JP4355241B2 - Data transmission device - Google Patents

Description

  The present invention relates to a data transmission apparatus, and more particularly to a data transmission apparatus that transmits data in an optimal transmission mode in digital transmission.

  In recent years, terrestrial digital television broadcasting and high-definition transmission technology are being established in digital transmission for transmitting data. As an example, it is suitable for application to digital transmission and terrestrial digital television broadcasting, and is characterized by orthogonal frequency division multiplexing (hereinafter referred to as OFDM modulation), which is characterized by being resistant to multipath fading and ghosting. )) As an example.

  This OFDM modulation system is defined as a standard (ARIB STD-B33 Japan Radio Industry Association, hereinafter abbreviated as ARIB STD). This OFDM modulation method is a kind of multi-carrier modulation method, and is a transmission method in which a predetermined amount of data to be transmitted is digitally modulated with n (n is several tens to several hundreds) carrier waves orthogonal to each other. FIG. 9 is a diagram for explaining the OFDM modulation system, and shows that a large number of digital modulation waves DC, Δf, 2Δf,... (N−1) Δf are added to obtain an OFDM modulation signal. ing. This OFDM modulation signal is composed of a repetitive signal having a symbol period A. The I-axis signal and the Q-axis signal are an I-axis signal and a Q-axis signal on an orthogonal coordinate axis, and are multiplexed so as to maintain an orthogonal relationship with each other.

  FIG. 10 shows a configuration of one symbol period A of the transmission signal thus OFDM-modulated. One symbol A (about 50 μsec) is composed of a guard interval GI and a valid data symbol DS. More specifically, for example, one symbol period A is composed of 1152 samples, the effective data symbol DS is composed of 1024 samples, and the guard interval GI is composed of 128 samples. The guard interval GI is a section in which a part GI ′ of the valid data symbol DS is copied. Therefore, GI and GI 'are composed of the same signal. In the OFDM digital transmission system, 1024 samples are referred to as 1K samples (also referred to as 1K mode; the same shall apply hereinafter). In addition, 2048 samples are 2K samples, and there are samples (modes) such as 1K, 2K,.

  As the above-mentioned digital modulation system, the 4-phase differential phase shift keying (DQPSK) is most often used, but there are many such as 16-value quadrature amplitude modulation (16QAM) and 64QAM. It is also possible to use a value modulation method. In the OFDM method, by adding a guard interval, it is possible to avoid deterioration due to intersymbol interference with respect to delayed waves with a delay time within the guard interval period, so strong resistance to multipath fading and ghosting. have.

  Here, an OFDM frame configuration defined in ARIB STD-B33 will be described. FIG. 11 shows an OFDM frame configuration, for example, a 1K full mode frame configuration. As shown in FIG. 11, this 1K full mode frame configuration includes five types of CP (Continual Pilot), TMCC (Transmission and Multiplexing Configuration Control), AC (Auxiliary Channel), Null (Null Carrier), and Data (Data Carrier). Is made up of careers. The number of carriers n is 857. Among them, there are 672 Data carriers (portions not shown in FIG. 11), 108 CPs, 66 ACs, 10 TMCCs, and 1 Null. The structure of this TMCC signal is as shown in FIG. This TMCC signal transmits various types of information defined in ARIB STD-B33, for example, information for identifying various modes such as modulation scheme, error correction, number of samples, etc. as a 204-bit (0 to 203 symbol) signal. To do.

  Thus, an example of the configuration of a conventional OFDM transceiver is shown in FIG. In FIG. 7, the transmitter 701 includes a main data encoding unit 702, an auxiliary data encoding unit 703, a TMCC conversion unit 704, and an OFDM modulation unit 705. The image signal is converted into a TS (Transport Stream) format digital signal D (hereinafter abbreviated as main data D) by an external encoder, for example, an MPEG (Moving Picture Experts Group) 2 encoder, and input. The signal is input from the signal terminal Din to the main data encoding unit 702. The main data encoding unit 702 appropriately performs convolutional encoding, puncturing of data, interleaving, and the like, and inputs the result to the OFDM modulation unit 705.

  On the other hand, auxiliary data AC (Auxiliary Channel) from the outside is input to the auxiliary data encoding unit 703 from the auxiliary data input terminal ACin, subjected to convolutional encoding, puncturing, interleaving, etc., and applied to the OFDM modulation unit 705. The auxiliary data AC is used for transmitting additional information such as voice and contact data, and can be used as appropriate.

