WO1999014874A1 - Procede et dispositif utilises pour le changement de frequence de reception dans un recepteur de systeme de radiodiffusion numerique - Google Patents

Procede et dispositif utilises pour le changement de frequence de reception dans un recepteur de systeme de radiodiffusion numerique Download PDF

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Publication number
WO1999014874A1
WO1999014874A1 PCT/SE1998/001624 SE9801624W WO9914874A1 WO 1999014874 A1 WO1999014874 A1 WO 1999014874A1 SE 9801624 W SE9801624 W SE 9801624W WO 9914874 A1 WO9914874 A1 WO 9914874A1
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WO
WIPO (PCT)
Prior art keywords
frequency
alternative
test
receptions
digital audio
Prior art date
Application number
PCT/SE1998/001624
Other languages
English (en)
Inventor
Richard Rebhan
Pierre Karlsson
Per Ruottinen
Jan Ossfeldt
Original Assignee
Teracom Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Teracom Ab filed Critical Teracom Ab
Priority to CA002303938A priority Critical patent/CA2303938A1/fr
Priority to EP98943168A priority patent/EP1032994A1/fr
Priority to AU91019/98A priority patent/AU9101998A/en
Publication of WO1999014874A1 publication Critical patent/WO1999014874A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
    • H03J1/0008—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor
    • H03J1/0058—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor provided with channel identification means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
    • H04H20/20—Arrangements for broadcast or distribution of identical information via plural systems
    • H04H20/22—Arrangements for broadcast of identical information via plural broadcast systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/24—Testing correct operation
    • H04L1/242—Testing correct operation by comparing a transmitted test signal with a locally generated replica
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04H—BROADCAST COMMUNICATION
    • H04H2201/00—Aspects of broadcast communication
    • H04H2201/10—Aspects of broadcast communication characterised by the type of broadcast system
    • H04H2201/20—Aspects of broadcast communication characterised by the type of broadcast system digital audio broadcasting [DAB]

Definitions

  • the present invention relates generally to a method and a device for change of reception frequency in a radio- frequency receiver, especially mobile radiofrequency receivers, in the intersection area between radio broadcasting regions with different broadcasting frequencies, especially in a radiofrequency receiver for a digital audio broadcasting system (DAB).
  • DAB digital audio broadcasting system
  • a conventional mobile FM-radio receiver such as a car radio, has to change reception frequency when moving from one broadcasting area/region covered by one transmitter to another broadcasting area/region covered by another transmitter.
  • Adjacent FM-radio broadcasting transmitters cannot transmit with the same radiofrequency, because if they did, due to the analog modulation of the radiofrequency signals, cross interference between the adjacent transmitters would arise. Therefore adjacent/ different FM-radiobroadcasting transmitters, independently if they broadcast different information in the same area or the same information in adjacent areas, transmit with sufficiently different frequencies to avoid cross interference.
  • Frequencies are reused in broadcast areas that are sufficiently distant from each other so that cross interference does not occur.
  • the FM-radio broadcasting system uses a relatively small bandwidth for each channel, this facilitates frequency changeover when a shift from one broadcasting transmitter to another is desired due to, for example, a transfer from one transmitter's broadcasting area to another.
  • Radio data system is an enhancement of and implemented into many analog FM-radio broadcasting systems.
  • RDS provides certain improvements to the functioning of frequency changeover.
  • An RDS FM-radio receiver will usually have the capability to store a list, received via RDS, of alternative frequencies for the current programme, for example a regionally or nationally broadcasted programme.
  • RDS FM-radio When the received audio level is low, an RDS FM-radio will quickly change reception frequency to one of the alternative frequencies to thereby measure the alternative frequency's field strength in a test reception.
  • the listener will usually not notice these short test receptions of alternative frequencies as the system utilizes short silences in speech or music in the current programme.
  • the audio output is preferably muted during the test receptions as well.
  • results of the test receptions will usually be the inputs to some sort of decision unit which will decide when and to which alternative frequency a frequency changeover should take place. This will probably, most of the time, be an unnoticeable function for the user, as it should be, letting, for example, a driver devote his full concentration on driving.
  • DAB digital audio broadcasting
  • COFDM coded orthogonal frequency division multiplexing
  • the DAB system uses a COFDM modulation technique which provides a robust method of information transfer. But due to, for exampel, the interleaving and the decoding of the digital data stream, the digital data stream cannot be interrupted for a test reception of an alternative frequency to thereby implement an unnoticeable method of test receiving alternative frequencies equivalent to that of the RDS system mentioned above. DAB is spectrally very robust but temporally somewhat more fragile. DAB can loose some sub carriers, due to, for example, fading, some of the time but the data stream cannot be cut off for a time period necessary for a test reception of alternative frequencies.
  • the DAB system broadcasts alternative frequencies of the current programme so that a list of these can be maintained in the receiver in a manner comparable to that of the RDS system.
  • the DAB receiver will, in accordance to the methods used previously in other systems, when the field strength of the received programme falls below a preset threshold or according to a tendency of the field strength, interrupt the reception of the programme and perform test receptions of the alternative frequencies in the list.
  • the reception of the current programme is unfortunately interrupted for a time interval, which can be considered annoying.
  • a DAB receiver can arbitrarily choose one of the alternative frequencies on the list and perform a frequency change inbetween two information frames.
