JP3511447B2 - Information data signal receiver and system using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information data signal receiver, or a specific data signal to be reproduced and an identification data signal for identifying the validity of the specific data signal are in the same frequency band. The present invention relates to a digital audio signal receiver in a system transmitted by a transmission wave of the above and a system using the same.

[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 147)
A digital audio broadcasting (hereinafter referred to as DAB) system conforming to the standard is entering the stage of practical use.

The basic structure of a transmission system in such a DAB system is shown in FIG. In FIG. 1, a digital audio signal obtained by simply sampling and quantizing an analog original audio signal at a predetermined rate, for example, a digital audio signal digitized by linear PCM is supplied to a high efficiency encoder 1. The high-efficiency encoder 1 performs so-called data compression, and more specifically, it is a layer II (MPE) of ISO / IEC 11172-3 which is an international standard system.
The input signal is processed by a compression method compliant with G audio layer II). This compression method is MUSICAM
(Masking pattern adapted Universal Subband Integr
It is also called ated Coding And Multiplexing) method, which reduces the necessary audio information by omitting the audio information in advance by using the masking characteristics of human hearing. The data signal thus compressed has a predetermined format as shown in FIG.

The MUSICAM format uses a predetermined frame (6144 bits) as a unit and is roughly divided into a header, side information, main audio data, and program-related data blocks. The header is ASSD
(Voice service synchronization data), DAB header and CRC
(Cyclic Redundancy Check) sub-block, side information is bit allocation information, ScF
It consists of SI (scale factor selection information) and scale factor sub-blocks, main audio data is occupied by sub-band sample signals, and program related data is stuffing, X-PAD (variable length program related data), ScF-. It consists of CRC (scale factor CRC) and F-PAD (fixed length program related data) sub-blocks. CRC in the header is D
AB header, bit allocation information and ScFSI
CRC used for.

The compression-encoded data signal of such a format is further converted into a channel coder 2.
, Where redundancy is added using convolutional coding for error correction. In addition to pure convolutional coding, this transmission line encoder also performs a process called punctured. This is a process of extracting a part of the convolutionally encoded data signal and transmitting it. In addition, in this process, a UEP (Unequal Error Protection) process is performed in which a high-importance portion is extracted less and a low-importance portion is increased in extraction amount. These processes will be briefly described with reference to an example. Data of a value represented by 1 bit as an input is converted into data of a value represented by 4 bits by convolutional coding, and redundant bits are added to the data. By the punctured processing, for example, 1 bit of the converted 4-bit data is extracted, and as a result, 3-bit data is output. In the case of this example, since 3 bits are finally obtained for 1 bit of the input,
The code rate (coding rate) is 1/3. In this way, the code rate corresponds to the ratio of the number of input / output bits in the transmission line encoder 2. In other words, the code rate is the number of information bits / the total number of output bits.

A high code rate value means that the number of redundant bits is small and the number of true coded bits (information bits) is large. Therefore, the protection level is low and the code rate value is low. Says that the protection level is high because there are many redundant bits and the number of true coded bits is small. In the case of music broadcasting, the protection level can be raised, and in the case of speech broadcasting, it can be lowered. In addition, the code rate in the transmission path encoder 2,
The number of sampling bits in the punctured process corresponds to each other.

The transmission line encoder 2 thus obtained
The output data signal of 1 is transferred to the time axis processor 3 and converted into a time interleaved data signal. Similar processing is performed on the original audio signals of the other channels, and finally converted into the time-interleaved data signal. The block diagram of FIG. 1 omits this. In addition to audio signals,
The general data signal is also subjected to the same processing and interleaving by using the coding blocks 4 and 5 and the time axis block 6. However, the general data signal is different from the audio signal in that the general data signal is subjected to high-efficiency encoding so as to adopt an unstructured bit stream or a packet multiplexing format. General data signals are used for weather forecasts and traffic information (TMC: Traffic Message Ch
annel), such as one-day program listings, is said to carry a wide range of text services that are not immediately required for receiver program selection.

The time-interleaved data signals thus obtained are supplied to a multiplexer (MUX) 7. The multiplexer 7 is controlled by the MUX controller 8, which controls the multiplexer 7 according to the service information given in advance.
ation Information) is generated. Multiplexer 7
Is the time division multiplexing of the input signal according to this MCI,
The multiple output is supplied to the frequency axis processor 9.

The frequency axis processor 9 is also a FIC generator 1.
The FIC data signal to be assigned to the FIC (Fast Information Channel) originated by 0 is also supplied and both this signal and the multiplex output from the multiplexer 7 are frequency interleaved. The FIC generator 10 is given the MCI from the MUX controller 8 and sub-blocks by this MCI and various other predetermined information and adds a CRC for the sub-blocked data to the main block data signal. Then, the data signal of this main block is subjected to the same convolutional coding as that performed by the transmission path encoders 2 and 4 to obtain the final FIC data signal. In the DAB system, the FIC data signal is not subjected to time interleaving, but the code rate is fixed to a relatively low 1/3, and the error correction capability of the receiving system is improved.

OFDM (Orthogonal Frequency Divisio
The n multiplex (orthogonal frequency division multiplex) modulator 11 is supplied with the main signal from the frequency axis processor 9 as well as the sync signal generated by the sync signal generator 12. OFD
The M modulator 11 modulates a large number of carriers that are orthogonal to each other with these signals to obtain an output. Although the principle of such modulation is already known, it will not be described in detail here, but the output of the OFDM modulator 11 provides an OFDM signal of a predetermined format as schematically shown in FIG.

That is, the OFDM signal is DAB
The unit is a transmission frame (for example, 24 ms in mode II) defined by the above, and thus forms a transmission frame sequence. One transmission frame is a synchronization channel,
It is roughly divided into FIC and MSC (main service channel) blocks. The synchronization channel block includes a null signal portion for coarse synchronization that corresponds to the absence of a transmission signal (RF signal) and a reference phase symbol that serves as a reference phase for differential QSPK demodulation in OFDM demodulation. The FIC block is divided into three and includes high speed information blocks 1 to 3. The MSC block is divided into 72 and includes data fields 1 to 72.