  As described above, the TMCC conversion unit 704 determines various modes of the OFDM transmission signal and transmits the information to the transmission side, and details thereof will be described with reference to FIG. First, in the transmission of an OFDM modulation signal, there are many transmission modes (for example, several tens of ways) such as a modulation scheme, a coding rate, a fast Fourier transform (hereinafter referred to as FFT (Fast Fourier Transform)) sample number, and the like. Exists. Accordingly, it is necessary to appropriately determine which mode is used to transmit the OFDM modulated signal and transmit it. As described above, an OFDM modulated signal is resistant to multipath fading, ghost, etc. of the transmission path, but it is needless to say that the transmission mode must be optimized in accordance with the condition of the transmission path. Yes.

  FIG. 8 is a block diagram illustrating a schematic configuration of the TMCC conversion unit 704. In FIG. 8, the TMCC conversion unit 704 includes a TMCC carrier data conversion unit 801, a modulation method changeover switch 802, a coding rate changeover switch 803, and an IFFT (Inverse Fast Fourier Transform) sample number changeover switch 804. ing. The modulation system changeover switch 802 selects one of the modulation systems such as DQPSK, QPSK, 16QAM, 32QAM, or 64QAM for the signals encoded by the main data encoding unit 702 and the auxiliary data encoding unit 703. Switch. For example, when the 16QAM modulation method is selected, the main data and auxiliary data described above are converted into an OFDM modulated signal by the OFDM modulation unit 205 using the 16QAM modulation method.

  Also, when encoding main data or auxiliary data, the encoding rate changeover switch 803 sets the encoding rate to, for example, 5/6, 3/4, 2/3, 1/2, or the like from the relationship of the transmission band. This switch needs to be compressed and transmitted, and switches the coding rate. Therefore, the coding rate is selected by this switch, and is output as an OFDM modulated signal from the OFDM modulation unit 705 at a coding rate of 3/4, for example.

  Further, the IFFT sample number changeover switch 804 is a switch for selecting a sample number from the number of samples such as 1K, 2K,. For example, if 1K samples are selected, they are converted into OFDM modulated signals at 1024 samples per symbol.

  As described above, when the modulation method changeover switch 802, the coding rate changeover switch 803, and the IFFT sample number changeover switch 804 are selected, the selected signals (hereinafter referred to as mode information) are transmitted to the TMCC carrier. The signal is input to the TMCC carrier data conversion unit 801 to be converted, and then modulated to an OFDM signal by the OFDM modulation unit 705 to be a signal having the OFDM frame configuration shown in FIG. 11 and transmitted to the receiver 707 via the transmission path 706. .

  The receiver 707 includes an OFDM demodulator 708, a main data decoder 709, and an auxiliary data decoder 710. The OFDM modulated signal transmitted from the transmitter 701 is OFDM demodulated in the OFDM demodulator 708. Here, the main data D and the auxiliary data AC are separated, and the main data D is subjected to deinterleaving, depuncturing, Viterbi decoding, and the like in the main data decoding unit 709 and output from the output signal terminal Dout to an external decoder or the like. . On the other hand, the auxiliary data AC is subjected to deinterleaving, depuncturing, Viterbi decoding, and the like in the auxiliary data decoding unit 710, and is output from the auxiliary data output terminal ACout.

  The conventional transmission / reception of an OFDM modulated signal has been described above. As is clear from the above description, there are many transmission modes such as a modulation scheme, a coding rate, and the number of IFFT samples in the transmission of an OFDM modulated signal. Therefore, it is necessary to appropriately determine which mode is used to transmit the OFDM modulated signal and transmit it. In actual operation, in order to determine which mode is the most suitable mode, data is actually used. If it is not transmitted, it is impossible to discriminate.

  In addition, a wireless communication method and a wireless communication device (see, for example, Patent Document 1) are related to a technique for improving transmission efficiency by selecting an optimal frequency and modulation method according to a line state or eliminating a communication disabled state. There is a description.

JP 2000-269938 A

  In the above prior art, when transmitting data, it is necessary to manually check all modes to check which mode is best for the transmitter / receiver of the OFDM modulation signal according to the condition of the transmission path. However, since there are hundreds of transmission modes for OFDM modulated signals, there is a problem that much labor is required just to perform setting and checking work.

