Modulation device, demodulation device, and program

Abstract

To enable easily detecting, writing and replacing a transmitting station identification code at a relay station without deteriorating the signal quality of a main broadcast line.SOLUTION: A modulation device 1 includes a subframe generator 17 for a transmitting station identification code which generates a subframe for a transmitting station identification code, which is a subframe for transmitting a transmitting station identification code that identifies a transmitting station; and a time division multiplexing frame constructor 19 that generates a time division multiplexing frame in which the subframe for the transmitting station identification code, a TMCC signal having transmission control information, and a subframe for hierarchical data, which is a subframe for transmitting video, audio, and subtitle data, are multiplexed into one frame by time division.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a modulation device, a demodulation device, and a program. [Background technology]

[0002] Conventionally, the Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) system has been known as a terrestrial digital broadcasting system. Furthermore, in order to improve the quality and functionality of terrestrial digital broadcasting, a next-generation advanced terrestrial broadcasting system that inherits the features of the ISDB-T system is being studied (for example, see Patent Document 1).

[0003] Non-patent document 1 states that, as a future issue for the advanced system, "when changing the transmission frequency after transitioning from the current terrestrial digital broadcasting system to the advanced terrestrial broadcasting system, a function that enables the receiver to identify the transmitting station will be desired, so it is desirable to consider technology that will enable information to realize this function to be superimposed on the broadcast waves."

[0004] Specifically, by assigning a unique number, a transmitting station identification code, to the main station and each relay station and superimposing this on the broadcast waves, for example, when switching from SFN (Single Frequency Network) to MFN (Multi Frequency Network), the receiver can identify the main station of the waves it is receiving, making it possible to smoothly perform re-channel scans when changing channels.

[0005] In addition, a method of superimposing an ID (transmitter station ID) that identifies a different transmitter for each transmitter on a transmission signal has been put to practical use in ATSC (Advanced Television System Committee) 3.0, a terrestrial broadcasting system in the United States (see, for example, Non-Patent Document 2). This uses a method called Layered Division Multiplexing (LDM) to superimpose a lower layer that includes the transmitter station ID on an upper layer that includes the control signal field. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-181709 A [Non-patent literature]

[0007] [Non-Patent Document 1] Ministry of Internal Affairs and Communications, "Report (Draft) of the Broadcasting System Committee of the Information and Communications Technology Subcommittee of the Information and Communications Council," [online], June 29, 2023, [Retrieved August 10, 2023], Internet<URL:https: / / www.soumu.go.jp / main_content / 000890352.pdf> [Non-Patent Document 2] Sung-Ik Park et al., “ATSC 3.0 Transmitter Identification Signals and Applications,” IEEE Trans. Broadcast., vol.63, no.1, pp.240-249, Mar.2017 Summary of the Invention [Problem to be solved by the invention]

[0008] The advantage of the superimposition of the transmitter ID in ATSC3.0 is that it does not affect the main broadcasting line such as video and audio, but it is not assumed that the transmitter ID will be "rewritten" at the relay station. This is because the ATSC3.0 network design is such that the system is designed to superimpose the transmitter ID for each transmitter on the signal that is distributed by optical fiber lines and has nothing superimposed on it.

[0009] On the other hand, Japan's terrestrial broadcasting has installed about 2,200 main stations and relay stations nationwide, and many of them use a unique method called "broadcast wave relay" that directly receives broadcast waves and retransmits them after signal processing, which is not available in the United States. Since there is no need to prepare a dedicated line to the relay station, it has a great advantage in terms of equipment costs and is widely used. Therefore, it is necessary for the relay station that relays the broadcast wave to rewrite the transmission station identification code (in this specification, to distinguish it from ATSC3.0, it is called "transmission station identification code" rather than "transmission station ID") that identifies the higher-level transmission station on the broadcast wave that has already been superimposed. In the superimposition method of the transmission station ID adopted in the above-mentioned ATSC3.0, the signal indicating the transmission station ID is not independent on the time axis or the frequency axis, and if the transmission station ID of the lower layer is replaced, the control signal of the higher layer must also be replaced. Therefore, the control signal needs to be demodulated once, which increases the circuit size and processing delay in terms of "rewriting the transmission station ID." Furthermore, if demodulation or replacement of the control signal fails, the impact will be enormous.

[0010] In view of the above circumstances, an object of the present invention is to provide a modulation device, a demodulation device, and a program that make it possible to easily detect, write, and replace a transmitting station identification code at a relay station without degrading the signal quality of the main broadcast line. [Means for solving the problem]

[0011] The gist of the present invention for solving the above problems is as follows.

[0012] (1) A modulation device comprising: a subframe generation unit for a transmitter identification code that generates a subframe for a transmitter identification code, which is a subframe for transmitting a transmitter identification code that identifies a transmitter station; and a time division multiplexing frame construction unit that generates an OFDM signal in which the subframe for the transmitter identification code, a TMCC (Transmission and Multiplexing Configuration Control) signal having transmission control information, and a subframe for hierarchical data, which is a subframe for transmitting video, audio, and subtitle data, are multiplexed into one frame by time division.

[0013] (2) The modulation device described in (1), wherein the subframe generation unit for transmitter station identification code generates a QPSK modulated signal by modulating an I axis with a signal obtained by shifting a first M-sequence signal based on the transmitter station identification code and modulating a Q axis with a signal obtained by shifting a second M-sequence signal based on the transmitter station identification code.

