DE4428606B4 - Method and arrangement for radio transmission of coded signals - Google Patents

Abstract

Method for radio transmission of coded signals, a carrier being modulated with signals from a plurality of logical channels which form a multiplex signal and being received by intermediate stations which pass the signals on to transceivers after transcoding, 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 multiplex signal in the at least one intermediate station are replaced by signals which are intended for the receivers of this intermediate station.

Description

The invention relates to a method and an arrangement for broadcast transmission of coded signals, one carrier with signals of several logical Channels, which form a multiplex signal, modulated and from intermediate stations is received, which forwards the signals after transcoding to receivers.

In television and radio broadcasting are mainly currently analog transmission method in use, such as the PAL method with residual sideband amplitude modulation or stereo FM method. Digital transmissions form in this Area an exception. In particular, the extremely high bandwidth requirement of digital video signals has so far had a general introduction to digital transmission methods prevented on television broadcasting.

Through modern procedures to reduce the Data rate of video signals are prerequisites for one given digital television broadcasting, which then also digital radio and digital data transmission includes. In particular, a multiplex method for the transmission of data-reduced Signals within the framework of the 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 over one Carrier that means about one conventional transmission channel can be. The multiplex process MPEG-2 is a packet multiplex process, in which a transport packet has a length of 188 bytes, of which 184 bytes are user data. Find precise information about the MPEG-2 process in ISO / IEC 13818 - 1 to 3.

An initially intended application The MPEG-2 multiplexing method consists of transmission via satellite or cable so-called cable head-ends, from which the received signals fed into broadband cable networks and distributed to the receivers become. A terrestrial broadcast to the cable head stations is not excluded. In the cable head-end stations. a transparent implementation the MPEG-2 multiplex signal from each to the cable headend used modulation methods, for example QPSK modulation, in that for that Modulation method provided for cable network, for example a 64-step quadrature amplitude modulation (64-QAM).

This requires considerable technical effort if local programs are to be inserted into the multiplex signal. This considerable effort mainly consists in the implementation of a re-multiplex function. Such a procedure is for example in WO 94/14279 described. Problems also arise if a program is contained in the MPEG-2 multiplex signals received by a cable head-end station, which for copyright reasons should not be forwarded to the receivers of this cable head-end station, for example.

The object of the invention is a Specify a method that allows in a simple way in intermediate stations, in particular cable head stations, one or more in a multiplex signal logical channels included to hide and / or a received multiplex signal Add signals.

This object is achieved according to the invention solved, that in at least one of the logical channels to the intermediate stations Transmit signals that are not for the recipients at least one of the intermediate stations are determined, and that these Signals in the multiplex signal in the at least one intermediate station be replaced by signals for the receivers of this intermediate station are determined.

With the method according to the invention can locally generated signals for Services, such as local television, into the multiplex signal, especially in the MPEG-2 multiplex signal, with little technical Inserted effort become. The MPEG-2 multiplex signal does not need to be in its multiplex components divided and then to be remultiplexed. Hiding one of the logical ones channels is easily possible where instead of the logical channel to be hidden, only placeholders or signals are to be used which are useful information for the respective receiver represent.

To correlate the time different logical channels To ensure within the MPEG-2 multiplex signal, so-called "time stamping" is provided. Opposite one complete Demultiplex function and subsequent complete remultiplex function are in the process of the invention no intervention in the time stamping procedure required. Monitoring is also eliminated compliance with maximum limits of the total data stream completely.

In the method according to the invention, the transmission capacity of the service to be inserted later is already occupied in a center forming the multiplex signal and is included in the multiplex formation. These channels can be assigned useful information for other intermediate stations. According to a development of the method according to the invention, however, it can also be provided that the at least for the recipient signals specific to an intermediate station are placeholder signals.

Another development of the method according to the invention is that those are logical Channels, which are not for the recipients at least an intermediate station contain certain signals, 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 various types Suitable for multiplex signals. However, there is a particularly favorable application in that the transfer to the intermediate stations with QPSK modulation of the carrier a multiplex signal and that the multiplex signal encoded Contains video, audio and data signals, the video signals are coded according to the MPEG standard.

In from a central multiplex unit Data channels already occupied by placeholders can be in the intermediate station a description of the respective local service in the sense of a Service information inserted become. Furthermore, with the method according to the invention an equivalent signal can be used for the Case inserted be that a Service within the received MPEG-2 multiplex signal fails.

In the method according to the invention can basically the transfer to the intermediate station by radio, especially satellites, however also about Cables are made. Also for the transmission of the signals from the intermediate stations to the receivers different transmission media possible.

An advantageous embodiment of the method according to the invention however, is that the Intermediate stations are cable head stations. The cable headend can the multiplex signals, in particular MPEG-2 multiplex signals, from satellites or about terrestrial radio networks supplied become.

With the currently planned digital cable channels it is intended that the transmission via cable by quadrature amplitude modulation of the digitally available recoded signals preferably carried out with 64 stages. As part of of the method according to the invention can however, other modulation methods for forwarding the signals too the receivers via cable be used.