  An object of the present invention is to provide a data transmission apparatus capable of transmitting data in an optimum mode according to the state of a transmission path.

  Another object of the present invention is to provide a data transmission apparatus capable of automatically switching transmission modes and selecting an optimal transmission mode.

  The present invention provides a data transmission apparatus for transmitting data between a transmitter and a receiver using an OFDM modulated signal, wherein the transmitter includes an OFDM modulation unit, at least a modulation scheme, a coding rate, and a number of samples of the OFDM modulated signal. A mode switching unit for switching one of them, and a mode information adding unit for adding the mode information of the switched mode to the OFDM modulated signal, and the receiver receives an OFDM modulated signal sent from the transmitter An OFDM demodulator for demodulating, a mode information identifying unit for identifying the mode information from the OFDM modulated signal, and a reception state determining unit for determining the reception state of the OFDM modulated signal sent from the transmitter.

  In the data transmission apparatus of the present invention, the mode switching unit further includes a mode switching control unit and a storage unit, and the storage unit includes a plurality of modulation schemes, a plurality of coding rates, and a plurality of the OFDM modulation signals. The mode switching control unit reads the plurality of modes stored in the storage unit, and operates the transmitter in the read mode. Configured.

  In the data transmission apparatus of the present invention, the reception state determination unit is configured to select an optimum mode for data transmission from error information of a demodulated signal obtained from the OFDM demodulation unit.

  In the data transmission apparatus of the present invention, the reception state determination unit determines the reception state of the OFDM modulated signal for each mode switched by the mode switching control unit of the transmitter, and receives the OFDM modulation signal. The reception state determination unit transmits mode switching information to the mode switching unit of the transmitter until the state becomes a predetermined reception state.

  Furthermore, in the data transmission apparatus of the present invention, the mode information identification unit further includes a storage unit, and the storage unit stores a reception state of the OFDM modulation signal of each mode output from the reception state determination unit. At the same time, the mode information in a predetermined reception state is transmitted to the mode switching unit of the transmitter.

  As described above, according to the present invention, an optimal transmission mode is selected according to the transmission path to be used, and it is possible to save the operator from switching the mode and confirming the transmission state. In addition, an optimum data transmission apparatus can be realized by transmitting a result detected on the reception side to the transmission side and automatically controlling the transmission mode to an optimum transmission mode.

  FIG. 1 is a block diagram showing a schematic configuration for explaining an embodiment of the present invention. In FIG. 1, 101 is a TMCC conversion unit, 102 is an OFDM modulation unit, 103 is an OFDM demodulation unit, and 104 is a TMCC identification unit. In addition, the same code | symbol is attached | subjected to the same thing as FIG. Hereinafter, the TMCC conversion unit 101, the OFDM modulation unit 102, the OFDM demodulation unit 103, and the TMCC identification unit 104 will be described with reference to FIGS.

  FIG. 2 is a block diagram showing a specific configuration of OFDM modulation section 102. In FIG. 2, the main data encoded by the main data encoding unit 702 is applied to the main data mapping unit 202 via the terminal 201. In the main data mapping unit 202, for example, in the case of 16QAM, 16 points are mapped on the IQ coordinates based on the main data. The CP generation unit 203 is a carrier signal generation unit having a constant amplitude in order to map the reference phase by BPSK (Binary Phase Shift Keying). This CP carrier is inserted once in 8 carriers in the carrier direction as shown in FIG.

  The auxiliary data mapping unit 205 receives the auxiliary data AC from the input terminal 204 and performs mapping such as 16QAM or QPSK. The TMCC conversion unit 206 is for switching the above-described modulation scheme, coding rate, number of IFFT samples, and the like, and details will be described with reference to FIG. TMCC information from the TMCC conversion unit 206 is mapped by the TMCC mapping unit 207, for example, DBPSK.