[0014] (3) A modulation device described in (1) or (2), wherein the time division multiplexing frame construction unit time division multiplexes the subframe for the transmitter station identification code only once per multiple frames, and the TMCC signal has a transmitter station identification code flag indicating whether the time division multiplexing frame includes the subframe for the transmitter station identification code.

[0015] (4) A demodulation device that demodulates an OFDM signal generated by the modulation device described in (1), comprising a transmitter identification code demodulation unit that calculates a correlation coefficient between a signal obtained by demodulating the transmitter identification code subframe and a previously generated M-sequence signal, and detects the transmitter identification code based on a peak position of the correlation coefficient.

[0016] (5) The demodulation device described in (4) further includes a TMCC demodulation unit that demodulates a TMCC signal having a transmitter identification code flag indicating whether or not the time division multiplexing frame includes a subframe for the transmitter identification code, and the transmitter identification code demodulation unit demodulates the transmitter identification code at a timing when the time division multiplexing frame includes the subframe for the transmitter identification code based on the transmitter identification code flag.

[0017] (6) According to one embodiment, a program causes a computer to function as the modulation device according to any one of (1) to (3).

[0018] (7) According to one embodiment, a program causes a computer to function as the demodulation device according to (4) or (5). Effect of the Invention

[0019] According to the present invention, it is possible to easily detect, write, and replace a transmitting station identification code at a relay station without degrading the signal quality relative to the main broadcast line. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a modulation device according to an embodiment. [Diagram 2] 1 is a block diagram showing an example of the configuration of a subframe generating unit for a transmitting station identification code in a modulation device according to an embodiment. FIG. [Diagram 3] 2 is a block diagram showing an example of the configuration of a PRBS (Pseudo-Random Binary Sequence) generating unit in a modulation device according to an embodiment. FIG. [Figure 4] 1 is a diagram showing an outline of a time division multiplexing frame generated by a modulation device according to an embodiment; [Diagram 5] 1 is a block diagram showing an example of the configuration of a demodulation device according to a first embodiment. [Figure 6] 2 is a block diagram showing an example of the configuration of a transmission station identification code demodulation unit in the demodulation device according to the first embodiment. FIG. [Figure 7] FIG. 1 is a system diagram of a transmission simulation. [Figure 8] FIG. 4 is a diagram showing an example of correlation coefficients obtained by a transmission simulation of the demodulation device according to the first embodiment. [Figure 9] FIG. 11 is a block diagram showing an example of the configuration of a demodulation device according to a second embodiment. [Figure 10] FIG. 11 is a diagram showing an example of correlation coefficients obtained by a transmission simulation of the demodulation device according to the second embodiment. [Figure 11] FIG. 11 is a block diagram showing an example of the configuration of a demodulation device according to a third embodiment. [Figure 12] FIG. 11 is a block diagram showing an example of the configuration of a transmission station identification code demodulation unit in a demodulation device according to a third embodiment. [Figure 13] FIG. 11 is a block diagram showing an example of the configuration of a delay profile generating unit in a demodulation device according to a third embodiment. [Figure 14] FIG. 11 is a diagram showing an example of a delay profile obtained by a transmission simulation of the demodulation device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, one embodiment will be described in detail with reference to the drawings.

[0022] <Modulation device according to one embodiment> Fig. 1 is a block diagram showing an example of the configuration of a modulation device 1 according to an embodiment. As shown in Fig. 1, the modulation device 1 includes a BICM (Bit-Interleaved Coded Modulation) processing unit 11 (11a, 11b, 11c), a level adjustment unit 12 (12a, 12b, 12c), a symbol processing unit 13, a pilot generation unit 14, a TMCC generation unit 15, a frame synchronization signal generation unit 16, a subframe generation unit 17 for a transmission station identification code, a transmission processing unit 18, and a time division multiplexing frame configuration unit 19. The symbol processing unit 13 includes a hierarchical synthesis unit 131, a band division unit 132, a time IL (Interleave) unit 133, a frequency IL unit 134, and a band synthesis unit 135. The transmission processing unit 18 includes an OFDM modulation unit 181, an IFFT (Inverse Fast Fourier Transform) unit 182, and a GI (Guard Interval) addition unit 183. The modulation device 1 is mounted in a transmitting station (transmitting device).

[0023] The modulating device 1 inputs data of multiple layers to each BICM processing unit 11. In this embodiment, the multiple layers are three layers, layer A, layer B, and layer C, and the data of layer A is input to the BICM processing unit 11a, the data of layer B is input to the BICM processing unit 11b, and the data of layer C is input to the BICM processing unit 11c. The modulating device 1 also inputs pilot arrangement information to the pilot generating unit 14, and inputs transmission control information to the TMCC generating unit 15. The transmission control information includes transmission parameters (modulation method, number of segments, coding rate, etc.) of each of the multiple layers.

[0024] The BICM processing units 11a, 11b, and 11c perform FEC (Forward Error Correction) block conversion processing, energy dispersal processing, BCH encoding processing, LDPC (Low Density Parity Check) encoding processing, bit interleaving processing, and carrier modulation processing on the data of the corresponding layer, generate carrier symbols, and output them to level adjustment units 12a, 12b, and 12c.

[0025] The level adjustment units 12 a , 12 b , and 12 c adjust the levels of the carrier symbols for each layer and output the results to a layer combining unit 131 .

