JP2006157948A - Transmission error generating status broadcast method of digital transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the operation of receiving electric waves having few burst error by the directional regulation of a receiving antenna, and make high-quality transmission achievable. <P>SOLUTION: In a digital transmission apparatus in a digital modulation system, a configuration forms a signal representing error-generating state in transmission from a received signal, has a means which video-signalizes the signal representing the formed error-generating state and a means which displays the video-making signal. By video-signalizing a generated pattern of an error in transmission data and displaying it, the generating state of the error can be acquired visually instantaneously, and the direction alignment operation of higher quality can be carried out easily. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement in a display function of a transmission state in a digital transmission apparatus using a digital modulation method.

In recent years, digital broadcasting has been studied in Europe, the United States, and Japan, and adoption of an orthogonal frequency division multiplexing (OFDM) modulation method is considered promising as a modulation method. This OFDM modulation system is a kind of multi-carrier modulation system, which is a combination of a large number of digital modulation waves. In this case, a QPSK (Quadrature Phase Shift Keying) system or the like is used as a modulation system for each carrier, and an OFDM signal that is a composite wave can be obtained. Here, this OFDM signal is expressed by a mathematical expression as follows. First, assuming that the QPSK signal of each carrier is α _k (t), this can be expressed by equation (1).

α _k (t) = a _k (t) · cos (2πkft) + b _k (t) · sin (2πkft) (1)
Here, k indicates a carrier number, and a _k (t) and b _k (t) are data of the k-th carrier and take a value of [−1] or [1]. Next, when the number of carriers is N, the OFDM signal is a combination of N carriers, and when this is β _k (t), this can be expressed by the following equation (2).

β _k (t) = Σα _k (t) (where k = 1 to N) (2)
By the way, in the OFDM modulation system, a guard interval is generally added to a signal in order to reduce the influence of multipath. This OFDM signal is composed of the above signal units. For example, the signal unit symbols include all 894 pairs of symbols of 1,072 samples obtained by adding 48 samples of guard interval data to 1024 samples of valid samples, and 6 sets of synchronization symbols. It consists of repetitions in units of streams called frames consisting of 900 symbols. FIG. 12 is a block diagram showing a basic configuration of a modem unit in an OFDM transmission apparatus according to the prior art. The transmission path encoding unit 1T generates a frame control pulse FST of the transmitter every 900 symbols which is a frame period, and supplies it to other blocks as a frame pulse signal indicating the start of a synchronization symbol period. The encoding unit 2T encodes the input data Dii and outputs data Rf and If mapped to the two axes of the I axis and the Q axis. An IFFT (Inverse Fast Fourier Transform) unit 3A regards these data Rf and If as frequency components and converts them into time-axis signals R (real component) and I (imaginary component) composed of 1024 samples. The guard adding unit 3B adds, for example, the waveform of the first 48 samples after the 1024 samples among the waveforms of the time axis signals R and I consisting of 1024 samples, and is an information symbol consisting of a total of 1072 samples of the time axis waveform. Rg and Ig are output. The 48 samples serve as a buffer band when the reflected wave is mixed. The synchronization symbol inserter 5 inserts a synchronization waveform consisting of 6 symbols stored in advance in a memory or the like into these information symbols Rg and Ig for every 894 samples, and generates frame-structured data Rsg and Isg. create. These data Rsg and Isg are supplied to the quadrature modulation processing unit 8, where they are generated by the D / A converter 81, the quadrature modulator 82, and the local oscillator 83 as an OFDM modulated wave signal RF by a carrier of the frequency Fc, Although not shown here, the signal is amplified and sent to the transmission line L via the transmission antenna. As the transmission band, a UHF band or a microwave band is used.

