Receiving apparatus, transmission system, and program

Abstract

To improve the stability and reliability of STL / TTL.SOLUTION: The reception device 30 includes a digital demodulation unit 31 that receives a modulation signal of encoded data via a wireless line and performs demodulation processing on the modulation signal to estimate first encoded data, an encoded data extraction unit 33 that receives a packet of the encoded data via a wired line and extracts second encoded data from the packet, an LLR combination control unit 35 that determines a synchronization reference indicating which of the first encoded data and the second encoded data is used as a reference to synchronize both of the first encoded data and the second encoded data and an LLR combination technique when combining LLRs of the first encoded data and the second encoded data, a synchronization unit 36 that synchronizes the first encoded data and the second encoded data according to the synchronization reference, and an LLR combination unit 39 that combines the LLRs of the first encoded data and the second encoded data according to the LLR combination technique.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a receiving device, a transmission system, and a program. [Background technology]

[0002] The STL (Studio to Transmitter Link) / TTL (Transmitter to Transmitter Link) (broadcast program) transmission method compatible with the advanced terrestrial television broadcasting system is expected to use multi-level quadrature amplitude modulation (QAM: Quadrature Amplitude Modulation: up to 4096QAM) OFDM and LDPC (Low Density Parity Check) code as the error correction code.

[0003] One method to improve the stability and reliability of STL / TTL is to use redundant wireless and wired lines (IP network). Redundancy methods include using a line that has lost part of the transmission signal for some reason and supplementing it with a line that is transmitting normally, switching between multiple lines, and combining signals transmitted over multiple lines.

[0004] Among the methods for combining and using signals transmitted over multiple lines, a technology has been proposed in which the LLR (Log-Likelihood Ratio) of the demodulated signal from a wireless line is combined with the LLR transmitted over a wired line, and then error correction decoding processing is performed to improve the stability and reliability of the line (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-022808 [Patent Document 2] Patent Publication No. 2021-192502 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when applying LLR combining technology to STL / TTL with redundancy using wireless and wired circuits, the transmission paths for the wireless and wired circuits are different, so the time at which the transmitted signal arrives at the receiving device differs. Therefore, unless the signals transmitted over the wireless and wired circuits are synchronized, the redundancy will not work properly. Furthermore, unless the combining method for the LLRs obtained from the wireless and wired circuits is optimized and the synchronization process during combining is properly performed, the maximum LLR combining effect cannot be achieved. For example, if LLR combining is always performed by synchronizing with the wireless circuit, if the received power of the wireless circuit decreases due to fading or other reasons and synchronization is lost, there is a risk of inconvenience, such as LLR combining being disabled until synchronization is re-established.

[0007] In view of the above circumstances, the object of the present invention is to provide a receiving device, a transmission system, and a program that can improve the stability and reliability of STL / TTL in an STL / TTL that is made redundant using wireless and wired lines. [Means for solving the problem]

[0008] The gist of the present invention for solving the above problems is as follows.

[0009] (1) A receiving device comprising: a digital demodulation unit that receives a modulated signal obtained by modulating coded data via a wireless line and performs a demodulation process on the modulated signal to estimate first coded data; a coded data extraction unit that receives a packet of the coded data via a wired line and extracts second coded data from the packet; an LLR synthesis control unit that determines a synchronization reference indicating whether the first coded data or the second coded data is to be used as a reference for synchronization of the two, and an LLR synthesis method to be used when synthesizing LLRs of the first coded data and the second coded data, depending on the status of the wireless line and the wired line; a synchronization unit that synchronizes the first coded data and the second coded data according to the synchronization reference; and an LLR synthesis unit that synthesizes LLRs of the synchronized first coded data and second coded data according to the LLR synthesis method.

[0010] (2) The receiving device described in (1) further includes a CNR monitoring unit that monitors the CNR in the wireless line and determines a CNR margin indicating a margin for a required CNR, and a packet loss monitoring unit that monitors packet loss in the wired line and determines a packet loss rate margin indicating a margin for a maximum packet loss rate at which no error occurs during error correction decoding, and the LLR combining control unit determines the synchronization reference and the LLR combining method based on the CNR margin and the packet loss rate margin.

