Title of Invention

A METHOD OF ADJUSTING TRANSMISSION PARAMETERS OF DIGITAL RADIO SIGNAL TRANSMITTER

Abstract A method of adjusting transmission parameters of digital radio signal transmitter, comprising receiving digital radio signals by at least one reception device the digital radio signals being emitted by the transmitter, transmitting data to the transmitter via a backward channel by the at least one reception device, transmitting at least parts of the received radio signals and reception parameters and channel parameters in the data, setting the transmission parameters as a function of the data by the transmitter, receiving the digital radio signals by more than one reception device, transmitting the digital broadcast signals at frequencies below 30 MHz. (fig.1)
Full Text

Method for setting transmission parameters for a transmitter for digital radio signals
Prior Art
The invention is based on a method for setting transmission parameters for a transmitter for digital radio signals in accordance with the generic part of the independent patent claim.
The DAB (Digital Audio Broadcasting) system is already in use, in which digital broadcast radio signals, particularly for mobile reception in motor vehicles, are transmitted. DRM (Digital Radio Mondial), as a digital broadcast radio transmission system, is designed for transmission bands below 30 MHz and is currently undergoing development. Transmission parameters are set using propagation predications, test runs and listener logs. This takes into account the regional environmental influences particularly significant to DRM. Changes over time can only be detected to an unsatisfactory extent using these methods.
Advantages of the Invention
By contrast, the inventive method for setting transmission parameters for a transmitter for digital radio signals having the features of the independent patent claim has the advantage that ascertaining the transmission and reception quality of the digital radio signals, particularly broadcast radio signals, and setting the transmission parameters are automated. To this end, a back channel is advantageously used which is independent of the radio channel for the digital broadcast radio signals. The inventive method matches the transmission quality of the digital broadcast radio signals to the regional conditions and improves it. In addition, the inventive method is used for checking the

transmitter.
The measures and developments cited in the dependent claims allow advantageous improvements of the method specified in the independent patent claim for setting transmission parameters for a transmitter for digital radio signals.
A particular advantage is that at least some of the digital broadcast radio signals received by the reception apparatus are transmitted to the transmitter directly, which means that the transmitter then performs evaluation itself. The reception apparatus thus acts only as a relay station, and the evaluation, which requires intensive computation, can be moved to the transmitter. This advantageously allows commercial reception units to be used provided that they have an interface for connection to a back channel, with a mobile telephone being connected to the reception apparatus. This is because they then need not have any function which transcends the normal functionality of the reception apparatus. The digital broadcast radio signals are then transmitted via a back channel which is either in wired form, for example the public telecommunication network, or in wireless form with a high level of error protection.
Alternatively or in addition, the reception apparatus may actually ascertain the channel parameters and the reception parameters from the received digital broadcast radio signals, which means that the transmitter then need only optimize its transmitter parameters using the channel parameters and reception parameters. This is advantageous if the reception apparatus has appropriate means, that is to say a processor which performs this evaluation, and normal operation of the reception apparatus, that is to say reception of digital broadcast radio signals and reproduction of these signals, is not disturbed in the

process. It is then possible to implement this evaluation option for the channel parameters by simply installing additional software on the processor in the reception apparatus. The reception parameters are evaluated by the reception apparatus anyway, and to this end functions then need to be provided which ensure that the reception parameters are transmitted to the transmitter. When evaluation in the transmitter and in the reception apparatus is combined, the received broadcast radio signals are [lacuna] the evaluation can be distributed such that the transmitter advantageously bears the main load of the evaluation, since a transmitter can more easily accommodate more computation power.
Another advantage is that the channel parameters ascertained are the Doppler spread, the echo delay-time difference, the signal-to-noise ratio, the cochannel and adjacent-channel interference, and that this provides comprehensive characterization of the transmission channel. The transmitter is then able to set its transmission parameters in optimum fashion.
Another advantage is that the reception apparatus ascertains the bit error rate and the failed checksum tests (CRC = Cyclic Redundancy Check) as reception parameters. These data are also ascertained in the reception apparatus when decoding the digital broadcast radio signals in normal operation, which means that the reception apparatus does not need to have any additional functionality for this purpose.
Another advantage is that the transmitter parameters to be optimized which are set are the transmission frequency, the channel coding, the source data rate, the transfer rate, the modulation and the transmission power. The transmission frequency affords the advantage that, if intense attenuation phenomena arrise at one frequency, there is a change to an alternative

