JP2004242191A - Receiving method and instrument thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a timing signal suitable for diversity composite processing while maintaining the stability of an instrument. <P>SOLUTION: A first demodulator 26 and a second demodulator 42 demodulate received data signals, respectively. A first non-protection timing generator 28 and a second non-protection timing generator 44 detect synchronous words from the data signal, and generate first frame synchronization timing signals based on the timing of the detected synchronous words. In a diversity composite part 46, diversity composite processing is performed to data signals outputted from the first demodulator 26 and the second demodulator 42 by using the first frame synchronization timing signal. A protection existing timing generator 12 generates a second frame synchronization timing signal which is used for timing for controlling a signal processor 10. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiving technique for receiving and demodulating a digitally modulated signal. In particular, the present invention relates to a receiving method and apparatus for diversity combining a plurality of signals.
[0002]
[Prior art]
2. Description of the Related Art In recent years, orthogonal frequency division multiplexing (hereinafter, referred to as “OFDM: Orthogonal Frequency Division Multiplexing”) has been used as a modulation method excellent in transmitting high-quality signals and improving frequency use efficiency in order to transmit information such as video and audio. A method is being considered. The OFDM system is a modulation system in which a large number of subcarriers are provided in a band of one channel, is resistant to ghost or multipath interference, and enables good reception at a mobile body. The OFDM system is employed in a terrestrial digital television broadcasting system together with an information source coding system for video and audio and a multiplexing system MPEG-2. A terrestrial digital television broadcasting transmission apparatus includes an encoding unit that converts analog signal information such as video and audio into a digital signal and compresses it, a multiplexing unit that combines a plurality of pieces of compressed information, and a transmission unit. It comprises a correction coding unit for correcting errors occurring therein, and a modulation unit for transmitting information efficiently after time interleaving and frequency interleaving.
[0003]
In addition, the transmission apparatus performs transmission multiplexing control (hereinafter, referred to as “transmission and multiplexing control” (hereinafter, referred to as “modulation scheme”, error correction convolutional coding rate, and time interleave length) in addition to information such as video and audio. , "TMCC: Transmission and Multiplexing Configuration Control" signal.
[0004]
Modulation of subcarriers to which a data signal is allocated in the terrestrial digital television broadcasting system includes four kinds of DQPSK (Differential Quadrature Phase Shift Keying), QPSK, 16QAM (Quadrature Amplitude Modulation), and 64QAM TM signals. Differential Binary Phase Shift Keying (DBPSK) is used for the modulation of the subcarriers, and the respective mapping methods are different (for example, see Patent Document 1). DQPSK is called a differential modulation method, and the others are called synchronous modulation methods, and the type and arrangement position of pilot signals inserted in each method are different.
[0005]
By the way, since a signal transmitted in reception at a mobile unit is affected by fading, received power fluctuates greatly, and it becomes difficult to maintain high-quality signal transmission. As a method for reducing quality deterioration due to fading, there is a diversity combining technique. This technique reduces fading fluctuations by receiving multiple independent signals and using them appropriately. This technique is basically based on three types: selective combining, equal gain combining, and maximum ratio combining. In particular, the selective combining selects and outputs the least degraded signal among a plurality of received signals. Is small.
[0006]
[Patent Document 1]
JP 2001-103029 A
[Problems to be solved by the invention]
In the diversity combining technique, a plurality of received signals can be combined based on a timing signal generated by the receiving apparatus and controlling the receiving apparatus. The timing signal is generally generated by performing a back protection or a front protection process in consideration of the stability of the receiving device and a system including the receiving device. Timing signals that have been subjected to backward protection and forward protection processing are not affected by short-term changes in the propagation environment. Therefore, when the actual propagation environment changes in a short period of time, the timing for controlling the receiving device may be different from the timing suitable for combining a plurality of signals. As a result, if diversity combining is performed at the timing when the receiving apparatus is controlled, there is a possibility that reception characteristics may deteriorate.
[0008]
The present invention has been made in view of such a situation, and an object of the present invention is to provide a receiving method and apparatus for performing diversity combining at a timing suitable for combining a plurality of signals while maintaining the stability of the receiving apparatus. . Another object of the present invention is to provide a receiving method and apparatus for generating a timing signal suitable for diversity combining.