[0011] (3) The receiving device according to (2), wherein the required CNR is stored in advance for each combination of transmission parameters of the encoded data.

[0012] (4) The receiving device according to (2) or (3), wherein the maximum packet loss rate is stored in advance for each combination of the code length and the coding rate of the coded data.

[0013] (5) A receiving device described in any of (2) to (4), wherein the synchronization unit synchronizes based on the second encoded data when the CNR margin is less than a first threshold and the packet loss rate margin is greater than or equal to a second threshold, and synchronizes based on the first encoded data when the CNR margin is greater than or equal to the first threshold and the packet loss rate margin is less than the second threshold.

[0014] (6) A receiving device described in any of (2) to (5), wherein the LLR synthesis unit selects the LLR of the second encoded data when the packet loss rate margin is greater than or equal to a threshold, and when the packet loss rate margin is less than the threshold, adds the LLRs of the first encoded data and the second encoded data, or selects the LLR of the first encoded data and the second encoded data, whichever has the larger absolute value.

[0015] (7) A transmission system comprising: a receiving device according to any one of (1) to (6); a first transmitting device that transmits the modulated signal via the wireless line; and a second transmitting device that transmits the packet via the wired line.

[0016] (8) A program for causing a computer to function as the receiving device according to any one of (1) to (6). [Effects of the Invention]

[0017] According to the present invention, it is possible to improve the stability and reliability of STL / TTL in an STL / TTL that is made redundant by a line line and a wired line. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram illustrating an example of the configuration of a transmission system according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating an example of an FEC (Forward Error Correction) block. [Figure 3A]FIG. 1 is a diagram illustrating an example of an OFDM (Orthogonal Frequency Division Multiplexing) frame. [Figure 3B] FIG. 1 is a diagram illustrating an example of an OFDM frame. [Figure 4] FIG. 10 is a diagram illustrating an example of an IP packet. [Figure 5] 2 is a diagram illustrating the processing of an IP packetization unit shown in FIG. 1. FIG. [Figure 6] FIG. 10 is a diagram illustrating an example of a required CNR for each combination of transmission parameters. [Figure 7] 2 is a diagram illustrating an example of processing performed by an LLR synthesis unit illustrated in FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0020] 1 shows only the main components of a transmission system according to an embodiment of the present invention. The transmission system 1 shown in FIG. 1 includes a first transmitting device 10, a second transmitting device 20, and a receiving device 30.

[0021] The transmission system 1 transmits data that has been error-correction coded using LDPC codes or other codes that can be decoded using LLR (Log-Likelihood Ratio) over wireless and wired lines, and on the receiving side, the LLRs transmitted over each line are combined at the LLR stage, and error-correction decoding is performed using the combined LLR. The transmission system 1 improves the stability and reliability of the lines by transmitting signals over multiple lines for redundancy.

[0022] The first transmitting device 10 transmits the modulated signal over a wireless channel using OFDM, single carrier, etc. In this embodiment, an example of transmission using OFDM is shown. The first transmitting device 10 includes an error correction coding unit 11 and a digital modulation unit 12.

[0023] The error correction encoder 11 performs BCH encoding and LDPC encoding on the transmission data related to the digital broadcasting to generate coded data (LDPC code) consisting of a plurality of FEC blocks. The transmission data is, for example, a TLV (Type Length Value) packet.

[0024] An example of an FEC block is shown in Figure 2. The FEC block shown in Figure 2 consists of a block header, a main signal, stuff bits, parity bits of the BCH code, and parity bits of the LDPC code. The block header, main signal, and stuff bits, which are information bits, are subjected to energy diffusion processing. The error correction encoder 11 sets an FEC block number in the block header of the FEC block. The FEC block number is a number (serial number) assigned to each FEC block to identify the FEC block. The error correction encoder 11 adds the parity bits of the BCH code, which is the outer code, and the parity bits of the LDPC code, which is the inner code, to the main signal after energy diffusion to form an FEC block. LDPC code length (FEC block code length) n ldpc is, for example, 17280 bits.

