WO2001056201A2

WO2001056201A2 - Ground station for use in radio transmission via satellite and method for generating a data stream that comprises a main program and an additional program

Info

Publication number: WO2001056201A2
Application number: PCT/EP2001/000876
Authority: WO
Inventors: Rainer Perthold; Heinz GERHÄUSER
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2000-01-26
Filing date: 2001-01-26
Publication date: 2001-08-02
Also published as: WO2001056201A3; AU2001237348A1

Abstract

The invention relates to a ground station (10) for generating a data stream (20) that comprises a main program and an additional program. Said ground station comprises a memory (12) that stores the additional program, which is for example a commercial, while the main program is a radio program produced in a sound studio. The ground station further comprises a multiplexer (14) with a first input (14a) for receiving the main program and a second input (14b) for receiving the additional program from the memory, and with an output. A control device (16) for controlling the multiplexer (14) switches, at a first interval, an output (14c) of the multiplexer (14) from the first input to the second input and at a second interval from the second input back to the first input, thereby inserting the additional program into the main program between the first interval and the second interval. The ground station further comprises a transmitter device (18) that is connected to the output of the multiplexer (14) on the input side and that is connected to a transmitting antenna (22) on the output side so as to provide the transmitting antenna with the data stream (20). The inventive method provides a simple means for inserting commercials into the data stream without requiring special devices in the sound studio. The ground station can easily detect at which intervals commercials were inserted. The commercials can be exchanged or updated via an optional remote maintenance device of the ground station with little effort.

Description

Ground station and method for generating a data stream with a main program and an additional program

description

The present invention relates to satellite-based broadcasting systems and in particular to a ground station for generating a data stream, which has a main program and an additional program. The main program is, for example, a radio program, while the additional program includes, for example, commercials keyed into the radio program.

For some time now, efforts have been made by "WorldSpace" to set up a satellite-based broadcasting system in North America and in other countries. The basic supply of the rural areas takes place via satellites. In densely built-up areas in which the satellites cannot be received seamlessly, terrestrial "re-roadcasting" is also used. H. the satellite signal is implemented by terrestrial receivers and re-transmitted via terrestrial transmitters.

The satellite-based radio system is designed to distribute a large number of individual radio programs across the board. Source coding in accordance with ISO MPEG Layer 3 is used for the audio signal that is generated in a recording studio. The audio signal and optionally data signals are then combined with auxiliary information in a ground station to form a so-called "broadcast channel". A broadcast channel can also include several audio and data signals, wherein several audio signals can include the same main program in several languages, for example.

For error protection, which is also referred to as FEC (FEC = Forward Error Correction = forward error correction) a Reed-Solomon code and a convolutional code are used at the broadcast channel level. The Viterbi algorithm, ie an algorithm that works on the principle of maximum likelihood estimation, is usually used for decoding the convolutional code. The broadcast channel is divided into several "prime rate channels" by means of a demultiplexer. The number of prime rate channels available depends on the broadcast channel data rate. A broadcast channel can have between 1 and 8 prime rate channels.

Each prime rate channel is then modulated onto its own frequency carrier. The modulated signals are superimposed and then fed to an RF output stage, which has an up-mixer, in order to convert the signal to be transmitted to an RF carrier frequency which is in the gigahertz range. The converted or highly mixed signal is then fed to a power amplifier, whereupon the amplified signal is supplied to a transmitting antenna. The transmitting antenna is used to transmit the amplified signal to a satellite. In the satellite, this signal is converted into a time-division multiplex bit stream, which is converted into an analog signal via a QPSK modulator, which is then sent directly to receivers by a transmitting antenna of the satellite, or which is sent to receiving stations in the case of terrestrial re-broadcasting which then "redistribute" the signal terrestrially.

The distance from the ground station to the satellite is called the uplink, while the distance from the satellite back to earth is called the downlink.

A worldspace ground station receives the audio signal either as an MPEG-encoded digital signal or as an uncompressed analog audio signal.

To add to the main program, ie the radio program, an additional program, for example in the form of commercials keying in, the additional program is treated as a main program in the recording studio in which the audio signal is generated. In other words, this means that the data signal that is transmitted from the recording studio to the ground station, for example by means of a dedicated line, already includes both the main program and the additional program. The insertion of advertising into a radio signal thus takes place in the recording studio.