If the high-speed information block is further subdivided,
In addition to the guard interval, the MSC is included in the block.
Various information data including information such as the above-mentioned MCI showing the arrangement or configuration form of multiplexing of data signals in, and information such as program service name (label), program content information, paging code, traffic message control, various identification codes, etc. The CRC code is provided together with the various information data. Further, it should be noted that the various information data in the FIC is information indicating that the traffic information is being broadcast in the MSC, such as TA data used in the RDS (Radio Data System) already put into practical use in Europe. (ASW: Announcement Switching)
Is also assigned.

As a receiver utilizing this ASW information, the receiver described in Japanese Patent Laid-Open No. 8-88572 recognizes the start of broadcasting of traffic information by the FIC and preferentially reproduces the corresponding traffic information voice. Has been realized. It is further noted that the data assigned to the FIC includes the data regarding the code rate set in the transmission encoder 2. Such code rate data includes punctured bits, that is, information indicating bits extracted by the punctured processing.

Further, it can be seen that the subdivided block of each MSC data field is composed of a guard interval arranged at the head and a data symbol following the guard interval, like the FIC block. The guard interval is provided to avoid the influence of intersymbol interference due to the influence of multipath, and in the actual form, a partial signal waveform within the effective symbol period is used. Still referring to FIG. 1, the MSC block is formed by a system of blocks 1, 2, 3 and a system of blocks 4, 5, 6 (that is, main voice information and actual traffic information voice data related to the ASW). Additional information such as is stored here), but there is no regular relationship with the audio frame as shown in FIG. 2 and it is assumed that at least a part of the audio frame contains. Can be caught.

The data signal corresponding to the FIC has a CRC code attached to each high-speed information block, whereas an MS
The data signal corresponding to C has no CRC. However, the FIC-compatible data signal is not time-interleaved, and the MSC-compatible data signal is time-interleaved. This is F
This is because the IC needs to be decoded well before the MSC, so that the FIC data signal can be quickly demodulated without the delay required for deinterleaving in order to reliably demodulate the MSC data signal. I am doing it. Furthermore, it should be noted that the FIC data signal has a constant code rate, whereas the code rate of the MSC data signal is variable, as already suggested. Since the MSC data signal is time-interleaved, its code rate is generally higher than that of the FIC data signal, and is about 1/2 on average.

The OFDM signal of such a format is converted into an analog signal by a D / A (digital-analog) converter 13 and further subjected to quadrature modulation by a quadrature modulator 14, and a frequency up-converter 15 and a power amplifier 16 are supplied. RF (Radio Fr
equency) signal will be radiated. By the way, as shown in FIG. 2, MUSI used for DAB
The CAM format data has a CRC partially attached, and a DAB header, bit allocation information, and a CR for ScFSI placed near the beginning of the CAM format data.
C (hereinafter, referred to as header CRC) and CRC (Sc) for scale factor (weighting coefficient for each audio subband)
Only two of them (F-CRC) are used.

Since CRC, which is an error detection bit, has only the error detection capability of a predetermined data block (usually, the detection capability changes depending on the number of bits of CRC), subband samples (signals) can be seen from FIG. CRC
Is not added, and therefore error detection by CRC of the sample signal is not performed at all. Instead, DAB
It is proposed in the receiving system to perform error correction of the sample signal by a Viterbi decoder. However, there is no guarantee that such sub-sampled signals with errors will be completely corrected by such Viterbi decoding.

Therefore, conventionally, there remains a possibility that the sample signal is erroneously demodulated in the receiving system and the sound is reproduced and output as it is. As a technique for avoiding such a defect, ScF for scale factor is used.
-It is possible to use the CRC and mute the reproduced voice in response to the error detection by the CRC. However, in the case of this technology, the occurrence of an error in the scale factor causes a great deal of damage to the reproduced sound of the sample signal, and it is assumed that the sample signal obviously causes reproduction failure and mute processing is performed. is there. In other words, unless an error in the scale factor occurs, audio reproduction of the subband sample signal is inevitably performed, and even if an error occurs in the subband sample signal itself, no mute is performed, It was output as a noisy voice.

In particular, an important point for the present invention, which will be described in detail below, is that in such a technique, the information reproduction of the MSC is interrupted by such a mute, even though the information reproduction of the FIC is performed well. It is a point that will be done. For example, the ASW information of the FIC is used when reproducing the traffic information sound accompanying the main sound, but the conventional receiving system monitors the content of this ASW information and turns on the ASW information, that is, the traffic information. The sound reproduction is performed on the corresponding traffic information sound data of the MSC after the sound is being provided or after it is detected that the sound is started. At this time, even if the receiving system recognizes that the traffic information is being provided by the ASW information of the FIC, the MU
CRC in audio frame of SICAM format
Therefore, the possibility of contradiction in which the subband sample signal carrying the corresponding traffic information voice is not reproduced cannot be denied because an error is detected and muting is performed as described above.

The inconvenience caused by this contradiction is, for example, in an in-vehicle audio system or the like, if traffic information is provided while music is being played by the disc player, the music playback of the disc player is temporarily stopped and the traffic information is output by voice output. This is conspicuous when it is configured to restart the music reproduction by the disc player after the end of the provision of.
That is, in this case, since the voice is muted as described above even though the traffic information is switched to the voice output, the silent state continues or the voice output becomes intermittent, which is convenient for the traffic information. The switching of sources to make a provision, on the contrary, results in a discomfort to the listener.