  • An object of the invention is to define a method and a device for providing an automatic change of reception frequency in a DAB receiver, especially a mobile DAB receiver, without any interruption or only a practically unnoticeable interruption of the current programme.
  • Another object of the invention is to define a method and a device which are able to deliver a preferable alternative frequency in a DAB receiver for a current programme without interrupting the current programme.
  • a further object of the invention is to define a method and a device which are able to test receive an alternative reception frequency for evaluation purposes in a DAB receiver without interrupting the currently received programme/ information.
  • a still further object of the invention is to define a method and a device which are able perform an automatic change of reception frequency to one alternative frequency which is preferable over the current frequency, when a DAB receiver is in the intersection between two or more broadcasting areas with different transmitter frequencies which transmit at least one common programme or programme type, without interrupting the received programme for test receptions of the alternative frequencies.
  • a receiver for carrying out the method according to the invention is also provided.
  • a DAB frame comprises a null symbol which is used to do a first very coarse synchronisation of the receiver to the transmitted signals.
  • the phase reference symbols which are the subsequent symbols, synchronises the receiver with the transmitter.
  • the null symbol was intended to be completely empty, but in later revisions of the DAB standard, the null symbol comprises a specially coded transmitter identification information (Til).
  • test receptions of alternative frequencies are performed during the currently received programme's null symbols.
  • a test reception performs a switch of the reception frequency from the currently received frequency to a frequency which is to be tested, and at the end of the test reception the reception frequency is switched back to the originally received frequency, i.e. the currently received frequency, unless a permanent switch of frequency is determined.
  • a switch of reception frequency has to be performed during test receptions because according to the invention only one reception chain is used. According to the invention a test reception is only performed as not to interfere with the reception of the currently received programme, i.e. the information carrying parts of the DAB frame.
  • the received Til of the alternative frequencies are used for evaluation purposes.
  • the current programme is not interrupted at all during the test receptions.
  • a subsequently determined frequency changeover can thereafter, with a high probability, be performed without any noticeable interruption.
  • a method for providing an automatic change of reception frequency in a digital audio broadcasting (DAB) system receiver between a currently received frequency and a, from a field strength point of view, preferable alternative reception frequency is also achieved according to the invention.
  • DAB digital audio broadcasting
  • the receiver only having one reception chain for DAB.
  • the preferable alternative reception frequency might well be the currently received frequency.
  • the currently received frequency is in a digital audio broadcasting system format comprising transmission frames where each transmission frame comprises multicarrier symbols and a coarse synchronisation symbol in the form of a null symbol.
  • the currently received frequency is meant to denote the frequency that is received when the procedure of the method according to the invention commences.
  • the method comprises a number of steps in a digital audio broadcasting receiver. First of all, a list of alternative frequencies is determined.
  • the list might consist of only one alternative frequency or a plurality.
  • the currently received frequency can preferably be included in the list.
  • the list might be assembled from all or selected frequencies from those included in the information received by the currently received DAB transmission, preprogrammed frequencies, one or more random frequencies generated, for example, from a random generator, all or selected frequencies in the neighbourhood of the currently received frequency, or all or selected frequencies in the frequency range of the digital audio broadcasting receiver or a combination of any of these possibilities.
  • test receptions of the alternative frequencies on the determined list are systematically performed. The test receptions are mainly performed during the null symbols of the digital audio broadcasting frames of the currently received frequency.
  • the test receptions are only performed during the null symbols of the currently received frequency or alternatively the test receptions are performed during the null symbols and at least during part of at least one phase reference symbol of the currently received frequency.
  • the test receptions of the alternative frequencies on the determined list are evaluated.
  • the alternative frequencies on the determined list are systematically test received at least once each before the evaluation of the test receptions.
  • the alternative frequencies on the determined list are systematically test received only once each before the evaluation of the test receptions.
  • the alternative frequencies on the determined list are systematically test received at least twice each before the evaluation of the test receptions and the evaluation of the test receptions is based on calculated tendency of the field strength of each alternative frequency on the determined list. Based on the evaluation of the test receptions of the alternative frequencies on the determined list, which one of the alternative frequencies or the currently received frequency is preferable from a field strength point of view is determined.
  • the currently received frequency might, as was mentioned previously, be included in the list of determined alternative frequencies, but it is important not to forget it as it might be the best one for the time being. When it has been determined which frequency is preferable the reception frequency is changed to the determined preferable reception frequency.
  • the changing of reception frequency to the determined preferable reception frequency is performed/ executed inbetween two digital audio broadcasting frames of the currently received frequency.
  • the determined preferable reception frequency might be the currently received frequency and in such a case the change of frequency is not to another frequency.
  • the method according to the invention thereby enables an automatic change of reception frequency in a digital audio broadcasting receiver without any interruption or only a practically unnoticeable interruption of the current programme.
  • At least one alternative frequency on the determined list can advantageously be a digital audio broadcasting system transmission.
  • the transmission frames of the different digital audio broadcasting systems preferably comprise transmitter identification information during the null symbols and which frames are preferably in principle synchronised.
  • At least one of the alternative frequencies on the determined list can advantageously be of the FM or AM radio broadcasting type and in a preferred embodiment the evaluation of the test receptions further comprises the step of determining what type of broadcasting system each alternative frequency broadcasts.
  • a method for test receiving alternative reception frequencies in a digital audio broadcasting (DAB) system receiver for the purpose of being able to determine a, from a field strength point of view, preferable alternative reception frequency.
  • the receiver tuned to a currently received frequency in a digital audio broadcasting system format receives a current programme/ information.