A disadvantage of this concept is the fact that the recording studio has to deal with the keying in of advertising at all, which on the one hand entails extensive correspondence between the recording studio and the commercial manufacturer, and on the other hand also means additional expenditure on equipment for the recording studio. The keying in of advertising in the recording studio is therefore both administrative and equipment-intensive for the recording studio on the one hand and for the advertising spot manufacturer on the other.

Furthermore, for the correct accounting of the advertising time or an external program provider who only wants to key in an additional program from time to time, the recording studio must record both the length of the additional program and the time of the additional program and, in the case of additional programs from different manufacturers, which additional program is keyed in has been. This also requires a considerable administrative effort for the recording studio. Finally, it is also costly for the recording studio and involves a lot of administrative overhead to replace old additional programs with new or updated additional programs, which is particularly important when different providers of additional programs want to key their additional programs into the radio program. For normal radio programs, however, this is the normal case, since a radio station is basically interested in broadcasting commercials from many different providers, so that it is either fully or at least partially financed. The object of the present invention is to provide a ground station and a method for generating a data stream, which has a main program and an additional program, which facilitate the keying in of additional programs into a main program.

This object is achieved by a ground station according to claim 1 or by a method according to claim 8.

The present invention is based on the finding that conventional keying in of additional programs into a main program within the recording studio itself has to be abandoned. Instead, it is much easier for everyone involved to run additional programs into a main program only in the ground station, which generates the RF signal to be emitted via an antenna. Typically, almost all devices that are required for this task are located in such ground stations. According to the invention, only modifiable modifications to existing ground stations are necessary in order to achieve a simple insertion of additional programs, for example in the form of commercials, into a main program, which can be a radio program.

For this purpose, the ground station preferably has a memory for storing the additional program already in compressed form, for example as an MPEG Layer 3 data stream or as an MPEG-AAC data stream. The ground station further comprises a multiplexer with two inputs and one output, the first input being intended to receive the main program from outside the ground station, while the second input is intended to be the additional program from the memory which is installed in the ground station , to recieve. The ground station further comprises a control device for controlling the multiplexer such that the output of the multiplexer at a first point in time from the first input to the second input is switched, and at a second point in time is switched again from the second input to the first input. The ground station further comprises a transmitting device which is connected to the output of the multiplexer and which is connected on the output side to a transmitting antenna in order to feed the data stream to the transmitting antenna. In a preferred embodiment, this transmitting antenna is the terrestrial transmitting antenna, which contributes to the uplink connection from the earth to a broadcast satellite.

Advertising spots are preferably already stored in coded form in a memory of the ground station. As soon as an advertisement is then to be loaded, the multiplexer is switched over so that the main program from the recording studio or the output data of the MPEG encoder no longer appear at the output of the multiplexer, but rather the additional program coming from the memory, which has an already existing data interface of the multiplexer is fed into the same.

The advantages of the present invention are that no devices beyond the ground station are required. The recording studio does not need to be equipped accordingly, which leads to considerable savings in costs and administrative expenses.

Another advantage is that the ground station can be easily adjusted to detect which commercials have been keyed in when.

Another advantage of the present invention is that the additional program, for example in the form of commercials, can be exchanged or modified via a remote maintenance device which is already present for the ground station.

Preferred exemplary embodiments of the present invention are described below with reference to the accompanying drawings. explained in detail. Show it:

1 shows a basic block diagram of a ground station according to the invention; and

Fig. 2 is a detailed block diagram of a preferred embodiment of a WorldSpace ground station, which is adapted for the inventive concept.

1 shows a schematic block diagram of a ground station 10 according to the invention. In its most general form, the ground station comprises a memory 12 for storing the additional program. The ground station further comprises a multiplexer 14 with a first input 14a, a second input 14b and an output 14c. The multiplexer 14 further comprises a control input 14d, which is connected to a control device 16. The ground station further includes a transmitter 18 for providing a data stream at an output 20, the data stream at the output 20 being capable of being delivered to a transmitting antenna 22 which establishes the uplink connection to a satellite (not shown in Fig. 1) can. The ground station 10 further comprises an input 24 via which a main program can be fed to the multiplexer 14.

