EP2854314B1 - Method and means for inserting emergency messages in a DAB Ensemble inside a tunnel - Google Patents

Description

The invention relates to a method for exchanging content in a DAB ensemble to form local windows within a single-frequency network, which is particularly suitable for alarming in a tunnel. The invention further relates to a device for this purpose.

It is known from extensive pilot projects and field tests that the contents of the sub-channel and the FIC are used to form what are known as local windows in a DAB single-frequency network (DAB = Digital Audio Broadcasting, ETSI EN 300 401 V1.4.1 (2006-06)) (FIC = Fast Information Channel) on the block boundaries of the CUs (CU = Capacity Unit) and the FIBs (FIB = Fast Information Block) can be exchanged for localized content if the time requirements for synchronicity in the single-frequency network are both from the transmitters of the global and of the local ensemble. CU's and FIB's with unchanged content can then be received undisturbed even in the transition area between global and local ensemble. CU's and FIB's that have been replaced cannot be decoded in the transition area.

It is also known that a DAB receiver is able to decode two identical superimposed DAB signals with different transit times without errors, as long as the transit time difference is less than or equal to the Guard Interval. The so-called guard interval is a protective distance between two successive DAB symbols and is approximately 246µs in transmission mode I, approximately 62µs in mode II, approximately 31µs in mode III and approximately 123us in mode IV.

In practice, the content of the sub-channels and the FIBs in the ETI data stream (ETI = Ensemble Transport Interface) of the global ensemble is replaced by local content to form a local window. The local ETI data stream thus formed is distributed to the DAB transmitters in the local area and the global ETI data stream to the DAB transmitters in the global area. Since the localization of the content requires a non-negligible processing time, the transmission of the global ensemble must be delayed by this processing time. This can be done by an explicit delay element or distributed over all DAB transmitters using the time stamp technique. This process is widely used in engineering.

The schematic structure of a DAB single-frequency network with a local window is described with reference to FIG Fig. 1 explained in more detail. The so-called ensemble multiplexer (101) combines the audio and data services to be broadcast together within an ensemble to form an ensemble in the form of the ensemble transport interface (ETI) defined in European Telecommunication Standard ETSI ETS 300 799 ed.1 (1997-09). This frame-oriented data stream is distributed to the DAB transmitters (103) via the ETI distribution network (102). The incoming ETI frames are in the DAB transmitter in a manner not shown via a dynamic or static Delay element adapted to the time requirements for synchronicity in the DAB single-frequency network, converted into DAB frames by a COFDM modulator and broadcast as a global ensemble (105) via a mixer with the following output stage at the desired frequency.

In order to form a local window, the global ensemble is also passed as an ETI data stream to a local multiplexer (108). This replaces individual sub-channels and FIBs with local content (109). The ETI data stream localized in this way is distributed via the local ETI distribution network (110) to one or more local DAB transmitters (111) and is broadcast by them as a local ensemble (106) on the same frequency as that of the global ensemble.

Due to the process, there is an overlap area (107) in which the global and local ensemble partially overlap destructively. This means that a DAB receiver (104) located in the overlap area can only receive the content that is contained in both the global and the local ensemble.

Fig. 2 shows the schematic structure of a DAB repeater with intercom for supplying a tunnel with DAB signals according to the prior art. A global DAB signal is received outside the tunnel by means of a directional antenna (201) and passed via a distributor (202) to a frequency-selective amplifier (203) and to a DAB reception module (207). The amplifier (203) filters the global DAB signal and amplifies it to a predefined level using automatic gain control and outputs it as a regenerated DAB signal (204).

The DAB reception module (207) demodulates the supplied global DAB signal and outputs the decoded FIC (209). In addition, it generates a synchronization signal (208), which is not shown in more detail, and which is used in the local multiplexer (210) and in the DAB low-power transmitter (212) for the time synchronization of the frames generated in each case.

The FIC (209) is used by the local multiplexer (210) to reconstruct the sub-channel configuration of the global DAB signal. The sub-channel configuration defines the identifier, data rate, start address, error protection and content type for each sub-channel. Based on this, the audio encoders (216) are configured for each sub-channel with regard to data rate and audio standard (DAB-Musicam, DAB-Plus or DMB) by the local multiplexer.

The alarm message (214) is distributed via a distributor (215) to the audio encoders (theoretically up to 64, practically approx. 20 audio encoders) and is compressed by them to the data rate set in each case. The local multiplexer forms a local ensemble which has the same logical structure as that of the global DAB signal. The local ensemble is transferred to the DAB micro-power transmitter (212) as an ETI data stream (211). The incoming ETI frames are adapted in the DAB micro-power transmitter (212) in a manner not shown to the time requirements for synchronicity in the DAB single-frequency network, converted into DAB frames by a COFDM modulator and via a Mixing stage with the following output stage at the desired frequency output as a DAB signal (213).

In the event of a dangerous situation, a switch (205) can be used to switch from the regenerated global DAB signal (204) to the local DAB signal (213). The respectively selected DAB signal is possibly further amplified and radiated into the area of the tunnel via one or more antennas (206). A DAB receiver located in the tunnel can therefore receive either the global DAB signal or the local DAB signal with alarm messages, depending on the danger situation. The use of a local multiplexer additionally requires the supply of the global ensemble to it. However, this additional effort is very impractical for small and medium-sized local windows, and it also results in permanent operating and rental costs for the line feed.

EP 2 461 610 discloses a method for broadcasting emergency information that is only relevant for a specific region. There is a first, general broadcast mode for digital radio signals and a second broadcast mode for emergency information, both of which are transmitted as an ETI data stream. If emergency information is available, the second mode is automatically selected by means of a switch and the emergency information is transmitted via an HF transmitter.

