Multiplexing device for inserting time information, multiplexing method, and program

Abstract

To provide a multiplexing device for inserting time information capable of facilitating stable clock regeneration.SOLUTION: According to an embodiment, a multiplexing device includes: a period generation part for generating a FEC block generation period and an OFDM frame generation period based on a modulation parameter; an N-times counting part for generating an NTP packet generation signal for each N-times of FEC block generation periods derived from the modulation parameter; an NTP packet generation part for generating an IP packet in NTP format; a TLV packet generation part for making a TLV packet from an inputted MMTP packet, and making a TLV packet from the IP packet in NTP format if the NTP packet generation signal has been generated; a FEC block generation part for inserting the TLV packet in a main signal region of a FEC block and outputting the FEC block; and an OFDM frame generation part for inserting the FEC block in an OFDM frame and outputting the OFDM frame.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a multiplexing device, a multiplexing method, and a program for inserting time information for synchronizing clocks on a transmitting side and a receiving side in 4K8K satellite broadcasting. [Background technology]

[0002] Conventionally, in 4K8K satellite broadcasting, a packet in the Network Time Protocol (NTP) format for synchronizing the clocks of the sending side and the receiving side is inserted at the beginning of the slot at the beginning of the frame (Non-Patent Documents 1 and 2). In addition, when hierarchical modulation is performed, the packet is inserted at the beginning slot of a low hierarchy (Non-Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent No. 6290127 [Patent Document 2] Japanese Patent No. 6517905 [Non-patent literature]

[0004] [Non-Patent Document 1] ARIB STD-B44 [Non-Patent Document 2] ARIB STD-B39 [Non-Patent Document 3] Ministry of Internal Affairs and Communications: Call for Comments on the Draft Report of the Broadcasting System Committee - "Technical Conditions for Broadcasting Systems" - Ministry of Internal Affairs and Communications | Press Releases | Call for Comments on the Draft Report of the Broadcasting System Committee (https: / / www.soumu.go.jp) (Retrieved June 27, 2023) Summary of the Invention [Problem to be solved by the invention]

[0005] However, such a conventional clock synchronization method has the following problems.

[0006] The MMT (MPEG Media Transport) standard does not prescribe anything equivalent to a PCR (Program Clock Reference) packet, which is a type of TS packet that transmits time information, as the TS (Transport Stream) standard does. Therefore, 4K8K satellite broadcasting synchronizes the time of the broadcast transmission system with the time of the receiver by sending IP (Internet Protocol) packets in NTP format at frame intervals.

[0007] However, in the advanced terrestrial digital broadcasting system, it is very difficult to send NTP format IP packets at a timing that perfectly matches the period of the OFDM (Orthogonal Frequency Division Multiplexing) frame.

[0008] For example, to solve the above problem, it is possible to send NTP format IP packets at any timing, as in the case of TS PCR packets, but because the MMT·TLV (Type Length Value) packets before and after them are variable length, the circuit configuration for acquiring the current time required for time synchronization on the receiving side becomes complicated. Also, the delay in error correction processing changes depending on the number of recursive error corrections, causing jitter, making stable clock recovery difficult.

[0009] An object of the present invention is to provide a multiplexing device, a multiplexing method, and a program for inserting time information, which are capable of solving the above problems. [Means for solving the problem]

[0010] The multiplexing device of the embodiment includes a period generating unit, an N-counting unit, an NTP packet generating unit, a TLV packet generating unit, an FEC (Forward Error Correction) block generating unit, and an OFDM frame generating unit. The period generating unit generates an FEC block generating period and an OFDM frame generating period based on a preset modulation parameter. The N-counting unit generates an NTP packet generating signal every N FEC block generating periods, which is an integer equal to or greater than 1 and is derived from the preset modulation parameter. The NTP packet generating unit generates an NTP-formatted IP packet based on the current time every time an NTP packet is generated. The TLV packet generating unit packetizes an input MMTP packet into a TLV packet, and when an NTP packet generating signal is generated, packetizes an NTP-formatted IP packet into a TLV packet. The FEC block generating unit puts the TLV packet from the TLV packet generating unit into a main signal area of ​​an FEC block, and outputs the FEC block. The OFDM frame generating unit puts the FEC block from the FEC block generating unit into an OFDM frame, and outputs the OFDM frame. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a multiplexing device to which the multiplexing method of the first embodiment is applied. [Diagram 2] FIG. 2 is a diagram showing the configuration of an FEC block traced based on Non-Patent Document 3. [Diagram 3] FIG. 3 is a table showing the configuration of an FEC block traced based on Non-Patent Document 3. [Figure 4] FIG. 4 is a table showing calculation conditions of the information rate traced based on Non-Patent Document 3. [Diagram 5] FIG. 5 is an information bit table traced based on Non-Patent Document 3. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a multiplexing device to which the multiplexing method of the second embodiment is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as the actual ones. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with respect to the previous drawings are given the same reference numerals, and detailed explanations and duplicated explanations are omitted as appropriate.

