JPH11274958A - Digital broadcast receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of comparison result obtained between the receiving states of the DAB and FM signals by comparing the receiving state evaluation of an FM receiving part that is decided, based on the error rate of RDS data with the receiving state evaluation of a DAB receiving part that is decided, based on the voice frame error rate included in the DAB data. SOLUTION: A system control part 1 decides whether a DAB receiving part is tuned to any of the ensembles. If the receiving part is tuned to an ensemble, the part 1 decodes the FIC data and extracts the information of the protection level and bit rate of each subchannel to store these information in a storage part 5. Then the evaluation reference value of the current selected subchannel is selected from among a table stored in the part 5, based on the held protection level information on each subchannel and the information on the subchannel under selection. The selected evaluation reference value is compared with the error rate that is calculated at the part 1. Then the receiving state of a DAB station is considered deteriorating, when the error rate is larger than the evaluation reference value, and a switching part 2 is controlled to reproduce the voices of an RDS station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiver, and more particularly to a digital audio broadcast receiver which is already in practical use in Europe.
ng) related to the receiver.

[0002]

2. Description of the Related Art As a system for transmitting and receiving a broadcast wave having a data signal of a predetermined format including a digital audio signal, a European standard (Eureka 14) is used.
There is a digital audio broadcasting (hereinafter referred to as DAB) system based on 7). In DAB, one ensemble is composed of a plurality of services, and each service is composed of a plurality of components such as English and German.

FIG. 5 shows an example of a service configuration of a DAB system. The services (three in this case) constituting the ensemble 1, each component (six in this case) and the D
FIG. 3 is a diagram illustrating a link with an OFDM signal transmitted from an AB station.

The OFDM signal transmitted from the DAB station is
It is divided into FIC (Fast Information Channel) and MSC (Main Service Channel).

Each sub-channel (Su) constituting the MSC
bCh1 to 63) have a correspondence with the above components, and the FIC includes information on services available in the ensemble and information indicating links between services, components, and subchannels.

[0006] Therefore, in DAB, when a certain ensemble is received, information on a plurality of services and components included in the ensemble can be obtained.
It is possible to switch instantly to different services and components without changing the reception frequency.

One of the uses of the DAB receiver for receiving the broadcast is a service follow-up function for FM stations that provide the same program. This function will be described below. In the DAB, various information data included in the FIC can include information about an FM station that broadcasts the same program as the program being received. For example, identification information and frequency information of an FM station that broadcasts the same program correspond to this.

Therefore, by acquiring such information from the FIC being received and controlling the RDS receiver based on this information, it is possible to detect the FM station broadcasting the same program.

Therefore, by comparing the reception states of both, DA
When the reception condition of the B receiver deteriorates, the reproduction output is switched to the audio output of the FM station that broadcasts the same program (service follow), so that good reproduction audio can be maintained.

On the other hand, in DAB, a bit rate of audio information and a protection level (1 to 5) for transmission can be defined for each sub-channel by the FIC.

The protection level indicates the strength against a transmission error (the larger the number, the higher the coding rate, the lower the redundancy and the weaker the error), and convolutional coding and coding according to the protection level. An encoding rate is defined by extracting (puncturing) a part of the subsequent signal. The DAB specifies that the average code rate obtained from the bit rate and the protection level of audio information takes a value of 0.34 to 0.75.

[0012]

Since the above-mentioned service follow selects a better reception state between the DAB signal and the FM signal, it is necessary to compare both reception states. Since both DAB receivers take completely different transmission forms, the reception state of the received DAB signal and the F
It is difficult to evaluate the reception state of the M signal with the same criterion, and as a result, the reliability of the comparison result does not increase.

As a method of detecting the reception state of the FM receiver, parameters such as the reception electric field strength and the distortion component (high-frequency component) of the detection output are well known, and even the DAB receiver has the same signal before and after the Viterbi decoder. The use of a parameter such as an error rate calculated by comparing data is expected, but the optimal parameter for comparing the reception state of the DAB signal and the FM signal has not yet been clearly defined,
There is room for study and improvement.