[0025] The digital modulation unit 12 performs interleaving and other processing on the coded data generated by the error correction coding unit 11, and then adds a TMCC (Transmission and Multiplexing Configuration Control), a pilot, and an additional information transmission signal (AC: Auxiliary Channel) to form an OFDM frame.

[0026] An example of an OFDM frame is shown in Figure 3. This shows the OFDM frame configuration for the mode standardized in ARIB STD-B71, "Portable Microwave-Band OFDM Digital Wireless Transmission System for Ultra-High Definition Television Broadcast Program Material Transmission." Carrier numbers are assigned horizontally (in the frequency direction) and symbol numbers are assigned vertically (in the time direction) of the OFDM frame. Figure 3A shows OFDM frames with carrier numbers 0 to 37, and Figure 3B shows OFDM frames with subsequent carrier numbers. Carrier symbols indicated with solid black are pilots, carrier symbols indicated with circles are TMCC, carrier symbols indicated with crossed diagonals are AC, carrier symbols indicated with a cross are null, and the rest are data.

[0027] The digital modulation unit 12 sets, in the TMCC, an OFDM frame number and a range of FEC block numbers for the encoded data included in the OFDM frame. The OFDM frame number is a number (sequential number) assigned to each OFDM frame to identify the OFDM frame. For the TMCC, DBPSK modulation or the like may be used, which simplifies demodulation processing in the receiving device 30.

[0028] Furthermore, the digital modulation unit 12 performs OFDM modulation processing on the OFDM frame to generate a modulated signal (OFDM signal). In the OFDM modulation processing, an IFFT (Inverse Fast Fourier Transform) process is performed to generate a time-domain effective symbol signal, and a guard interval is inserted at the beginning of the effective symbol signal, followed by orthogonal modulation processing and D / A conversion processing. The digital modulation unit 12 emits the OFDM signal via a terrestrial broadcast transmission path (wireless network) through a transmitting antenna. In this embodiment, the number of bits per OFDM frame is equal to the LDPC code length n ldpc The integral multiple of the modulation multi-value number is used.

[0029] The second transmission device 20 sequentially receives the coded data generated by the error correction coding unit 11 of the first transmission device 10 via a LAN (Local Area Network). The second transmission device 20 includes an IP packetization unit .

[0030] The IP packetizer 21 generates an IP packet by adding a header to the encoded data received from the first transmitting device 10. The IP packetizer 21 stores an integer multiple or an integer multiple of the number of FEC blocks in the data portion (payload) of the IP packet. The IP packetizer 21 also sets, in the header of the IP packet, the OFDM frame number corresponding to the IP packet and the FEC block number of the encoded data stored in the IP packet. The IP packetizer 21 then transmits the generated IP packet to the receiving device 30 via the IP network.

[0031] An example of an IP packet is shown in Figure 4. Here, the number of bits transmitted in one OFDM frame is defined as the FEC block code length n ldpc Let's say the number of FEC blocks is 20. Figure 4(a) shows an example where one entire FEC block is stored in the data portion of one IP packet. Figure 4(b) shows an example where one FEC block is divided into two parts and each part is stored in the data portion of one IP packet. If an FEC block is divided into n parts, the same FEC block number will be set in the headers of n IP packets.

[0032] When transmitting encoded data over a wired line, burst errors may occur. To deal with burst errors, the IP packetizer 21 may set the write and read directions of the encoded data and packetize it into IP packets.