  The clock CK (frequency 16 MHz) necessary for processing in the transmitter Tx is supplied from the clock oscillator 6 to each block as the transmitter clock CKd. The OFDM modulated wave signal RF transmitted as described above is input to the quadrature demodulation processing unit 9 of the receiver Rx via a receiving antenna (not shown), and the frequency Fc supplied from the voltage controlled oscillator 93 by the quadrature demodulator 91. The signal is multiplied by the local oscillation signal of ′, quadrature demodulated into a baseband signal, digitized by the A / D converter 92, and converted into data R′sg and I′sg. These data R'sg and I'sg are supplied to an FFT (Fast Fourier Transform) unit 3C, where a gate signal for determining a data period of 1024 samples to be used as an FFT is generated based on the pulse FSTrc. Then, by excluding 48 samples that are buffer bands, the time-axis waveform signals R′sg and I′sg are converted into frequency component signals R′f and I′f. On the other hand, the data R'sg and I'sg are also input to the synchronization detector 4, where a synchronization symbol group is detected, and thereby a pulse FSTr serving as a frame pulse is extracted. This pulse FSTr becomes a frame control pulse of the receiver Rx and is supplied to each block of the receiver Rx. These frequency component signals R′f and I′f are identified and decoded by the decoding unit 2R to become data D′ o, which is output as a continuous signal Dout by the transmission path decoding unit 1R. The

  Next, details of each part will be described. The transmission path encoding unit 1T performs interleaving processing, energy spreading processing, error correction code processing, and the like in order to prevent data errors due to various errors that may be mixed during transmission. The encoding unit 2T converts the signal Dii into information of predetermined points on the I and Q axes using the mapping ROM, and replaces the signal in the period corresponding to the unnecessary carrier with 0 to generate data Rf and If. To do. The IFFT converter 3A converts the input signals Rf and If into time-axis waveforms R and I having a symbol period determined by the clock CKd and the pulse FST. Specifically, this can be realized by using PDSP 16510 of Pressy. The guard adding unit 3B includes a delay unit that delays the signals R and I input thereto by 1024 samples, and a switch that selects a delayed output only from the 1025th to 1072th samples. These are added by the clock CK and the pulse FST. You can decide the timing. The symbols consisting of all 1072 samples obtained here are information symbols Rg, Ig by adding a time axis waveform between 48 samples from the first sample to the 1025th sample to the 1072 sample. The synchronization insertion unit 5 inserts the synchronization symbol group into the generated guarded time signals Rg and Ig and outputs the result. As one of the synchronization symbol groups, the purpose of the NULL symbol insertion is to roughly find the existence of the synchronization symbol group by a null symbol period in which there is no signal. The purpose of inserting the SWEEP symbol is to accurately obtain the symbol switching point, and the SWEEP symbol is a waveform that changes from the lower limit frequency of the transmission band to the upper limit frequency in one symbol period. The quadrature modulation processing unit 8 performs D / A conversion on the real part signal Rsg and the imaginary part signal Isg by the D / A converter 81, and the quadrature modulator 82 performs the real part signal on Modulation is performed with the carrier signal of the frequency fc from the oscillator 83 as it is, and the imaginary part signal is subjected to quadrature modulation by modulating the carrier signal of the frequency fc of the oscillator 83 with a signal shifted in phase by 90 °. The signals are combined to obtain an OFDM modulated wave signal.

In the receiver Rx, the transmitted OFDM signal is input to the orthogonal demodulation processing unit 9. In this processing, contrary to the transmitter Tx, the output demodulated by the carrier signal of the frequency Fc ′ output from the voltage controlled oscillator 93 is taken out by the quadrature demodulator 91 as a real part signal, and the carrier signal is extracted by 90 °. The phase-shifted and demodulated output is taken out as an imaginary part signal. Then, each demodulated analog signal of the real part and the imaginary part is converted into a digital signal by the A / D converter 92. The synchronization detector 4 searches for a frame break from the received signals R′sg and I′sg, outputs a frame reference FSTrc, and outputs a correlation output VC. Then, the FFT unit 3C delimits symbols based on the pulse FSTrc, performs OFDM demodulation by performing Fourier transform as described above, and outputs data R′f and I′f. The decryption unit 2R identifies the data R′f and I′f by, for example, a ROM table method, and calculates the data D′ o. The transmission path decoding unit 1R performs deinterleaving processing, energy despreading processing, error correction processing, and the like, and outputs continuous digital data Dout, an error flag signal Se that is an error correction processing status, and a receiver clock signal CK _RX . . In order to convert the received signal into an image, it is necessary to decode digital data obtained by OFDM demodulation into an image using an MPEG decoder.