[0026] The hierarchical combining unit 131 combines the carrier symbols of the respective layers and outputs the combined carrier symbol to the band dividing unit 132.

[0027] The band dividing unit 132 divides the combined carrier symbols into each band by performing band dividing processing on the combined carrier symbols. Then, the band dividing unit 132 outputs the band-divided carrier symbols to the time IL unit 133. For example, the band dividing unit 132 divides a part of the C layer data into adjustment bands as necessary.

[0028] The time IL unit 133 performs interleaving processing on the band-divided carrier symbols in the time direction (i.e., the symbol arrangement direction in each carrier) to generate a time interleaved signal. Then, the time IL unit 133 outputs the time interleaved signal to the frequency IL unit 134.

[0029] The frequency IL unit 134 performs interleaving processing in the frequency direction on the time interleaved signal input from the time IL unit 133 to generate a frequency interleaved signal. Then, the frequency IL unit 134 outputs the frequency interleaved signal to the band synthesis unit 135.

[0030] The band synthesis unit 135 synthesizes the frequency interleaved signals of the respective bands to generate a data segment, and outputs the generated data segment to the OFDM modulation unit 181.

[0031] The pilot generation unit 14 generates a pilot signal based on the pilot arrangement information, and outputs the pilot signal to the OFDM modulation unit 181. The pilot signal is a signal that is known to the demodulation device.

[0032] The TMCC generator 15 generates a TMCC signal having the transmission control information based on the transmission control information, and outputs the TMCC signal to the time division multiplexing frame constructor 19. The TMCC signal has at least one bit of a transmitting station identification code flag that is linked to the appearance of a subframe that transmits a transmitting station identification code. The transmitting station identification code flag will be described in detail later.

[0033] The frame synchronization signal generator 16 generates a frame synchronization signal and outputs it to the time division multiplexing frame constructor 19. The frame synchronization signal is a synchronization signal that is transmitted at the beginning of a time division multiplexing frame.

[0034] The subframe generator 17 for transmitting station identification code generates a subframe for transmitting a transmitting station identification code that identifies a transmitting station (transmitting device). Conventional modulation devices do not have a function for transmitting a transmitting station identification code. In this embodiment, the transmitting station identification code is described as a 12-bit numerical value, but the number of bits of the transmitting station identification code is not limited to this.

[0035] Fig. 2 shows a configuration example of the transmission station identification code subframe generation unit 17. The transmission station identification code subframe generation unit 17 shown in Fig. 2 includes a first PRBS generation unit 171, a second PRBS generation unit 172, a signal sequence shift unit 173, a carrier modulation unit 174, a pilot generation unit 175, an OFDM modulation unit 176, an IFFT unit 177, and a GI addition unit 178.

[0036] The first PRBS generating unit 171 generates a PRBS (pseudo random binary signal sequence) signal constituting the real part of the signal. The second PRBS generating unit 172 generates a PRBS signal constituting the imaginary part of the signal. The PRBS signal can be generated using an M sequence (Maximum Length Sequence), which is a pseudorandom number generation algorithm. The M sequence is generated by a p-bit shift register and has a period of 2 p It is a series of -1.

[0037] 3(a) shows an example of a circuit for the first PRBS generating unit 171, and FIG. 3(b) shows an example of a circuit for the second PRBS generating unit 172. FIGS. 3(a) and 3(b) show an example of a circuit for the second PRBS generating unit 172. 1i ,W 2i The PRBS generator circuit based on equations (1) and (2) is shown in FIG. 1. The initial values ​​of the shift register of the circuit are all 1. 1i The first M-sequence signal in which 0 is assigned to 1 and 1 to -1 is a n And W 2i The second M-sequence signal in which 0 is assigned to 1 and 1 to -1 is n Here, n represents a signal index and is equivalent to an OFDM subcarrier number, which will be described later. Subframe generator 17 for transmitter station identification code transmits a 12-bit transmitter station identification code according to the shift amount of the M sequence generated by equations (1) and (2).

[0038]

number

[0039] In another example, an M sequence generated by a generator polynomial of degree 12 may be used. Fig. 3(c) shows an example of a circuit for the first PRBS generator 171 when the generator polynomial is equation (3), and Fig. 3(d) shows an example of a circuit for the second PRBS generator 172 when the generator polynomial is equation (4).

[0040]

number

[0041] The signal sequence shift unit 173 shifts the first M sequence signal a n Shifted c m,n and the second M-sequence signal b n d shifted m,n If the transmitter identification code is m (0≦m<4096), the shifted M-sequence signal c m,n ,d m,nIt is expressed by formulas (5) and (6). Here, N represents the number of subcarriers per OFDM symbol (N > 4096).

[0042]

Number

[0043] The M sequence has an autocorrelation peak only once per period. Therefore, the correlation coefficient Φ(k) with the signal sequence before shifting is expressed by formula (7), and signal detection can be performed by utilizing the fact that a peak occurs only at k = m when 0 ≤ k < N. The M-sequence signal b n , d n is the same.

[0044]

Number

[0045] The carrier modulation unit 174 modulates the MSB (0th bit, I-axis, real axis) by c m,n and modulates the LSB (1st bit, Q-axis, imaginary axis) by d m,n to generate a QPSK modulation signal s m,n . That is, the carrier modulation unit 174 generates a QPSK modulation signal s m,n with the signal points on the I-axis being the sequence signal c m,n and the signal points on the Q-axis being the sequence signal d m,n . Here, let the subcarrier number of the subframe transmitting the station identification code be n. The QPSK modulation signal s m,n is expressed by formula (8).