[0033] 5 shows an example of processing by the IP packetizer 21. In this example, the number of data carriers in the OFDM frame is 1600, the number of symbols is 216, the number of modulation levels in the OFDM modulation is N, and the FEC block code length is n ldpcis set to 17,280 bits. In this case, the number of transmission bits per OFDM frame is 1600 × 216 × N = 17,280 × 20 × N. The IP packetizer 21 writes the LDPC code horizontally into memory in OFDM units of 17,280 / n [bits]. In other words, the FEC block is divided into n parts and folded back. Next, the IP packetizer 21 reads the data vertically from memory and stores each read column as one packet of data. Therefore, the data length of the IP packet is 8 × 20 × N [bits] = 20N [bytes].

[0034] When OFDM modulation is performed with 256QAM, the modulation multi-level number N is 8. In this case, the number of IP packets and the data length of the IP packets change as shown in Table 1 according to the division number n of the FEC block. [Table 1]

[0035] 1 again, the receiving device 30 includes a digital demodulation unit 31, a CNR monitoring unit 32, an encoded data extraction unit 33, a packet loss monitoring unit 34, an LLR synthesis control unit 35, a synchronization unit 36, an LLR calculation unit 37, an LLR conversion unit 38, an LLR synthesis unit 39, and an error correction decoding unit 40.

[0036] The digital demodulation unit 31 receives an OFDM signal (modulated signal) obtained by OFDM-modulating encoded data from the first transmission device 10 via a wireless line, and performs OFDM demodulation processing on the OFDM signal. In the OFDM demodulation processing, A / D conversion processing, orthogonal modulation processing, guard interval removal processing, and FFT (Fast Fourier Transform) processing are performed to generate a frequency-domain symbol signal. Furthermore, the digital demodulation unit 31 performs equalization processing and deinterleaving processing to estimate the first encoded data. Then, the digital demodulation unit 31 outputs the first encoded data to the synchronization unit 36. Furthermore, the digital demodulation unit 31 outputs transmission parameters related to wireless transmission of the encoded data (e.g., modulation multi-level number, LDPC code length, coding rate) to the CNR monitoring unit 32.

[0037] The CNR monitoring unit 32 constantly monitors the CNR (Carrier-to-Noise Ratio) in the wireless link. Then, the CNR monitoring unit 32 calculates a CNR margin indicating the margin of the current CNR with respect to the required CNR in the transmission parameters input from the digital demodulation unit 31. The CNR margin is, for example, a value obtained by subtracting the required CNR from the current CNR. Then, the CNR monitoring unit 32 outputs the wireless link margin to the LLR combination control unit 35. Note that the CNR margin may be calculated in the LLR combination control unit 35.

[0038] An example of the required CNR for each combination of transmission parameters is shown in Fig. 6. As shown in Fig. 6, the required CNR has a different value for each combination of transmission parameters related to wireless transmission, such as the modulation multi-level number, the code length / coding rate of the LDPC code, etc., and is stored in advance in the receiving device 30.

[0039] The encoded data extraction unit 33 receives the IP packets of encoded data from the second transmission device 20 via a wired line, and extracts the second encoded data from the IP packets. Then, the encoded data extraction unit 33 outputs the second encoded data to the synchronization unit 36.

[0040] The packet loss monitor 34 constantly monitors packet loss in the wired line. The packet loss monitor 34 then calculates a packet loss margin indicating the margin of the current packet loss rate with respect to the tolerable packet loss rate (the maximum packet loss rate at which no errors occur during error correction decoding) for the code length and coding rate of the coded data (LDPC code) being used. The packet loss margin is, for example, a value obtained by subtracting the current packet loss rate from the tolerable packet loss rate. The tolerable packet loss rate is pre-stored in the receiving device 30 for each combination of the code length and coding rate of the coded data. The packet loss monitor 34 then outputs the packet loss margin to the LLR combining control unit 35. Note that the packet loss margin may also be calculated in the LLR combining control unit 35.