The emergency information is encoded in the method and converted to a predetermined bit rate that is smaller than the smallest bit rate of the broadcast signals of the first mode.

Fill bits are also inserted into the emergency information data stream, which compensate for the difference between the predetermined bit rate and the bit rates of the digital broadcast signals.

Disadvantage of in EP 2 461 610 The proposed solution is that the radio signals of the first mode are supplied as an ETI data stream, which, as already explained above, leads to permanent operating and rental costs for the line feed. Furthermore, the transmission of both modes is not synchronized with one another in time, which results in considerable reception interference in the overlap area and during the switchover between the two modes.

EP 2 328 287 reveals similar EP 2 461 610 a procedure for broadcasting emergency information that is only relevant for a specific region. The method also aims to outshine several regular radio signals using the same emergency information. The emergency information is encoded in the method and converted to a predetermined bit rate that is smaller than the smallest bit rate of the regular radio signals received by means of the HF receiver. Furthermore, filler data are inserted into the emergency information data stream, which compensate for the difference between the predetermined bit rate and the bit rates of the regular broadcast signals.

Disadvantage of in EP 2 328 287 The proposed solution is that the regular radio signals are fed in by means of separate repeaters. Furthermore, the transmission of the emergency information is not synchronized with the regular radio program, which causes considerable reception interference occur in the overlap area and during the switchover.

EP 0 944 194 discloses a method for a DAB receiver. In a first circuit part, the DAB signal to be received is amplified by means of analog signal processing, filtered and mixed down to a low intermediate frequency. The pre-processed DAB signal is digitized as IQ data using an analog / digital converter. The digital demodulation of the DAB baseband takes place in a second circuit part. As a result, the original components of a DAB ensemble (FIC and sub-channel) are available as a bit stream. A sub-channel selected by the user is converted into PCM data using MPEG audio decoders, which are then transferred to a loudspeaker or headphones for audibility via a digital / analog converter with the following amplifier.

During digital demodulation, the zero symbol contained in the DAB signal is used to determine the start of a DAB frame. The PRS symbol following the zero symbol serves as a reference symbol for differential phase demodulation. Furthermore, by comparing the received PRS symbol with the known PRS sequence, correction parameters for the deviation in the frequency position and in the time domain can be determined. The correction parameters can then be used to readjust the oscillators contained in the analog circuit part or to improve the frame synchronization.

DE 197 44 420 discloses a method for localizing DAB content that relies on the delivery of the global ensemble waived as an ETI data stream and instead used a modified COFDM modulator in the DAB transmitter, which is synchronized to the global DAB signal with respect to the DAB frame and only transmits the CUs of the content to be exchanged. No RF signal is transmitted at the locations of the CUs that are not to be changed. A DAB receiver accordingly receives both localized and non-localized content in the area of the transmission of the local transmitter.

Disadvantage of in DE 197 44 420 The proposed solution is that the DAB receiver has to meet increased requirements with regard to the dynamic reception behavior, because the field strengths of the local and global signal components differ considerably due to the process, since the existing global components must be covered with the transmission of the local signal components.

WO 2006/035242 discloses a method similar DE 197 44 420 , which also does not feed the global ensemble as an ETI data stream and instead uses a frequency-selective amplifier with automatic gain control and a DAB receiver. The frequency-selective amplifier is used to process and feed the global DAB signal into the local area of the local window. This method is generally used in technology and is known under the term repeater.

The DAB receiver receives the global DAB signal and derives configuration and synchronization information for it the local multiplexer. The local multiplexer creates an alternative ensemble in which the original sub-channel contents are replaced, for example, by alarm messages, with a separate audio encoder being used for each audio sub-channel. The local ensemble generated in this way is temporarily broadcast in the area of the local window, for example of a car tunnel, during an emergency situation as an alternative to the global ensemble.

Disadvantage of in WO 2006/035242 The proposed solution is that a system-specific audio encoder is necessary for each audio sub-channel to be replaced, at least if different data rates and different audio standards are used. This increases the effort considerably in large or complex ensembles.

So if it is necessary to insert an alarm message in a DAB signal to replace the audio content of all audio sub-channels, a separate audio encoder has been required for this at least for each data rate and per audio standard. This large number of audio encoders represents a considerable cost problem, especially in large and complex DAB ensembles.

The object of the invention is to eliminate the disadvantages of the prior art. In particular, an improved method for localizing content in a DAB single-frequency network is specified, which is suitable for signaling alarm information in a tunnel or local windows.

This object is solved by the features of claims 1 and 8. Appropriate configurations of the inventions result from the features of the subclaims.

1. (a) Verteilen (316) der einzublendenden Alarmmeldung (315) auf Audio-Encoder (317, 318, 319), die jeweils genau einen der im globalen DAB-Ensemble enthaltenen Audio-Standards umfassen;
2. (b) Komprimieren der verteilten Alarmmeldung mittels der Audio-Encoder (317, 318, 319) auf eine Datenrate, die kleiner oder gleich der niedrigsten im globalen DAB-Ensemble vorkommenden Audio-Datenrate ist;
3. (c) Reformatieren (324) der komprimierten Alarmmeldungen aus Schritt (b) auf jede im globalen DAB-Ensemble vorkommende Audio-Datenrate (321), insbesondere durch Einfügen von Fülldaten;
4. (d) Auswahl (326) jeweils einer reformatierten Alarmmeldung (325) aus Schritt (c) pro Audio-Sub-Channel, welche die gleiche Datenrate und den gleichen Audio-Standard wie der jeweilige Audio-Sub-Channel des globalen DAB-Ensembles besitzt; und
5. (e) Einblenden der im Schritt (d) ausgewählten Alarmmeldungen (327) in die jeweiligen Audio-Sub-Channels des lokalen DAB-Ensembles, umfassend die Teilschritte
   1. (i) Empfang eines globalen DAB-Ensembles (301) und Demodulation (310) des enthaltenen FIC;
   2. (ii) Anpassen (311) der im FIC aus Teilschritt (i) enthaltenen FIG 0/0, indem das Feld CIF-Count um eine Anzahl N erhöht wird, wobei N so gewählt wird, dass N*24ms größer oder gleich der Gesamtverarbeitungszeit für den FIC ist;
   3. (iii) Verkürzen (312) einer im FIC aus Teilschritt (ii) signalisierten Rekonfiguration um N CIF-Rahmen, wobei N dem Wert aus Teilschritt (ii) entspricht; und
   4. (iv) Einblenden des im Teilschritt (ii) gewonnenen FIC in das lokale DAB-Ensemble.