[0046]

Number

[0047] The pilot generation unit 175 generates a predetermined pilot signal and outputs it to the OFDM modulation unit 176.

[0048] The OFDM modulation unit 176 generates OFDM symbols (corresponding to OFDM symbols constituting a subframe for a transmitter identification code) by inserting pilot signals at predetermined frequency intervals into the subcarriers QPSK modulated by the carrier modulation unit 174. Then, the OFDM modulation unit 176 outputs the OFDM symbols, which are frequency domain signals, to the IFFT unit 177.

[0049] The IFFT unit 177 performs IFFT processing on the OFDM symbol inputted from the OFDM modulation unit 176 to generate an effective symbol signal, and outputs it to the GI adding unit 178 .

[0050] The GI adding unit 178 adds a GI, which is a signal obtained by copying a part of the end of the effective symbol signal, to the beginning of the effective symbol signal input from the IFFT unit 177, to generate a subframe for a transmitting station identification code. The guard interval length may be the longest. The GI adding unit 178 then outputs the subframe for a transmitting station identification code to the time division multiplexing frame constructing unit 19.

[0051] Frequency interleaving and time interleaving are not performed on the transmitter identification code. The arrangement pattern of the pilot signals is, for example, (Dx, Dy) = (3, 1). Here, Dx is the spacing between pilot signals in the carrier direction, and Dy is the spacing between pilot signals in the symbol direction. The FFT size is, for example, 8k (8192).

[0052] In ATSC3.0, coding based on one Gold sequence and BPSK modulation are performed. Normally, correlation by preferred pair is performed on a signal modulated on a bit-by-bit basis, so strictly speaking, in the case of QPSK modulated signal (2-bit modulation), the waveform of correlation with the transmission waveform is not clean, so there is a concern of erroneous detection. Therefore, the transmitter identification code subframe generating unit 17 modulates the real part and imaginary part of QPSK, which is 2-bit modulation, separately by 1-bit modulation, and generates two types of M-sequence signals that are uncorrelated with each other and performs modulation.

[0053] 1 again, OFDM modulation unit 181 generates an OFDM symbol (corresponding to an OFDM symbol constituting a hierarchical data subframe) by inserting a pilot signal input from pilot generation unit 14 into a data segment input from band synthesis unit 135. Then, OFDM modulation unit 181 outputs the OFDM symbol, which is a frequency domain signal, to IFFT unit 182.

[0054] The IFFT unit 182 performs IFFT processing on the OFDM symbol inputted from the OFDM modulation unit 181 to generate an effective symbol signal, and outputs the effective symbol signal to the GI addition unit 183 .

[0055] The GI adding unit 183 adds a GI, which is a signal obtained by copying a part of the end of the effective symbol signal, to the beginning of the effective symbol signal input from the IFFT unit 182, to generate a subframe for hierarchical data. The GI is set so that the delay time of the multipath delay wave does not exceed the GI length. Then, the GI adding unit 183 outputs the subframe for hierarchical data to the time division multiplexing frame constructing unit 19.

[0056] The time division multiplexing frame construction unit 19 generates a time division multiplexing frame (OFDM signal) by multiplexing the hierarchical data subframe (the hierarchical data subframe, which is a subframe for transmitting video, audio, and subtitle data) output by the GI addition unit 183, the frame synchronization signal output by the frame synchronization signal generation unit 16, the TMCC signal output by the TMCC generation unit 15, and the transmitting station identification code subframe output by the transmitting station identification code subframe generation unit 17 into one frame by time division, and outputs the frame to the outside of the modulation device 1.

[0057] In this way, the modulation device 1 according to the present invention multiplexes the subframe for the transmitter identification code in a time division manner. Since the subframe for the transmitter identification code is an OFDM symbol independent on the time axis, it is possible to easily write the transmitter identification code and replace it at the relay station, and there is no degradation of the signal quality of other transmission data such as the TMCC signal and hierarchical data. This is because the OFDM signal received at the relay station is a time-domain waveform, and the writing and replacement of the transmitter identification code is performed in the time domain, so there is no need to convert it to a frequency-domain waveform by FFT (First Fourier Transform) processing.

[0058] On the other hand, since the subframe for the transmitter identification code is inserted in the time domain, the transmission capacity of the main broadcast line is slightly reduced. Therefore, instead of providing a subframe for the transmitter identification code in every OFDM frame, the subframe for the transmitter identification code may be inserted at a fixed interval and the transmitter identification code transmission flag described in the TMCC signal may be turned on only at that time. The transmitter identification code is information that does not change once it is determined, and the receiving device does not need to receive it all the time. For example, it may be inserted at a frequency that allows it to be obtained by turning on the power and receiving broadcast waves for one minute. If it is inserted at a sufficiently long interval, for example once every 256 frames, the impact on the transmission capacity of the main broadcast line will be negligible.

[0059] Therefore, the time division multiplexing frame constructing unit 19 may time division multiplex a subframe for a transmitting station identification code only once per multiple frames. The TMCC signal may have a transmitting station identification code flag indicating whether or not the time division multiplexing frame includes a subframe for a transmitting station identification code. In this embodiment, if the time division multiplexing frame includes a subframe for a transmitting station identification code, the transmitting station identification code flag is turned on, and if the time division multiplexing frame does not include a subframe for a transmitting station identification code, the transmitting station identification code flag is turned off.