[0041] The LLR combining control unit 35 determines a synchronization reference indicating which of the first coded data and the second coded data should be used as a reference for synchronizing the two, and an LLR combining method to use when combining the LLRs of the first coded data and the second coded data, depending on the conditions (status) of the wireless link and the wired link, i.e., based on the CNR margin input from the CNR monitoring unit 32 and the packet loss rate margin input from the packet loss monitoring unit 34. The LLR combining control unit 35 then outputs information indicating the synchronization reference to the synchronization unit 36 ​​and outputs information indicating the LLR combining method to the LLR combining unit 39. That is, the LLR combining control unit 35 indicates the synchronization reference to the synchronization unit 36 ​​and indicates the LLR combining method to the LLR combining unit 39. A specific example of LLR combining control will be described later.

[0042] The synchronization unit 36 ​​determines the synchronization position between the first encoded data input from the digital demodulation unit 31 and the second encoded data input from the encoded data extraction unit 33. The synchronization position can be determined by setting consecutive OFDM frame numbers and FEC block numbers at regular intervals in the transmission signals of the wireless and wired circuits. As described above, the first transmission device 10 assumes that one OFDM frame will be transmitted with a number of bits equal to an integer multiple of the LDPC code length multiplied by the modulation multi-level number. The first transmission device 10 sets consecutive FEC block numbers in the block headers included in the FEC blocks of the LDPC code, and sets ranges of OFDM frame numbers and FEC block numbers in the TMCC of the OFDM subcarriers. The second transmission device 20 assumes that one packet will contain an integer multiple or a multiple of the LDPC code length in the data portion of one packet. The synchronization unit 36 ​​extracts the OFDM frame numbers and FEC block numbers from the first encoded data and the second encoded data to determine the synchronization position of the signals.

[0043] Furthermore, the synchronization unit 36 ​​synchronizes the first coded data and the second coded data using either the first coded data or the second coded data as a reference in accordance with the synchronization reference instructed by the LLR combination control unit 35. That is, when the synchronization reference is the first coded data, the synchronization unit 36 ​​synchronizes the first coded data and the second coded data using the first coded data as a reference, and when the synchronization reference is the second coded data, the synchronization unit 36 ​​synchronizes the first coded data and the second coded data using the second coded data as a reference. The synchronization unit 36 ​​then outputs the synchronized first coded data to the LLR calculation unit 37 and outputs the synchronized second coded data to the LLR conversion unit 38.

[0044] The LLR calculation unit 37 compares the signal point coordinates of the first coded data input from the synchronization unit 36 ​​with predetermined signal point coordinates, and calculates a first LLR for each bit of the coded data based on the Euclidean distance between both coordinates. That is, the log-likelihood ratio of the n-th bit is expressed as the logarithm of the ratio between the likelihood function where the value bn of the n-th bit is 0 and the likelihood function where the value bn of the n-th bit is 1. Then, the LLR calculation unit 37 outputs the first LLR to the LLR combination unit 39.

[0045] The LLR conversion unit 38 converts the second coded data input from the synchronization unit 36 ​​into a second LLR. For example, 0 and 1 of the second coded data are converted into predetermined values ​​(for example, 15 and −15). The LLR conversion unit 38 sets 0 when a packet loss occurs in the second coded data. Then, the LLR conversion unit 38 outputs the second LLR to the LLR synthesis unit 39.

[0046] The LLR combining unit 39 combines the first LLR input from the LLR calculation unit 37 and the second LLR input from the LLR conversion unit 38 for each bit in accordance with the combining method instructed by the LLR combination control unit 35, to obtain an LLR combined value. The LLR combining unit 39 outputs the LLR combined value to the error correction decoding unit 40.

[0047] Fig. 7 shows an example of the processing by the LLR synthesizing unit 39. The "0" of the second LLR means packet loss. When the LLR synthesizing unit 39 is instructed by the LLR synthesis control unit 35 to add the first LLR and the second LLR, it outputs the value obtained by adding the first LLR and the second LLR as shown in the "Addition" row of Fig. 7. Also, when the LLR synthesizing unit 39 is instructed by the LLR synthesis control unit 35 to select the LLR with the larger absolute value from the first LLR and the second LLR, it outputs the LLR with the larger absolute value from the first LLR and the second LLR as shown in the "Selection of Maximum Absolute Value" row of Fig. 7.