  The modulation integration unit 208 sequentially selects the main data D, CP data, auxiliary data AC, and TMCC information mapped in accordance with the carrier arrangement pattern shown in FIG. An IFFT (inverse first Fourier transform) 209 regards an input signal as a frequency component and creates a time waveform (effective data symbol DS) of 1024 samples. By this processing, orthogonal multi-carrier modulation is performed. The guard adding unit 210 adds a part GI ′ of the time waveform of the last part of the effective data symbol DS as a guard interval GI before it, and creates a waveform of one symbol period A. The DA conversion unit 211 is a digital / analog conversion unit that converts an analog signal into an analog signal, and quadrature-modulates the input of the I component and the Q component and converts the analog signal into, for example, a 20.45 MHz analog IF signal. The IF conversion unit 212 is an intermediate frequency conversion unit that converts, for example, an IF signal of 130 MHz. The transmission high-frequency unit 213 converts the frequency of the IF signal into a microwave band, amplifies the power, and then transmits the signal from the output terminal 214 to the receiver 707 via the transmission line 706. Note that the system clock generator for driving the OFDM modulator and the like are omitted.

  Next, the configuration of OFDM demodulation section 103 will be described using FIG. In FIG. 3, an OFDM modulated signal transmitted from a receiver 701 via a transmission line 706 is received by a reception high frequency unit 302 from a terminal 301, converted to an intermediate frequency by an IF conversion unit 303, and supplied to an AD conversion unit 304. Is done. In the AD conversion unit 304, for example, an analog IF signal of 20.45 MHz is orthogonally demodulated, converted into a digital signal, and converted into an I-component and Q-component signal in an orthogonal coordinate system. An FFT (First Fourier Transform) unit 305 obtains a frequency component from a time waveform composed of 1024 samples.

  The demodulation unit 306 includes a CP extraction & interpolation unit 307, a correction unit 308, and a separation unit 309. The CP extracting & interpolating unit 307 takes out the CP carriers arranged every eight lines, and generates correction data indicating the phase and amplitude changes occurring in the data carrier based on the phase and amplitude components of the CP carrier. The correction unit 308 reversely corrects the characteristics generated during transmission of the data carrier based on the correction data generated by the CP extraction & interpolation unit 307, and corrects the phase and amplitude of the data carrier. The separation unit 309 separates the main data carrier component, the auxiliary data carrier component, and the TMCC information. The main data identification unit 310 obtains the transmission data value of the main data carrier from the obtained mapping point, and outputs it from the terminal 313. The auxiliary data identification unit 311 obtains the transmission data value of the auxiliary data carrier from the obtained mapping point, and outputs it from the terminal 713. Details of the TMCC identification unit 312 will be described with reference to FIG. Note that a time synchronization control unit for controlling the operation timing and period of each unit of the OFDM demodulation unit 103 is omitted.

  Next, the TMCC conversion unit 206 in FIG. 2 is for switching the modulation scheme, coding rate, number of IFFT samples and the like described above, and details will be described with reference to FIG. TMCC information from the TMCC conversion unit 206 is mapped by the TMCC mapping unit 207, for example, 16QAM or QPSK. The TMCC conversion unit 206 will be described with reference to FIG. FIG. 4 is a block diagram illustrating a schematic configuration of the TMCC conversion unit 206. In FIG. 4, a TMCC conversion unit 206 includes a TMCC carrier data conversion unit 401, a modulation scheme automatic switching unit 402, a coding rate automatic switching unit 403, an IFFT sample number automatic switching unit 404, and each mode automatic switching control unit 405. ing. Although conventional transmission / reception of OFDM modulated signals has been described, as is clear from the above description, since there are many transmission modes such as modulation scheme, coding rate, number of IFFT samples, etc. in OFDM modulated signal transmission, OFDM modulation is required. It is necessary to appropriately determine which mode is used to transmit the signal and transmit the signal. However, in actual operation, it is impossible to determine which mode is the most suitable mode unless data is actually transmitted, which requires a lot of labor and time. .

  Therefore, in the present invention, the optimum transmission mode of the data transmission apparatus, that is, various transmission modes such as a modulation method, a coding rate, and the number of IFFT samples are sequentially switched and transmitted. The TMCC conversion unit 206 is configured and operates as described above. Each mode automatic switching control unit 405 includes, for example, a storage unit 406 such as a ROM, and the above-described various modes are stored in the storage unit 406. For example, with respect to the OFDM modulation scheme, a part or all of the modulation scheme used for data transmission such as DQPSK, QPSK, 16QAM, 32QAM, 64QAM, etc. is stored. As for the coding rate, a part or all of the coding rate at the time of coding, such as 5/6, 3/4, 2/3 or 1/2, is stored. Further, as the number of IFFT samples, for example, the number of samples such as 1K, 2K,. Hereinafter, each modulation method, each coding rate, and each sample number will be referred to as each mode.