[0060] Figure 4 shows an outline of a time division multiplexing frame generated by the time division multiplexing frame constructor 19. The vertical axis indicates frequency, and the horizontal axis indicates time. Figure 4(a) shows a time division multiplexing frame F1 when the transmitter identification code subframe is not time division multiplexed. In this case, the TMCC generator 15 turns off the transmitter identification code transmission flag of the TMCC signal. The time division multiplexing frame F1 is a frame obtained by time division multiplexing a frame synchronization signal A, a TMCC signal B, and a hierarchical data subframe C.

[0061] 4(b) shows a time division multiplexed frame F2 in the case where a subframe for a transmitting station identification code is time division multiplexed. In this case, the TMCC generator 15 turns on the transmitting station identification code transmission flag of the TMCC signal. The time division multiplexed frame F2 is a frame in which a frame synchronization signal A, a TMCC signal B, a subframe for hierarchical data C, and a subframe for a transmitting station identification code D are time division multiplexed.

[0062] <Demodulation device according to the first embodiment> Next, a demodulation device according to a first embodiment will be described.

[0063] Fig. 5 is a block diagram showing an example of the configuration of a demodulation device 2 according to the first embodiment. The demodulation device 2 shown in Fig. 5 includes a reception processing unit 21, a pilot extraction unit 22, a channel estimation unit 23, an equalization unit 24, a frequency-time DIL (Deinterleave) unit 25, an LLR calculation unit 26, an error correction decoding unit 27, a TMCC demodulation unit 28, a transmission station identification code demodulation unit 29, and a frame synchronization signal demodulation unit 30. The demodulation device 2 is mounted on a receiving device or a measurement device. The demodulation device 2 demodulates the OFDM signal generated by the modulation device 1.

[0064] The reception processing unit 21 performs demodulation processing on the OFDM signal received from the modulation device 1, and outputs a received signal (OFDM frame). The reception processing unit 21 includes a GI removal unit 211, an FFT unit 212, and a frame synchronization unit 213.

[0065] The GI removal unit 211 removes the GI from the received OFDM signal and outputs the signal to the FFT unit 212 .

[0066] The FFT unit 212 performs FFT processing on the OFDM signal input from the GI removal unit 211 to generate a complex baseband signal in the frequency domain, and outputs the signal to the frame synchronization unit 213.

[0067] The frame synchronization unit 213 synchronizes the OFDM frames.

[0068] The pilot extraction unit 22 extracts a pilot signal from the received signal input from the frame synchronization unit 213 and outputs it to the channel estimation unit 23 .

[0069] The channel estimation unit 23 estimates a channel response of a propagation path between the modulation device 1 and the demodulation device 2 (between the transmission and reception antennas) based on the pilot signal input from the pilot extraction unit 22 and a preset pilot signal. Then, the channel estimation unit 23 outputs the channel response for each carrier to the equalization unit 24.

[0070] The equalization unit 24 executes equalization processing of the complex baseband signal input from the frame synchronization unit 213 based on the channel response input from the channel estimation unit 23, and corrects propagation path distortion. Then, the equalization unit 24 outputs the equalized complex baseband signal (equalized signal) to the frequency / time DIL unit 25.

[0071] The transmission model is the transmitted signal x n , the received signal y n , noise w n , and the channel response h is expressed as follows:

[0072]

number

[0073] The transmitted signal at time t is a QPSK modulated signal s m,n , and the frequency f of the nth subcarrier nIt is expressed by equation (10) using

[0074]

number

[0075] The equalization unit 24 performs equalization processing by complex division expressed by equation (11) using the channel response input from the channel estimation unit 23, and calculates an equalized signal.

[0076]

number

[0077] The frequency / time DIL unit 25 performs deinterleaving processing in the frequency direction and the time direction on the equalized signal input from the equalization unit 24 to generate a deinterleaved signal. The deinterleaving processing in the frequency direction is processing to return data rearranged in the frequency direction by the frequency IL unit 134 of the modulation device 1 to the original order. The deinterleaving processing in the time direction is processing to return data rearranged in the time direction by the time IL unit 133 of the modulation device 1 to the original order. Then, the frequency / time DIL unit 25 outputs the generated deinterleaved signal to the LLR calculation unit 26.

[0078] The LLR calculation unit 26 compares the signal point coordinates of the deinterleaved signal input from the time / frequency DIL unit 25 with predetermined signal point coordinates, and calculates an LLR (log-likelihood ratio) for each bit based on the Euclidean distance between both coordinates. Then, the LLR calculation unit 26 outputs the calculated LLR to the error correction decoding unit 27.

[0079] The error correction decoding unit 27 performs error correction decoding (for example, LDPC decoding) using the LLR input from the LLR calculation unit 26, and decodes the signal transmitted from the modulation device 1 to generate hierarchical data.

[0080] The TMCC demodulation unit 28 extracts the TMCC signal from the received signal input from the frame synchronization unit 213, and demodulates the extracted TMCC signal. Then, the TMCC demodulation unit 28 outputs a transmission station identification code transmission flag of the TMCC signal to the transmission station identification code demodulation unit 29.

[0081] The frame synchronization signal demodulation section 30 extracts the frame synchronization signal from the received signal input from the frame synchronization section 213, and demodulates the extracted frame synchronization signal.