  • the DAB format of the currently received frequency comprises transmission frames. Each transmission frame comprises multicarrier symbols and a coarse synchronisation symbol in the form of a null symbol.
  • the currently received frequency is meant to denote the frequency that is received when the procedure of the method according to the invention commences .
  • the method comprises a number of steps in a digital audio broadcasting receiver. First of all, a list of alternative frequencies is determined.
  • the list might consist of only one alternative frequency or a plurality.
  • the currently received frequency can preferably be included in the list.
  • the list might be assembled from all or selected frequencies from those included in the information received by the currently received DAB transmission, preprogrammed frequencies, one or more random frequencies generated, for example, from a random generator, all or selected frequencies in the neighbourhood of the currently received frequency, or all or selected frequencies in the frequency range of the digital audio broadcasting receiver or a combination of any of these possibilities.
  • test receptions of the alternative frequencies on the determined list are systematically performed. The test receptions are mainly performed during the null symbols of the digital audio broadcasting frames of the currently received frequency.
  • the test receptions are only performed during the null symbols of the currently received frequency or alternatively the test receptions are performed during the null symbols and at least during part of at least one phase reference symbol of the currently received frequency.
  • the test receptions of the alternative frequencies on the determined list are evaluated.
  • the alternative frequencies on the determined list are systematically test received at least once each before the evaluation of the test receptions.
  • the alternative frequencies on the determined list are systematically test received only once each before the evaluation of the test receptions.
  • the alternative frequencies on the determined list are systematically test received at least twice each before the evaluation of the test receptions and the evaluation of the test receptions is based on calculated tendency of the field strength of each alternative frequency on the determined list. Based on the evaluation of the test receptions of the alternative frequencies on the determined list, which one of the alternative frequencies or the currently received frequency is preferable from a field strength point of view is determined.
  • the currently received frequency might, as was mentioned previously, be included in the list of determined alternative frequencies, but it is important not to forget it as it might be the best one for the time being.
  • the method according to the invention thereby enables the delivery of a preferable alternative frequency in a digital audio broadcasting receiver for a current programme/ information without interrupting the current programme/ informa- tion.
  • At least one alternative frequency on the determined list can advantageously be a digital audio broadcasting system transmission.
  • the transmission frames of the different digital audio broadcasting systems preferably comprise transmitter identification information during the null symbols and which frames are preferably in principle synchronised.
  • At least one of the alternative frequencies on the determined list can advantageously be of the FM or AM radio broadcasting type and in a preferred embodiment the evaluation of the test receptions further comprises the step of determining what type of broadcasting system each alternative frequency broadcasts .
  • the aforementioned objects are also achieved by a method for test receiving alternative reception frequencies in a digital audio broadcasting system receiver for the purpose of being able to evaluate alternative reception frequencies .
  • the receiver tuned to a currently received frequency in a digital audio broadcasting system format receives a current programme/ information.
  • the DAB format of the currently received frequency comprises transmission frames. Each transmission frame comprises multicarrier symbols and a coarse synchronisation symbol in the form of a null symbol.
  • the currently received frequency is meant to denote the frequency that is received when the procedure of the method according to the invention commences.
  • the method comprises a number of steps in a digital audio broadcasting receiver. First of all, a list of alternative frequencies is determined. The list might consist of only one alternative frequency or a plurality. The currently received frequency can preferably be included in the list.
  • the list might be assembled from all or selected frequencies from those included in the information received by the currently received DAB transmission, preprogrammed frequencies, one or more random frequencies generated, for example, from a random generator, all or selected frequencies in the neighbourhood of the currently received frequency, or all or selected frequencies in the frequency range of the digital audio broadcasting receiver or a combination of any of these possibilities.
  • the selection can, for example, be based on the geographical location of the corresponding receiver.
  • the test receptions are only performed during the null symbols of the currently received frequency or alternatively the test receptions are performed during the null symbols and at least during part of at least one phase reference symbol of the currently received frequency.
  • the test receptions of the alternative frequencies on the determined list are evaluated.
  • the alternative frequencies on the determined list are systematically test received at least once each before the evaluation of the test receptions.
  • the alternative frequencies on the determined list are systematically test received only once each before the evaluation of the test receptions.
  • the alternative frequencies on the determined list are systematically test received at least twice each before the evaluation of the test receptions and the evaluation of the test receptions is based on calculated tendency of the field strength of each alternative frequency on the determined list.
  • the method according to the invention thereby enables an evaluation of alternative frequencies on a determined list without interrupting the currently received programme/information.
  • At least one alternative frequency on the determined list can advantageously be a digital audio broadcasting system transmission.
  • the transmission frames of the different digital audio broadcasting systems preferably comprise transmitter identification information during the null symbols and which frames are preferably in principle synchronised.
  • At least one of the alternative frequencies on the determined list can advantageously be of the FM or AM radio broadcasting type and in a preferred embodiment the evaluation of the test receptions further comprises the step of determining what type of broadcasting system each alternative frequency broadcasts.
  • the aforementioned objects are also achieved by a method for test receiving an alternative reception frequency in a digital audio broadcasting system receiver for the purpose of being able to evaluate an alternative reception frequency.
  • the receiver tuned to a currently received frequency in a digital audio broadcasting system format receives a current programme/ information.
  • the DAB format of the currently received frequency comprises transmission frames. Each transmission frame comprises multicarrier symbols and a coarse synchronisation symbol in the form of a null symbol.
