 23 , 24 , 25 .

The MPEG-2 standard largely leaves open how many channels 1 to n are combined to form an MPEG-2 multiplex signal. Since the total bandwidth is limited, the greater the number of channels, the higher the data reduction - that is, the lower the quality of the signal being reproduced. The MPEG-2 multiplex signal generated by the multiplexer 11 is fed via a channel encoder 26 and a QPSK modulator 27 to an output 28 , from where it is sent to a transmitter, not shown.

The carrier-frequency MPEG-2 multiplex signal is received in the head stations and fed to an input 31 of a QPSK demodulator 32 . The demodulated MPEG-2 multiplex signal is decoded in a channel decoder 33 , at the output 34 of which the MPEG-2 multiplex signal is available in the baseband. A bit clock signal and a packet clock signal are produced in the channel decoder 33 , which can be supplied via outputs 35 , 36 coders 37 , 38 , 39 , which encode video, audio and data signals from local sources 40 , 41 , 42 . The local sources can be formed, for example, by facilities of a local television studio.

The output signals of the coders 37 , 38 , 39 are combined in a multiplexer 43 and fed to a device for replacing data packets into the MPEG-2 multiplex signal, which essentially consists of a multiplexer 44 and a control circuit 45 . At 46, this is supplied with the information as to which or which packets of the MPEG-2 multiplex signal are to be replaced. Furthermore, the control circuit 45 receives the MPEG-2 multiplex signal from which it recognizes the packets to be replaced on the basis of identification signals ID and controls the multiplexer 44 for the signals to be used for the duration of these packets.

With the signals used, the MPEG-2 multiplex signal is then fed to a channel encoder 47 and a 64-QAM modulator 48 , from whose output 49 the modulated signal can be fed into a cable network.

Claims (8)

1. A method for radio transmission of coded signals, wherein a carrier is modulated with signals from a plurality of logical channels and is received by intermediate stations which forward the signals after transcoding to receivers, characterized in that in at least one of the logical channels up to the intermediate stations Signals are transmitted which are not intended for the receivers of at least one of the intermediate stations and that these signals in the at least one intermediate station are replaced by signals which are intended for the receivers of this intermediate station. 2. The method according to claim 1, characterized in that which are not for the recipients of at least one Intermediate signals are placeholder signals. 3. The method according to any one of the preceding claims, characterized in that those logical channels, which are not for the recipients at least one Intermediate station contain certain signals that Transmission capacity for one or more video signals and / or one or more audio signals and / or data signals exhibit. 4. The method according to any one of the preceding claims, characterized in that the transmission up to the Intermediate stations by using QPSK modulation of the carrier a multiplex signal and that the multiplex signal contains encoded video audio and data signals, the  Video signals are encoded according to the MPEG standard. 5. The method according to any one of the preceding claims, characterized in that the intermediate stations Cable head-ends are. 6. The method according to claim 5, characterized in that the transmission via cable Quadrature amplitude modulation of the digitally available transcoded signals, preferably with 64 stages. 7. Arrangement in an intermediate station, preferably in a cable head station, for performing the method according to one of the preceding claims, characterized in that a bit clock signal and a packet clock signal are derived from the signals received by the intermediate station, with which locally generated signals are intended for the receivers of the intermediate station, are synchronized, and that the signals received by the intermediate station and the locally generated signals can be fed to a device ( 44 ) for replacing data packets. 8. Arrangement according to claim 7, characterized in that the received signals via a QPSK demodulator ( 32 ) can be fed to a channel decoder ( 33 ), that the output signals of the channel decoder ( 33 ) of the device ( 44 ) for replacing data packets can be supplied that A bit clock signal and a packet clock signal are generated by the channel decoder ( 33 ), with which coders ( 37 , 38 , 39 ) for local signal sources ( 40 , 41 , 42 ) can be synchronized, the output signals of which via a multiplexer ( 43 ) of the device ( 44 , 45 ) for replacing data packets, and that a channel encoder ( 47 ) and a QAM modulator ( 48 ) for transmission to the receivers are connected to the output of the device ( 44 , 45 ) for replacing data packets.