  The data transmission apparatus of the present invention first selects an optimum mode of the data transmission apparatus before use. That is, the data transmission apparatus needs to be operated by selecting an optimum transmission mode because the state of the transmission path changes depending on the setting location. Accordingly, each mode automatic switching control unit 405 selects one from each mode stored in the storage unit 406, and sets the data transmission apparatus to that mode. For example, in the OFDM modulation scheme, DQPSK is selected, the modulation scheme automatic switching unit 402 is controlled, and the modulation scheme of the OFDM modulation unit is set to DQPSK. At the same time, information indicating that the modulation method is DQPSK (hereinafter referred to as mode information. The same shall apply hereinafter) is sent to the TMCC carrier data conversion unit 401. For the coding rate, for example, 5/6 is selected and the coding rate automatic switching unit 403 is controlled to set the coding rate of the OFDM modulation unit to 5/6. At the same time, information (mode information) indicating that the coding rate is 5/6 is sent to the TMCC carrier data conversion unit 401. Further, as the number of IFFT samples, 1K samples are selected, and the IFFT sample number automatic switching unit 404 is controlled to set the IFFT 209 of the OFDM modulation unit to 1K samples. At the same time, information (mode information) indicating that the number of IFFT samples is 1K samples is sent to the TMCC carrier data conversion unit 401. The TMCC carrier data conversion unit 401 uses the modulation mode, coding rate, and number of samples mode information transmitted from the modulation mode automatic switching unit 402, the coding rate automatic switching unit 403, and the IFFT sample number automatic switching unit 404, respectively. Data is converted and sent to the OFDM modulation unit 102. The sending method is sent as the TMCC signal shown in FIG. 12, but in particular, the TMCC signal is transmitted to the receiver 707 using, for example, several bits of setting data (configured with 41 bits).

  The receiver 707 identifies mode information from the TMCC signal sent from the transmitter 701, sets the OFDM demodulator 103 so that data can be demodulated in the transmission mode, and demodulates the data. This will be described with reference to FIG. FIG. 5 is a block diagram showing a schematic configuration of the TMCC identification unit. In FIG. 5, the TMCC identifying unit 312 includes a TMCC carrier data determining unit 501, an FFT sample number automatic determining unit 502, an encoding rate automatic determining unit 503, a modulation scheme automatic determining unit 504, and a control unit 506.

  Thus, the TMCC carrier data (shown in FIG. 12) of the signals demodulated by the demodulator 306 of the OFDM demodulator 103 is processed by the TMCC carrier data discriminator 501 with the number of FFT samples in the OFDM transmission scheme, The mode information of the rate and the modulation method is separated, respectively, and the modulation method, coding rate, and FFT sample number are automatically set by the FFT sample number automatic determination unit 502, the coding rate automatic determination unit 503, and the modulation method automatic determination unit 504, respectively. It is determined and supplied to the control unit 506. The control unit 506 includes a storage unit 507 and stores these determined signals. At the same time, the demodulation unit 306 and the FFT unit 305 can demodulate in each mode sent, that is, the data sent from the transmitter 701 as described above is modulated by DQPSK. Since the coding rate is 5/6 and the number of samples is 1K samples, the demodulation unit 306 and the FFT unit 305 are set and demodulated so that data is demodulated in these modes.

On the other hand, the output of the demodulation unit 306 is supplied to the reception state automatic determination unit 505. The automatic reception state determination unit 505 is a determination unit that determines whether data transmitted through the transmission line in the above-described transmission mode is good or not. An embodiment of this discrimination unit will be described with reference to FIG. In FIG. 6, the output of the demodulator 306 is normally error-corrected by the Viterbi corrector 601 and the RS corrector and returned to the original data. Accordingly, the reception state automatic determination unit 505 includes counters 603 and 604, the counter 603 is a counter that counts errors before Viterbi correction, and the counter 604 is a counter that counts errors before RS correction. is there. For example, the optimum operation mode can be selected by selecting the operation mode of the data transmission device based on the count value of the counter. For example, when the data transmission apparatus of the present invention is used in a range of about 6 hours, if the BER (Bit Error Rate) is about 1 × 10 ⁻⁴ , for example, it can be used in that mode. Show. Further, when the data transmission device of the present invention is used for 24 hours, the BER is determined to be used, for example, at 1 × 10 ⁻⁵ or less. Note that the criteria for this determination are not limited to those described above, but are appropriately selected depending on the configuration of the data transmission device, the condition of the transmission path, the reliability of the data, and the like, and are determined experimentally. Can do.