  • the currently received frequency is meant to denote the frequency that is received when the procedure of the method according to the invention commences.
  • the method comprises a number of steps in a digital audio broadcasting receiver. First of all the test reception of the alternative frequency is performed. The test reception is mainly performed during a null symbol of a digital audio broadcasting frame of the currently received frequency.
  • the test reception is only performed during a null symbol of the currently received frequency or alternatively the test reception is performed during a null symbol and at least during part of at least one phase reference symbol of the currently received frequency.
  • the test reception of the alternative frequency is evaluated.
  • the alternative frequency is test received at least once before an evaluation of the test receptions .
  • the alternative frequency is test received only once before the evaluation of the test reception.
  • the alternative frequency is test received at least twice before an evaluation of the test receptions and the evaluation of the test receptions is based on a calculated tendency of the field strength of the alternative frequency. The method according to the invention thereby enables the an evaluation of an alternative frequency without interrupting the currently received programme/ information.
  • a device for test receiving alternative reception frequencies in a digital audio broadcasting system receiver for the purpose of being able to evaluate alternative reception frequencies.
  • the receiver tuned to a currently received frequency in a digital audio broadcasting system format receives a current programme/ information.
  • the DAB format of the currently received frequency comprises transmission frames. Each transmission frame comprises multicarrier symbols and a coarse synchronisation symbol in the form of a null symbol.
  • the currently received frequency is meant to denote the frequency that is received before the device commences to test receive alternative frequencies according to the invention.
  • the device comprises means for determining a list of alternative frequencies. The list might consist of only one alternative frequency or a plurality. The currently received frequency can advantageously be included in the list.
  • the list might be assembled from all or only selected frequencies from those included in the information received by the currently received DAB transmission, preprogrammed frequencies, one or more random frequencies generated, for example, from a random generator, all or only selected frequencies in the neighbourhood of the currently received frequency, or all or only selected frequencies in the frequency range of the digital audio broadcasting receiver or a combination of any of these possibilities.
  • the device further comprises means for systematically performing test receptions of the alternative frequencies on the determined list. The test receptions are mainly performed during the null symbols of the digital audio broadcasting frames of the currently received frequency.
  • the device also comprises means for evaluating the test receptions of the alternative frequencies on the determined list. The evaluation can be performed either after or interleaved with the the test receptions of the alternative frequencies.
  • the device is able to perform an evaluation of alternative frequencies on a determined list without interrupting the currently received programme/information.
  • the device preferably further comprises means for determining which one of the alternative frequencies or the currently received frequency is preferable from a field strength point of view. The determination is based on the evaluation of the test receptions of the alternative frequencies on the determined list. The device is thereby enabled to deliver a preferable alternative frequency for a current programme/ information in a digital audio broadcasting receiver without interrupting the current programme/ information.
  • the device preferably further comprises means for changing the reception frequency to the determined preferable reception frequency.
  • the means for changing the reception frequency to the determined preferable reception frequency executes a change of frequency inbetween two digital audio broadcasting frames of the currently received frequency.
  • the device is thereby able to automatically change the reception frequency in a digital audio broadcasting receiver without any interruption or only a practically unnoticeable interruption of the current programme.
  • the means for systematically performing the test receptions only performs test receptions during the null symbols of the currently received frequency.
  • the means for systematically performing the test receptions performs test receptions during the null symbols and at least during part of at least one phase reference symbol of the currently received frequency.
  • the means for systematically performing test receptions systematically performs test receptions of the alternative frequencies at least once each before the means for evaluating the test receptions evaluates the test receptions. In other embodiments the means for systematically performing test receptions systematically performs test receptions of the alternative frequencies only once each before the means for evaluating the test receptions evaluates the test receptions. In alternative embodiments the means for systematically performing test receptions systematically performs test receptions of the alternative frequencies at least twice each before the means for evaluating the test receptions evaluates the test receptions and that the means for evaluating the test receptions bases its evaluation on a calculated tendency of the field strength of each alternative frequency on the determined list.
  • At least one alternative frequency on the determined list is a digital audio broadcasting system transmission and where the transmission frames of the different digital audio broadcasting systems comprises transmitter identification information during the null symbols which transmitter identification information is used by the means for evaluating the test receptions.
  • at least one of the alternative frequencies on the determined list is of the FM or AM radio broadcasting type and that the means for evaluating the test receptions further determines what type of broadcasting system each alternative frequency broadcasts.
  • a device and a method for test receiving alternative frequencies without interrupting the current programme By providing a device and a method for test receiving alternative frequencies without interrupting the current programme, a plurality of advantages over prior art systems are obtained. Depending on how the frames are synchronised between the current reception frequency and an alternative frequency to which a change is to be performed, a more or less unnoticeable change can be executed. Under favourable conditions even a data transfer can be changed from one reception frequency to another without any loss of information.
  • the device and method according to the invention will work just as well in a mobile receiver as in a stationary receiver.
  • a stationary receiver might be located in an area which is an intersection of two or more broadcasting areas with different transmitter frequencies in such a way that under certain conditions, weather conditions for example, one reception frequency is better than the other(s), and under different conditions another reception frequency is superior.
  • the invention can also advantageously be utilised in a single frequency network where a full coverage DAB network is not yet achieved and where analog FM or AM broadcasting is utilised to complement the DAB network and thereby provide complete coverage for regional and/or national programmes.