[0048] The error correction decoding unit 40 performs LDPC decoding using the LLR synthesis value input from the LLR synthesizing unit 39 and then performs BCH decoding. In LDPC decoding, the transmitted bits are decoded by repeatedly performing operations using the LLR according to a known decoding algorithm such as the sum-product decoding method.

[0049] <Specific Example of LLR Synthesis Control> The LLR synthesis control unit 35 determines whether the state of the wireless line and the state of the wired line are good or bad at every predetermined time. The good state of the wireless line means that the CNR margin is equal to or greater than the first threshold value, and the bad state of the wireless line means that the CNR margin is less than the first threshold value. The good state of the wired line means that the packet loss rate margin is equal to or greater than the second threshold value, and the bad state of the wired line means that the packet loss rate is less than the second threshold value. The LLR synthesis control unit 35 gives instructions to the synchronization unit 36 and the LLR synthesizing unit 39 as follows, for example, according to the states of the wireless line and the wired line.

[0050] <<Synchronization Reference>> When the state of the wireless line is bad and the state of the wired line is good, the LLR synthesis control unit 35 determines the synchronization reference as "the second encoded data (wired line)", and the synchronization unit 36 performs synchronization based on the second encoded data. When the state of the wireless line is good and the state of the wired line is bad, the LLR combining control unit 35 determines the synchronization reference as "the first encoded data (wireless line)", and the synchronization unit 36 performs synchronization based on the first encoded data. When the states of both the wireless line and the wired line are good, the LLR combining control unit 35 determines the synchronization reference as the one with higher reliability between the first encoded data and the second encoded data in view of the status of the lines being used, and instructs the synchronization unit 36. When the states of both the wireless line and the wired line are bad, the LLR combining control unit 35 determines the synchronization reference as the encoded data of the line whose line state does not deteriorate continuously between the first encoded data and the second encoding in view of the status of the lines being used, and instructs the synchronization unit 36.

[0051] <<LLR Combining Method>> When the state of the wired line is good, the LLR combining control unit 35 determines the LLR combining method as "selection of the second LLR", and the LLR combining unit 39 selects the LLR of the second encoded data. When the state of the wired line is not good, regardless of the state of the wireless line, the LLR combining control unit 35 determines the LLR combining method as "addition or selection of the maximum absolute value", and the LLR combining unit 39 adds the first LLR and the second LLR or selects the one with the larger absolute value between the first LLR and the second LLR. When the state of the wireless line is good and the state of the wired line is bad, the LLR combining control unit 35 may determine the LLR combining method as "selection of the first LLR". However, since there is a possibility of sudden fading, it is considered that determining the LLR combining method as "addition or selection of the maximum absolute value" results in better accuracy.

[0052] Since it is expected that the conditions of the wireless line and the wired line may change suddenly, a buffer is provided for processing to enable seamless switching. Furthermore, when the synchronization reference is the first encoded data (wireless line), even if synchronization is lost, processing may be continued for a certain period of time based on the timing at which synchronization was last achieved, and if the synthesis processing proceeds normally, synthesis may be continued as is. Furthermore, when the LLR synthesis control unit 35 receives a signal from the error correction decoding unit 40 indicating that errors continue to occur during error correction decoding, it may instruct the synchronization unit 36 ​​to perform synchronization processing again.

[0053] As described above, the receiving device 30 switches the synchronization reference in the synchronization unit 36 ​​and the combining method in the LLR combining unit 39 in accordance with the status of the wireless line and the wired line, in response to an instruction from the LLR combining control unit 35. Therefore, according to the present invention, it is possible to improve the stability and reliability of STL / TTL, and thereby improve the line availability rate.

[0054] <Program> A computer capable of executing program instructions may be used to function as the first transmitting device 10, the second transmitting device 20, and the receiving device 30. Here, the computer may be a general-purpose computer, a special-purpose 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.