According to the invention, a method for fading in alarm messages within a DAB single-frequency network, in particular within a tunnel, is provided, wherein global DAB signals are broadcast as a DAB ensemble in the DAB single-wave network and a transmitter operated in the DAB single-wave network broadcasts the global ones DAB signals overlaid with a local DAB signal synchronous to the DAB single-wave network, the configuration of which is derived from the FIC of the global DAB signal. The method according to the invention comprises the steps:

1. (a) distributing (316) the alarm message (315) to be faded in to audio encoders (317, 318, 319), each of which comprises exactly one of the audio standards contained in the global DAB ensemble;
2. (b) compressing the distributed alarm message by means of the audio encoders (317, 318, 319) to a data rate which is less than or equal to the lowest audio data rate occurring in the global DAB ensemble;
3. (c) reformatting (324) the compressed alarm messages from step (b) to each audio data rate (321) occurring in the global DAB ensemble, in particular by inserting filler data;
4. (d) Selection (326) of a reformatted alarm message (325) from step (c) per audio sub-channel, which has the same data rate and the same audio standard as the respective audio sub-channel of the global DAB ensemble ; and
5. (e) displaying the alarm messages (327) selected in step (d) in the respective audio sub-channels of the local DAB ensemble, comprising the substeps
   1. (i) receiving a global DAB ensemble (301) and demodulating (310) the contained FIC;
   2. (ii) Adapting (311) the FIG 0/0 contained in the FIC from sub-step (i) by increasing the field CIF-Count by a number N, N being selected such that N * 24 ms greater than or equal to the total processing time for is the FIC;
   3. (iii) shortening (312) a reconfiguration signaled in the FIC from sub-step (ii) by N CIF frames, N corresponding to the value from sub-step (ii); and
   4. (iv) Fading the FIC obtained in sub-step (ii) into the local DAB ensemble.

The proposed method makes it possible to reduce the number of audio encoders to one per audio standard. For this purpose, the alarm message is first compressed to the lowest audio data rate within the DAB ensemble for each audio standard used. Only when you key into the sub-channel the already compressed audio data stream is adapted to the respective data rate of the sub-channel by simply inserting filler data.

The invention is based on the consideration that the audio subchannels to be replaced have different data rates, but the same audio message is to be transmitted. However, the quality of the audio message is of secondary importance for the alarm application purpose, so that even low data rates, ie high compressions of the audio data stream with reduced audio quality, are permissible. Accordingly, it would be permissible to compress the audio message to a low data rate with an acceptable loss of quality using a single audio encoder, and only when the keying into the audio sub-channel the data rate of the compressed audio message by inserting filler data to the data rate of the to increase the respective audio sub-channels. It is crucial that the insertion of filler data is much easier than audio compression for a large number of sub-channels.

In addition, according to the invention, no additional frequency-selective amplifier with automatic gain control is required in order to temporarily radiate the global ensemble into the area of the local window. Instead, according to the invention, the digital receive branch and the digital transmit branch are shared for the global DAB signal and the local DAB signal.

The method according to the invention can be used in DAB single-wave networks both to supply a tunnel Alarm messages as well as a local window can be applied. In addition to feeding alarm messages, the process can also be used to feed general local information.

The specified method has the advantage over the previously known solutions that only one audio encoder is required for compression of the alarm messages per audio standard and the otherwise conventional analog frequency-selective amplifier is replaced by digital modules.