An advantageous arrangement in one Intermediate station, preferably in a cable head station, wherein A carrier with signals from several logical channels that form a multiplex signal form, modulated and received by the intermediate station, which forwards the signals after transcoding to receivers, whereby in at least one of the logical channels up to the intermediate station Transmit signals that are not for the recipients the intermediate station are determined and these signals in the multiplex signal in the intermediate station are replaced by signals for the receivers of this intermediate station are characterized by the fact that from the intermediate station received signals derived a bit clock signal and a packet clock signal with which locally generated signals that are intended for the receiver of the Intermediate are destined to be synchronized and that of the intermediate station received signals and the locally generated Signals of a device for replacing data packets in the multiplex signal supplied are.

It is preferably provided that the received Signals about a QPSK demodulator can be fed to a channel decoder that the output signals the channel decoder of a device for replacing data packets supplied are that of generates a bit clock signal and a packet clock signal to the channel decoder with which coder for local Signal sources are controllable, the output signals via a Multiplexers can be fed to the device for replacing data packets, and that at the output of the device for replacing data packets a channel encoder and a QAM modulator for the transfer to the recipients are connected.

Embodiments of the invention are shown in the drawing using several figures and in the description below explained. It shows:

1 a block diagram of an arrangement in a head station and

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

In the 2 The arrangement shown is known per se and is described, for example, in the conference proceedings of the 16th annual conference of the FKTG, Nuremberg, May 16-20, 1994, pp. 67 ff. A so-called transport multiplexer 11 combines all signals to be transmitted into one MPEG-2 multiplex signal. Of the n inputs of the transport multiplexer 11 are in 2 only two with the output of another multiplexer each 12 . 13 shown occupied. The other multiplexers 12 . 13 summarize the signals belonging to a program, usually video, audio and data signals. These are in the case of the multiplexer 12 of entrances 14 . 15 . 16 via coder 17 . 18 . 19 and in the case of the multiplexer 13 of entrances 20 . 21 . 22 via coder 23 . 24 . 25 fed.

The MPEG-2 standard largely leaves open how many channels 1 up to n can be combined to form an MPEG-2 multiplex signal. Since the entire 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 one from the multiplexer 11 Generated MPEG-2 multiplex signal is via a channel encoder 26 and a QPSK modulator 27 one output 28 fed from where it is directed to a transmitter, not shown.

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

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

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

Claims (8)

Method for radio transmission of coded signals, a carrier being modulated with signals from a plurality of logical channels which form a multiplex signal and being received by intermediate stations which pass the signals on to transceivers after transcoding, characterized in that in at least one of the logical channels signals are transmitted to the intermediate stations which are not intended for the receivers of at least one of the intermediate stations, and that these signals in the multiplex signal in the at least one intermediate station are replaced by signals which are intended for the receivers of this intermediate station. A method according to claim 1, characterized in that the not for the recipients signals at least one intermediate station placeholder signals are. Method according to one of the preceding claims, characterized characterized that logical ones Channels, which are not for the recipients at least an intermediate station contain certain signals, the transmission capacity for one or multiple video signals and / or one or more audio signals and / or Have data signals. Method according to one of the preceding claims, characterized characterized that the transfer to the intermediate stations with QPSK modulation of the carrier a multiplex signal and that the multiplex signal encoded Includes video audio and data signals, the video signals are coded according to the MPEG standard. Method according to one of the preceding claims, characterized characterized that the Intermediate stations are cable head stations. A method according to claim 5, characterized in that transmission over cable by quadrature amplitude modulation of the digitally available transcoded signals, preferably with 64 stages. Arrangement in an intermediate station, preferably in a cable head-end station, a carrier being modulated with signals from a plurality of logical channels which form a multiplex signal and received by the intermediate station, which forwards the signals after transcoding to receivers, in at least one of the logical ones Channels are transmitted to the intermediate station signals which are not intended for the receivers of the intermediate station and which signals in the multiplex signal in the intermediate station are replaced by signals which are intended for the receivers of this intermediate station, characterized in that from the intermediate station received signals are derived a bit clock signal and a packet clock signal with which locally generated signals intended for the receivers of the intermediate station are synchronized, and that the signals received by the intermediate station and the locally generated signals of a device ( 44 ) can be fed to replace data packets in the multiplex signal. Arrangement according to claim 7, characterized in that the received signals via a QPSK demodulator ( 32 ) a channel decoder ( 33 ) that the output signals of the channel decoder ( 33 ) the facility ( 44 ) to replace data packets that can be supplied by the channel decoder ( 33 ) a bit clock signal and a packet clock signal are generated, with which encoders ( 37 . 38 . 39 ) for local signal sources ( 40 . 41 . 42 ) whose output signals can be synchronized via a multiplexer ( 43 ) the facility ( 44 . 45 ) can be fed to replace data packets, and that at the output of the device ( 44 . 45 ) a channel encoder to replace data packets ( 47 ) and a QAM modulator ( 48 ) for transmission to the recipients are closed.