[0013] (First embodiment) Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a block diagram showing an example of the configuration of a multiplexing device to which the multiplexing method of the first embodiment is applied.

[0015] That is, the multiplexing device 10 of this embodiment includes a period generating unit 11, an N-times counting unit 12, a time generating unit 13, an NTP packet generating unit 14, a TLV packet generating unit 15, an FEC block generating unit 16, an OFDM frame generating unit 17, and an STL (Studio to Transmitter Link) transmission packet generating unit 18.

[0016] When the multiplexing device 10 supports a plurality of hierarchical layers, such as for full-segment and one-segment, an FEC block generator 16 and an OFDM frame generator 17 are provided for each layer. Fig. 1 shows, as an example, an FEC block generator 16 (#1) and an OFDM frame generator 17 (#1) corresponding to a layer for full-segment, and an FEC block generator 16 (#2) and an OFDM frame generator 17 (#2) corresponding to a layer for one-segment, but the number of layers is not limited to two.

[0017] The period generating unit 11 generates an FEC block generating period b and an OFDM frame generating period c based on a preset modulation parameter a. Then, the period generating unit 11 outputs the FEC block generating period b to the N-times counting unit 12 and each of the FEC block generating units 16 (#1, #2), and outputs the OFDM frame generating period c to each of the OFDM frame generating units 17 (#1, #2).

[0018] The N-times counting unit 12 generates an NTP packet generation signal d every N FEC block generation periods b, which is an integer greater than or equal to 1 and is derived from the modulation parameter a, and outputs the generated NTP packet generation signal d to the NTP packet generating unit 14 and the TLV packet generating unit 15.

[0019] As described in Non-Patent Document 3, the modulation parameter a is composed of (A) the size of the FEC block, (B) the coding rate, (C) the carrier modulation method, and (D) the FFT (Fast Fourier Transform) size of the subframe section.

[0020] (A) The size of the FEC block is N shown in FIG. 2, which is based on the diagram disclosed in Non-Patent Document 3. LDPC It is.

[0021] (B) The coding rate is shown in FIG. 3, which is based on the diagram disclosed in Non-Patent Document 3.

[0022] (C) The carrier modulation scheme is also shown in FIG. 3, which is based on the diagram disclosed in Non-Patent Document 3.

[0023] (D) The FFT size in the subframe section is shown in FIG. 4, which is based on the diagram disclosed in Non-Patent Document 3.

[0024] FIG. 5 is also based on the diagram disclosed in Non-Patent Document 3, but in the calculation of the information bit rate in FIG. LDPC = 61,920 (Normal code).

[0025] In the following, the above four modulation parameters are abbreviated as A, B, C, and D, and three specific examples ((1), (2), and (3)) will be used for explanation.

[0026] (1) When B is 2 / 16, C is QPSK, and D is 8K FFT, the main signal is 8,432 bits from Fig. 3(a), and the information rate is 1.19 Mbps from Fig. 5(a). Therefore, the period of the FEC block is 8,432 / (1.19*1000000)=0.007085714 seconds ≒ 7.09 milliseconds.

[0027] (2) If B is 7 / 16, C is 64QAM, and D is 16K FFT, the main signal is 30,032 bits from Fig. 3(a), and the information rate is 13.35Mbps from Fig. 5(b). Therefore, the period of the FEC block is 30,032 / (13.35*1000000)=0.002249588 seconds ≒ 2.25 milliseconds.