• (e1) Empfang eines globalen DAB-Signals (301), Filterung, Demodulation und Wandlung in digitale IQ-Daten (303) mittels digitalem IQ-Demodulator (302), wobei die digitalen IQ-Daten das DAB-Basisbandsignal repräsentieren;
• (e2) Bestimmung des Transmissions-Modes (305) mittels Transmission-Mode-Detektor (304), durch Auswertung der Länge des Nullsymbols innerhalb der digitalen IQ-Daten (303) aus Teilschritt (e1);
• (e3) Erzeugen eines Impulses (307) mittels Null-Symbol-Detektor (306), der den Beginn des Nullsymbols innerhalb der digitalen IQ-Daten (303) aus Teilschritt (e1) markiert;
• (e4) Analyse (308) des Phasenreferenzsymbols innerhalb der digitalen IQ-Daten (303) aus Teilschritt (e1) und Ableiten eines Stellwertes (309) zur Frequenzkorrektur;
• (e5) Demodulation (310) des FIC innerhalb der digitalen IQ-Daten (303) aus Teilschritt (e1);
• (e6) Anpassen (311) der im FIC aus Teilschritt (e5) enthaltenen FIG 0/0, indem das Feld CIF-Count um eine Anzahl N erhöht wird, wobei N so gewählt wird, dass N*24ms größer oder gleich der Gesamtverarbeitungszeit für den FIC ist;
• (e7) Verkürzen (312) einer im FIC aus Teilschritt (e6) signalisierten Rekonfiguration um N CIF-Rahmen, wobei N dem Wert aus Teilschritt (e6) entspricht;
• (e8) Extrahieren (313) der Ensemble-Konfiguration (MCI) aus dem FIC des Teilschritts (e7) und Einfügen dieser in die MCI-Datenbank (320);
• (e9) Bestimmen der im DAB-Ensemble verwendeten Audio-Datenraten (321) und der Audio-Standards durch Auswerten der MCI-Datenbank (320) aus Teilschritt (e8);
• (e10) Bestimmen der Konfiguration (322) der im DAB-Ensemble enthaltenen Audio-Sub-Channel durch Auswerten der MCI-Datenbank (320) aus Teilschritt (e8);
• (e11) Bestimmen der Konfiguration (323) der im DAB-Ensemble enthaltenen Daten-Sub-Channel durch Auswerten der MCI-Datenbank (320) aus Teilschritt (e8);
• (e12) Generieren (328) von Fülldaten (329) für alle im DAB-Ensemble enthaltenen Daten-Sub-Channel, entsprechend der Konfiguration aus Teilschritt (e11);
• (e13) Optionales Austauschen (314) von Textinformationen der im FIC aus Teilschritt (e7) enthaltenen FIG 1/0, FIG 1/1, FIG 1/3, FIG 1/4, FIG 1/5 und FIG 1/6;
• (e14) Verzögern des Impulses (307) aus Teilschritt (e3) durch ein Verzögerungsglied (331), so dass der ausgegebene Startimpuls (332) genau auf den Beginn des nächsten Nullsymbols fällt;
• (e15) Bilden des DAB-Basisbandsignals (334) in Form digitaler IQ-Daten mittels COFDM-Modulator (333), durch Zusammenfassen und Modulieren des im Teilschritt (e7) oder (e13) gewonnenen FIC (330), der im Teilschritt (e12) generierten Inhalte der Daten-Sub-Channels (329) sowie der im Schritt (d) gebildeten Inhalte der Audio-Sub-Channels, wobei der COFDM-Modulator (333) die Stellgrößen Transmission-Mode (305) und Frequenzkorrektur (309) einbezieht und das Nullsymbol des DAB-Basisbandsignals (334) erst mit dem Startimpuls (332) aus Teilschritt (e14) ausgibt.
• (e16) Umschalten zwischen den digitalen IQ-Daten (303) aus Teilschritt (e1) und den digitalen IQ-Daten (334) aus Teilschritt (e15) mittels Schalter (335) je nach Gefahrensituation - beispielsweise im Tunnel -, wobei die Umschaltung vorzugsweise innerhalb des Nullsymbols erfolgt;
• (e17) Digitale Filterung des in Teilschritt (e16) gewählten IQ-Datenstroms mit anschließender Modulation auf die Frequenz des DAB-Gleichwellennetzes mittels digitalem IQ-Modulator (336);
• (e18) Bilden von Taktsignalen (339, 340) für den digitalen IQ-Demodulator (302) und den digitalen IQ-Modulator (336) mittels Oszillator (338) und Korrektur von Frequenzabweichungen über den Stellwert (309) aus Teilschritt (e4);
• (e19) und Abstrahlen des im Teilschritt (e17) erzeugten DAB-Signals (337) in einen lokal begrenzten Bereich, insbesondere in den Bereich eines Tunnels.

In one embodiment, step (e) of the method according to the invention comprises the following substeps:

• (e1) receiving a global DAB signal (301), filtering, demodulating and converting into digital IQ data (303) by means of a digital IQ demodulator (302), the digital IQ data representing the DAB baseband signal;
• (e2) determining the transmission mode (305) by means of a transmission mode detector (304), by evaluating the length of the zero symbol within the digital IQ data (303) from sub-step (e1);
• (e3) generating a pulse (307) by means of a zero symbol detector (306) which marks the start of the zero symbol within the digital IQ data (303) from substep (e1);
• (e4) analysis (308) of the phase reference symbol within the digital IQ data (303) from sub-step (e1) and deriving an actuating value (309) for frequency correction;
• (e5) demodulation (310) of the FIC within the digital IQ data (303) from substep (e1);
• (e6) adapting (311) the FIG 0/0 contained in the FIC from sub-step (e5) by increasing the field CIF-Count by a number N, N being selected such that N * 24ms greater than or equal to the total processing time for is the FIC;
• (e7) shortening (312) a reconfiguration signaled in the FIC from sub-step (e6) by N CIF frames, N corresponding to the value from sub-step (e6);
• (e8) extracting (313) the ensemble configuration (MCI) from the FIC of substep (e7) and inserting it into the MCI database (320);
• (e9) determining the audio data rates (321) and the audio standards used in the DAB ensemble by evaluating the MCI database (320) from substep (e8);
• (e10) determining the configuration (322) of the audio subchannels contained in the DAB ensemble by evaluating the MCI database (320) from substep (e8);
• (e11) determining the configuration (323) of the data subchannels contained in the DAB ensemble by evaluating the MCI database (320) from substep (e8);
• (e12) generation (328) of filler data (329) for all data subchannels contained in the DAB ensemble, in accordance with the configuration from substep (e11);
• (e13) Optional exchange (314) of text information contained in the FIC from sub-step (e7) FIG 1/0, FIG 1/1, FIG 1 / 3 . FIG 1/4, FIG 1/5 and FIG 1/6 ;
• (e14) delaying the pulse (307) from sub-step (e3) by a delay element (331), so that the output pulse (332) which is output falls exactly on the beginning of the next zero symbol;
• (e15) Forming the DAB baseband signal (334) in the form of digital IQ data using a COFDM modulator (333), by combining and modulating the FIC (330) obtained in sub-step (e7) or (e13), which in sub-step (e12 ) generated contents of the data subchannels (329) and the contents of the audio subchannels formed in step (d), the COFDM modulator (333) incorporating the manipulated variables transmission mode (305) and frequency correction (309) and outputs the zero symbol of the DAB baseband signal (334) only with the start pulse (332) from substep (e14).
• (e16) Switching between the digital IQ data (303) from substep (e1) and the digital IQ data (334) Sub-step (e15) by means of switches (335) depending on the dangerous situation - for example in the tunnel - the switchover preferably taking place within the zero symbol;
• (e17) digital filtering of the IQ data stream selected in sub-step (e16) with subsequent modulation to the frequency of the DAB single-frequency network by means of a digital IQ modulator (336);
• (e18) forming clock signals (339, 340) for the digital IQ demodulator (302) and the digital IQ modulator (336) by means of an oscillator (338) and correction of frequency deviations via the manipulated variable (309) from substep (e4);
• (e19) and radiating the DAB signal (337) generated in sub-step (e17) into a locally limited area, in particular into the area of a tunnel.