In addition, even if the receiving system can recognize the ASW information indicating the provision of traffic information, the traffic information voice cannot always be reproduced well due to the signal form based on the code rate defined in the DAB. I also found out. That is, as mentioned above,
The FIC data signal has a lower code rate (stronger to error) than the MSC data signal, so that even if the same transmission wave is used, the FIC is within the error correction limit on the receiving side, but the MSC is outside the error correction limit. ASW belonging to such FIC data signal
A situation may occur in which the corresponding traffic information voice data belonging to the MSC data signal cannot be correctly decoded even if the information data can be decoded. Such a situation also leads to the above problem.

[0022]

Therefore, the present invention has been made in view of the above-mentioned points, and an object of the present invention is to make good use only in a situation where specific information can be truly reproduced in a receiving system. It is to provide an information data signal receiver capable of reproducing specific information. Another object of the present invention is to provide a specific data signal (including additional information signal such as traffic information voice data signal) to be reproduced, and an identification data signal for identifying that the specific data signal is valid. In a system in which the specific data signal is transmitted by the same transmission wave, even if the code rate of the specific data signal and the code rate of the identification data signal are different, it is possible to properly reproduce the information of the specific data signal at a proper timing. It is to provide an information data signal receiver capable of performing.

[0023]

An information data signal receiver according to the present invention is a transmission wave in which a specific information data signal and an identification data signal for identifying the validity of this signal are transmitted in the same frequency band. Which is an information data signal receiver for receiving the transmission wave and demodulated into a predetermined digital signal by a reception demodulation means, a decoding means for decoding the digital signal, and a decoding process by the decoding means. Error detection means for obtaining the error amount of the digital signal, evaluation means for evaluating the error amount, identification data detection means for detecting the identification data signal from the decoded output of the decoding means, and error amount by the evaluation means Control means for reproducing and outputting the specific information data signal related to the identification data signal based on the evaluation result and the identification data signal. It is characterized in Rukoto.

The system according to the present invention is a system using an information data signal receiver, in which a specific information data signal and an identification data signal for identifying that this signal is valid are transmitted in the same frequency band. An information data signal receiver for receiving a transmission wave, the reception demodulation means for receiving the transmission wave and demodulating into a predetermined digital signal, the decoding means for decoding the digital signal, and the decoding processing by the decoding means. The error detection means for obtaining the error amount of the recognized digital signal, the evaluation means for evaluating the error amount, the identification data detection means for detecting the identification data signal from the decoded output of the decoding means, and the evaluation means. Information data signal having control means for generating a reproduction output control signal based on the evaluation result of the error amount and the identification data signal. A receiver, an audio signal output source different from the receiver, and selectively outputs one of the output audio signal of the audio output source and the output audio signal of the receiver according to the reproduction output control signal. And a means for outputting a sound according to the selection output of the selecting means.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 shows a schematic configuration of a DAB receiver of one embodiment as a digital audio signal receiver according to the present invention. In FIG. 4, the RF signal captured by the receiving antenna 31 is supplied to the front end 32 as a tuning means. Front end 3
2 cooperates with the phase locked loop 33 to convert a signal of a desired frequency of the RF signal into an intermediate frequency signal, and supplies the intermediate frequency signal to the quadrature demodulator 34. The phase-locked loop 33 generates a local oscillation frequency signal for frequency conversion in the high-frequency amplification section of the front end 32 in response to the tuning signal from the control section 30 and outputs a substantial tuning operation, that is, a tuning frequency. Make settings.

The quadrature demodulator 34 demodulates the QPSK wave, and comprises, for example, two mixers, a local oscillator and a phase shifter. One mixer mixes the oscillation signal output from the local oscillator with the intermediate frequency signal and outputs the in-phase component signal I of the baseband signal. The other mixer mixes the intermediate frequency signal with the signal obtained by phase shifting the oscillation signal output from the local oscillator by 90 ° by the phase shifter, and outputs the quadrature component signal Q of the baseband signal.

The in-phase and quadrature component signals I and Q are A / D
It is supplied to the (analog / digital) converter 35. A
The / D converter 35 converts the in-phase and quadrature component signals I and Q into digital signals and supplies them to the OFDM demodulator 36.
The OFDM demodulator 36 is the OFDM modulator 1 shown in FIG.
The reverse of the modulation process by 1 (fast Fourier transform (FF
T) and differential demodulation for each carrier for the signal for each carrier obtained thereby), and the demodulation principle thereof is well known in various literatures and will not be described in detail here.

The demodulation output of the OFDM demodulator 36 has the format shown in FIG. 3, and the time / frequency axis processor 3
The reverse processing of the time interleaving and the frequency interleaving, that is, the time / frequency deinterleaving is performed by 7 and supplied to the error corrector 38. As the error corrector 38, a Viterbi decoder is practically used. The Viterbi decoder performs inverse punctured processing (which will be clarified later) from the de-interleaved demodulated signal to determine the most probable value data string signal. Further, such Viterbi decoding is a decoding for solving the convolutional coding performed in the transmission path encoders 2 and 5 in FIG. 1, and the input convolutional coded signal is converted into the high-efficiency encoder 1 in FIG. It can be said that it is converted into a signal having the same value display as the output signals of 4 and 4.

The Viterbi-decoded signal is sent to the signal distribution circuit 3
9 is supplied. The signal distribution circuit 39 distributes the FIC data signal among the input signals to the control unit 30 and the MSC data signal to the audio decoder 40 and the data decoder 41. More specifically, the data signal related to the audio signal of the MSC data signal is supplied to the audio decoder 40, and the data signal related to the general data signal is supplied to the data decoder 41. Audio decoder 40
Is a so-called MUSICA that performs decoding (that is, decompression of data) corresponding to the high-efficiency encoder 1 in FIG.
It is an M recorder. The data decoder 41 performs decoding corresponding to the high efficiency encoder 4 in FIG.

Here, the data signal supplied to the audio decoder 40 has a format in which the audio frame shown in FIG. 2 is used as a unit. The audio decoder 40 decodes this data signal so as to restore it to the original digital audio signal, and the decoded output as the decoding result is a D / A (digital / analog) converter 43.
And the error information obtained during the decoding, that is, the error detection information based on at least one of the header CRC and the ScF-CRC is transferred to the control unit 30. The decoding process of the audio decoder 40 includes a header detection process for recognizing the start of a voice frame. The header detection information obtained by this header detection processing is also transferred to the control unit 30.