Accordingly, an object of the present invention is to increase the reliability of the result of comparison between the reception state of a DAB signal and the reception state of an FM signal.

[0015]

According to the first aspect of the present invention, an FM receiver including an RDS decoder, a DAB receiver, a reception state of the FM receiver, and a reception state of the DAB receiver are described. And a control unit that controls the reproduction output of the reception unit, which indicates a better reception state, to be the output of the receiver, wherein the control unit performs a block error of the RDS data. First evaluating means for evaluating a receiving state of the FM receiving unit based on a rate;
A second evaluation unit for evaluating a reception state of the DAB receiving unit based on a frame error rate of an audio frame included in the B data, an evaluation result obtained by the first evaluation unit, and an evaluation result obtained by the second evaluation unit. Comparing means for comparing
It is characterized by having.

According to a second aspect of the present invention, in the first aspect of the present invention, the control unit includes a calculating unit for calculating the block error rate and the frame error rate, The number of blocks to be calculated and the number of frames to be calculated for the frame error rate are set to be substantially the same.

According to a third aspect of the present invention, in the first aspect of the present invention, the second evaluation means includes the DAB
Based on the protection level information included in the data,
It is characterized in that evaluation criteria are changed.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the second evaluation means includes the DAB
The evaluation criteria are changed based on bit rate information included in the data.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram of a digital broadcast receiver provided with an RDS receiver according to an embodiment of the present invention. The receiver includes a DAB receiving unit for receiving digital broadcasting, an FM receiving unit for receiving RDS broadcasting, a system control unit 1, and a switching unit 2.
, An amplifier 3, a speaker 4, and a storage unit 5.

The DAB receiving section includes a DAB-FE (DAB front end) 11 for performing tuning control for the DAB station, an A / D converter 12 for converting a received analog signal into a digital signal, and demodulates an OFDM wave. (Fast Fourier Transform) unit 13, a Viterbi decoding unit 14 for error correction, and an audio decoder (Musica) for restoring compressed audio data (Musicam Data) to original audio data
m Decoder) 15 and the like, but the specific configuration of each section is known in various documents and will not be described in detail here. Further, the audio decoder 15 outputs information on an error of the audio frame of the received data to the system control unit 1.

The FM receiving section includes an FM-FE (Front End for FM) 21 for performing tuning control to the FM station, an FM signal for amplifying the intermediate frequency (IF) signal, and detecting a composite signal from the signal. The detector 22 extracts an RDS signal from the composite signal and demodulates the RDS signal.
Although a decoder 23 and the like are included, such a configuration is also known in various documents and will not be described in detail here. Further, the FM receiving unit also outputs information on the block error of the received RDS data to the system control unit 1.

The system control unit 1 includes a DAB receiving unit, an FM
While controlling the receiving unit, the DAB receiving unit
The IC information is read, and various information data included in the data is stored in the storage unit 5. The stored information includes:
Information on services available in the ensemble, information indicating links between services, components, and sub-channels, information on FM stations (PI code, FI (Freque
ncy Information) list information). Note that the system control unit 1 reads the read P so that the FM receiving unit can receive the candidate station for service follow.
The I-code and the FI list information are output to the FM-FE 21 and the RDS decoder 23.

The system control unit 1 further controls the switching unit 2. Specifically, the DAB receiving unit has the FM
The reception status is better than the receiver (or the reception status is almost the same)
If it is determined that the receiving condition is satisfied, the reproduction sound of the DAB receiving unit is selectively output. If it is determined that the receiving condition of the FM receiving unit is better than that of the DAB receiving unit, the reproduction of the FM receiving unit is performed. Selectively output audio. The output reproduced sound is amplified by the amplifier 3 and output from the speaker 4. The above is DA
4 is an outline of a B receiver.