The main program, which can be a radio or television program, for example, is generated in a sound or television studio. Depending on the embodiment, the main program can consist of analog audio data. In this case the ground station comprises an MPEG encoder between the input 24 and the input 14a of the multiplexer in order to compress the analog audio signal. If the recording studio already has an MPEG encoder on the output side, then no encoder is required within the ground station 10. It should be noted that not only MPEG methods can be used to compress data, but also any other known compression algorithms. The additional program, which can be, for example, an advertising spot, is stored in the memory 12 within the ground station 10. If the additional program is already stored in compressed form, no data compressor is required between the output of the memory and the second input 14b of the multiplexer 14. In the other case, in which the additional program is stored analogously in the memory, an encoder can be provided between the output of the memory 12 and the second input 14b of the multiplexer 14. Usually the output 14c of the multiplexer is connected to the first input 14a of the multiplexer, so that the main program is continuously transmitted to the satellite. If an additional program is to be keyed into the main program, the controller 16 will control the multiplexer 14 in such a way that the main program no longer comes to the transmitting antenna, but an additional program stored in the memory 12. For this purpose, the second input 14b of the multiplexer 14 is then connected to the output 14c of the multiplexer.

If main program data is continuously supplied to the ground station 10 via the input 24, as is the case, for example, in the case of a live transmission, the main program data can simply be discarded during the time in which the additional program is keyed in.

If it is not a live transmission but a recorded program, the main program data arriving at the time the additional program is transmitted can be stored, for example, in a buffer of the multiplexer 14. Alternatively, however, the supply of the main program to the ground station can be interrupted in this interval.

In an alternative exemplary embodiment, the ground station already has a memory between the input 24 and the first input 14a of the multiplexer in order to store the entire main program data already within the ground station. store in such a way that the time of transmission from the recording studio to the ground station does not coincide with the time of radio transmission of the data stream.

2 shows a preferred exemplary embodiment of the present invention within a WorldSpace ground station, which is also referred to as a processed feeder link station. The ground station again comprises the input 24, but in contrast to the exemplary embodiment shown in FIG. 1, an MPEG encoder 30 is now present between the input 24 and the first input 14a of the multiplexer. The ground station also includes a data interface 32, which is commonly used to transmit data in addition to audio signals. This data interface 32 is used according to the invention in order to supply the additional program stored in the memory 12 to the multiplexer 14 via a data connection 34 in the event that an additional program is keyed into the main program. The multiplexer 14 is in turn controlled by the controller 16.

The multiplexer 14 further comprises a device for forming the so-called broadcast channel. In the preferred exemplary embodiment shown in FIG. 2, the transmitting device (reference number 18 in FIG. 1) comprises a demultiplexer for demultiplexing the broadcast channel and for generating the individual prime rate channels. The transmitting device further comprises a frequency division multiplex modulation device, which is denoted by the reference symbol 18a, and a downstream summator in order to supply a frequency multiplexing signal which is fed to the RF stage 18b of the transmitting device. In particular, the summed frequency multiplex signal is mixed up using a known arrangement and then amplified (HPA = High Power Amplifier) in order to be fed to the antenna 22 on the output side. The RF stage 18b of the transmitter further comprises a low noise amplifier (LNA) and an output for controlling the direction of transmission of the antenna 22. The ground station also includes a monitoring and control computer 40 which is coupled to both memory 12 and controller 16. It should be noted that in a preferred embodiment of the present invention, memory 12 and controller 16 for controlling multiplexer 14 are part of monitoring and control computer 40. Only for reasons of illustration, these elements are shown in FIG. 2 as separate devices.