The control unit 30 receives the error detection information and the header detection information, executes a predetermined arithmetic processing based on the information and the FIC data signal from the signal distribution circuit 39, and reproduces the reproduction according to the calculation result. The output control signal is supplied to the audio decoder 40. The audio decoder specifies which channel of the audio signal in the MSC should be decoded or output by this reproduction output control signal.

More specifically, the control section 30 controls the FIC decoder 3 for detecting the ASW information signal in the FIC data signal.
A, an error rate of the input data signal under a predetermined condition is calculated based on A and the error detection information and the header detection information from the audio decoder 40, and it is determined whether or not the calculated error rate is larger than a predetermined value. And an AND gate 3C which receives the ASW information signal and the error evaluation signal as an input. Thereby, the control unit 30
Is a reproduction output control that becomes significant only when the ASW information signal indicates that traffic information is provided and the error evaluation signal indicates that the error rate of the input data signal of the audio decoder 40 is smaller than a predetermined value. I am trying to generate a signal.

When the reproduction output control signal becomes significant, that is, becomes high level in this example, the audio decoder 40 selects the voice channel of the traffic information in the MSC in response to the high level reproduction output control signal. As a result, the decoding switching is performed from the existing audio channel, for example, the audio channel of the main broadcast program to the audio channel of the traffic information, and thereafter, the decoding processing and decoding of the traffic information audio signal are performed until the reproduction output control signal becomes low level. Output will be performed.

When the reproduction output control signal becomes low level, the audio decoder 40 restarts the decoding process for the audio channel that has been decoded immediately before the decoding process for the traffic information audio channel. In addition to the reproduction output control signal described here, the audio decoder 40 originally has a function of performing decoding switching according to an input from the operation unit provided in the receiver. That is, the input data signal of the audio decoder 40 has a plurality of audio channels, and in the case of the audio decoder 40 having a single configuration, the decoding process is normally performed for the audio channel designated by the user.
Further, various modes can be selected by the operation unit. For example, the audio decoder 40 is
If the mode for preferentially reproducing and outputting traffic information is specified, the audio channel of the main broadcast program is automatically switched to the audio channel of traffic information according to the reproduction output control signal as described above, and this mode is specified. If not, it is possible to switch to the traffic information channel only when the user issues a channel selection command of the traffic information audio channel regardless of the reproduction output control signal.

The audio decoder 40 also includes a header C
Depending on RC or ScF-CRC, the corresponding digital side information signal (a signal excluding the subband sample signal,
When the data error (see FIG. 2) is detected, the device itself mutes the decoded output audio signal corresponding to the detected data error. The D / A converter 42 analogizes the audio signal decoded and output in this way, and the analog audio signal obtained by this is
The speaker 45 is driven via the amplifier 44, and the sound is reproduced.

Also on the output side of the data decoder 41,
An audio reproduction system similar to the audio decoder 40 can be configured. However, since the information handled by the data decoder 41 includes not only audio but also images and the like and has a wide range of uses, its configuration will not be described in detail here. The control unit 30 is composed of, for example, a microcomputer. Although the control unit 30 is described here as selecting the front end 32 and controlling the audio decoder 40, the input control and the mode control from the operation unit are also included.
It also controls various controls of the entire receiver. Such control unit 3
It is needless to say that 0 can cooperate with such operation or input means to execute various controls or modes other than the above for other constituent blocks. The details will be omitted.

In the above description, the control unit 30 is provided with the functional blocks 3A to 3C as a hardware configuration, but this configuration is actually easy to realize as software of a microcomputer.
FIG. 5 shows a processing procedure of reproduction output control executed by the control unit 30 in this case, which will be described in detail below. Figure 5
In, the control unit 30 calls this reproduction output control processing routine at the start of reception or during operation. As the beginning of such processing, the control unit 30 clears the counter N indicating the number of voice frames (see FIG. 2) and the counter n indicating the number of error occurrences for initialization (step S).
1). Then, the control unit 30 determines whether or not the header detection information indicating the arrival of the beginning of the audio frame has been received from the audio decoder 40 (step S2), and if not received, this determination is continued, and when it is received. Increments the frame counter N by 1 (step S
3).

After step S3, the control unit 30 sends the header CRC or ScF-CR from the audio decoder 40.
It is determined whether or not the error detection information based on C is sent (step S4). If there is error detection information, the error counter n is incremented by 1 (step S5) and the process proceeds to step S6. If there is no error detection information, the process proceeds from step S4 to step S6 immediately. The audio decoder 40 generates error detection information for each audio frame and resets the error detection information at the end of one audio frame.

In step S6, it is determined whether or not the value of the frame counter N has reached a predetermined value Nm. This predetermined value Nm is the number of frames required for the error rate calculation processing in this routine, and an integer of 2 or more can be set as appropriate. In step S6,
If N ≠ Nm, the process proceeds to the previous step S2, while N
= Nm, n is divided by N and the division result is stored in the register X (step S7). Where X is
Since it means (the number of voice frames in which an error is detected: n) / (the predetermined number of voice frames: N), it corresponds to the error rate.

The flow of steps S2 to S6 will be described in detail. The error detection determination in step S4 is performed for Nm voice frames, that is, Nm times. In step S5, the number of times the error detection is determined out of the Nm number of error detection determinations is performed. Therefore, the flow of steps S2 to S6 can be rephrased as a process of counting the number of error occurrences in consecutive Nm voice frames. Therefore, the error rate X is inevitably obtained for every Nm consecutive audio frames.