  By the way, as described above, OFDM is a kind of multi-carrier modulation system. As a feature of OFDM, even if the level of some carriers drops and the data assigned to these carriers is lost, lost data can be recovered from the data assigned to many remaining normal carriers by error correction processing. is there. Usually, as shown in FIG. 13, the error occurrence state in the receiver can be confirmed by BER (bit error rate) display by the LED. However, this BER state indicates the ratio of error data to data received within a certain time, and the error occurrence pattern is unknown. That is, even if the BER is the same, if an error occurs randomly in the entire transmission band due to noise or the like, error correction can be performed from normal data. However, when a continuous burst error occurs due to frequency selective fading or instantaneous interruption, normal data cannot be obtained and error correction becomes impossible. When these data are visualized, it is possible that normalization can be performed in the case of a random error, but it cannot be performed in the case of a burst error. In general, as shown in FIG. 13, the received electric field strength can be confirmed on the receiver side by a meter or the like.

By the way, when the digital transmission apparatus as described above is used for radio wave transmission while moving, such as a marathon relay, the direction of receiving strong radio waves by accurately directing the receiver antenna to the transmission antenna of a moving relay car or the like Adjustment work is required. Hereinafter, this direction adjustment work is shortened and referred to as a square tone. Such a marathon relay or the like is called mobile relay or mobile transmission. In the case of traditional analog transmission, in most cases, the transmission quality becomes better as the electric field is stronger. However, in the case of digital transmission, when the same BER state is obtained, radio waves with a random error are received even if the reception electric field is weaker than receiving radio waves with a strong reception electric field and presence of burst errors. It is overwhelmingly often that a good transmission state can be obtained.
JP 10-28065 A

  In the conventional configuration described above, as a means for grasping the transmission state, in the BER state displayed by the LED, only the ratio of errors existing in the data received within a certain time is displayed. Is unknown. Moreover, the radio wave with the strongest received electric field intensity displayed by a meter or the like is not always high quality. As described above, in performing the direction adjustment work, there is a drawback that high-quality transmission cannot always be realized only by information on the BER state and the received electric field strength. The present invention eliminates these drawbacks, displays information indicating the occurrence of transmission errors as video signals, facilitates the operation of the direction adjuster to receive radio waves with few burst errors, and realizes high-quality transmission This is the first purpose. Secondly, the error occurrence information visualized so that the direction adjuster does not have to look at a large number of display monitors is synchronized with other video signals to display the information in a superimposed state. The purpose.

  In order to achieve the first object, the present invention generates a signal indicating an error occurrence state in transmission from a received signal in a digital transmission apparatus using a digital modulation method, and converts the generated signal indicating the error occurrence state into a video signal. And a means for displaying the imaged signal as an image. Further, the signal indicating the error occurrence state is an error flag signal indicating an error correction processing state, and the means for converting to the video signal is to convert the error flag signal into a video signal according to the generation position and the number of occurrences. is there. Further, a signal indicating the error occurrence state is stored in a storage device, and all errors that have occurred regardless of the blanking period of the video signal are displayed. Further, the signal indicating the error occurrence state converted into the video signal is displayed with different luminance or hue in a period in which an error has occurred and a period in which no error has occurred. In order to achieve the second object, the video signal converted to the error occurrence state is superimposed on another video signal in synchronism with other video signals. Further, in combination with an image codec, the video signal obtained by reception and decoding is configured to have a means for synchronizing and superimposing a signal indicating the error occurrence state that has been converted into the video signal.

  As described above, according to the present invention, it is possible to realize a digital transmission apparatus capable of displaying a transmission error occurrence state as a video signal, and to obtain an error occurrence state instantly and visually. Higher quality direction adjustment work can be easily performed. In addition, since the video signal is converted into a video signal, a general video monitor can be used as a display device, so that an optimal size display can be performed according to the situation. Note that when the transmission state is measured and collected, it is converted into a video signal format, so that a large amount of data can be recorded easily and inexpensively by recording on a VTR or the like.