frequency. The channel coding can be made more complex or simpler according to the error rate, this needing to be regarded in connection with the transfer rate and with the source data rate. The source data rate needs to be increased if transmission conditions are very good. It is thus possible to transmit a large amount of useful data. If conditions are poor, the channel code rate can be increased for a fixed transfer rate by reducing the source data rate. This then increases the level of error protection. The modulation can also be altered such that the depth of modulation is increased or reduced, provided that this is possible- With a poor signal-to-noise ratio, the transmission power needs to be increased in particular, and this can be reduced if there is a very good signal-to-noise ratio on the reception apparatus.
Another advantage is that, if different data are transmitted as services in the digital broadcast radio signals, with the services being assigned different priorities, the source data rate and the transfer rate can be assigned to these services according to priority. If, by way of example, data are transmitted in addition to the normal broadcast radio program, then, under poor transmission conditions, the source data rate can be retained for the broadcast radio program while it is reduced for the data service in order to allow for the poor transmission conditions.
Another advantage is that, if a transmission is made in packets, the repetition rate of the packets is altered according to the transmission quality. Under poor conditions, the repetition rate is accordingly increased, which means that the likelihood of correct reception of the packets is likewise increased. Under very good transmission conditions, the repetition rate can be reduced, so that the net transfer rate is ultimately increased. Hence, more information is then

transmitted in a prescribed time interval without repetition.
It is advantageous when OFDM (Orthogonal Frequency Division Multiplex) signals are used that, depending on transmission conditions, the transmission parameters matched to the transmission conditions are the carrier interval and the length of the guard interval. Such altered transmission parameters need to be communicated to the reception apparatus, preferably in a service data part which is always transmitted in the same way. This then allows correct evaluation of the received data by the reception apparatus.
Another advantage is that the reception apparatus compares the reception parameters and/or the channel parameters, provided that the reception apparatus evaluates the channel parameters itself, with threshold values in order to ascertain whether transmission to the transmitter via the back channel is necessary in order to adjust the transmitter parameters. Transmission bandwidth is thus advantageously saved, since the reception apparatus transmits to the transmitter only if the transmission parameters need to be adjusted. This defines a permissible operating range for the transmission parameters.
Another advantage is that transmission data and reception parameters are transmitted only at particular times which are prescribed, since experience has shown that the transmission parameters do not need to be adjusted permanently. The effects such as environmental influences, which affect transmission quality, are to some extent dependent on the day or indeed change from month to month.
Another advantage is that the back channel is operated in duplex mode, which means that the reception apparatus can be controlled and/or polled by the

transmitter. In this case, the back channel needs to be provided either as a radio channel or as a combination comprising a radio channel and wired transmission. In particular, transmission over the Internet is advantageous in this context, since it is then possible to store the reception parameters ascertained by the reception apparatus, and the transmitter can then retrieve them at particular times. To this end, reference appliances can advantageously be used which are used only for checking the reception quality of the digital broadcast radio signals, these reference appliances simultaneously monitoring a plurality of transmissions using time division multiplexing and/or frequency division multiplexing.
Another advantage is that the transmitter is operated in a simultaneous broadcasting network, with the data ascertained by the reception apparatus then being transmitted to a control centre which then transmits appropriate data to the individual transmitters.
Another advantage is that the inventive method is used for digital broadcast radio signals which are transmitted at below 30 MHz. These signals are particularly susceptible to environmental influences, which means that in this case it is necessary to optimize the transmitter parameters on the basis of measurements by reception apparatuses.
Finally, another advantage is that a transmitter and a reception apparatus each have means for carrying out the inventive method.
Drawing
Exemplary embodiments of the invention are illustrated in the drawing and are explained in more detail in the description below. In the drawing