Next, the operation of the system control unit 1 according to the present invention will be described in detail. FIG. 2 is a flowchart showing the operation of the system control unit 1 in the service follow mode. Note that this flowchart is executed in response to an instruction to perform a service follow being input by a user.

When an instruction to perform service follow is input by the user, the system control unit 1
It is determined whether the AB receiving unit is tuned to any ensemble (step S1).

In the case of tuning to any one of the ensembles, FIC data to be transmitted can be obtained. This is decoded, and from this, information on the protection level and bit rate of each sub-channel is obtained.
Information on services available in the ensemble, services,
A component, information indicating a link between sub-channels, PI code, FI list information, etc. are extracted and stored in a storage unit 5.
(Step S2).

Thereafter, the service desired by the user is selected based on the acquired information, and the selected service is output from the speaker 4 (step S3).

After outputting the audio, the system control unit 1
The error rate is calculated based on each error information supplied from the receiving unit and the FM receiving unit. A specific method of calculating the error rate will be described later.

Next, in step S5, the calculated DA
The error rate of the B signal is compared with a reference value. At this time, first, based on the information on the protection level of each sub-channel acquired and held in step S2 and the information on the currently selected sub-channel, The reference value for evaluating the reception state of the currently selected sub-channel is selected from a corresponding table in the storage unit 5.

FIG. 3 shows an example of a table configured in the storage unit 5. The table is created corresponding to the protection level (PL), and is configured so that reference values corresponding to the protection levels 1 to 5 that can be selected by DAB can be obtained.

For example, if the protection level of the currently selected component is 1, a reference value 1 is determined as a corresponding reference, and this is selected as a reference value for comparison.

Next, in step S5, the determined reference value is compared with the currently calculated error rate. As a result of the comparison, the error rate calculated this time is smaller than the reference value (step S
5; small), the reception state of the DAB station has not deteriorated, so the flow returns to step S4, where the error rate is calculated again based on the error information supplied at that time, and the reference value is set in step S5. Compare with Therefore, when the reception state is good, the loop of steps S4 and S5 is circulated.

On the other hand, as a result of comparing the determined reference value with the currently calculated error rate, if it is determined that the currently calculated error rate is larger than the reference value (step S5: large), DAB
Since it means that the reception condition of the station has deteriorated, the process shifts to step S6 to determine whether service follow-up to the RDS station broadcasting the same program is possible. Specifically, a reference value for FM is provided in the same manner as in step S5, and the reference value for FM-R is set.
By comparing the error rate of the DS station with that of the DAB station, it is determined whether or not there is an FM-RDS station of the same program with a better reception state.

If it is determined in step S6 that the service follow is possible, the switching unit 2 is controlled to reproduce the sound of the RDS station.

On the other hand, if it is determined in step S6 that an RDS station suitable for service follow cannot be found,
Since service follow cannot be performed, the process returns to step S4.
The monitoring of the reception status of both receivers is continued. For example, if the receiving state of the FM receiving unit is improved during this monitoring, step S6
It is determined that the service follow is possible, and the switching unit 2 is controlled to reproduce the sound of the RDS station.

The above is the operation of the service follow. In the present invention, when the reception state of the DAB station is evaluated in step S5, the optimum evaluation reference value is determined based on the information on the currently selected sub-channel. Determined and configured to be able to judge the deterioration of the reception status based on this reference value, so that the sense of noise and judgment result can always be matched regardless of the protection level of the selected sub-channel. It became.

Next, the error rate calculation processing in step S4 will be described in detail. In the present invention, an error rate detected by each receiving unit is used as a parameter for evaluating the reception state of the DAB signal and the FM signal. Specifically, F
The receiving state of the RDS station received by the M receiving unit is configured to be evaluated based on the block error rate of the received RDS data, and the receiving state of the DAB station received by the DAB receiving unit is received. The configuration is such that the determination is made based on the frame error rate of audio data (MusicamData) constituting the sub-channel in the DAB data. this is,
Based on the following findings.