1. (A) eine Einrichtung zum Verteilen (316) der einzublendenden Alarmmeldung (315);
2. (B) genau einen Audio-Encoder (317, 318, 319) für jeden im globalen DAB-Ensemble vorkommenden Audio-Standard, wobei diese die Alarmmeldung von (A) auf eine Datenrate komprimieren, die kleiner oder gleich der kleinsten im globalen DAB-Ensemble vorkommenden Audio-Datenrate ist;
3. (C) eine Verarbeitungseinheit (324) zum Reformatieren der komprimierten Alarmmeldungen von (B) auf jede im globalen DAB-Ensemble vorkommende Audio-Datenrate mittels Einfügen von Fülldaten;
4. (D) eine Verarbeitungseinheit zur Auswahl (326) jeweils einer reformatierten Alarmmeldung (325) von (C) pro Audio-Sub-Channel, welche die gleiche Datenrate und den gleichen Audio-Standard wie der jeweilige Audio-Sub-Channel des globalen DAB-Ensembles besitzt; und
5. (E) eine Verarbeitungseinheit zum Einblenden (333) der von (D) ausgewählten Alarmmeldungen (327) in die jeweiligen Audio-Sub-Channels des lokalen DAB-Ensembles, einschließlich
   1. (i) des Empfanges eines globalen DAB-Ensembles (301) und der Demodulation (310) des enthaltenen FIC;
   2. (ii) des Anpassens (311) der im FIC aus Teilschritt (i) enthaltenen FIG 0/0, indem das Feld CIF-Count um eine Anzahl N erhöht wird, wobei N so gewählt wird, dass N*24ms größer oder gleich der Gesamtverarbeitungszeit für den FIC ist;
   3. (iii) Verkürzen (312) einer im FIC aus Teilschritt (ii) signalisierten Rekonfiguration um N CIF-Rahmen, wobei N dem Wert aus Teilschritt (ii) entspricht; und
   4. (iv) des Einblendens des im Teilschritt (ii) gewonnenen FIC in das lokale DAB-Ensemble.

According to the present invention, a device for displaying alarm messages within a DAB single-frequency network, in particular within a tunnel, is also provided, global DAB signals being broadcast as a DAB ensemble in the DAB single-wave network and synchronized with the DAB single-wave network local DAB signal are irradiated, the configuration of which is derived from the FIC of the global DAB signal. The device comprises

1. (A) means for distributing (316) the alarm message (315) to be displayed;
2. (B) exactly one audio encoder (317, 318, 319) for each audio standard occurring in the global DAB ensemble, these compressing the alarm message from (A) to a data rate which is less than or equal to the smallest in the global DAB ensemble. Ensemble occurring audio data rate is;
3. (C) a processing unit (324) for reformatting the compressed alarm messages from (B) to each audio data rate occurring in the global DAB ensemble by inserting filler data;
4. (D) a processing unit for selecting (326) a reformatted alarm message (325) from (C) per audio sub-channel, which has the same data rate and the same audio standard as the respective audio sub-channel of the global DAB Owns ensembles; and
5. (E) a processing unit for inserting (333) the alarm messages (327) selected by (D) into the respective audio sub-channels of the local DAB ensemble, including
   1. (i) receiving a global DAB ensemble (301) and demodulating (310) the contained FIC;
   2. (ii) adapting (311) the FIG 0/0 contained in the FIC from sub-step (i) by increasing the field CIF-Count by a number N, N being chosen so that N * is 24ms greater than or equal to the total processing time for the FIC;
   3. (iii) shortening (312) a reconfiguration signaled in the FIC from sub-step (ii) by N CIF frames, N corresponding to the value from sub-step (ii); and
   4. (iv) fading the FIC obtained in sub-step (ii) into the local DAB ensemble.

Fig. 1

den schematischen Aufbau eines DAB-Gleichwellennetzes mit lokalem Fenster nach dem Stand der Technik,

Fig. 2

den schematischen Aufbau eines DAB-Repeaters mit Einsprechen nach dem Stand der Technik,

Fig. 3

eine Ausführungsform des erfindungsgemäßen Verfahrens und der erfindungsgemäßen Vorrichtung zum Austausch von Inhalten in einem DAB-Ensemble zur Alarmierung in einem Tunnel.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. Show it:

Fig. 1

the schematic structure of a DAB single-wave network with local window according to the prior art,

Fig. 2

the schematic structure of a DAB repeater with speech according to the prior art,

Fig. 3

an embodiment of the inventive method and the inventive device for exchanging content in a DAB ensemble for alarming in a tunnel.

Fig. 3 schematically shows an embodiment of the inventive method for exchanging content in a DAB ensemble for alarming in a tunnel. A global DAB signal is received outside the tunnel by means of a directional antenna (301) and via a digital IQ demodulator (302) amplified, filtered and digitized, the result is the DAB baseband prepared in this way in the form of digital IQ data (303).