[0028] (3) If B is 14 / 16, C is 4096QAM, and D is 32K FFT, the main signal is 60,272 bits from Fig. 3(a), and the information rate is 54.92Mbps from Fig. 5(c). Therefore, the period of the FEC block is 60,272 / (54.92*1000000)=0.001097451≒1.10 milliseconds.

[0029] In the three specific examples ((1), (2), and (3)) described regarding the modulation parameter a, the FEC block period ranges from 1.10 ms to 7.09 ms. Current terrestrial digital broadcasting uses TS, and the transmission cycle of PCR packets containing time information is approximately 100 ms. In addition, in the new 4K8K satellite broadcasting, NTP format packets are transmitted at the beginning of each frame, so the transmission cycle is approximately 33 ms.

[0030] For example, if one tries to use N to make the period of the FEC block approximately the same as the cycle of the new 4K8K satellite broadcasting, in the case of (1), 33 (milliseconds) / 7.09 (milliseconds) = 4.66, so the maximum value of N for which the period of the FEC block does not exceed 33 milliseconds is 4, and the value of N that is closest to 33 milliseconds is 5.

[0031] In the case of (2), 33 milliseconds / 2.26 (milliseconds)=14.67, so the maximum value of N for which the period of the FEC block does not exceed 33 milliseconds is 14, and the value of N that is closest to 33 milliseconds is 15.

[0032] In the case of (3), 33 milliseconds / 1.10 (milliseconds)=30.07, so the maximum value of N for which the period of the FEC block does not exceed 33 milliseconds is 30, and the value of N that is closest to 33 milliseconds is also 30.

[0033] That is, the sending side and the receiving side determine in advance a rule to find N such that the period of N FEC blocks does not exceed 33 milliseconds, or to find N that is closest to 33 milliseconds. Also, a rule may be established to change the target period of 33 milliseconds according to some modulation parameter a.

[0034] If N is a fixed value (for example, 10), N is determined independently of the modulation parameter a, and the interval for sending NTP format packets is 7.09*10=70.9 milliseconds in the case of (1), 2.25*10=22.5 milliseconds in the case of (2), and 1.10*10=11.0 milliseconds in the case of (3).

[0035] In practice, since the modulation parameter a is fixed during operation, it is conceivable to fix N for each layer, but N can be calculated in such a way that the interval at which NTP format packets are sent is constant.

[0036] Returning to FIG.

[0037] The time generating unit 13 generates the current time e and outputs it to the NTP packet generating unit 14 .

[0038] The NTP packet generating unit 14 generates an NTP-formatted IP packet f based on the current time e every time an NTP packet generation signal d is generated, and outputs the generated NTP-formatted IP packet f to the TLV packet generating unit 15.

[0039] The TLV packet generator 15 converts the input MMTP packet g into a TLV packet h. When an NTP packet generation signal d is generated by the N-times count unit 12, the TLV packet generator 15 converts an NTP format IP packet f into a TLV packet h. The TLV packet h is then output to each of the FEC block generators 16 (#1, #2). In FIG. 1, as an example, the TLV packet h is shown as a TLV packet h (#1) output to the FEC block generator 16 (#1) and a TLV packet h (#2) output to the FEC block generator 16 (#2).

[0040] The TLV packet generator 15 also has a NULL TLV generator 15a that performs stuffing with a NULL TLV packet so that the TLV packet h is completed at the end of the main signal area of ​​the FEC block immediately before receiving the NTP packet generation signal d from the N-times count unit 12. This ensures that the TLV packet h starts at the beginning of every N FEC blocks, and the TLV packet h, which is an NTP format IP packet f converted into a TLV packet h, is placed at the beginning of the FEC block.

[0041] The FEC block generator 16 puts the TLV packet h from the TLV packet generator 15 into the main signal area of ​​the FEC block, and outputs this FEC block i to the OFDM frame generator 17. At this time, the FEC block generator 16 puts the TLV packet h including the NTP packet generated every N FEC block generation periods b into the beginning of the main signal area of ​​the FEC block i. In FIG. 1, there are shown an FEC block generator 16(#1) that puts the TLV packet h(#1) from the TLV packet generator 15 into the main signal area of ​​the FEC block, and an FEC block generator 16(#2) that puts the TLV packet h(#2) from the TLV packet generator 15 into the main signal area of ​​the FEC block, and outputs the FEC block i(#2).