FIG. 4 is a diagram comparing RDS data with audio data transmitted by DAB. In FIG. 4A,
FIG. 4B shows a configuration of DAB audio data.
3 shows a configuration of DS data.

As is well known, the RDS data has an offset A
~ D constitutes one group with four data blocks,
This is a transmission method capable of detecting the presence or absence of an error in a block unit, and one block is composed of 22 ms.

On the other hand, the audio data of DAB is MPEG1
Compliant with layer 2, one frame is composed of 24 ms. Not only the data of each subband but also the DAB header, bit allocation information, S
Information such as cFSI is arranged. Furthermore, DA
A CRC provided for error detection of B header, bit allocation information and ScFSI, and a CRC provided for error detection of a scale factor are included in one frame. Therefore, the presence / absence of an error can be detected by the CRC in units of frames (hereinafter, referred to as blocks in the same manner as RDS data for convenience of description).

The applicant has noticed that the length of one block in both systems is substantially the same, and uses the block error rate of audio data to determine the reception state of the DAB station.
To determine the receiving state of the station, the block error rate of the RDS data was used.

The reason for this is as follows. If the number of blocks serving as the denominator of the block error rate is set to be substantially the same, the time error of the data group used for the judgment is reduced by 10% between the two methods.
This is because it is possible to determine the reception state under extremely close conditions.

Further, there is a proportional relationship between the block error rate of the RDS data and the sense of noise of the analog voice.
Can be accurately correlated with the FM error reception state.

Therefore, the reliability of the comparison result can be improved by comparing the block error rates.

In the above embodiment, the control unit 1 calculates both error rates.
The calculation may be performed in the FM receiving unit.
Further, in the above embodiment, the evaluation criterion for the reception state of the DAB station is changed at the protection level of the sub-channel. However, the present invention is not limited to this. It is also possible to configure to determine.

[0046]

As described above, according to the present invention,
Since the configuration is such that the block error rate of the RDS data is compared with the frame error rate of the audio frame included in the DAB data, the reception state can be determined under extremely close conditions, and the reliability of the comparison result can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a digital broadcast receiver including an RDS receiving unit according to a first embodiment of the present invention.

FIG. 2 is a flowchart executed by the system control unit 1.

FIG. 3 is a table configured inside a storage unit 5;

FIG. 4 is a diagram comparing DAB data and RDS data.

FIG. 5 is an example of a service configuration of a DAB system.

[Explanation of symbols]

 1 System control unit 2 Switching unit 3 Amplifier 4 Speaker 5 Storage unit 11 Front end 12 A / D conversion FFT 14 Viterbi decoder 15 Music cam decoder 16 Re-encoding unit 21 Front end 22 Detector 23・ RDS decoder

Claims (4)

[Claims] An FM receiver including an RDS decoder;
AB receiver, reception status of the FM receiver, and DAB
A control unit that controls the reproduction output of the reception unit that indicates a good reception state by comparing the reception state with the reception state of the reception unit as an output of the receiver, the control unit comprising: The FM based on the block error rate of the RDS data
First evaluating means for evaluating a receiving state of a receiving section; second evaluating means for evaluating a receiving state of the DAB receiving section based on a frame error rate of an audio frame included in the DAB data; A digital broadcast receiver, comprising: comparison means for comparing the evaluation result by the evaluation means with the evaluation result by the second evaluation means. 2. The apparatus according to claim 1, wherein the control unit includes a calculating unit configured to calculate the block error rate and the frame error rate, wherein the number of blocks to be calculated and the target of the frame error rate are calculated. 2. The digital broadcast receiver according to claim 1, wherein the number of frames to be set is set to be substantially the same. 3. The digital broadcast receiver according to claim 1, wherein said second evaluation means changes an evaluation criterion based on protection level information included in said DAB data. 4. The digital broadcast receiver according to claim 1, wherein said second evaluation means changes an evaluation criterion based on bit rate information included in said DAB data.