  • test receptions are performed on alternative FM or AM frequencies instead of on DAB frames and that the evaluation of the test receptions are adapted according to the type of test reception performed.
  • Fig. 1 shows a block diagram of one DAB frame
  • Fig. 2 shows a frequency coverage map
  • Fig. 3 temporally shows null symbols of several different transmitting frequencies
  • Fig. 4 shows a block diagram of a receiver according to the invention.
  • Fig. 5 shows a flow chart of how the reception frequency in a receiver is changed according to one method of the invention.
  • FIG. 1 shows a block diagram of one DAB frame.
  • DAB frames are sent in succession.
  • a DAB frame mainly comprises a synchronisation channel 101, 102, a fast information channel (FIC) 103, and a main service channel (MSC) 104.
  • the synchronisation channel comprises a null symbol 101 and at least one phase reference symbol 102.
  • the fast information channel (FIC) 103 is, for example, used for multiplex configuration information (MCI) and service information (SI).
  • MCI multiplex configuration information
  • SI service information
  • the main service channel 104 carries the desired useful information which can be a number of coded audio programmes/channels, one or more digital information transfers, or a combination of these. Usually more than one programme/channel or information transfer is coded into the main service channel.
  • a DAB frame is configured to provide a robust way of transferring information, i.e. packets of digital information, from a transmitter to a receiver without any feedback through, for example, a back channel.
  • information i.e. packets of digital information
  • a DAB frame is assembled in the following manner; Packets of digital information are coded, error protected, and then time interleaved. These are thereafter multiplexed into the main service channel 104 according to a predetermined, but changeable, service configuration.
  • the multiplexer output is frequency interleaved and combined with multiplex control and service information which travel in the fast information channel 103 in order to avoid the time interleaving process.
  • very rugged synchronisation symbols 102 are added before applying orthogonal frequency division multiplexing (OFDM) and differential quadrature phase-shift keying (QPSK) modulation onto a a large number of carriers to form the DAB signal.
  • OFDM orthogonal frequency division multiplexing
  • QPSK differential quadrature phase-shift keying
  • the fast information channel 103 and the main service channel 104 cannot be interrupted for any substantial length of time without causing a substantial interruption of the received programme/information before the interleaving is complete again.
  • the null symbol 101 is used for coarse synchronisation and was originally intended to be completely empty, as the name implies. Later revisions of the DAB standard has introduced the possibility to use the null symbol 101 for transmitter identification. Transmitter identification is accomplished by transmitting a TII specific for the transmitter in question during the null symbol 101. This means that in an SFN the only deviating information transmitted by the transmitters is the TII during the null symbol and therefore the TII is coded in a special way and transmitted at a low power level to thereby avoid any interference problems and to enable the null symbol 101 to still function as a null symbol.
  • test receptions can be performed during the null symbol 101 and possibly during part of the synchronisation symbol 102 without interfering with the currently received programme and its necessary information carrying parts 103, 104.
  • Test receptions of other frequencies can only be performed when the current programme is not disturbed since only one reception chain necessary and used according to the invention.
  • FIG. 2 shows a frequency coverage map over four different broadcasting regions 211, 212, 213, 214, each region broad- casting with a different frequency.
  • Each broadcasting region 211, 212, 213, 214 has at least one transmitter 221, 231, 222, 232, 242, 223, 224.
  • a first broadcasting region 211 comprises two transmitters 221, 231, to be able to cover the whole first region 211.
  • the two transmitters 221, 231, of the first region 211 transmit at the same frequency and thereby takes advantage of the DAB system.
  • a second broadcasting region 212 comprises three transmitters 222, 232, 242, to cover the whole second region 212.
  • the number of necessary transmitters can, for example, depend on the geography of the region or transmitter output power level.
  • the first and second regions 211, 212 are single frequency networks on a small scale.
  • Each one of the third and fourth broadcasting regions 213, 214 comprises a single respective transmitter 223, 224.
  • These broadcasting regions 213, 214 can be of the DAB, FM, or AM type.
  • the invention is not restricted to what type of broadcasting system a mobile receiver enters or a stationary receiver is in the vicinity of, but only that the currently received programme is transmitted from a DAB system since the invention deals with performing test receptions of alternative frequencies without interruption of the received DAB frames. It will be assumed in the following that all of the broadcasting regions 211, 212, 213, 214, are of the DAB type.
  • the broadcasting regions 211, 213, (the first and third 211, 213) broadcast at least one common programme/ information channel, the programme being the one that our mobile receiver 290 is receiving when travelling along a road 200 that goes through the first and third broadcasting regions 211, 213, in our example.
  • a receiver would preferably change to an alternative frequency that transmits the same type of programme that is currently received.
  • the change to an alternative frequency is a bit more reluctant, i.e. the current frequency and therefore current programme would be allowed to degrade a bit more before a change is performed than when the same programme is available and a change back and forth can be performed without, for example, a listener noticing these changes.
  • the DAB standard has provisions for not only broadcasting alternative frequencies that transmit the same programme to the receiver, but also alternative frequencies that transmit the same type of programme, i.e. news, pop music, jazz, sport etc.
  • Test receptions of alternative frequencies is preferably done continuously, but change to an alternative frequency will usually only be close at hand when a receiver is located in a region/intersection 219 between two or more broadcasting regions 211, 213, as is illustrated in figure 2.
  • test receptions of alternative frequencies are performed during the null symbols of the currently received DAB frames.