[0009]
[Means for Solving the Problems]
One embodiment of the present invention relates to a receiving device. The apparatus includes an input unit that inputs a plurality of signals each formed in a frame format, a first timing generation unit that generates a first frame synchronization timing from the input signals, and a plurality of input units. A second timing generation unit that generates a second frame synchronization timing by referring to timings of a plurality of frames for each of the signals, a synthesis unit that synthesizes the input signals at the first frame synchronization timing, And a signal processing unit that performs signal processing on the resulting signal at the second frame synchronization timing.
A “frame” generally includes a plurality of signals, but here, the number of signals included in a frame may be one.
[0010]
The combining unit may include a storage unit that stores the combined signal for a period corresponding to a difference between the first frame synchronization timing and the second frame synchronization timing. The combining section may combine the input signals at the second frame synchronization timing when the generation of the first frame synchronization timing has failed.
[0011]
“Synthesizing” includes not only adding a plurality of signals but also performing statistical processing on a plurality of signals and adding them, or selecting one of the plurality of signals. It is assumed that the processing is sufficient.
[0012]
According to the above-described apparatus, the timing for synthesizing a plurality of signals and the timing for processing the synthesized signal are set as different timings, and the corresponding processes are executed. Therefore, both stability and characteristics can be improved. .
[0013]
Another embodiment of the present invention relates to a receiving method. The method includes the steps of: respectively inputting a plurality of signals each formed in a frame format; generating a first frame synchronization timing from the plurality of input signals; Generating the second frame synchronization timing by referring to the timings of the plurality of frames, synthesizing the plurality of input signals at the first frame synchronization timing, and synthesizing the synthesized signals at the second frame synchronization timing Performing signal processing.
[0014]
It should be noted that any combination of the above-described components, and the components and expressions of the present invention that are mutually substituted among methods, apparatuses, computer programs, recording media storing computer programs, data structures, and the like, are also included in the present invention. This is effective as an aspect of the invention.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The present embodiment relates to a terrestrial digital television broadcasting system, and transmits a signal obtained by modulating information to be transmitted from a transmission device by an OFDM system. Further, a synchronization word for generating a frame synchronization timing signal is added to the transmitted signal. The receiving device receives the transmitted signal with a plurality of antennas, generates a frame synchronization timing (hereinafter, referred to as “first frame synchronization timing”) signal from the plurality of received signals based on a synchronization word, A final frame synchronization timing (hereinafter, referred to as “second frame synchronization timing”) signal is generated in consideration of the backward protection and the forward protection.
[0016]
Since the first frame synchronization timing signal reflects the fluctuation of the propagation environment in the plurality of received signals, good characteristics can be obtained by performing diversity combining processing on the plurality of received signals based on the timing signals. There is a possibility that the timing signal fluctuates greatly according to the fluctuation of the propagation environment. On the other hand, the second frame synchronization timing signal generally has little fluctuation and is stable, and thus is suitable for controlling the entire receiving apparatus. The receiving apparatus according to the present embodiment performs the diversity combining process based on the first frame synchronization timing signal and converts the second frame synchronization timing signal into a second frame synchronization timing signal in order to achieve both the improvement of the reception characteristics by the diversity combining process and the stability of the system. Based on this, the entire receiving apparatus is controlled.
[0017]
1A to 1D show a data structure according to the present embodiment. FIG. 1A shows the configuration of one OFDM frame in the time domain. As shown, one OFDM frame is composed of 204 OFDM symbols. Usually, a television program such as a moving image is transmitted by a plurality of OFDM frames. FIG. 1B shows a configuration of one OFDM symbol. One OFDM symbol includes a valid signal corresponding to data of a television program and an invalid signal corresponding to a guard interval. The period of the effective signal corresponds to fast Fourier transform (hereinafter, referred to as “FFT”) timing. FIG. 1C shows the effective signal of FIG. 1B in the frequency domain. The effective signal has 13 OFDM segments having the same frequency bandwidth and null signals at both ends. In the terrestrial digital television system, one detailed image television program may be assigned to all 13 OFDM segments, or a different television program is assigned to each of the 13 OFDM segments by dividing the plurality into 13 OFDM segments. Is also good.
[0018]
In particular, the partial reception method is a service mode in which one television program is assigned to only one OFDM segment, and the receiving device receives only the one OFDM segment. Normally, when one television program is allocated to one OFDM segment, the central OFDM segment, that is, OFDM segment 0 in FIG. 1C is used. FIG. 1D shows the configuration of one OFDM segment, which is composed of N subcarriers. A group of data signals called a data segment and a pilot signal are assigned to each subcarrier. N is 108 in mode 1, 216 in mode 2, and 432 in mode 3.