The ground station enables a broadcaster to feed a program into the WorldSpace system via the satellite's on-board processor. The uplink connection to the satellite is made using frequency division multiplexing. One frequency is assigned to an elementary data channel of the WorldSpace system. Each of these channels carries user data at a rate of 16 kilobits per second and, as has been explained, is referred to as the prime rate channel. On board the satellite, the prime rate channels are converted into a time-division multiplex signal and sent to the WorldSpace receivers as a frame-synchronized signal with a frame duration of 432 ms. At the beginning of each frame, a synchronization sequence and control information are sent out. The control information contains the information that a receiver needs to process the user data, i. H. the broadcast channel to gain from the time-division multiplex signal. From the different service components belonging to one or more broadcast channels, the ground station generates the transmit signal in the form of the individual prime rate channels, which, as shown in FIG. 2, are each modulated onto their own carrier frequency ,

The audio data stream comes from the studio of the program provider. According to the invention, the commercials are already layer 3-coded on the control computer 40 or in the memory 12 of the ground station. As soon as an advertisement is to be imported, the broadcast channel multiplexer 14 reconfigured so that the output data of the MPEG encoder 30, ie the main program, is no longer sent to the satellite, but rather the commercial supplied via the data interface 32.

In a preferred embodiment of the present invention, the monitoring and control computer 40 further comprises means for logging the keying in of additional programs in order to provide information about when which commercials were introduced. This takes the cost of logging and billing off the commercials from the recording studio.

The monitoring and control computer 40 is, as represented schematically by a channel 42, from a central control point, e.g. B. the recording studio, remotely controllable. The monitoring and control computer 40 can preferably be controlled remotely in such a way that an exchange of the commercials or an update of the commercials in the memory 12 can also take place via this data connection. This makes it easy to delete old commercials or to store new commercials in a ground station.

Claims

claims

1. Ground station (10) for generating a data stream (20), which has a main program and an additional program, with the following features:

a memory (12) for storing the additional program;

a multiplexer (14) with the following features:

a first input (14a) for receiving the main program;

a second input (14b) for receiving the additional program from the memory (12); and

an output (14c);

a control device (16) for controlling the multiplexer (14), such that the output (14c) of the multiplexer (14) is switched from the first input (14a) to the second input (14b) at a first time and to a second Time is switched again from the second input (14b) to the first input (14a) in order to key the additional program into the main program between the first time and the second time; and

a transmission device (18) which is connected on the input side to the output (14c) of the multiplexer and which is connected on the output side to a transmission antenna (22) in order to feed the data stream to the transmission antenna.

2. Ground station according to claim 1, in which at least one commercial is stored in the memory (12) as an additional program.

3. Ground station according to claim 1 or 2, wherein the first Input (14) of the multiplexer is arranged to receive the main program, which has been generated in a recording studio separate from the ground station (10) and has been compressed according to an MPEG method, and

in which the memory (12) is arranged to store the additional program in a form coded according to an MPEG method.

4. Ground station according to one of the preceding claims,

in which the multiplexer (14) is designed to generate a broadcast channel from the main program and the additional program and to carry out a forward error correction in order to provide the broadcast channel with redundancy in order to provide a protected broadcast channel receive;

the transmitting device further comprising means (18a) for demultiplexing the broadcast channel and for generating a plurality of prime rate channels, and means for modulating the prime rate channels so that each prime rate channel has its own carrier frequency is assigned to obtain a frequency division multiplex signal, and

the transmitting device further comprising a device for converting the frequency division multiplex signal to a transmitting carrier frequency, an amplifier device and an antenna output (20) which is connected to the transmitting antenna (22) in order to obtain a ground station-satellite communication connection.

5. Ground station according to one of the preceding claims,

in which the memory (12) is part of a monitoring and configuration subsystem (40) of the ground station.

6. Ground station according to one of the preceding claims,

in which the memory (12) is arranged to be loaded and read out by means of a remote control (42) for the ground station.

7. Ground station according to one of the preceding claims,

in which the memory (12) stores a plurality of different additional programs, the ground station also having the following feature:

means for logging the activities of the control device (16) in order to record when which additional program has been scanned into the data stream.

8. A method for generating a data stream, which has a main program and an additional program, in a ground station, with the following steps:

Save the additional program;

Receiving the main program with a first input of a multiplexer;

Receiving the additional program from the memory with a second input of the multiplexer;

Controlling the multiplexer so that an output of the multiplexer switches from the first input to the second input at a first point in time and switches again from the second input to the first input at a second point in time, to the additional program between the first point in time and the second point in time key into the main program; and Sending the data stream, which has a main program and an additional program.