  • Figure 3 temporally illustrates null symbols of several different transmitting frequencies 351, 352, 353, 354, where the top one 351 is assumed to be the currently received DAB frequency 351 with its DAB frames and corresponding null symbols 311, 321, 331, 341 occuring during respective time periods 310, 320, 330, 340.
  • the other three frequencies 352, 353, 354, can, for example, correspond to the respective broadcasting regions 212, 213, 214, of figure 2, which have been broadcasted as alternative frequencies. They can be alternative frequencies if they, for example, transmit the same programme/information, the same type of programme, or just be something that broadcasts something. Most probably, the DAB frames transmitted by different transmitters with different frequencies 351, 352, 353, 354, will be sufficiently synchronised so that the null symbols 321, 322, of the different respective DAB frames occur at substantially the same time 320. Irrespectively if the frames are synchronised or not, the time periods 310, 320, 330, 340 are when the null symbols 311, 321, 331, 341 of the currently received frequency 351 occur, i.e. when the test receptions of the alternative frequencies 352, 353, 354, occur.
  • test receptions of alternative frequencies can either be performed continuously or only when the reception level of the currently received frequency starts to deteriorate. In the example, test receptions will preferably be performed at least when the mobile receiver 290 is on its way to enter a new broadcasting region 213.
  • the receiver determines that an alternative frequency will provide a superior reception quality compared to the currently received frequency, which is when a change of reception frequency is initiated.
  • a changeover to the third alternative frequency 353 broadcasted in the third region 213 is a probable outcome.
  • the alternative frequencies are not necessarily DAB transmissions and even if they are, it is not necessary for the invention that they are synchronised.
  • the receiver performs test receptions of alternative frequencies during the null symbols of the currently received DAB transmission and frequency. Independently of what is received during these test receptions of the alternative frequencies, an evaluation of the received signals is performed.
  • a prediction as to the tendency, stronger and stronger or weaker and weaker, of the received signal can also possibly be done to support the determination as to what frequency a change should be executed to and also when this should happen.
  • the evaluation may comprise a determination of what type of signals are received, i.e. DAB, FM, or AM, so that an evaluation may take into account not only the received signal strength but also the received signal strength in view of the type of received signals.
  • the determination of what type of signals that are received can be performed by using fast fourier transform (FFT) for a frequency analysis over time and/or an attempt at decoding the received signals.
  • FFT fast fourier transform
  • FIG. 4 shows a block diagram of a receiver according to the invention.
  • the receiver will preferably either comprise an antenna 470 or means for connecting an external antenna. Signals picked up by the antenna 470 will preferably first of all be amplified in a preamplifier/ tuner 471 which preferably comprises mixing means for transposing the received signals to an intermediate frequency (IF).
  • IF intermediate frequency
  • the heart of a DAB receiver will process its signals in a digital form and if a quadrature demodulator 472 is realised in digital form the quadrature demodulator 472 will have an analog to digital converter (A/D converter) at the input or if the quadrature demodulator 472 is realised in analog form then it will have an analog to digital converter on its output.
  • A/D converter analog to digital converter
  • the processing according to the invention is performed digitally by a digital signal processing means 473 preferably in conjunction with the ordinary digital signal processing that is required for extracting the received programme/information in a robust manner. Assuming that this is a DAB radio receiver, then the extracted programme, which is in a digital format, needs to be converted to analog signals in a digital to analog converter (D/A converter) 474. Unless very low levels of sound is adequate, then the analog signals needs to be amplified in an amplifier 475 before the analog signals are fed to a speaker 476, headphones, or the like.
  • D/A converter digital to analog converter
  • the present invention can be put into apparatus-form either as pure hardware, as pure software or as a combination of hardware and software. If the method according to the invention is realised in the form of software, it can be completely independent or it can be one part of a larger programme.
  • the software can suitably be located in a general purpose computer or in a dedicated computer.
  • Fig. 5 shows a flow chart of how the reception frequency in a receiver is changed according to one method of the invention.
  • an optional field strength measuring step 580 the field strength of the currently received frequency is measured.
  • the measured field strength of the currently received frequency is either compared to a fixed threshold value or used in a field strength prediction computation with which a tendency is computed and thereafter compared with model tendencies. If the field strength is above the fixed threshold or does not show a weakening tendency, then the procedure returns to field strength measuring step 580. On the other hand, if the field strength is below a fixed threshold or shows a weakening tendency, then the procedure proceeds to null symbol step 582 which will be described in full below.
  • These two optional steps 580, 581 are optional, the method according to the invention, as described below, can be performed continuously, initiated by another program, or initiated on demand by other methods/ devices than by the method which has been described in relation to the two optional steps 580, 581.
  • test receptions of alternative frequencies are performed, for example according to the previously described optional steps 580, 581, then it is determined, in a null symbol step 582, when in time the null symbols appear.
  • test receptions of alternative frequencies are performed during the null symbols of the currently received DAB frames.
  • the information transfer part of the DAB frame is not interrupted and only the TII of the currently received frequency is lost for that frame.
  • the TII is probably the only part of a DAB frame that will be the same when DAB frames are received from the same transmitter, the loss of the TII from a few frames will not affect the reception in any way.
  • the reception frequency of the receiver is switched to an alternative frequency, during a null symbol and only during the null symbol, in an alternative frequency step 583.
  • the alternative frequency that is switched to will preferably come from a list that is maintained by the receiver by means of information received from DAB.