[0019]
Note that a synchronization word for establishing frame synchronization is added to the OFDM frame, and the receiving device generally generates a frame synchronization timing signal based on the synchronization word. Further, in the terrestrial digital television system, a synchronization word and an inverted synchronization word obtained by inverting the synchronization word are repeatedly arranged for each OFDM frame, but here, the synchronization word and the inverted synchronization word are not distinguished.
[0020]
FIG. 2 shows a configuration of a valid signal after FFT. Although this signal includes thousands of subcarriers, these subcarriers are classified into subcarriers for TMCC signals, subcarriers for pilot signals, and the like, in addition to subcarriers for data signals. As described above, these subcarriers are divided into 13 OFDM segments, and these 13 OFDM segments are divided into a maximum of three layers. The subcarrier for the data signal is modulated by the modulation scheme specified by the TMCC signal for each layer, and the subcarrier for the TMCC signal is modulated by DBPSK.
[0021]
Each OFDM frame is composed of 204 OFDM symbols. In addition, a pulse indicating a data signal start position is included in a valid signal of each OFDM symbol, and a plurality of TMCC signals are located at predetermined positions based on the position of the pulse. Is inserted. Since the plurality of TMCC signals in the same OFDM symbol all have the same information, the OFDM segment to be partially received also includes the TMCC signal. Also, a plurality of pilot signals are inserted at predetermined positions in each OFDM symbol. The null signal is inserted at both ends of the signal in the frequency domain.
[0022]
3A and 3B show a constellation of a DBPSK-modulated TMCC signal. According to DBPSK modulation, each bit of the TMCC signal is encoded as the phase difference of the carrier between the signal in one OFDM symbol and the signal in the previous OFDM symbol. Specifically, “0” is encoded as a phase difference of 0 degrees, and “1” is encoded as a phase difference of 180 degrees. When encoding a bit of "0", when the I-axis component of the signal in the immediately preceding OFDM symbol is negative, the I-axis component of the signal in the target OFDM symbol is also negative. On the other hand, when the bit of “1” is encoded, when the I-axis component of the signal in the immediately preceding OFDM symbol is negative, the I-axis component of the signal of the target OFDM symbol is positive. In any case, the Q signal is always “0”.
[0023]
FIG. 4 shows a configuration of the receiving apparatus 100 according to Embodiment 1. The receiving device 100 includes a signal processing unit 10 and a protected timing generation unit 12. The signal processing unit 10 includes a first tuner unit 14, a first A / D conversion unit 16, a first synchronization unit 18, a first FFT unit 20, a first AFC unit 22, a first TMCC decoding unit 24, a first demodulation unit 26, The unprotected timing generator 28, the second tuner 30, the second A / D converter 32, the second synchronizer 34, the second FFT 36, the second AFC 38, the second TMCC decoder 40, the second demodulator 42, (2) Unprotected timing generator 44, diversity synthesizer 46, frequency deinterleaver 48, time deinterleaver 50, demapper 52, bit deinterleaver 54, Viterbi decoder 56, byte deinterleaver 58, energy despreading A unit 60, an RS decoding unit 62, an MPEG decoding unit 64, and a D / A conversion unit 66 are included.
[0024]
The first tuner unit 14 receives the RF signal modulated by the OFDM modulation method in a transmission device (not shown) and down-converts the RF signal into a baseband signal. Here, it is assumed that the received signal is only one OFDM segment. The first A / D converter 16 converts an analog signal into a digital signal, and outputs a signal of a real axis (hereinafter, referred to as “I axis”) component and an imaginary axis (hereinafter, “Q axis”) using Hilbert transform or the like. ) Component signal. The first synchronization unit 18 performs synchronization processing such as clock synchronization and symbol synchronization. In addition, narrow-band frequency synchronization within a subcarrier interval is also performed with respect to the frequency deviation of the frequency oscillator between the transmitting device and the receiving device 100 (not shown). The first FFT unit 20 converts a signal on the time axis into a signal on the frequency axis by FFT. The first AFC unit 22 performs broadband frequency synchronization on a subcarrier interval basis with respect to the frequency deviation of the frequency oscillator between the transmitting device and the receiving device 100 (not shown) from the FFT signal. When the stability of the frequency oscillator of the receiving device 100 is high, the AFC 22 becomes unnecessary.