In the above description, for example, if the BER of the reception state automatic determination unit 505 is 1 × 10 ⁻⁴ or more, good data transmission cannot be performed in the selected transmission mode. In this case, as described above with reference to FIG. 4, each mode automatic switching control unit selects the next transmission mode from the storage unit 406. For example, in the OFDM modulation method, QPSK is selected, and the modulation method automatic switching unit 402 is controlled to set the modulation method of the OFDM modulation unit to QPSK. At the same time, mode information indicating that the modulation method is QPSK is sent to the TMCC carrier data conversion unit 401. As for the coding rate, for example, 3/4 is selected, and the coding rate automatic switching unit 403 is controlled to set the coding rate of the OFDM modulation unit to 3/4. At the same time, mode information indicating that the coding rate is 3/4 is sent to the TMCC carrier data conversion unit 401. Further, as the number of IFFT samples, 2K samples are selected, and the IFFT sample number automatic switching unit 404 is controlled to set the IFFT 209 of the OFDM modulation unit to 2K samples. At the same time, mode information indicating that the number of IFFT samples is 2K samples is sent to the TMCC carrier data conversion unit 401. In the TMCC carrier data conversion unit 401, information on the modulation method, coding rate, and number of samples respectively sent from the modulation method automatic switching unit 402, the coding rate automatic switching unit 403, and the IFFT sample number automatic switching unit 404 is received as carrier data. And sent to the OFDM modulation section 102. The OFDM modulation unit 102 uses several bits of TMCC signal setting data (consisting of 41 bits) as the TMCC signal, and places the mode information on the TMCC signal, and transmits the TMCC signal to the receiver 707. Note that the demodulation of received data and the determination of the reception state are the same as described above, and a detailed description thereof will be omitted. In this way, the transmission modes are sequentially switched, the optimum transmission mode corresponding to the transmission path can be selected, and the data transmission apparatus can be set to that mode.

  Next, another embodiment of the present invention will be described with reference to FIG. FIG. 13 is a block diagram illustrating a schematic configuration of an embodiment in which a control signal from the receiver 707 is transmitted to the transmitter 701 via the transmission path 1301. In addition, the code | symbol of each part respond | corresponds to the code | symbol of each part of FIG.1, FIG4 and FIG.5. In the above embodiment, it is explained that the determination result of whether the mode of the data transmitted in the TMCC identification unit 104 is good or not is obtained, and when it is not good, the transmission mode is switched appropriately on the transmitter side. I explained about sending. However, various methods are conceivable as a method of feeding back the determination result on the receiver side to the transmitter side. For example, in the first method, each mode automatic switching control unit 405 selects one transmission mode and transmits data, the reception state automatic determination unit 505 determines the result, and the result is transmitted from the receiver 707 side to the transmitter 701. This is a method of informing the side and selecting the next transmission mode. In the second method, each mode automatic switching control unit 405 on the transmitter side sequentially switches the transmission mode at predetermined intervals, and on the receiver side, the BER (Bit Error Rate) in each transmission mode is set to the TMCC shown in FIG. The BER stored in the storage unit 507 of the identification unit 312 is then determined, the optimum transmission mode is determined, only the result is notified from the receiver side to the transmitter side, and data is transmitted in the transmission mode. It is a method to do. In any of these methods, the operator can communicate wirelessly or by wire, but the determination result can also be transmitted as a signal as shown in FIG.

  In FIG. 13, for example, the result determined by the TMCC identification unit 104 is transmitted to the TMCC conversion unit 101 via a transmission path (including wireless and wired) 1301, and the control unit 405 is switched and stored in the storage unit 406. It is also possible to automatically read out the transmission mode being switched and to switch automatically. In this case, the BER is determined every time a determination result is output on the receiver side, and if the predetermined BER is not reached, the transmission mode is sequentially switched, or transmission is automatically performed at a predetermined interval on the transmitter side. It is also possible to transmit data by sequentially switching the mode, select an optimal transmission mode from among them, transmit the signal to the receiver side, and transmit the data in the optimal transmission mode. In any case, a data transmission apparatus to which the present invention is applied has an advantage that data can be transmitted in an optimal transmission mode as appropriate according to the state of the transmission path.