"Figure 1 shows a transmission system and Figure 2 shows the inventive method in the form of a flowchart.
Description
Digital broadcast radio systems have various transmission modes in which they can be operated. A transmission mode is characterized by a set of transmission parameters. The transmission parameters include all parameters which can be set at the transmitter end in the source coder, in the modulator and in the transmission amplifier. They include, by way of example, the source data rate, the code rate and the transmission power. The transmission modes are used to ensure sufficiently good transmission quality in various transmission channels. These different properties of the transmission channels arise as a result of different transmission frequencies and fluctuating propagation conditions. Particularly in the channels below 30 MHz, very intense fluctuations in the channel parameters such as Doppler spread, echo delay-time difference and signal-to-noise ratio can arise as a function of time. This also results in fluctuations in the reception parameters. The reception parameters include all parameters which are measured by the receiver and which indicate the transmission parameters and the reception quality, such as the bit error rate.
For the fluctuations in the transmission channel, it is possible to distinguish between short-term ones in the range of seconds and minutes and longer-term ones in the range of hours, days and months.
According to the invention, a reception apparatus therefore uses a back channel to transmit data which have been obtained from received digital broadcast radio signals to a transmitter. The data are used to transmit transmission data and reception parameters, so

that the transmitter sets the transmission parameters on the basis of these data. The transmission data are either the received digital broadcast radio signals themselves or channel parameters which are calculated by the reception apparatus using the received digital broadcast radio signals. The reception parameters and the channel parameters are compared with threshold values by the reception apparatus in order to open the back channel only if these threshold values are exceeded or undershot and to transmit the data for optimizing the transmission parameters to the transmitter. Alternatively, it is possible for the data from the reception apparatus to be transmitted from the reception apparatus to the transmitter at particular prescribed times. By operating the back channel in duplex mode, it is possible for the transmitter to request data from the reception apparatus or to control the reception apparatus in order to measure particular signals. In this case, a reception apparatus may receive various broadcast radio signals transmitted at various frequencies.
Figure 1 shows a transmission system where a transmitter 13 is transmitting digital broadcast radio signals to a reception apparatus 14. A back channel 12 designed to operate in duplex mode is used to provide a further connection between the reception apparatus 14 and the transmitter 13.
The transmitter 13 has a data source 1, a source coding section 2, a modulator 3, a transmission amplifier 4, an antenna 5, a processor 6 and a communications device 11. The reception apparatus 14 has an antenna 7, a radio-frequency receiver 8, a processor 9 and a communications device 10.
The data source 1 delivers digital data to a first data input of a source coding section 2. A second data input of the source coding section 2 has the processor 6

connected to it. The output data from the source coding section 2 are transmitted to a first data input of the modulator 3. A second data input of the modulator 3 has the processor 6 connected to it. The output data from the modulator 3 are routed to a first data input of a transmission amplifier 4. A second data input of the transmission amplifier 4 has the third data output of the processor 6 connected to it. A data input/output is used to connect the processor 6 to the communications device 11. An output of the transmission amplifier 4 has the antenna 5 connected to it. A data input/output is used to connect the communications device 11 to the back channel 12.
The antenna 7 is connected to an input of the radio-frequency receiver 8. A data input/output is used to connect the radio-frequency receiver 8 to the processor 9. A second data input/output is used to connect the processor 9 to the communications device 10. The second data input/output communications of the device 10 is connected to the back channel 12.
The data to be transmitted are transmitted from the data source 1 to the source coding section 2. In this case, the data source 1 is a data memory from which the broadcast radio signals to be transmitted are read in order to be transmitted to the source coding section 2. The data memory provided in this case is a player for audio media, a CD-ROM drive. Alternatively, the data source 1 can be a microphone with connected electronics which are used to digitize the acoustic signals that have been converted into electrical signals.
The source coding section 2 reduces the data volume of the data coming from the data source 1 by removing from the data any irrelevance which is not required for reconstructing these data in the reception apparatus
14.