[0025]
The first TMCC decoding unit 24 performs DBPSK demodulation of the TMCC signal and detects the TMCC signal. The first demodulation unit 26 demodulates the data signal that has been FFTed by the first FFT unit 20 using QPSK, 16QAM, and 64QAM.
[0026]
Further, the first demodulation unit 26 detects the reliability of each subcarrier from the dispersion of the SP using the SP (Scattered Pilot) signal among the pilot signals (see Reference: “Error Considering Terrestrial Transmission Channel Characteristics”). Control, 1998 ITE Annual Meeting 3-1). However, since the SP is included only in the synchronous modulator of QPSK, 16QAM, and 64QAM, the reliability information is detected only by the synchronous modulator. The detection result is output as a signal of about 3 bits that can be reflected in weighting for Viterbi soft decision described later. The reliability of the pilot signal carrier is also detected in the same manner as the data signal carrier. Note that the SP is inserted once in 12 subcarriers and once in 4 OFDM symbols in the synchronous modulation section. The first unprotected timing generator 28 detects a synchronization word from the data signal and generates a first frame synchronization timing signal based on the timing of the detected synchronization word.
[0027]
Second tuner unit 30, second A / D conversion unit 32, second synchronization unit 34, second FFT unit 36, second AFC unit 38, second TMCC decoding unit 40, second demodulation unit 42, second unprotected timing generation unit 44 Are the first tuner unit 14, the first A / D conversion unit 16, the first synchronization unit 18, the first FFT unit 20, the first AFC unit 22, the first TMCC decoding unit 24, the first demodulation unit 26, the first unprotected timing, respectively. It has the same function as the generation unit 28.
[0028]
Diversity combining section 46 performs diversity combining processing on the data signals output from first demodulating section 26 and second demodulating section 42, and outputs the combined data together with pulses and the like. In the diversity combining process, the first frame synchronization timing signal generated by the first unprotected timing generator 28 and the second unprotected timing generator 44 is used. Generally, these first frame synchronization timing signals are different from each other due to a difference in propagation environment. In order to match them, one of the first frame synchronization timing signals is delayed, or two first frame synchronization timing signals are subjected to statistical processing such as averaging to obtain a new one first frame synchronization timing signal. Generate a synchronization timing signal. Alternatively, only one of them may be used. As the diversity combining process, for example, the reliability information detected by the first demodulation unit 26 or the second demodulation unit 42 is compared between the output signals of the first demodulation unit 26 and the output signal of the second demodulation unit 42, and the higher reliability is determined. Select to combine.
[0029]
The frequency deinterleaving section 48 rearranges the data signals rearranged in the frequency direction by the frequency interleaving processing in the original order, and the time deinterleaving section 50 executes the data rearranged in the time direction by the time interleaving processing. Rearrange the signals in their original order. Further, the demapping unit 52 obtains a reference point on a constellation corresponding to each modulation scheme, selects the closest reference point for each data signal, and generates information for specifying the reference point.
[0030]
After the data signal is subjected to bit deinterleaving by the bit deinterleaving unit 54, the data signal is subjected to soft-decision Viterbi decoding by the Viterbi decoding unit 56. Further, after being subjected to byte deinterleaving in a byte deinterleaver 58, energy despreading in an energy despreader 60, Reed-Solomon code decoding in an RS decoder 62, and MPEG2 decoding in an MPEG decoder 64, The signal is converted into an analog signal by the D / A converter 66 and output.
[0031]
The protected timing generator 12 considers backward protection and forward protection for the first frame synchronization timing signal generated by the first unprotected timing generator 28 and the second unprotected timing generator 44, A second frame synchronization timing signal is generated. The second frame synchronization timing signal is used for timing for controlling the signal processing unit 10. In order to correct an error between the first frame synchronization timing signal and the second frame synchronization timing signal, for example, a buffer may be provided in the diversity combining unit 46.