  • signals are received from the alternative frequency and measured and analysed in a measuring step 584.
  • the receiver switches reception frequency back to the currently received frequency in a switch-back step 585, for reception of the information carrying part of the frame.
  • a more alternatives test step 586 tests if there are more alternative frequencies to perform a test reception on. If there are more alternative frequencies, then the procedure preferably continues, either with the null symbol step 582 or with the alternative frequency step 583 depending on the specific implementation. On the other hand, if there are no more alternative frequencies, then the procedure continues to a determination step 587.
  • the determination step 587 analyses the measurements which were taken during the measurement step 585 on the alternative frequencies and preferably the field strength measurements taken on the currently received frequency and determines in view of all the measurements if a switch/ change of reception frequency should be done and if so to what alternative frequency.
  • a change reception frequency test step 588 will direct the procedure in the correct direction in view of the outcome of the determination step 587. If it is determined that the receiver should change reception frequency, then the procedure continues to a change reception frequency step 589. If, on the other hand, the circumstances are such that the currently received frequency is still that which is preferable, then the procedure continues either to step 580, step 582, or step 583, or to something completely different, all depending on the specific implementation of the invention.
  • the invention can basically be described as a device and a method which provide means to enable a change of reception frequency without any or very little interruption to the received programme.
  • FIG 1 A first figure.

Abstract

Procédé et dispositif pour l'essai de réception de fréquences d'autres fréquences de réception sans interruption de la réception des séquences RAN de la fréquence de réception en cours d'utilisation dans un récepteur RAN. Une séquence RAN comprend un symbole nul qui est utilisé pour une synchronisation très grossière du récepteur par rapport aux signaux émis. Les essais de réception d'autres fréquences ont lieu pendant les symboles nuls du programme en cours de réception, lequel n'est pas du tout interrompu pendant lesdits essais. Une permutation de fréquence déterminée ultérieurement peut être assurée, avec une grande probabilité, sans interruption perceptible.
PCT/SE1998/001624 1997-09-16 1998-09-14 Procede et dispositif utilises pour le changement de frequence de reception dans un recepteur de systeme de radiodiffusion numerique WO1999014874A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CA002303938A CA2303938A1 (fr) 1997-09-16 1998-09-14 Procede et dispositif utilises pour le changement de frequence de reception dans un recepteur de systeme de radiodiffusion numerique
EP98943168A EP1032994A1 (fr) 1997-09-16 1998-09-14 Procede et dispositif utilises pour le changement de frequence de reception dans un recepteur de systeme de radiodiffusion numerique
AU91019/98A AU9101998A (en) 1997-09-16 1998-09-14 Method and device for change of reception frequency in a digital audio broadcasting system receiver

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9703331A SE9703331D0 (sv) 1997-09-16 1997-09-16 Method and device for change of reception
SE9703331-0 1997-09-16

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WO1999014874A1 true WO1999014874A1 (fr) 1999-03-25

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WO2001022632A1 (fr) * 1999-09-20 2001-03-29 Teracom Ab Systeme de radiodiffusion
DE19956933A1 (de) * 1999-11-26 2001-06-21 Bosch Gmbh Robert Empfänger für analog und digital übertragene Rundfunkprogramme
WO2001050648A1 (fr) * 1999-12-29 2001-07-12 Teracom Ab Procede et dispositif d'un recepteur en diversite
EP1139564A2 (fr) * 2000-03-31 2001-10-04 Pioneer Corporation Récepteur de radiodiffusion comportant un dispositif de balayage de fréquences alternatives sans perturber la réception d'un programme radiophonique sélectionné
EP1191722A2 (fr) * 2000-09-14 2002-03-27 Sony Corporation Appareil et méthode pour la réception de signaux de radiodiffusion audionumérique DAB
EP1211829A2 (fr) * 2000-12-04 2002-06-05 SANYO ELECTRIC Co., Ltd. Récepteur pour la réception de transmissions de radiodiffusion numérique, comportant un syntoniseur pour sélectionner un émetteur parmi une pluralité d'émetteurs
EP1172952A3 (fr) * 2000-07-11 2005-04-06 Pioneer Corporation Récepteur pour la réception d'émissions radiophoniques numériques comportant un dispositif pour détecter le niveau d'erreur et le niveau du signal des émissions radiophoniques
EP1626534A1 (fr) * 2004-08-09 2006-02-15 Samsung Electronics Co., Ltd. Procédé et dispositif pour faire la distinction entre services dans toutes le bandes de fréquences et dans une bande de fréquence specifique
US7231404B2 (en) 2003-01-31 2007-06-12 Nokia Corporation Datacast file transmission with meta-data retention
US7343487B2 (en) 2001-10-10 2008-03-11 Nokia Corporation Datacast distribution system
EP2091164A3 (fr) * 2008-02-13 2010-07-14 Sony Corporation Appareil de réception radio et procédé de rétablissement des sorties