When the error rate X is calculated in this way, the control section 30 determines whether or not the value of X is smaller than a predetermined value Xth (step S8). Step S8
If the value of X is smaller than the predetermined value Xth, whether or not the ASW information in the FIC data signal from the signal distribution circuit 39 indicates that traffic information is being provided (that is, A
Whether SW is on or not) is determined (step S9), and if this is on, a signal for controlling the audio decoder 40 to perform decoding processing and decoding output of traffic information voice is generated (step S10). On the other hand, step S
8, if the value of X is greater than or equal to the predetermined value Xth, and therefore it can be determined that the error rate of the input data signal of the audio decoder 40 is considerably large, the decoding processing of the main broadcast program audio is performed regardless of the ASW information. And a signal for controlling the audio decoder 40 to produce a decoded output (step S1A). The main broadcast program to be reproduced in step S1A can correspond to the channel selected by the user as mentioned above, or the preset default channel.

Even when it is determined in step S9 that the ASW is off, the process proceeds to step S1A and the main broadcast program sound is reproduced. As described above, in the present embodiment, the traffic information is switched to the voice channel on the condition that the ASW is on and the error amount due to the CRC of the input data signal of the audio decoder 40 is sufficiently small. . That is, the reproduction output of the traffic information voice is allowed only when the situation in which it is estimated that the CRC error is not likely to be detected is determined. Therefore, in the present embodiment, unlike the conventional example in which the ASW is turned on and the channel is immediately switched to the traffic information voice channel, in a situation where many errors due to CRC are detected, the traffic information voice channel is turned on even when the ASW is turned on. Since the switching to the channel is not performed, it is possible to prevent a silent state or an intermittent audio output state due to the audio mute of the CRC detection error response after switching to the channel, and to prevent a sound that gives a discomfort to the listener. Can be suppressed. Next, a second embodiment according to the present invention will be described.

FIG. 6 shows a schematic structure of the DAB receiver of the second embodiment, and the same parts as those in FIG. 4 are designated by the same reference numerals. In FIG. 6, unlike the configuration of FIG. 4, the reproduction output control process is performed without using the error detection information and the header detection information from the audio decoder 40. Therefore, the control unit 30a is provided with means for generating a reproduction output control signal based on the input / output signal of the error corrector 38.

More specifically, the output signal of the T / F processor 37 is a convolutionally coded signal and is supplied to the buffering means 3D provided in the control section 30a. The error corrector 38 solves this convolutional coding,
The re-encoding means 3E provided in the control unit 30a re-convolutionally encodes the Viterbi decoded output that has undergone such convolutional encoding and has been error-corrected by the corrector, thereby inputting to the error corrector 38. To generate a convolutionally coded signal having the same value representation as. That is, a corrected convolutional coded signal is obtained from the re-encoding means 3E. The buffering means 3D takes in the convolutionally encoded signal from the T / F processor 37, delays it by the processing time of the error corrector 38 and the re-encoding means 3E, and supplies it to the comparison means 3F. The comparison means 3F is also supplied with the corrected convolutional coded signal from the re-encoder 3E and compares both input signals. Such comparison includes a process of determining whether each bit is a match / mismatch, and the number of mismatches (or the ratio of the number n of mismatch bits to the predetermined number m of determination bits: n / m).
Generate an estimated error rate signal corresponding to This estimated error rate signal is supplied to the evaluation means 3G, and the evaluation means 3G
Only when the error rate signal is smaller than a predetermined value, a high level error rate evaluation signal is generated and supplied to the AND gate 3C. The other input of the AND gate 3C is supplied with the ASW information signal from the FIC decoder 3A as in the case of FIG.

As a result, the control section 30a has the comparison means 3F.
The reproduction operation of the traffic information channel of the audio decoder 40 responding to the ASW is allowed only when the bit mismatch detected at 1 is sufficiently small. The buffering means 3D achieves comparison of both signals for the same sample period. Further, the control unit 30a receives the FIC data signal from the signal distributor 39 by the FIC decoder 3A. The re-encoding means 3E is also provided with code rate information as a decoding result of the FIC data signal by the FIC decoder 3A, and also performs punctured processing according to this code rate information.

As described above, in the transmission system, punctured processing is performed in the channel coding. As a result, the signal input to the error corrector 38 in the receiving system also has a form in which only the number of bits corresponding to the code rate is extracted by the punctured processing. The error corrector 38 itself detects the data related to the code rate in the FIC data signal and identifies the code rate data including the sampling information indicating which bit has been extracted from the detected data. Then, the error corrector 38 applies a decoding process to the bit-missed input signal (punctured signal) in conformity with the sampling information. More specifically, a bit having an indefinite value is assigned to the sampling bit indicated by the sampling information, and a pure convolutional coded signal (the convolutional code performed before the punctured processing in the channel encoder 2 in FIG. (Corresponding to the converted signal) and Viterbi decoding is performed on this signal.

As described above, the error corrector 38 performs the decoding process while performing the so-called inverse punctured process adapted to the input data, so that the re-encoding means 3E is used.
In order to match the punctured signal from the T / F processor 37 (buffering means 3D), the code rate data in the FIC data signal is used again to perform the punctured processing adapted to the data. The comparison means 3F enables comparison of the same punctured signals.

The comparison means 3F uses the re-encoded signal from the re-encoding means 3E as a comparison reference, and outputs the difference between the encoded signal from the buffering means 3D with respect to this comparison reference as an error. That is, the comparison means 3F
The re-encoded signal has been subjected to appropriate error correction,
An error is generated on the assumption that the signal has the correct value. Therefore, if the error corrector 38 itself performs an improper correction action on the input signal, the comparison reference becomes inappropriate and the obtained error is also unreliable. Therefore, in this embodiment, the estimated error rate signal and the reproduction output control signal are generated on the basis of such an assumption.

In the above description, the control unit 30a is provided with the functional blocks 3A and 3C to 3G as a hardware configuration, but this configuration is actually easy to implement as software of a microcomputer. FIG. 7 shows a processing procedure of reproduction output control executed by the control unit 30a in this case, which will be described in detail below.