In the modulator 3, error protection is added to the data by the channel coding and can be used to reconstruct incorrectly received data. In addition, the data are modulated. First, the information contained in the data is modulated using angle modulation, in this case quadrature amplitude modulation, and then the modulation symbols produced in this manner are distributed over mutually independent frequency carriers (OFDM) . In addition, the data to be transmitted have a guard interval added to them which ensures that multipath propagation does not result in any useful data overlapping. In addition, the useful data have a service data part added to them which is necessary for synchronization and for reception.
In the transmission amplifier 4, the data modulated in this manner are converted into analog signals and are amplified. The antenna 5 is then used to transmit the broadcast radio signals. The processor 6 optimizes the settings for the source coding section 2, for the modulator 3 and for the transmission amplifier 4 on the basis of data which the processor 6 receives from the communications device 11. The communications device 11 receives these data in turn via the back channel 12 from the communications device 10 in the reception apparatus 14.
The reception apparatus 14 uses the antenna 7 to receive the digital broadcast radio signals broadcast by the transmitter 13. These broadcast radio signals are then filtered by the radio-frequency receiver 8, are amplified and are converted into an intermediate frequency. Digitization is also performed in the radio-frequency receiver 8. The digital data are then transmitted to the processor 9, which performs demodulation, initially OFDM demodulation and then demodulation of the QAM-modulated signals, error correction and source decoding. The processor 9 determines the reception parameters to be the bit error

rate and the failed checksum tests which are determined during the channel decoding. The processor 9 also removes from the digital broadcast radio signals particular data as the transmission data. These transmission data in the case of DRM are the "SDC" (Static Data Channel) symbols and pilots which are transmitted with known phase and amplitude and which can therefore be used for determining channel parameters characterizing the radio channel. Using these transmission data, either the processor 9 determines the channel parameters or these data are transmitted to the transmitter 13 via the back channel 12 by means of the communications device 10. In addition, , the reception parameters determined by the reception apparatus 14 are transmitted to the transmitter 13.
The back channel 12 is in this case a combination comprising radio transmission using a mobile radio system, for example GSM (Global System for Mobile Communication) or GPRS (General Packet Radio System) or UMTS (Universal Mobile Telecommunication System), and a wired type of transmission via the public telecommunications network, that is to say ISDN or the Internet. Alternatively, it is possible for a pure radio link or a pure wired link to exist between the transmitter 13 and the reception apparatus 14, It is also possible for more than one reception apparatus to receive the digital broadcast radio signals and to communicate these data to the transmitter 13 via a back channel. It is then up to the transmitter 13 to perform optimization using these various data from . the individual reception apparatuses.
Figure 2 shows the inventive method in the form of a flowchart. In method step 15, the reception apparatus 14 uses the antenna 7 to receive the digital broadcast radio signals. The digital broadcast radio signals are then, as shown above, processed by the radio-frequency

receiver 8 and are converted to give digital signals. The data are then transmitted to the processor 9.
In method step 16, the processor 9 determines the reception parameters. To this end, the processor 9 determines the bit error rate during channel decoding, with the channel coding indicating how many bits have been received incorrectly. In addition, the received digital broadcast radio signals have data which are provided to form checksums. These checksums also provide an indication of whether or not the transmitted data have been transmitted correctly. The processor 9 counts the failed checksums per transmitted data volume and indicates the bit error rate and the number of failed checksums as the reception parameters in order to transmit them to the transmitter 13.
In method step 17, a check is performed to determine whether the receiver 14 or the transmitter 13 needs to evaluate the digital broadcast radio signals in order to determine the channel parameters. If this is the case, the reception apparatus 19 uses the processor 9 to evaluate the digital broadcast radio signals in method step 19. The transmission parameters determined are the Doppler spread, the echo delay-time difference, the signal-to-noise ratio and the cochannel and adjacent-channel interference for the received digital broadcast radio signals. These parameters are not static.
The Doppler spread describes the time-selective properties of the transmission channel. In this context, time-dependent attenuation (fading) can be observed. The echo delay-time difference depicts the property of multipath propagation that the same signal can be sent to the receiver via different paths. This is well known in mobile radio systems and broadcast radio systems. The signal-to-noise ratio depicts the ratio of the useful signal to noise. As a simple gauge.