[0042] The OFDM frame generation unit 17 inserts the FEC block i from the FEC block generation unit 16 into an OFDM frame, and outputs this OFDM frame j to the STL transmission packet generation unit 18. Fig. 1 illustrates an OFDM frame generation unit 17(#1) that outputs an OFDM frame j(#1) into which the FEC block i(#1) from the FEC block generation unit 16(#1) has been inserted, to the STL transmission packet generation unit 18, and an OFDM frame generation unit 17(#2) that outputs an OFDM frame j(#2) into which the FEC block i(#2) from the FEC block generation unit 16(#2) has been inserted, to the STL transmission packet generation unit 18.

[0043] The STL transmission packet generation unit 18 acquires each OFDM frame j (#1, #2) output from each OFDM frame generation unit 17 (#1, #2), and converts the acquired OFDM frames j (#1), j (#2) into the format of packets k (#1), k (#2) for IP transmission, respectively, and outputs them.

[0044] Next, the operation of the multiplexing device 10 of this embodiment configured as above will be described.

[0045] In the multiplexing device 10, a preset modulation parameter a is acquired by a period generating unit 11 and an N-times counting unit 12, and the period generating unit 11 generates an FEC block generating period b and an OFDM frame generating period c according to the modulation parameter a.

[0046] In the N-counting unit 12, N derived from the modulation parameter a is used to generate an NTP packet generation signal d for every N FEC block generation periods b. Note that N may be sent as a descriptor. Sending N as a descriptor will be described in the second embodiment.

[0047] In the NTP packet generation unit 14, the current time e held by the time generation unit 13 is acquired each time an NTP packet generation signal d is received, and an NTP format IP packet f is generated based on the current time e. The generated NTP format IP packet f is output to the TLV packet generation unit 15.

[0048] In the TLV packet generator 15, normally, an input MMTP packet g is converted into a TLV packet h, and when an NTP packet generation signal d is received, an NTP format IP packet f from the NTP packet generator 15 is converted into a TLV packet h.

[0049] In the TLV packet generator 15, immediately before receiving the NTP packet generation signal d, the NULL TLV generator 15a performs stuffing with a NULL TLV packet as necessary so that the TLV packet h is completed at the end of the main signal area of ​​the FEC block. This ensures that the TLV packet h starts at the beginning of every N FEC blocks, and the TLV packet h, which is the NTP format IP packet f converted into the TLV packet h, can be placed at the beginning of the FEC block.

[0050] In addition, the TLV packet generator 15 determines which layer the output TLV packet h belongs to based on the destination port number and IP address specified in the MMTP packet g, and outputs the TLV packet h to the FEC block generator 16 that processes that layer. For example, an NTP format IP packet is output only to a layer with high error correction capability, or an NTP format IP packet is also output to a layer with low error correction capability. In this case, an identifier for identifying this can be sent.

[0051] In the FEC block generator 16 , the input TLV packet h is inserted into the main signal area of ​​an FEC block, and this FEC block i is output to the OFDM frame generator 17 .

[0052] In the OFDM frame generating unit 17, the input FEC block i is inserted into an OFDM frame j, and the frame is output to an STL transmission packet generating unit .

[0053] In the STL transmission packet generator 18, the input OFDM frame j data of each layer is converted into a packet k format for IP transmission to STL, such as XMI format or STLP format, and output to the receiver. In the case of the STLP format, the FEC block generator 16 and the OFDM frame generator 17 simply perform generation virtually to obtain pointer information and the like required for creating the STLP format.

[0054] Note that an OFDM modulator may be provided in place of the STL transmission packet generator 18, and the OFDM frames j of each layer may be OFDM modulated collectively and output to a transmitter (power amplifier).