  The overall block configuration of the present invention is shown in FIG. This includes a transmitter Tx having the same configuration as that of the prior art shown in FIG. 12, a receiver Rx having the same configuration, and a video conversion unit 7A. The error flag signal Se output from the receiver Rx is connected to the video conversion unit 7A. As an example of the error flag signal Se, it can be realized by using the 76th pin output (BERR output) of the Viterbi decoder STEL-2060 of Stanford Telecom. An example in which an error flag is output will be given. For example, when DQPSK (Differential Quadrature Phase Shift Keying) is used for encoding, the data mapping positions are point A, point B, point C, point D as shown in FIG. 4 points. When the data transmitted as point A from the transmitter side is received at point E on the receiver side due to disturbances such as noise existing in the transmission path, it is recognized as point B data, an error occurs, and an error flag is generated. Changes from L level to H level.

  FIG. 2 shows an embodiment of a specific configuration of the video conversion unit 7A of the present invention, which will be described below. The error flag signal Se obtained from the receiver Rx is connected to the gate 7A-2. The blanking period signal BLK, the color subcarrier signal SC, and the video synchronization signal C.SYNC output from the video synchronization signal generator 7A-1 are a gate 7A-2, a color synthesizer 7A-4, and an adder 7A-, respectively. 3 is input. The error flag gate signal Seg output from the gate 7A-2 is input to the color synthesizer 7A-4. The colored error flag signal Seg ′ output from the color synthesizer 7A-4 is input to the adder 7A-3. The adder 7A-3 converts the colored error flag signal Seg ′ into a video signal and outputs it. Here, an example of an error display image converted into a video signal will be described with reference to FIG. As shown in the figure, the image changes according to the number of errors that occur. For example, when there is a random error, as the error increases, the number of images (dots) representing the error increases as shown in FIG. Further, when there is a burst error, as the error increases, the thickness of the image (horizontal line) representing the error increases as shown in FIG. The display update depends on the update cycle of the video signal.

  FIG. 3 shows an example of a specific configuration of the color synthesizer 7A-4, which will be described below. The color subcarrier signal SC is input to the color converter 7A-4-1. The error flag gate signal Seg and the converted color subcarrier signal SC ′ output from the color converter 7A-4-1 are input to the adder 7A-4-2. The adder 7A-4-2 outputs a colored error flag signal Seg ′. Note that the color synthesizer 7A-4 uses error display to display a period in which an error has occurred and a period in which no error has occurred with different luminance or hue. For example, for NTSC, the color subcarrier signal SC is a 3.58 MHz signal obtained by dividing a 14.3 MHz clock by four. By adding the signal SC ′ in which the amplitude and phase of the color subcarrier signal SC are changed in the color converter 7A-4-1 and the error flag gate signal Seg in the adder 7A-4-2, the color is added. An error flag signal Seg ′ is obtained. Further, in order to prevent the error flag signal Se from being generated during the blanking period, the blanking period is forcibly set to the level L by using the BLK signal that becomes the level L during the blanking period. However, when this configuration is used, an error in the blanking period is not displayed as a video.

  Therefore, a configuration capable of displaying an error in the blanking period is shown in FIG. 5 and will be described. This includes a transmitter Tx having the same configuration as that of the prior art shown in FIG. 12, a receiver Rx having the same configuration, and a video conversion unit 7B with a storage device. The error flag signal Se from the receiver Rx is connected to the video converter with storage device 7B. FIG. 6 shows a specific configuration of the video converter with storage device 7B, which will be described below. The error flag signal Se obtained from the receiver Rx is connected to a FIFO (First In First Out) memory 7B-2. The video synchronization signal C.SYNC output from the video synchronization signal generator 7B-1 is input to the timing pulse generator 7B-3 and the adder 7B-4. The timing pulse generator 7B-3 outputs a read reset signal RRES and a read enable signal RE to the FIFO memory 7B-2 in response to the signal C.SYNC. The rate-converted error flag signal Se ′ output from the FIFO memory 7B-2 is input to the adder 7B-4. The adder 7B-4 outputs a video signal. The relationship between the signal Se and the signal C.SYNC is shown in FIG. By using this configuration, all errors can be displayed.