just the signal level can also be used in this context. This also provides a gauge of the attenuation. The cochannel and adjacent-channel interference indicates how adjacent channels interfere with one another through crosstalk. These channel parameters are ascertained from the digital broadcast radio signals.
In method step 18, the channel parameters are then transmitted with the reception parameters via the back channel 12 using the communications device 10. If it has been established in method step 17 that the channel parameters are ascertained by the transmitter 13, then the transmission data, that is to say the broadcast radio signals and the reception parameters ascertained by the reception apparatus 14, are transmitted to the transmitter 13 in method step 18. The communications devices 10 and 11 are produced according to which back channel is used. If a landline network is used, the communications devices 10 and 11 are in the form of modems. If a radio channel is used, a transmission/reception station is necessary. In one development, it is possible for the transmission data and the reception parameters to be stored on an Internet page in order to be subsequently retrieved by the transmitter 13 at prescribed times. If the back channel is in duplex form, as illustrated in the present case, then it is also possible for the reception apparatus 14 to be controlled by the transmitter 13, specifically such that data are requested from the reception apparatus at particular times. It is also possible to change the reception frequencies in this context. Such a measure can in that case be implemented particularly on reference appliances provided for the purpose.
In method step 19, the processor 6 checks whether the transmitter 13 needs to evaluate the digital broadcast radio signals or whether they have already been evaluated. This is contained in the data which have

been transmitted to the transmitter 13 via the back channel 12. If no evaluation has been performed by the reception apparatus 14, then in method step 20 this evaluation is performed as illustrated above by the processor 6. The transmitter parameters are then optimized in method step 21. Optimization of the transmitter parameters in method step 21 is also performed immediately if it has been established in method step 19 that evaluation has already been performed. For optimizing the transmitter parameters, it is necessary to ensure that the transmitter 13 respectively loads particular sets of values for the transmitter parameters at particular values for the reception parameters and channel parameters, and then transmits these values [lacuna] the source coding section 2, the modulator 3 and the transmission amplifier 4. In this case, the situation is advantageously such that the channel parameters and reception parameters are used to form a code number which is then compared with these threshold values in order to load the appropriate set of transmission parameters. Alternatively, it is also possible for the processor 6 to calculate a set of transmission parameters from the channel parameters and reception parameters. In this case, the processor 6 then knows a model which can be used for this calculation.
In method step 22, the transmission parameters are then set as appropriate, so that the digital broadcast radio signals are now transmitted using the optimized transmission parameters.
Alternatively, the back channel 12 can also be in the form of a simplex channel, in which case transmission is possible only from the reception apparatus 14 to the transmitter 13.
If data are transmitted in a packet mode, then the repetition rate is a settable transmission parameter.

Various services, audio or video or data or prioritized data can be taken into account in different ways when setting the transmission parameters-




We Claims
1. Method for setting transmission parameters for a transmitter (13) for digital radio signals, particularly broadcast radio signals, where at least one reception apparatus (14) receives the digital radio signals broadcast via the transmitter (13), characterized in that the at least one reception apparatus (14) uses a back channel (12) to transmit data to the transmitter (13), in that at least portions of the received radio signals and/or reception parameters and channel parameters are transmitted in the data, and in that the transmitter (13) sets the transmission parameters on the basis of the data.
2. Method according to Claim 1, characterized in that the at least portions of the received digital radio signals are used by the transmitter (13) to set the transmission parameters, the transmitter (13) ascertaining the reception parameters and the channel parameters from the at least portions of the received digital radio signals.
3. Method according to Claim 1 or 2, characterized in that the reception parameters and the channel parameters evaluated by the reception apparatus (14) using the at least portions of the received digital radio signals are used by the transmitter (13) to set the transmission parameters.
4. Method according to Claim 2 or 3, characterized in that, to set the transmission parameters, the channel parameters are used to determine the Doppler spread, the echo delay-time difference, the signal-to-noise ratio and the cochannel and adjacent-channel interference for the received digital radio signals.
5. Method according to Claim 4, characterized in that, to set the transmission parameters, the reception