The transmission mode (305) is determined from the digital IQ data (303) by assessing the zero symbol length using a transmission mode detector (304).

The start of the zero symbol and thus the start of the DAB frames in the digital IQ data (303) is determined by a zero symbol detector (306). The start of the zero symbol is marked by a pulse (307). The pulse (307) is delayed via a delay element (331) and output as a start pulse (332) such that the start pulse (332) falls on the beginning of the next zero symbol. The duration of the delay depends on the transmission mode and is 96ms in Mode I, 24ms in Mode II, 24ms in Mode III and 48ms in Mode IV.

Deviations in the sampling rate or frequency deviations (309) are determined by analyzing (308) the phase reference symbol within the digital IQ data (303), for example by autocorrelation or correlation with the known sequence for the phase reference symbol.

An oscillator (338) provides the system clocks (339 and 340) for the digital IQ demodulator (302) and the digital IQ modulator (336). If the frequency deviates, the oscillator is adjusted accordingly via the control value (309).

A FIC demodulator (310) performs the demodulation for the FIC symbols in the digital IQ data (303). The FIC demodulated in this way contains basic configuration information about the DAB ensemble. Due to the system, the FIC is delayed compared to the DAB signal (301) and must be corrected accordingly. For this purpose, the CIF count contained in FIG. 0/0 is increased by the value of N by means of the first FIC processing unit (311) and the reconfiguration possibly signaled in the FIC is shortened by N CIF frames by the second FIC processing unit (312) , The value for N is preferably chosen so that N * 24ms is greater than or equal to the total delay time of the FIC.

The third FIC processing unit (313) extracts the ensemble configuration (MCI) from the FIC and stores it in the MCI database (320). All audio data rates (321) and the audio standards used are determined from the data collected therein. Furthermore, a list with configuration data of the audio sub-channel (322) and a list with configuration data of the data sub-channel (323) are created. A generator (328) delivers appropriate filler data (329) for each data sub-channel in accordance with the configuration (323).

The alarm message (315) is routed via a distributor (316) to the audio encoders (317, 318, 319), only one encoder being available for each audio standard. Each audio encoder (317, 318, 319) compresses the alarm message to the lowest data rate available in the ensemble or an even lower data rate. The alarm messages compressed in this way are propagated in the first audio processing unit (324) and adapted to the respective data rate in accordance with the configuration (321) by inserting filler data. From these reformatted alarm messages (325), the second audio processing unit (326) selects the appropriate alarm message with the appropriate data rate and the appropriate audio standard in accordance with the configuration (322) for each audio sub-channel.

Optionally, the fourth FIC processing unit (314) replaces the text information contained in the FIC FIG 1/0, FIG 1/1, FIG 1 / 3 . FIG 1/4, FIG 1/5 and FIG 1/6 by means of suitable textual information and passes the modified FIC (330) to the COFDM modulator (333).

The COFDM modulator (333) combines the FIC (330), the data subchannel (329) and the audio subchannel (327) and carries out the baseband modulation, using the control value frequency correction (309) and the transmission mode is observed. The baseband modulated in this way is output as a stream of digital IQ data (334), the output of the zero symbol contained only beginning with the start pulse (332).

Depending on the dangerous situation, the digital IQ data (303) of the global DAB signal or the IQ data (334) of the local DAB signal are selected via the changeover switch (335), a changeover during the zero symbol avoiding interference.

The digital IQ data stream selected by the changeover switch (335) is digitally filtered by the digital IQ modulator (336), mixed to the frequency of the DAB single-frequency network and analog output. The analog DAB signal (337) generated in this way is possibly further amplified and radiated into the area of the tunnel via one or more antennas. A DAB receiver located in the tunnel can therefore receive either the global DAB signal or the local DAB signal with alarm messages, depending on the danger situation.

An embodiment of the device according to the invention is shown in Fig. 3 identified by reference numerals (300).

Abbreviations

DAB

Digital audio broadcasting

STI

Service transport interface
The STI defines a data stream format for the transmission of audio and data services from the studio or radio house to the central ensemble multiplexer.

ETI

Ensemble transport interface
The ETI defines a data stream format for the transmission of the ensemble from the ensemble multiplexer to the transmitters.

RDI

Receiver data interface
The RDI defines a data stream format for the transmission of data decoded by a DAB receiver (FIC and sub-channel) to external audio or data service decoders.

EDI

Encapsulation of DAB interfaces
The EDI enables the transmission of ETI and STI over IP-based transmission links.

FIC

Fast Information Channel
The FIC is a special transmission channel within a DAB signal. It contains in particular the MCI, the service information and the ensemble information. The FIC is organized in the form of FIBs.

FIB

Fast information block
The FIB is the data unit of the FIC with a length of 32 bytes. It contains up to 30 bytes for user data and 2 bytes for a checksum. The user data are filled with FIG's.

FIG

Fast Information Group
The FIG is an information unit from a set of predefined structures. The FIG is organized hierarchically and is differentiated by type and extension. FIG 0/0 contains, for example, the ensemble information with ensemble ID and CIF count.

MCI

Multiplex configuration information
The MCI is signaled in the FIC and describes the logical structure of the ensemble.

PRS

Phase Reference symbol
The PRS is the second symbol in a DAB frame that has a predefined structure. It is used in the DAB receiver as a reference for decoding the following symbols.

CU

Capacity unit
A CU is the smallest addressable unit in a DAB frame and represents 64bit.

SAD

Start address in CU
The SAD describes the starting position of a sub-channel in multiples of CUs.

CIF

Common interleave frame
The CIF describes a logical 24ms frame consisting of FIC and MSC. Depending on the DAB transmission mode, one, two or four CIFs form a DAB frame.

MSC

Main Service Channel
The MSC is the set of all sub-channels contained in the DAB ensemble.

glossary

multiplex

is a combination of different data streams into a common data stream.

ensemble

is a multiplex consisting of one or more sub-channels, the FIC and possibly other data streams.