  Next, a case where the error occurrence state is superimposed on another video will be described with reference to FIG. This configuration is an error occurrence state video superimposing unit 7C instead of the video conversion units 7A and 7B in FIGS. The error flag signal Se is connected to the gate 7C-2. The external video signal is input to the external video synchronization type sync signal generator 7C-1 and the adder 7C-3. The blanking period signal BLK output from the external video synchronization type synchronization signal generator 7C-1 is connected to the gate 7C-2. The error flag gate signal Seg output from the gate 7C-2 is connected to the adder 7C-3. The adder 7C-3 adds the external video signal and the error flag gate signal Seg, and outputs an error occurrence state superimposed video signal. FIG. 9 shows the configuration of the external video synchronization type synchronization signal generator 7C-1. The external video signal is input to the synchronization extractor 7C-1-1. The extracted synchronization signal output from the synchronization extractor 7C-1-1 is input to the synchronization signal generator 7C-1-2. The synchronization signal generator 7C-1-2 outputs a blanking period signal BLK.

FIG. 10 shows a configuration of an image / audio transmission system in which the transmission system of the present invention is combined with an image codec and an error occurrence state video is superimposed on an MPEG decoded image. The input video signal and audio signal are converted into compressed digital data Din by the MPEG-ENC (encoder) unit TxM according to the reference clock CK _TX from the transmitter Tx. The data transmitted and demodulated by the receiver Rx is input to an MPEG-DEC (decoder) unit RxM that performs decompression as Dout. The image signal expanded by the MPEG-DEC unit RxM is input to the error occurrence state video superimposing unit 7C, and after the error occurrence state is superimposed in the same manner as described above, the error occurrence state superimposed video signal is output. The

The block diagram which shows one Example of the whole structure of this invention The block diagram which shows an example of the image | video conversion part 7A of this invention The schematic diagram which shows an example of the display image of the error occurrence state of this invention Block diagram showing an example of a color synthesizer 7A-4 of the present invention The block diagram which shows the other Example of the whole structure of this invention The block diagram which shows an example of the video conversion part 7B with a memory | storage device of this invention The schematic diagram which shows the relationship between the error flag signal Se of this invention, and a video signal Block diagram showing an example of the error occurrence state video superimposing unit 7C of the present invention Block diagram showing an example of an external video synchronization type synchronization signal generator 7C-1 of the present invention The block diagram which shows an example of the transmission state-decoded image superimposition type transmission system of this invention Schematic diagram explaining data mapping position when error flag is output Block diagram showing an example of a transmission device having a conventional configuration Schematic diagram showing a display example of BER and received electric field strength in a conventional receiver

Explanation of symbols

Tx: transmitter, Rx: receiver, 7A: video conversion unit, 7B: video synchronization signal generator with storage device, 7C: error occurrence state video superimposition unit, 7A-1, 7B-1: video synchronization signal generator, 7A-2: Gate, 7A-3, 7A-4-2, 7B-1: Adder, 7A-4: Color synthesizer, 7A-4-1: Color converter, 7B-2: FIFO memory, 7B- 3: Timing pulse generator, 7C-1-1: Sync extractor, 7C-1-2: Sync signal generator, TxM: MPEG-ENC section, RxM: MPEG-DEC section.

Claims (4)

In a transmission error occurrence state notification method of a digital transmission apparatus using a digital modulation method,
On the receiving side, a signal indicating an error occurrence state in transmission of received data is extracted, and the extracted signal indicating the transmission error occurrence state is extracted between the images indicating transmission errors according to the time interval at which the transmission error occurs. A transmission error occurrence state notification method comprising: converting to a video signal that changes, and displaying the converted video signal as an image representing the occurrence state of the transmission error. In the transmission error occurrence state notification method according to claim 1,
The signal representing the transmission error occurrence state is an error flag signal representing an error correction state, and when the signal is converted into the video signal, the occurrence interval between images representing the transmission error depends on the time interval at which the error flag signal is generated. Transmission error occurrence notification characterized by converting to a changing video signal and displaying the image as an image indicating whether a random error or a burst error has occurred when the converted video signal is displayed as an image Method. The transmission error occurrence state notification method according to claim 1 or 2,
The signal representing the transmission error occurrence state converted into the video signal is at least one of luminance or hue in a period in which a transmission error has occurred in the reception data and a period in which no transmission error has occurred in the reception data. A transmission error occurrence state notification method characterized by displaying differently. The transmission error occurrence state notification method according to claim 1,
A transmission characterized by superimposing a signal representing a transmission error occurrence state converted into the video signal in synchronization with another video signal, and displaying an image representing the transmission error occurrence state together with the other video. Error occurrence state notification method.

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