US7835706B2 (en) 2004-06-30 2010-11-16 Silicon Laboratories, Inc. Local oscillator (LO) port linearization for communication system with ratiometric transmit path architecture
EP2802094A1 (fr) * 2013-05-09 2014-11-12 Frontier Silicon Limited Système de récepteur radio numérique et procédé
US9065577B2 (en) 2013-05-09 2015-06-23 Frontier Silicon Limited Digital radio receiver system and method
WO2016074693A1 (fr) 2014-11-10 2016-05-19 Bayerische Motoren Werke Aktiengesellschaft Procédé et dispositif pour recevoir un service de diffusion comprenant une commutation entre des transmissions de diffusion audio numérique (dab) et des transmissions de diffusion/multidiffusion multimédia améliorée (embms)

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Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001022632A1 (fr) * 1999-09-20 2001-03-29 Teracom Ab Systeme de radiodiffusion
DE19956933A1 (de) * 1999-11-26 2001-06-21 Bosch Gmbh Robert Empfänger für analog und digital übertragene Rundfunkprogramme
WO2001050648A1 (fr) * 1999-12-29 2001-07-12 Teracom Ab Procede et dispositif d'un recepteur en diversite
EP1139564A3 (fr) * 2000-03-31 2005-06-08 Pioneer Corporation Récepteur de radiodiffusion comportant un dispositif de balayage de fréquences alternatives sans perturber la réception d'un programme radiophonique sélectionné
EP1139564A2 (fr) * 2000-03-31 2001-10-04 Pioneer Corporation Récepteur de radiodiffusion comportant un dispositif de balayage de fréquences alternatives sans perturber la réception d'un programme radiophonique sélectionné
US7184726B2 (en) 2000-03-31 2007-02-27 Pioneer Corporation Broadcast receiver
US7039127B2 (en) 2000-07-11 2006-05-02 Pioneer Corporation Digital broadcast receiving apparatus
EP1172952A3 (fr) * 2000-07-11 2005-04-06 Pioneer Corporation Récepteur pour la réception d'émissions radiophoniques numériques comportant un dispositif pour détecter le niveau d'erreur et le niveau du signal des émissions radiophoniques
EP1191722A3 (fr) * 2000-09-14 2004-07-14 Sony Corporation Appareil et méthode pour la réception de signaux de radiodiffusion audionumérique DAB
EP1191722A2 (fr) * 2000-09-14 2002-03-27 Sony Corporation Appareil et méthode pour la réception de signaux de radiodiffusion audionumérique DAB
EP1211829A2 (fr) * 2000-12-04 2002-06-05 SANYO ELECTRIC Co., Ltd. Récepteur pour la réception de transmissions de radiodiffusion numérique, comportant un syntoniseur pour sélectionner un émetteur parmi une pluralité d'émetteurs
EP1211829A3 (fr) * 2000-12-04 2005-12-14 SANYO ELECTRIC Co., Ltd. Récepteur pour la réception de transmissions de radiodiffusion numérique, comportant un syntoniseur pour sélectionner un émetteur parmi une pluralité d'émetteurs
US7343487B2 (en) 2001-10-10 2008-03-11 Nokia Corporation Datacast distribution system
US7437549B2 (en) 2001-10-10 2008-10-14 Nokia Corporation Datacast distribution system
US7231404B2 (en) 2003-01-31 2007-06-12 Nokia Corporation Datacast file transmission with meta-data retention
US7853620B2 (en) 2003-01-31 2010-12-14 Nokia Corporation Datacast file transmission with meta-data retention
US7835706B2 (en) 2004-06-30 2010-11-16 Silicon Laboratories, Inc. Local oscillator (LO) port linearization for communication system with ratiometric transmit path architecture
EP1873973A1 (fr) * 2004-08-09 2008-01-02 Samsung Electronics Co., Ltd. Procédé et dispositif pour faire la distinction entre des services dans toutes le bandes de fréquences et dans une bande de fréquence spécifique
US7436825B2 (en) 2004-08-09 2008-10-14 Samsung Electronics Co., Ltd. Method and apparatus for distinguishing between services of all frequency bands and specific frequency band
EP1626534A1 (fr) * 2004-08-09 2006-02-15 Samsung Electronics Co., Ltd. Procédé et dispositif pour faire la distinction entre services dans toutes le bandes de fréquences et dans une bande de fréquence specifique
EP1988668A3 (fr) * 2004-08-09 2008-12-03 Samsung Electronics Co., Ltd Procédé et appareil pour distinguer entre services disponibles en toutes les bandes de fréquence et services dispobibles dans une bande de fréquence spécifique
EP2091164A3 (fr) * 2008-02-13 2010-07-14 Sony Corporation Appareil de réception radio et procédé de rétablissement des sorties
EP2802094A1 (fr) * 2013-05-09 2014-11-12 Frontier Silicon Limited Système de récepteur radio numérique et procédé
US9065577B2 (en) 2013-05-09 2015-06-23 Frontier Silicon Limited Digital radio receiver system and method
US9455793B2 (en) 2013-05-09 2016-09-27 Frontier Silicon Limited Digital radio receiver system and method
WO2016074693A1 (fr) 2014-11-10 2016-05-19 Bayerische Motoren Werke Aktiengesellschaft Procédé et dispositif pour recevoir un service de diffusion comprenant une commutation entre des transmissions de diffusion audio numérique (dab) et des transmissions de diffusion/multidiffusion multimédia améliorée (embms)
US9917666B2 (en) 2014-11-10 2018-03-13 Bayerische Motoren Werke Aktiengesellschaft Method and device for receiving a broadcast service comprising switching between digital audio broadcasting (DAB) transmissions and enhanced multimedia broadcast/multicast transmissions (EMBMS)

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SE9703331D0 (sv) 1997-09-16
AU9101998A (en) 1999-04-05
EP1032994A1 (fr) 2000-09-06
CA2303938A1 (fr) 1999-03-25

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