parameters are used by the at least one reception apparatus (14) to determine the bit error rate for the received digital radio signals and the number of failed checksum tests.
6. Method according to Claim 5, characterized in that the transmission parameters set are transmission frequencies and/or the channel coding and/or the source data rate and/or the modulation and/or the transmission power and/or the transfer rate.
7. Method according to Claim 6, characterized in that, if the transfer rate can be distributed over different services, the transfer rate and/or the source data rate is assigned to the different services on the basis of their priority,
8. Method according to Claim 6 or 7, characterized in that, if the digital radio signals are transmitted in a packet mode, the repetition rate of packets is set as a transmission parameter,
9. Method according to Claim 6, 7 or 8 characterized in that, if the digital radio signals are transmitted using orthogonal frequency division multiplexing (OFDM), the further transmission parameters set are the carrier interval and the length of the guard interval.
10. Method according to one of the preceding claims, characterized in that the channel parameters and/or the reception parameters are compared with at least one threshold value, and in that the data are transmitted via the back channel (12) only if the at least one threshold value is exceeded or undershot.
11 - Method according to one of the preceding claims, characterized in that the channel parameters and/or reception parameters are evaluated at particular times.

12. Method according to one of the preceding claims, characterized in that the back channel (12) is operated in duplex models . Method according to one of the preceding claims, characterized in that the transmitter (13) is operated in a simultaneous broadcasting network, where the at least one reception apparatus is connected to a control center in the simultaneous broadcasting network.
14. Method according to one of the preceding claims, characterized in that the digital radio signals are transmitted at transmission frequencies below 30 MHz.
15. Transmitter for carrying out the method according to one of Claims 1 to 14, characterized in that the transmitter has a data source (1), a source coding section, a modulator (3), a transmission amplifier (4), an antenna (5) , a processor (6) for ascertaining the transmission parameters and a first communications device (11) for communication via the back channel.
16. Reception apparatus for carrying out the method according to one of Claims 1 to 14, characterized in that the reception apparatus has an antenna (7) for receiving the digital broadcast radio signals, a radio-frequency receiver (8), a processor (9) for ascertaining the reception and/or channel parameters and a second communications device (10) for communication via the back channel (12).

17. A method for setting transmission parameters from a transmitter for digital radio signals, substantially as hereinabove described and illustrated with reference to the accompanying drawings.


Documents:

068-chenp-2003-abstract.pdf

068-chenp-2003-claims filed.pdf

068-chenp-2003-claims granted.pdf

068-chenp-2003-correspondnece-others.pdf

068-chenp-2003-correspondnece-po.pdf

068-chenp-2003-description(complete) filed.pdf

068-chenp-2003-description(complete) granted.pdf

068-chenp-2003-drawings.pdf

068-chenp-2003-form 1.pdf

068-chenp-2003-form 26.pdf

068-chenp-2003-form 3.pdf

068-chenp-2003-form 5.pdf

068-chenp-2003-other documents.pdf

abs-68-chenp-2003.jpg


Patent Number 208645
Indian Patent Application Number 68/CHENP/2003
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 06-Aug-2007
Date of Filing 10-Jan-2003
Name of Patentee M/S. ROBERT BOSCH GMBH
Applicant Address Postfach 30 02 20 70442 Stuttgart
Inventors:
# Inventor's Name Inventor's Address
1 LAUTERBACH, Thomas Von-Soden-Strasse 32 90475 N├╝rnberg (DE).
2 HOFMANN, Frank Dachsweg 5 31139 Hildesheim (DE).
PCT International Classification Number H04L 1/00
PCT International Application Number PCT/DE2001/001804
PCT International Filing date 2001-05-11
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 100 35 041.0 2000-07-19 Germany