In FIG. 7, the control section 30a calls this reproduction output control processing routine at the start of reception or during operation, and at the beginning of the processing, a counter M for counting the number of bits to be compared and the number of bit error occurrences. The counter n indicating is cleared for initialization (step S1)
1). Then, the control unit 30a uses the T / F processor 37 to
The convolutional coded signal A (1, 2, ..., M) for m bits is fetched (step S12). Here, m represents a predetermined number of bits to be compared in a later step, and A
(X) represents, for example, a signal of the x-th bit from the first bit in the m bits in the convolutionally encoded signal.

When the input convolutional coded signal is taken in, the control section 30a generates a convolutional coded signal B to be compared with this (step S13). More specifically, the control unit 30a controls the convolutionally coded signal A (1, 2, ..., M).
, And the error-corrected decoded signal B ′ (1, 2, ..., M ′) output from the error corrector 38 is fetched, and the re-encoder 3E receives the signal B ′. The same convolutional coding as the eggplant is applied, and this signal B '
Then, the punctured processing according to the code rate related information in the FIC data signal as described above is performed to obtain the final corrected convolutional coded signal B (1,2, ..., m).

The control unit 30a that has generated the corrected convolutional coded signal B in this way increments the bit counter M by one (step S14). After step S14, the control unit 30a determines whether or not the input coded signal A and the corrected coded signal B match between the bits indicated by the counter M (step S15). If they do not match, the bit error counter n is incremented by 1 (step S16), and step S1 is performed.
On the other hand, if they match, the process immediately moves from step S15 to step S17.

In step S17, the value of the bit counter M is a predetermined bit number m (that is, the number of bits of the signals A and B held in steps S12 and S13).
It is determined whether or not This predetermined number of bits m
Is the number of bits required for the error rate calculation processing in this routine, and an integer of 2 or more can be set appropriately. If M ≠ m in step S17, the process proceeds to step S14, while if M = m, n is m.
The division result is stored in the register X '(step S18). Here, X'is (the number of bits determined to be unmatched (error): n) / (the predetermined number of determination bits: m)
Since it means that, it corresponds to the error rate.

The flow of steps S14 to S17 will be described in detail. The mismatch determination in step S15 is performed for m bits, that is, m times. Then, step S16 counts the number of times the mismatch is determined among the m determinations. Therefore, the flow of steps S14 to S17 can be rephrased as a process of counting the number of bit error occurrences between consecutive m-bit A and B encoded signals. Therefore, the error rate X'is inevitably obtained for every m consecutive bits.

When the error rate X'is calculated in this way, the control section 30a determines whether or not the value of X'is smaller than a predetermined value X'th (step S19). If the value of X'is smaller than the predetermined value X'th in step S19, whether or not the ASW information in the FIC data signal from the signal distribution circuit 39 indicates that traffic information is being provided (that is, ASW is Whether it is on or not is determined (step S20), and if it is on, a signal for controlling the audio decoder 40 to perform decoding processing and decoding output of traffic information voice is generated (step S21). On the other hand, in step S19, the value of X ′ is the predetermined value X ′.
If th is equal to or more than th, therefore, if it is determined that the error rate of the input data signal of the error corrector 38 is considerably large, ASW
A signal is generated for controlling the audio decoder 40 so as to perform decoding processing and decoding output of the main broadcast program sound regardless of the information (step S22). Also in step S22, the channel selected by the user or a preset default channel can be reproduced and output.

Even when it is determined in step S20 that the ASW is off, the process proceeds to step S22 and the main broadcast program sound is reproduced. In this embodiment, not only the ASW is turned on, but also the traffic amount is switched to the voice channel on condition that the error amount (X ') of the input data signal of the error corrector 38 is sufficiently small. . A large estimated error rate X'means that when the audio data signal received at that time is reproduced, a voice containing a lot of noise components can be obtained. In such a situation, even if the ASW is turned on, the traffic information It has been achieved to suppress the audio output. Here C
Although RC is not used, the reproduction output of the traffic information voice is allowed only when it is determined that the input data signal error of the error corrector 38 is estimated not to be detected so much. Therefore, also in the present embodiment, in the situation where the received data signal cannot be reproduced sufficiently well, even if the ASW is turned on, the traffic information is not switched to the voice channel. It is possible to prevent a noise-like voice output state and suppress a voice that gives a listener an unpleasant feeling.

Further, it is possible to realize an embodiment in which the first and second embodiments are combined to more reliably prevent the noise voice or the silent state after switching to the traffic information channel. FIG. 8 shows a schematic configuration of the DAB receiver according to the third embodiment, and the same parts as those in FIGS. 4 and 6 are designated by the same reference numerals.

In FIG. 8, the control unit 30b has a first error rate calculation / evaluation means 3B. The first error rate calculation / evaluation means 3B is similar to the processing shown in FIG. 4, and the header CRC or ScF from the audio decoder 40.
-The first error evaluation signal indicating the superiority or inferiority evaluation result of the error rate X is generated for every Nm unit frames based on the error detection information by CRC and the header detection information.

On the other hand, the means 3D to 3G used in the control unit 30a of FIG. 6 also cooperate with each other to execute the processing shown in FIG. 7, and the second error based on the input / output of the error corrector 38. Generate an evaluation signal. The second error evaluation signal indicates the superiority / inferiority evaluation result of the error rate X ′ for every m bits. The control unit 30b also uses a 3-input AND gate 3C 'instead of the 2-input AND gate. This AND gate 3C 'receives the above-mentioned first and second error evaluation signals in addition to the ASW data signal, and when all these signals are significant, that is, at high level, the reproduction output control signal is set to high level. The reproduction mode of the traffic information channel is designated to the Seiseme audio decoder 40.

Even in the reproduction output control achieved by the control unit 30b, when the received data signal cannot be reproduced sufficiently well, the traffic information is switched to the voice channel even if the ASW is turned on. Since it is not present, it is prevented that a noise-like audio output state is obtained after switching to the channel. Moreover, by using the two error evaluation signals, the prevention effect is further improved.