[0032]
FIG. 5 shows an example of success and failure of establishing frame synchronization. Here, for convenience of explanation, it is assumed that the diversity combining process is not considered, and the case of performing the diversity combining process will be described later. “Frame number” is a number indicating the order of an OFDM frame. The “synchronization word detection state” indicates whether or not the synchronization word added to the OFDM frame has been detected from the received data signal in the first unprotected timing generation unit 28 in FIG. The signal indicating the timing generated based on this is the first frame synchronization timing signal. Here, it is assumed that detection was possible at frame number 1 and not at frame number 2. The “number of backward protections” indicates the number of times that synchronization word detection has succeeded consecutively for backward protection. The maximum number is set to two, and to zero if synchronization word detection fails. I'm back.
[0033]
“Forward protection count” indicates the number of times that the detection of the synchronization word has failed consecutively from the state where the number of back protection is 2 for the forward protection, but the maximum number is set to 2 and the detection of the synchronization word succeeds. If so, it is returned to zero. The “frame synchronization established state” indicates whether frame synchronization has been established in consideration of the above result. “OK” indicates a state where frame synchronization has been established, and “NG” indicates a state where frame synchronization has not been established. In order to transition from a state where frame synchronization has not been established to a state where frame synchronization has been established, the number of backward protections needs to be 2, that is, the synchronization word must be detected twice consecutively. On the other hand, in order to make a transition from a state where frame synchronization is established to a state where frame synchronization is not established, the number of forward protections needs to be 2, that is, detection of a synchronization word must be failed twice consecutively. . The signal indicating the timing thus generated is the second frame synchronization timing signal.
[0034]
FIG. 6 also shows an example of success and failure in establishing frame synchronization. Here, diversity combining processing is considered. The state of synchronization in the first receiving unit and the second receiving unit corresponding to two antenna branches, and the state of synchronization after diversity reflecting the states are shown. Further, the “frame synchronization established state (without protection)” indicates the establishment of synchronization without considering backward protection or forward protection, and the result is the same as the “synchronization word detection state”. On the other hand, the “frame synchronization established state (with protection)” indicates the establishment of synchronization when the backward protection and the forward protection are considered up to twice.
[0035]
After the diversity, "x" indicating that synchronization has not been established is described when the synchronization establishment state of the corresponding first reception unit and second reception unit is both "NG". On the other hand, when the synchronization establishment state is “OK” in one or both of the first receiving unit and the second receiving unit, “○” indicating that synchronization has been basically established is described. When the synchronization establishment state of both the first receiving unit and the second receiving unit is “OK”, one of the timings is selected. Therefore, in the synchronization establishment state of the first reception unit or the second reception unit corresponding to the “frame synchronization establishment state (with protection)” after the diversity, the detection of the synchronization word has failed. If the timing at which the state becomes “OK” is selected, an error may occur in the data signal after the diversity, so “Δ” is described. In the “frame synchronization established state (no protection)”, there is no “Δ” that may cause an error in the data signal, so that the characteristics can be improved by the diversity combining process.
[0036]
The operation of receiving apparatus 100 having the above configuration is as follows. RF signals received by the two antennas are input to the first tuner unit 14 and the second tuner unit 30, respectively. The first A / D conversion unit 16 and the second A / D conversion unit 32 convert these signals into baseband digital signals, respectively, and the first FFT unit 20 and the second FFT unit 36 perform FFT, and then perform first demodulation. The unit 26 and the second demodulation unit 42 demodulate. The first unprotected timing generation unit 28 and the second unprotected timing generation unit 44 generate a first frame synchronization timing signal from the FFT signal, and the diversity synthesizing unit 46 also generates the first frame synchronization timing signal. Then, the demodulated signals are combined. The protected timing generator 12 generates a second frame synchronization timing signal from the first frame synchronization timing signal. The synthesized signal is processed in the frequency deinterleaving section 48 and thereafter based on the second frame synchronization timing signal.
[0037]
The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and that such modifications are also within the scope of the present invention. . Such modified examples are described below.
[0038]
In the present embodiment, data reception by the OFDM method has been described as an example. However, as a modification, the present invention may be applied to a transmission method using another modulation method capable of displaying a constellation. According to this modification, it can be applied to various transmission methods.
[0039]
In the present embodiment, the demapping processing is performed by the demapping unit 52, but this may be changed to the predemapping processing. The pre-demapping processing is to perform the demapping processing before the time deinterleaving processing or the frequency deinterleaving processing, and is proposed in Japanese Patent Application Laid-Open No. 2001-320345. In the pre-demapping process, unlike normal demapping data, first data indicating a reference point on a constellation corresponding to a modulation scheme, and second data indicating a magnitude of a shift between the reference point and the data. Is generated. The predemapping data needs to be converted into demapping data after time deinterleaving. However, since the demapping data requires three times the information amount (maximum 18 bits) of the data indicating the reference point (maximum 6 bits). On the other hand, in the predemapping data, the first data has a maximum of 6 bits, and the second data always has 6 bits, and can be represented by a maximum of 12 bits in total.