[0082] The transmitter identification code demodulator 29 calculates a correlation coefficient between the signal obtained by demodulating the transmitter identification code subframe and an M-sequence signal generated in advance within the transmitter identification code demodulator 29, and detects the transmitter identification code from the peak position of the correlation coefficient. If the TMCC signal has a transmitter identification code flag, the transmitter identification code demodulator 29 demodulates the transmitter identification code at the timing when the time division multiplexing frame includes the transmitter identification code subframe, based on the transmitter identification code flag. In other words, the transmitter identification code demodulator 29 operates only when the transmitter identification code flag is on.

[0083] Fig. 6 shows an example of the configuration of the transmission station identification code demodulation unit 29. The transmission station identification code demodulation unit 29 shown in Fig. 6 includes a first PRBS generation circuit 291, a second PRBS generation circuit 292, a transmission signal generation unit 293, a correlation coefficient calculation unit 294, and a transmission station identification code detection unit 295.

[0084] Similar to the transmitter identification code subframe generator 17 of the modulation device 1, the first PRBS generator 291 generates the M-sequence signal a n The second PRBS generating circuit 292 generates an M-sequence signal b n Generate.

[0085] The transmission signal generator 293 generates a transmission signal with a transmission station identification code m=0 (M sequence signal c 0,n ,d 0,n ) and outputs it to the correlation coefficient calculation unit 294.

[0086] The correlation coefficient calculation unit 294 calculates the correlation coefficient between the transmission signal input from the transmission signal generation unit 293 and the equalized signal of the subframe for the transmission station identification code input from the equalization unit 24 by using the formula (12). n ' is a noise component, and its correlation with the transmitted signal is negligibly small.

[0087]

number

[0088] The transmitting station identification code detection unit 295 detects the transmitting station identification code from the position of the peak value of the correlation coefficient.

[0089] As an example, a transmission simulation was carried out with a transmitting station identification code of 511 to verify the processing of the modulation device 1 and demodulation device 2 according to the present invention.

[0090] FIG. 7 shows a system diagram of the transmission simulation. FIG. 8 shows the correlation coefficient, which is the output of correlation coefficient calculation unit 294, obtained by the transmission simulation. In this example, the transmitting station identification code is set to 511. Also, the signal power to noise power ratio (C / N) is set to 20 dB, assuming fixed reception of terrestrial broadcasting. Since the correlation coefficient is a complex number, its absolute value |Φ(k)| is plotted on the vertical axis. The correlation coefficient reaches its peak value only when k=511. That is, it can be seen from FIG. 8 that the transmitting station identification code can be detected as 511.

[0091] <Demodulation device according to the second embodiment> Next, a demodulation device according to a second embodiment will be described.

[0092] Fig. 9 is a block diagram showing an example of the configuration of a demodulation device 2a according to the second embodiment. The demodulation device 2a shown in Fig. 9 includes a reception processing unit 21, a pilot extraction unit 22, a channel estimation unit 23, an equalization unit 24, a frequency-time DIL unit 25, an LLR calculation unit 26, an error correction decoding unit 27, a TMCC demodulation unit 28, a transmission station identification code demodulation unit 29a, a frame synchronization signal demodulation unit 30, a delay profile generation unit 31a, and an FFT window setting unit 32a. The demodulation device 2a differs from the demodulation device 2 in that it further includes the delay profile generation unit 31a and the FFT window setting unit 32a. Also, the demodulation device 2a differs from the demodulation device 2 in that the input of the transmission station identification code demodulation unit 29a is a received signal before equalization processing.

[0093] The delay profile generating unit 31a receives the pilot signal extracted by the pilot extracting unit 22 and generates a delay profile. Then, the delay profile generating unit 31a estimates the delay amount τ of the SFN wave relative to the main wave based on the delay profile, and outputs the delay amount τ to the FFT window setting unit 32a.

[0094] The FFT window setting unit 32a inputs the delay amount τ estimated by the delay profile generating unit 31a and controls the FFT window position. By controlling the phase adjustment of the received signal by the FFT window position, it becomes possible to identify each transmitting station even in a so-called SFN (Single Frequency Network) environment in which signals having multiple transmitting station identification codes are mixed. This is effective in determining whether there is a risk that may occur during channel reorganization.

[0095] The processing of the transmitting station identification code demodulation unit 29a is the same as that of the transmitting station identification code demodulation unit 29 of the demodulation device 2. However, the correlation coefficient calculation unit 294 receives the received signal before equalization instead of the equalized signal.

[0096] As an example, assume an SFN environment with two stations with different transmitter identification codes. The two transmitters are A and B, respectively, and their identification codes are l and m. Also, the channel response is h 1,n ,h 2,nWith the delay amount being τ, the transmission model can be expressed as equation (13) by modifying equation (9).

[0097]

number

[0098] If the transmitter identification code is the same value (m=l), the same signal waveform will be transmitted as in the main broadcast line, and it will be the same as the conventional SFN.

[0099]

number

[0100] In the transmitter identification code demodulation unit 29 of the demodulation device 2, the channel response is estimated using the pilot signal, thereby estimating the transmission signal. On the other hand, since the first term on the right side of the equation (13) is a signal waveform that differs for each transmitter station, both sides of the equation (13) are converted into the channel response h^ n Therefore, the transmitter ID code demodulation unit 29a substitutes equation (13) before equalization into equation (12) and detects the transmitter ID code by correlation with the transmission signal with m=0, as shown in equation (15).