Sub-Channel

is a logical container for a data stream, which can contain an audio service or one or more data services.

service

is a radio program.

Audio service

is a radio program that contains audio content (e.g. music, speech).

Data service

is a radio program that contains data content (e.g. websites, images, text messages).

DAB Icon

is a logical information unit that represents multiple data bits within a symbol clock.

Guard interval

is the protection interval between two neighboring DAB symbols, which among other things avoids the crosstalk of successive symbols.

Zero symbol

is the first symbol in a DAB frame, for the duration of the zero symbol no signal or only a signal of very low transmission power is transmitted.

Phase Reference symbol

is the second symbol in a DAB frame that has a fixed predefined structure. It is used in the DAB receiver as a reference for decoding the following symbols.

Multiplex configuration information

describes the logical structure of a DAB ensemble, including the services and the sub-channels, their position in the DAB framework, their size, their error protection and their content type.

SFN

is a network of transmitters that broadcast the same signal from different locations on the same frequency. For this purpose, the transmitters are synchronized in time. The waves emitted in this way sometimes overlap destructively in space. By choosing suitable modulation methods, however, favorable overlay effects outweigh and transmission errors can be corrected using error protection.

Synchronicity in the single-wave network

is when all neighboring transmitters broadcast their signal on the same frequency synchronized in time, i.e. that the transmission of the DAB frames begins at the same time or that the time deviation is only a fraction of the guard interval.

local window

is an area in the single-frequency network in which one or more transmitters broadcast partially modified content compared to all other transmitters in the single-frequency network. For example, in the area of the local window, the national messages are replaced by local messages.

Contribution Network

Feeder network based on STI, is used between service, service multiplexer and ensemble multiplexer.

Distribution network

Distribution network based on ETI or EDI, is used between the ensemble multiplexer and the transmitters to distribute the DAB ensemble.

COFDM modulator

is a module of a DAB transmitter that modulates the FIC and the sub-channel, using a special multi-carrier method called Coded Orthogonal Frequency-Division Multiplexing.

CIF frame

is a logical unit that combines the FIC and the sub-channels for 24ms DAB transmission.

LIST OF REFERENCE NUMBERS

101

Ensemble Multiplexer

102

ETI distribution network

103

DAB transmitter

104

DAB receivers

105

Broadcasting area of the global DAB ensemble

106

Broadcasting area of the local DAB ensemble

107

Overlap area of the global and local DAB ensemble

108

local ensemble multiplexer

109

local audio or data service

110

ETI distribution network of the local DAB ensemble

111

DAB transmitter

201

receiving antenna

202

Radio frequency distributor

203

frequency selective amplifier

204

regenerated DAB signal

205

RF switch

206

transmitting antenna

207

DAB receiver module

208

Signal with time information

209

decoded FIC

210

Ensemble multiplexer

211

ETI data stream

212

COFDM modulator or DAB low-power transmitter

213

DAB signal with alarm message

214

Audio source with alarm message

215

Distributor for audio signals

216

Audio Encoder

300

device according to the invention

301

receiving antenna

302

digital IQ demodulator

303

digital IQ data with regenerated DAB ensemble

304

Transmission-mode detector

305

Control value for transmission mode

306

Null symbol detector

307

Signal for the start of the zero symbol

308

Processing unit for PRS analysis

309

Control value for frequency correction

310

FIC demodulator

311

first FIC processing unit

312

second FIC processing unit

313

third FIC processing unit

314

fourth FIC processing unit

315

Audio source with alarm message

316

Distributor for audio signals

317

Audio encoder for DAB-Plus

318

Audio encoder for DAB Musicam

319

Audio encoder for DMB

320

MCI data base

321

Configuration data of the first type

322

Configuration data of the second type

323

Configuration data of the third type

324

first audio processing unit

325

reformatted audio data streams

326

second audio processing unit

327

selected audio data streams

328

Fill data generator

329

generated data sub-channels

330

modified FIC

331

delay

332

Trigger signal for starting the DAB frame

333

COFDM Modulator

334

digital IQ data with DAB ensemble and alarm message

335

Switch for digital IQ data

336

digital IQ modulator

337

transmitting antenna

338

oscillator

339

System clock for digital IQ demodulator

340

System clock for digital IQ modulator

Claims (8)

1. A method for displaying alert messages within a DAB common-wave network, wherein in the DAB common-wave network global DAB signals are emitted as a DAB ensemble and a transmitter operated in the DAB common-wave network jams the global DAB signals synchronously to the DAB common-wave network with a local DAB signal the configuration of which is derived from the FIC of the global DAB signal,
   wherein it comprises the steps of

   (a) distributing (316) the alert message (315) to be displayed among audio encoders (317, 318, 319) each comprising exactly one of the audio standards contained in the global DAB ensemble;

   (b) compressing the distributed alert message by means of the audio encoders (317, 318, 319) to a data rate being less or equal to the lowest audio data rate present in the global DAB ensemble;

   (c) reformatting (324) the compressed alert messages of step (b) to each audio data rate (321) present in the global DAB ensemble;

   (d) selecting (326) one reformatted alert message (325) each from step (c) per audio sub-channel that has the same data rate and the same audio standard as the respective audio sub-channel of the global DAB ensembles; and

   (e) displaying the alert messages (327) selected in step (d) into the respective audio sub-channels of the local DAB ensemble comprising the individual steps of

   (i) receiving a global DAB ensemble (301) and demodulating (310) the included FIC;

   (ii) adjusting (311) the FIG 0/0 included in the FIC of individual step (i) by increasing the field CIF count by a number N, wherein N is selected such that N*24ms is larger as or equal to the total processing time for the FIC;