[0040]
For example, 18-bit data of “00000,000,000,000,000101,011” in the demapping process is represented by 12-bit data of “0000010,110,011” in the predemapping process. In this modification, the bit width of the data is reduced by the predemapping process before the frequency deinterleaving process and the time deinterleaving process that require a large amount of memory, thereby reducing the memory usage.
[0041]
In the present embodiment, based on the first frame synchronization timing signal generated by the first unprotected timing generation unit 28 and the second unprotected timing generation unit 44, the diversity combining unit 46 performs diversity of a plurality of received signals. Perform synthesis processing. However, when the first unprotected timing generation unit 28 and the second unprotected timing generation unit 44 cannot generate the first frame synchronization timing signal due to the influence of the propagation environment or the like, the first protected non-protected timing generation unit 12 generates the first frame synchronization timing signal. A second frame synchronization timing signal may be used. According to this modification, even when the first frame synchronization timing signal is not generated, the diversity combining process can be performed.
[0042]
【The invention's effect】
According to the present invention, diversity combining can be performed at a timing suitable for combining a plurality of signals while considering the stability of the receiving device. Further, it is possible to generate a timing signal suitable for diversity combining while considering the stability of the receiving apparatus.
[Brief description of the drawings]
FIGS. 1A to 1D are diagrams illustrating a data structure according to an embodiment; FIG.
FIG. 2 is a diagram showing a configuration of an effective signal after Fourier transform according to the embodiment.
FIGS. 3A and 3B are diagrams showing a constellation of a TMCC signal.
FIG. 4 is a diagram showing a configuration of a receiving device according to an embodiment.
FIG. 5 is a diagram illustrating an example of success and failure of establishing frame synchronization according to the embodiment;
FIG. 6 is a diagram showing an example of success and failure of establishing frame synchronization according to the embodiment.
[Explanation of symbols]
Reference Signs List 10 signal processing unit, 12 protected timing generation unit, 14 first tuner unit, 16 first A / D conversion unit, 18 first synchronization unit, 20 first FFT unit, 22 first AFC unit, 24 first TMCC decoding unit, 26 first 1 demodulation section, 28 first unprotected timing generation section, 30 second tuner section, 32 second A / D conversion section, 34 second synchronization section, 36 second FFT section, 38 second AFC section, 40 second TMCC decoding section, 42 2nd demodulation section, 44 2nd unprotected timing generation section, 46 diversity combining section, 48 frequency deinterleaving section, 50 time deinterleaving section, 52 demapping section, 54 bit deinterleaving section, 56 Viterbi decoding section, 58 byte decoding section Interleave section, 60 energy despreading section, 62 RS decoding section, 64 MPEG decoding section, 66 D / A The conversion unit, 100 receiving device.

Claims (4)

An input unit for inputting a plurality of signals each formed in a frame format,
A first timing generation unit that generates a first frame synchronization timing from the plurality of input signals;
A second timing generation unit configured to generate a second frame synchronization timing by referring to timings of a plurality of frames for each of the plurality of input signals;
A combining unit that combines the plurality of input signals at the first frame synchronization timing;
A signal processing unit that performs signal processing on the synthesized signal at the second frame synchronization timing;
A receiving device comprising: 2. The storage device according to claim 1, wherein the synthesis unit includes a storage unit that stores the synthesized signal for a period corresponding to a difference between the first frame synchronization timing and the second frame synchronization timing. 3. Receiver. The receiving device according to claim 1, wherein the combining unit combines the plurality of input signals at the second frame synchronization timing when generation of the first frame synchronization timing has failed. . Inputting a plurality of signals each formed in a frame format,
Generating a first frame synchronization timing from the plurality of input signals;
Generating a second frame synchronization timing by referring to timings of a plurality of frames for each of the plurality of input signals;
Synthesizing the plurality of input signals at the first frame synchronization timing;
Signal processing the synthesized signal at the second frame synchronization timing;
A receiving method comprising:

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