  As described above, the transmitter side uses the TMCC carrier to transmit data while automatically switching part or all of the transmission modes of the data transmission apparatus, and the receiver side sets the BER during transmission in each mode. Since it is possible to detect and determine which mode is optimal for transmission from this determination result, it is possible to save the trouble of checking the quality of each mode.

  Although the present invention has been described in detail above, the present invention is not limited to the embodiments of the data transmission device described herein, and can be widely applied to data transmission devices other than those described above. Needless to say.

It is a block diagram for demonstrating one Example of this invention. 1 is a schematic block diagram illustrating an OFDM modulation unit of the present invention. The schematic block diagram explaining the OFDM demodulation part of this invention is shown. The block diagram for demonstrating one Example of the TMCC modulation part used by this invention is shown. The block diagram for demonstrating one Example of the TMCC identification part used by this invention is shown. The block diagram of one Example of the reception status automatic determination part used by this invention is shown. The block diagram for demonstrating an example of the conventional OFDM transmission apparatus is shown. It is a block diagram which shows an example of the conventional TMCC conversion part. It is a figure for demonstrating the structure of an OFDM signal. It is a figure for demonstrating the waveform of 1 symbol period of an OFDM signal. It is a figure for demonstrating the frame structure of an OFDM modulation system. It is a figure for demonstrating TMCC carrier data. It is a block diagram for demonstrating other one Example of this invention.

Explanation of symbols

  101, 206, 704: TMCC conversion unit, 102, 705: OFDM modulation unit, 103, 708: OFDM demodulation unit, 104: TMCC identification unit, 201: main data input terminal, 202: main data mapping unit, 203: CP generation 204: auxiliary data input terminal, 205: auxiliary data mapping unit, 207: TMCC mapping unit, 208: modulation integration unit, 209: IFFT, 210: guard addition unit, 211: DA conversion unit, 212: IF conversion unit, 213: Transmission high frequency unit, 214: Output terminal, 301: Input terminal, 302: Reception high frequency unit, 303: IF conversion unit, 304: AD conversion unit, 305: FFT, 306: Demodulation unit, 307: CP extraction & interpolation unit 308: Correction unit 309: Separation unit 310: Main data identification unit 311: Auxiliary data identification unit 312: TM C identification unit, 313: main data output terminal, 314: auxiliary data output terminal, 401: TMCC carrier data conversion unit, 402: modulation scheme automatic switching unit, 403: coding rate automatic switching unit, 404: IFFT sample number automatic switching 405: each mode automatic switching control unit, 406: storage unit, 501: TMCC carrier data determination unit, 502: FFT sample number automatic determination unit, 503: coding rate automatic determination unit, 504: modulation scheme automatic determination unit, 505: Reception state automatic determination unit, 506: Control unit, 507: Storage unit, 601: Viterbi correction unit, 602: RS correction unit, 603: Error counter before Viterbi correction, 604: Error counter before RS correction, 701: Transmitter 702: Main data encoding unit 703: Auxiliary data encoding unit 706: Transmission path 707: Reception unit 709: Main data Goka unit, 710: auxiliary data decoding unit.

Claims (1)

In a data transmission apparatus that transmits data using an OFDM modulated signal between a transmitter and a receiver,
The transmitter, the OFDM modulation unit, a storage unit for storing a plurality of modulation schemes, a plurality of coding rates, and a plurality of modes represented by a plurality of number of samples of the OFDM modulated signal, stored in the storage unit A mode switching unit having a mode switching control unit for sequentially switching the plurality of modes at predetermined intervals and transmitting the data from the transmitter , and mode information for adding mode information of the switched modes to the OFDM modulation signal and adding unit, it consists of,
The receiver includes an OFDM demodulator that demodulates an OFDM modulated signal sent from the transmitter , and error information of the demodulated signal obtained from the OFDM demodulator , and a reception state of the OFDM modulated signal sent from the transmitter A receiving state discriminating unit that discriminates the mode information from the OFDM modulated signal, stores the receiving state of the OFDM modulated signal of each mode output from the receiving state discriminating unit, and stores each of the stored A mode information identifying unit that selects a predetermined mode from the reception state of the OFDM modulation signal of the mode, and transmits mode switching information for switching to the predetermined mode to the mode switching unit of the transmitter;
A data transmission device comprising:

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