The control section 30b can be implemented by software by referring to the flowcharts of FIGS. 5 and 7 already described in detail, and by appropriately combining necessary steps by those skilled in the art. In the above embodiment, the switching control between the main broadcast program channel selection state and the traffic information program channel selection state was explained exclusively, but the invention is not limited to the main broadcast program and the traffic information program,
The present invention is applicable. That is, the present invention can be applied to the control when switching from one channel selection state to another specific channel selection state, and the switching source is not limited to the channel selection state.

FIG. 9 is shown as a simple example in the case where the switching source is a reproduction state from another source different from the receiver. FIG. 9 shows a partial schematic configuration of an audio or audiovisual system in which the DAB receiver 51 and the disc player 52 as described above are compatible with each other to perform sound reproduction.

In FIG. 9, the reproduction output control signal obtained as described above is externally output to the selector 53 which selectively outputs the analog audio output signal of the receiver 51 and the analog audio output signal of the disc player 52. Used as selection control signal. The selector 53 relays one of the selected audio output signals to the drive amplifier 54, and the drive amplifier 54 drives the speaker 55 according to the relayed audio output signal.

According to this structure, the disc player 52
When the receiver 51 detects that the ASW is turned on and a good reproduction output can be obtained during the sound output by the selector 53, the reproduction output control signal is generated.
In response to the reproduced output signal thus generated, the audio output signal from the receiver 51 is supplied to the drive amplifier 54 in place of the audio output signal from the disk player 52 up to that point. Further, when the non-generation of the reproduction output control signal is output, the selector 53 again selects and outputs the audio output signal from the disc player 52. Therefore, the user of such a system can interrupt and preferentially listen to the voice of the traffic information while the music is being reproduced by the disc player 52.

The present invention is not limited to such a disc player, and a so-called normal FM radio broadcast tuner may be used as the switching target, and various modes are possible. In the embodiment realized by software in each of the above embodiments, the ASW is turned on / off after the evaluation of the error rate or the estimated error rate.
Although the off state is determined, the error rate or the estimated error rate may be evaluated after determining the on / off state of the ASW.

Further, in each of the above embodiments, the switching destination is the traffic information channel, but the general concept of the present invention does not limit this. That is, instead of the traffic information channel, for example, the channel of weather forecast or emergency news information may be the switching destination. Further, the switching destination is not limited to the audio channel.
If a general data system using the data decoder 41 is used, it is possible to establish switching destinations of various information channels such as characters and images.

Further, although Nm, m and other parameters have been described by giving concrete numerical values in the above-mentioned respective embodiments, it goes without saying that they are not limited to these values.
Further, in each of the above-described embodiments, the receiver adapted to a specific DAB system and the system using the receiver have been described, but basically, the receiver is not limited only to the DAB system. In short, the present invention can be applied to any system having a system for receiving a digital voice signal and an identification signal, and is effective for a data format in which the demodulation sensitivity of the identification signal may be higher than the demodulation sensitivity of the digital voice signal. It will be. In particular, the mode of estimating the error of the data signal based on the input / output of the error corrector 38 in the above-described embodiment can be said to be extremely effective for the digital signal of the format having no error detection signal.

In addition, although various means are limitedly described in the above embodiment, it is possible to appropriately modify them within a range that can be designed by those skilled in the art.

[0069]

As described in detail above, according to the present invention,
It is possible to provide an information data signal receiver capable of reproducing the specific information satisfactorily only in the situation where the specific information can be truly reproduced in the receiving system. In addition, a specific data signal (including an additional information signal such as a traffic information voice data signal) for which information is to be reproduced and an identification data signal for identifying that the specific data signal is valid are transmission waves in the same frequency band. In the system transmitted by the method 1, even if the code rate of the specific data signal and the code rate of the identification data signal are different, the specific data signal can be properly reproduced at a proper timing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a transmission system in a DAB system.

FIG. 2 is a diagram showing a format of an audio frame conforming to the MPEG audio layer II in the DAB system.

FIG. 3 is a diagram showing a form of a transmission frame in a DAB system.

FIG. 4 is a block diagram showing a schematic configuration of a DAB receiver of one embodiment according to the present invention.

5 is a flowchart showing a processing procedure of reproduction output control executed by a control unit in the receiver of FIG.

FIG. 6 is a block diagram showing a schematic configuration of a DAB receiver of a second embodiment according to the present invention.

7 is a flowchart showing a processing procedure of reproduction output control executed by a control unit in the receiver of FIG.

FIG. 8 is a block diagram showing a schematic configuration of a DAB receiver of a third embodiment according to the present invention.

FIG. 9 is a block diagram showing a schematic configuration of a system using a DAB receiver of a fourth embodiment according to the present invention.

[Explanation of symbols]

1,4 High-efficiency encoder 2,5 Transmission line encoder 3,6 Time-axis processor 7 Multiplexer 8 Multiplexer controller 9 Frequency-axis processor 10 FIC generator 11 OFDM modulator 12 Synchronization signal generator 13 D / A converter 14 Quadrature modulator 15 Frequency up converter 16 Power amplifier 17 Transmission antenna 30, 30a, 30b Control unit 3A FIC decoder 3B Error rate calculation evaluation means 3C, 3C 'AND gate 3D Buffer means 3E Recoding means 3F Comparison means 3G Evaluation means 31 Reception antenna 32 Front end 33 PLL 34 Quadrature demodulator 35 A / D converter 36 OFDM demodulator 37 T / F processor (time / frequency de-interleaver) 38 Error corrector (Viterbi decoder) 39 Signal distributor 40 Audio decoder 41 Data decoder 43 D / A converter 4 drive amplifier 45 loudspeaker 51 DAB receiver 52 disc player 53 selector 54 driving amplifier 55 loudspeaker