   (iii) shortening (312) a reconfiguration signaled in the FIC of individual step (ii) by N CIF frames, wherein N corresponds to the value of individual step (ii); and

   (iv) displaying the FIC obtained in individual step (iii) into the local DAB ensemble.
2. The method according to claim 1, wherein displaying in step (e) comprises the individual steps of

   (e1) receiving a global DAB signal (301), filtering, demodulating and converting it into digital IQ data (303) by means of the digital IQ demodulator (302), wherein the digital IQ data represent the DAB baseband signal;

   (e2) determining the transmission mode (305) by means of the transmission mode detector (304) by evaluating the length of the zero symbol within the digital IQ data (303) of individual step (e1);

   (e3) generating a pulse (307) by means of the zero symbol detector (306) that marks the beginning of the zero symbol within the digital IQ data (303) of individual step (e1);

   (e4) analyzing (308) the phase reference symbol within the digital IQ data (303) of individual step (e1) and deriving a control value (309) for frequency correction;

   (e5) demodulating (310) the FIC within the digital IQ data (303) of individual step (e1);

   (e6) adjusting (311) the FIG 0/0 included in the FIC of individual step (e5) by increasing the field CIF count by a number N, wherein N is selected such that N*24ms is larger than or equal to the total processing time for the FIC;

   (e7) shortening (312) a reconfiguration signaled in the FIC of individual step (e6) by N CIF frames, wherein N corresponds to the value of individual step (e6);

   (e8) extracting (313) the ensemble configuration (MCI) from the FIC of individual step (e7) and inserting it into the MCI database (320);

   (e9) determining the audio data rates (321) used in the DAB ensemble and the audio standards by evaluating the MCI database (320) of individual step (e8);

   (e10) determining the configuration (322) of the audio sub-channels included in the DAB ensemble by evaluating the MCI database (320) of individual step (e8);

   (e11) determining the configuration (323) of the data sub-channels included in the DAB ensemble by evaluating the MCI database (320) of individual step (e8); and

   (e12) generating (328) filling data (329) for all the data sub-channels included in the DAB ensemble in accordance with the configuration of individual step (e11).
3. The method according to claim 2, characterized in that it further comprises the step of

   (e13) interchanging (314) text information of the FIG 1/0, FIG 1/1, FIG 1/3, FIG 1/4, FIG 1/5, and FIG 1/6 included in the FIC of individual step (e7).
4. The method according to claim 2 or claim 3, characterized in that it further comprises the steps of

   (e14) delaying the pulse (307) of individual step (e3) via a delay element (331) such that the output starting pulse (332) exactly falls on the beginning of the next zero symbol;

   (e15) forming the DAB baseband signal (334) in the form of digital IQ data by means of the COFDM modulator (333) by grouping and modulating the FIC (330) obtained in individual step (e7) or (e13), the contents of the data sub-channels (329) generated in individual step (e12) as well as the contents of the audio sub-channels formed in step (d), wherein the COFDM modulator (333) includes the control variables transmission mode (305) and frequency correction (309) and outputs the zero symbol of the DAB baseband signal (334) only with the starting pulse (332) of individual step (e14);

   (e16) switching between the digital IQ data (303) of individual step (e1) and the digital IQ data (334) of individual step (e15) by means of switch (335) depending on the risk situation;

   (e17) digitally filtering the IQ data stream selected in individual step (e16) while subsequently modulating to the frequency of the DAB common-wave network by means of digital IQ modulator (336);

   (e18) forming timing signals (339, 340) for the digital IQ demodulator (302) and the digital IQ modulator (336) by means of oscillator (338) and correcting of frequency deviations via the control value (309) of individual step (e4); and

   (e19) emitting the DAB signal (337) generated in individual step (e17) into a locally limited region.
5. The method according to claim 4, characterized in that in step (e16) it is switched within the zero symbol.
6. The method according to claim 4 or claim 5, characterized in that in step (e19) it is emitted into the region of a tunnel.
7. The method according to any of the preceding claims, characterized in that the audio standards in step (a) are selected from a group comprising audio standards according to ETSI EN 300 401 (Musicam), ETSI TS 102 563 (DAB-Plus), and ETSI TS 102 428 (DMB).
8. A device for displaying alert messages within a DAB common-wave network, wherein in the DAB common-wave network global DAB signals are emitted as a DAB ensemble and are jammed synchronously to the DAB common-wave network with a local DAB signal the configuration of which is derived from the FIC of the global DAB signal,
   the device comprising

   (A) means for distributing (316) the alert message (315) to be displayed;

   (B) exactly one audio encoder (317, 318, 319) for each audio standard present in the global DAB ensemble, wherein these compress the alert message of (A) to a data rate that is lower than or equal to the lowest audio data rate present in the global DAB ensemble;

   (C) a processing unit (324) to reformate the compressed alert messages of (B) to each of the audio data rates present in the global DAB ensemble by means of inserting filling data;

   (D) a processing unit for selecting (326) one reformatted alert message (325) of (C) each per audio sub-channel that has the same data rate and the same audio standard as the respective audio sub-channel of the global DAB ensemble; and

   (E) a processing unit for displaying (333) the selected alert messages (327) of (D) in the respective audio sub-channel of the local DAB ensemble including

   (i) receiving a global DAB ensemble (301) and demodulating (310) the included FIC;

   (ii) adjusting (311) the FIG 0/0 included in the FIC of individual step (i) by increasing the field CIF count by a number N, wherein N is selected such that N*24ms is larger than or equal to the total processing time for the FIC;

   (iii) shortening (312) a reconfiguration signaled in the FIC of individual step (ii) by N CIF frames, wherein N corresponds to the value of individual step (ii); and

   (iv) displaying the FIC obtained in individual step (iii) in the local DAB ensemble.

Images