[0101]

number

[0102] The first term on the right-hand side of equation (15) represents station A, the second term on the right-hand side represents station B, and the third term on the right-hand side represents noise. Here, the third term on the right-hand side, like equation (9), is the correlation between noise and the transmitted signal and is therefore small enough to be ignored. Additionally, the second term on the right-hand side is multiplied by a phase rotation coefficient that varies constantly depending on the subcarrier number n. Under conditions where N is sufficiently large, the second term on the right-hand side also becomes small enough to be ignored, both in terms of its real and imaginary parts, after addition. Therefore, equation (15) can be expressed as equation (16), and the transmitting station identification code m can be detected in the same way as equation (12).

[0103]

number

[0104] On the other hand, the delay amount τ between stations A and B can be estimated based on the delay profile. Using the delay amount τ thus obtained, the antiphase rotation term exp(j2πf nτ ) is multiplied. The processing of the FFT window setting unit 32a corresponds to this calculation. Equation (13) is expressed as equation (17).

[0105]

number

[0106] Similarly to equation (15), when the correlation coefficient with the transmission signal of m=0 is calculated, equation (18) is obtained.

[0107]

number

[0108] As described above, the first and third terms on the right-hand side of equation (18) are negligibly small, so equation (18) can be expressed as equation (19), and station B can also detect the transmitting station identification code.

[0109]

number

[0110] Fig. 10 shows the correlation coefficient, which is the output of correlation coefficient calculation unit 294, obtained by a transmission simulation. In this example, the transmitter identification code of station A is set to 511, and the transmitter identification code of station B is set to 1000. The delay amount is set to 10 μs, and the reception power ratio of stations A and B is set to 1 dB. Since the correlation coefficient is a complex number, its absolute value |Φ(k)| is plotted on the vertical axis. It can be seen from Fig. 10 that the transmitter identification codes of both stations A and B were detected.

[0111] <Demodulation device according to the third embodiment> Fig. 11 shows a block configuration of a demodulation device according to the third embodiment. The demodulation device 2b shown in Fig. 11 includes a reception processing unit 21, a pilot extraction unit 22, a channel estimation unit 23, an equalization unit 24, a frequency-time DIL unit 25, an LLR calculation unit 26, an error correction decoding unit 27, a TMCC demodulation unit 28, a transmission station identification code demodulation unit 29b, a frame synchronization signal demodulation unit 30, a delay profile generation unit 31b, and an FFT window setting unit 32b. The demodulation device 2b differs from the demodulation device 2 in that it further includes a delay profile generation unit 31b and an FFT window setting unit 32b. Also, the demodulation device 2b differs from the demodulation device 2 in that the input of the transmission station identification code demodulation unit 29b is a received signal before equalization processing.

[0112] The difference between the demodulator 2b and the demodulator 2a is that the demodulator 2b outputs a delay profile for each transmitting station. The demodulator 2a generates a delay profile from the detected pilot signal and estimates the delay between transmitting stations, but since it cannot distinguish between multipaths, it is difficult to estimate an accurate delay amount in an environment where multiple multipaths exist. Therefore, the demodulator 2b does not estimate the delay amount, but rather calculates the correlation of the transmitting station identification code while shifting the FFT window position little by little, and plots the peak to output a delay profile for each transmitting station.

[0113] Fig. 12 shows an example of the configuration of the transmitting station identification code demodulation unit 29b. The difference from the transmitting station identification code demodulation unit 29 shown in Fig. 6 is that the correlation coefficient (corresponding to Fig. 8) is also output to the delay profile generation unit 31b. While the demodulation device 2a obtains the correlation coefficient when the FFT window position is fixed to the main wave, the demodulation device 2b repeats this process while shifting the FFT window position little by little.

[0114] 13 shows an example of the configuration of the delay profile generating unit 31b. The delay profile generating unit 31b includes an FFT window position control unit 311, a correlation peak detection unit 312, and a delay amount vs. correlation peak plot unit 313.

[0115] The FFT window position control section 311 controls the FFT window position, and outputs the amount by which the FFT window position is shifted as the amount of delay with respect to the main wave to the delay amount vs. correlation peak plot section 313 and the FFT window setting section 32b.

[0116] The correlation peak detection unit 312 detects the peak of the absolute value (hereinafter referred to as the “correlation peak”) of the correlation coefficient (corresponding to FIG. 8) input from the transmission station identification code demodulation unit 29b each time the FFT window position changes, and outputs it to the delay amount vs. correlation peak plot unit 313.

[0117] The delay amount versus correlation peak plot unit 313 plots the correlation peak of each transmitting station versus the delay amount, and outputs the result to the outside as a delay profile for each transmitting station.

[0118] Fig. 14 shows a delay profile that is the output of delay profile generator 31b, obtained by a transmission simulation. The horizontal axis represents the delay amount, and the vertical axis represents the correlation peak. In this example, the delay difference between stations A and B is 2 μs, and the reception power ratio between stations A and B is 1 dB. It can be confirmed from Fig. 14 that a correct delay profile has been obtained.

[0119] <Program> A computer capable of executing program instructions can be used to function as the above-mentioned modulation device 1 and demodulation devices 2, 2a, and 2b. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (Personal Computer), an electronic notepad, etc. The program instructions may be program code, code segments, etc. for performing the necessary tasks.