[0055] The computer includes a processor, a storage unit, an input unit, an output unit, and a communication interface. The processor may be a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an SoC (System on a Chip), or the like, and may be configured with multiple processors of the same or different types. The processor reads and executes programs from the storage unit to control the above components and perform various arithmetic processing. Note that at least a portion of these processing contents may be implemented by hardware. The input unit is an input interface that accepts user input operations and acquires information based on the user operations, such as a pointing device, keyboard, or microphone. The output unit is an output interface that outputs information, such as a display or speaker. The communication interface is an interface for communicating with external devices.

[0056] The program may be recorded on a computer-readable recording medium. Using such a recording medium, the program can be installed on a 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. Furthermore, the program may be downloaded from an external device via a network.

[0057] Furthermore, the above-described receiving device 30 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 content that realizes each function of the receiving device 30. The same applies to the first transmitting device 10 and the second transmitting device 20.

[0058] Although the above-described embodiments have been described as typical examples, it will be apparent 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 construed as being limited by the above-described embodiments, and various modifications or alterations can be made without departing from the scope of the claims. For example, it is possible to integrate multiple building blocks shown in the block diagrams of the embodiments, or to divide one building block. [Explanation of symbols]

[0059] 1 Transmission System 10 First transmitting device 11 Error correction coding section 12 Digital modulation section 20 Second transmitting device 21 IP Packetization Unit 30 Receiving device 31 Digital demodulation section 32 CNR monitoring department 33 Encoded data extraction unit 34 Packet loss monitoring section 35 LLR synthesis control section 36 Synchronization section 37 LLR calculation unit 38 LLR conversion unit 39 LLR synthesis section 40 Error correction decoding unit

Claims

1. a digital demodulation unit that receives a modulated signal obtained by modulating coded data via a wireless line and performs a demodulation process on the modulated signal to estimate first coded data; an encoded data extraction unit that receives the packets of encoded data via a wired line and extracts second encoded data from the packets; an LLR combination control unit that determines a synchronization reference indicating whether the first encoded data or the second encoded data is used as a reference for synchronization of the two, and an LLR combination method for combining LLRs of the first encoded data and the second encoded data, depending on states of the wireless line and the wired line; a synchronization unit that synchronizes the first encoded data and the second encoded data in accordance with the synchronization standard; an LLR synthesis unit that synthesizes LLRs of the synchronized first coded data and second coded data according to the LLR synthesis technique; A receiving device comprising:

2. a CNR monitoring unit that monitors the CNR in the wireless line and obtains a CNR margin that indicates a margin for a required CNR; a packet loss monitoring unit that monitors packet loss in the wired line and calculates a packet loss rate margin that indicates a margin for a maximum packet loss rate at which no error occurs during error correction decoding, The receiving device according to claim 1 , wherein the LLR combining control unit determines the synchronization reference and the LLR combining method based on the CNR margin and the packet loss rate margin.

3. 3. The receiving device according to claim 2, wherein the required CNR is stored in advance for each combination of transmission parameters of the encoded data.

4. The receiving device according to claim 2 , wherein the maximum packet loss rate is stored in advance for each combination of a code length and a coding rate of the coded data.

5. The receiving device described in claim 2, wherein the synchronization unit synchronizes based on the second encoded data when the CNR margin is less than a first threshold and the packet loss rate margin is greater than or equal to a second threshold, and synchronizes based on the first encoded data when the CNR margin is greater than or equal to the first threshold and the packet loss rate margin is less than the second threshold.

6. 3. The receiving device according to claim 2, wherein the LLR synthesis unit selects the LLR of the second encoded data when the packet loss rate margin is equal to or greater than a threshold, and when the packet loss rate margin is less than the threshold, adds the LLRs of the first encoded data and the second encoded data, or selects the LLR of the first encoded data or the second encoded data, whichever has a larger absolute value.

7. A receiving device according to any one of claims 1 to 6; a first transmitting device that transmits the modulated signal via the wireless line; a second transmitting device that transmits the packets via the wired line; A transmission system comprising:

8. A program for causing a computer to function as the receiving device according to claim 1.

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