Front page continued (72) Inventor Toshihito Ichikawa 25, Nishimachi, Kawagoe-shi, Saitama Prefecture 1 Nishimachi, Pioneer Co., Ltd. Kawagoe factory (72) Inventor Jan Van Holik Belgium Elpemere B-9420 Industrezona Joseph Caldenstraat 31 Pioneer Electronics Manufacturing Manufacturing Envelope (56) Reference JP-A-7-240906 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04L 1/00

Claims (10)

(57) [Claims] 1. An information data signal receiver for receiving a transmission wave in which a specific information data signal and an identification data signal for identifying that this signal is valid are transmitted in the same frequency band, wherein said transmission Reception demodulation means for receiving a wave and demodulating into a predetermined digital signal, decoding means for decoding the digital signal, error detection means for obtaining an error amount of the digital signal recognized in the decoding processing by the decoding means, and An evaluation means for evaluating the error amount, an identification data detection means for detecting the identification data signal from the decoded output of the decoding means, an evaluation result of the error amount by the evaluation means, and the identification data signal based on the identification data signal. And a control means for reproducing and outputting a specific information data signal related to the information data signal receiver. 2. The transmission wave includes a sequence of data blocks including a digital voice signal, a digital additional information signal incidental thereto, and an error detection signal for the digital additional information signal, and the decoding means includes: The audio decoder includes a voice decoder for decoding a data block and detecting a data error of the digital additional information signal by the error detection signal, wherein the error detecting means is provided by the voice decoder with respect to the number of decoding processes of the data block in the voice decoder. An error rate signal is generated according to the ratio of the number of times the data error is detected, the evaluation unit determines whether the error rate signal is smaller than a predetermined value, and the control unit causes the evaluation unit to detect the error. It is determined that the rate signal is smaller than a predetermined value, and the identification data detection means detects the identification data signal. 2. The information data signal receiver according to claim 1, wherein control is performed to reproduce and output a specific information data signal related to the identification data signal when the information data signal is output. 3. The information data signal receiver according to claim 2, wherein the error detecting means updates the error rate signal every predetermined number of the data blocks. 4. When the audio decoder detects a data error of the digital additional information signal by the error detection signal, the audio decoder itself mutes a decoded output audio signal corresponding to the detected data error. The information data signal receiver according to claim 2 or 3, characterized in that: 5. The transmission wave includes at least a sequence of data blocks in which a digital speech signal has been subjected to convolutional coding for error correction, and the decoding means solves the convolutional coding of the data blocks. And an audio decoder for decoding the data block corrected by the error correction means, wherein the error detection means buffers an input signal of the error correction means. Buffer means, and re-encoding means for convolutionally encoding the output signal of the error correction means,
And comparing means for comparing the output signal of the buffer means with the encoded output signal of the re-encoding means for a predetermined number of bits, and generating an estimated error rate signal according to the number of mismatched bits of the two. , The evaluation means determines whether the estimated error rate signal is smaller than a predetermined value,
The control means, when the evaluation means determines that the estimated error rate signal is smaller than a predetermined value and the identification data detection means detects the identification data signal, specific information data related to the identification data signal. 2. The information data signal receiver according to claim 1, which controls to reproduce and output a signal. 6. The predetermined number of bits is a number obtained by dividing the number of constituent bits of the data block or a number smaller than the number of constituent bits, and the error detecting means sets the predetermined number of bits for each predetermined number of bits. The information data signal receiver according to claim 5, wherein the estimated error rate signal is updated. 7. The digital audio signal receiver according to claim 2, wherein the data block is an audio frame based on MPEG audio. 8. The transmitted wave includes a digital voice signal, a digital additional information signal incidental to the digital voice signal, and an error detection signal for the digital additional information signal, and at least the digital voice signal is convoluted for error correction. An error correction unit that includes a sequence of encoded data blocks, wherein the decoding unit performs error correction on the data blocks by solving convolutional encoding of the data blocks;
An audio decoder which decodes the data block corrected by the error correction means and detects a data error of the digital additional information signal by the error detection signal, wherein the error detection means includes the data block in the audio decoder. Means for generating a first error signal according to the ratio of the number of times the audio decoder detects the data error with respect to the number of decoding processes, the buffer means for buffering the input signal of the error correction means, and the error correction means. Re-encoding means for convolutionally encoding the output signal of, and the output signal of the buffer means and the encoded output signal of the re-encoding means are compared for a predetermined number of bits to obtain the number of unmatched bits of both. Comparing means for generating a second error signal in response to the first and second error signals. The control means determines whether or not the error signals are smaller than respective corresponding predetermined values, and the control means determines that the first and second error signals are smaller than respective corresponding predetermined values, and 2. The information data signal receiver according to claim 1, wherein when the identification data detecting means detects the identification data signal, control is performed to reproduce and output a specific information data signal related to the identification data signal. 9. The reproduction output control of the specific information data performed by the control means is performed by designating a target of a decoding process or a decoding output in the audio decoder to the specific information data. Item 2
9. An information data signal receiver according to any one of items 1 to 8. 10. A system using an information data signal receiver, wherein a specific information data signal and an identification data signal for identifying the validity of this signal are transmitted in the same frequency band. An information data signal receiver for reception, comprising: a reception demodulation unit that receives the transmission wave and demodulates it into a predetermined digital signal, and a decoding unit that decodes the digital signal.
Error detection means for obtaining the error amount of the digital signal recognized in the decoding processing by the decoding means, evaluation means for evaluating the error amount, and identification data detection for detecting the identification data signal from the decoded output of the decoding means. Means, an information data signal receiver having a control means for generating a reproduction output control signal based on the evaluation result of the error amount by the evaluation means and the identification data signal, and an audio signal output source different from the receiver. Selecting means for selectively outputting either one of the output audio signal of the audio output source and the output audio signal of the receiver according to the reproduction output control signal, and the audio according to the selected output of the selecting means. And a means for outputting.