[0120] The computer includes a processor, a storage unit, an input unit, an output unit, and a communication interface. The processor may be a central processing unit (CPU), a micro processing unit (MPU), a graphics processing unit (GPU), a digital signal processor (DSP), a system on a chip (SoC), or the like, and may be composed of multiple processors of the same type or different types. The processor reads out a program from the storage unit and executes it to control each of the above components and perform various arithmetic processing. At least a part of the processing contents may be realized by hardware. The input unit is an input interface that receives a user's input operation and acquires information based on the user's operation, and is a pointing device, a keyboard, a microphone, or the like. The output unit is an output interface that outputs information, and is a display, a speaker, or the like. The communication interface is an interface for communicating with an external device.

[0121] The program may be recorded on a computer-readable recording medium. By using such a recording medium, the program can be installed on the computer. Here, the recording medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a CD-ROM, a DVD-ROM, or a USB (Universal Serial Bus) memory. In addition, the program may be in a form that is downloaded from an external device via a network.

[0122] For example, a program for functioning as the transmitting device 1 causes a computer to execute the steps of generating a subframe for a transmitting station identification code, and generating a time division multiplexed frame by multiplexing the subframe for the transmitting station identification code, the TMCC signal, and the subframe for hierarchical data into one frame by time division. For example, a program for functioning as the demodulating device 2 causes a computer to execute the steps of calculating a correlation coefficient between a signal obtained by demodulating the subframe for the transmitting station identification code and a previously generated M-sequence signal, and detecting a transmitting station identification code from the peak position of the correlation coefficient.

[0123] The above-mentioned modulation device 1 may be configured with one or more semiconductor chips. The semiconductor chip may be equipped with a CPU that executes a program that describes the processing contents that realize each function of the modulation device 1. The same applies to the demodulation devices 2, 2a, and 2b.

[0124] Although the above-mentioned embodiment has been described as a representative example, it is obvious to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiment, and various modifications or changes can be made without departing from the scope of the claims. For example, it is possible to integrate multiple building blocks shown in the configuration diagram of the embodiment, or to divide one building block. [Explanation of symbols]

[0125] 1 Modulation device 2,2a,2b Demodulator 11a, 11b, 11c BICM processing section 12a, 12b, 12c Level adjustment section 13 Symbol Processing Section 14 Pilot Generation Unit 15 TMCC generation section 16 Frame sync signal generator 17 Subframe generator for transmitter identification code 18 Transmission processing unit 19 Time division multiplexing frame component 21 Receiving processing unit 22 Pilot Extraction Section 23 Channel Estimation Unit 24 Equalization section 25 Hours DIL Section 25 Frequency DIL section 26 LLR calculation unit 27 Error correction decoding section 28 TMCC demodulation section 29, 29a, 29b Transmitter identification code demodulation unit 30 Frame sync signal demodulation section 31a, 31b Delay profile generator 32a,32b FFT window setting section 131 Hierarchical synthesis section 132 Band division section 133 Time IL Department 134 Frequency IL section 135 Band synthesis section 171 1st PRBS generation section 172 2nd PRBS generation section 173 Signal sequence shift section 174 Carrier Modulation Section 175 Pilot Generation Unit 176,181 OFDM Modulation Section 177,182 IFFT section 178,183 GI Addition Part 211 GI removal section 212 FFT section 213 Frame Synchronization Unit 291 1st PRBS generation circuit 292 2nd PRBS generation circuit 293 Transmission signal generator 294 Correlation coefficient calculation section 295 Transmitter identification code detection unit 311 FFT window position control section 312 Correlation peak detection unit 313 Delay vs. correlation peak plot

Claims

1. a subframe generator for a transmitting station identification code that generates a subframe for a transmitting station identification code, which is a subframe for transmitting a transmitting station identification code that identifies a transmitting station; a time division multiplexing frame constructing unit that generates an OFDM signal by multiplexing the transmitter identification code subframe, a TMCC signal having transmission control information, and a hierarchical data subframe, which is a subframe for transmitting video, audio, and subtitle data, into one frame by time division; A modulation device comprising:

2. 2. The modulation device according to claim 1, wherein the subframe generation unit for transmitter identification code generates a QPSK modulated signal by modulating an I axis with a signal obtained by shifting a first M-sequence signal based on the transmitter identification code, and modulating a Q axis with a signal obtained by shifting a second M-sequence signal based on the transmitter identification code.

3. a time division multiplexing frame constructing unit time division multiplexing the transmitting station identification code subframe only once per multiple frames; 3. The modulation device according to claim 1, wherein the TMCC signal has a transmitting station identification code flag indicating whether the time division multiplexing frame includes a subframe for the transmitting station identification code.

4. A demodulation device for demodulating an OFDM signal generated by the modulation device according to claim 1, a transmitter identification code demodulation unit that calculates a correlation coefficient between a signal obtained by demodulating the transmitter identification code subframe and a previously generated M-sequence signal, and detects the transmitter identification code based on a peak position of the correlation coefficient.

5. a TMCC demodulation unit that demodulates a TMCC signal having a transmitter identification code flag indicating whether or not the time division multiplexing frame includes the transmitter identification code subframe, 5. The demodulation device according to claim 4, wherein the transmitting station identification code demodulation section demodulates the transmitting station identification code at a timing when the time division multiplexing frame includes the subframe for the transmitting station identification code, based on the transmitting station identification code flag.

6. A program for causing a computer to function as the modulation device according to claim 1.

7. A program for causing a computer to function as the demodulation device according to claim 4.

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