[0055] As described above, according to the multiplexing device 10 of the present embodiment, it is possible to focus on the FEC block i, which is a unit for performing error correction, and transmit an IP packet f in NTP format at the beginning of each of N FEC blocks i. In this case, the OFDM frame of the terrestrial digital advanced broadcasting standard, which corresponds to the frame of 4K8K satellite broadcasting, is not used, but the FEC block i, which is the unit for error correction, is used.

[0056] According to the multiplexing device 10 of the present embodiment, the overhead of inserting an IP packet f in NTP format can be reduced, and N can be determined according to the modulation parameter a so that clock recovery can be performed on the receiving side. The frame of a 4K8K satellite broadcast is about 33 msec, and this period allows both overhead suppression and clock recovery, but the FEC block i has a period of several msec depending on the modulation parameter a, and sending an IP packet f in NTP format for each FEC block i results in a large overhead. Therefore, the overhead can be suppressed by sending an NTP packet k for each N FEC blocks i (N is an integer equal to or greater than 1) according to the modulation parameter a.

[0057] In addition, when multiple hierarchies with different error correction capabilities are used, transmission can be limited to only the hierarchies with high error correction capabilities, but it is also possible to allow transmission in both the hierarchies with high and low error correction capabilities. In 4K8K satellite broadcasting, it is the head of the frame, and when hierarchical transmission with different error correction capabilities is performed, NTP format IP packets are sent only in one hierarchy. However, in the service of the advanced terrestrial digital broadcasting system, it is highly likely that services equivalent to the current terrestrial digital one-segment (high error correction capabilities) and full-segment (low error correction capabilities) will be realized, and when receiving full-segment, specifications will be provided that allow reception processing to be completed using only information from the full-segment hierarchy. Note that the lower hierarchy of 4K8K satellite broadcasting is only used during rain attenuation, so when there are multiple hierarchies, there is no need to send NTP format IP packets in the higher hierarchy.

[0058] In addition, since an NTP-format IP packet f is sent for every N FEC blocks i, similar to 4K8K satellite broadcasting, alignment processing is performed with a NULL TLV packet at the end of the main signal portion consisting of one or more FEC blocks i, including the FEC block i immediately before the NTP-format IP packet f is sent.

[0059] As described above, the multiplexing device 10 of this embodiment can transmit an NTP format IP packet f to the beginning of an FEC block i for every N FEC blocks i, where N is determined according to the modulation parameter a.

[0060] Furthermore, the layer that transmits the IP packet f in the NTP format can be at least a layer with high error tolerance, and for example, it can be transmitted in a plurality of layers including a layer with high error tolerance.

[0061] Furthermore, in the FEC block i immediately preceding the FEC block i in which the NTP format IP packet f is sent for each of N FEC blocks i, alignment can be achieved with a NULL TLV packet as necessary so that the TLV packet h is completed.

[0062] In this way, the multiplexing device 10 of this embodiment can transmit clock information to the receiving side with a simple circuit configuration, which enables the receiving side to acquire time for clock recovery at a constant cycle according to the modulation parameter a.

[0063] Second embodiment A multiplexing device to which a multiplexing method according to a second embodiment of the present invention is applied will be described.

[0064] FIG. 6 is a block diagram illustrating an example of the configuration of a multiplexing device according to the second embodiment.

[0065] The multiplexing device 10A of this embodiment is a modified example of the multiplexing device 10 of the first embodiment, and uses N specified by a user, rather than N derived by the N-times counting unit 12. In Fig. 6, the same components as those in the first embodiment are given the same reference numerals. In the following explanation, overlapping explanations will be avoided and only the different parts will be explained.

[0066] The multiplexing device 10A uses a user-specified N. Therefore, the N-times counting unit 12 does not derive N from the modulation parameter a, and the user-specified N is input to the N-times counting unit 12.

[0067] The multiplexing device 10A also includes a descriptor generator 19. The value of N designated by the user is also input to the descriptor generator 19. The descriptor generator 19 adds the input value of N to the descriptor m as additional information (e.g., N=15). Then, the descriptor generator 19 outputs the descriptor m to which the value of N has been added to the TLV packet generator 15.

[0068] The TLV packet generator 15 performs the operations described in the first embodiment, and in addition, embeds a descriptor m in the TLV packet h. Then, the TLV packet h with the embedded descriptor m is output to the FEC block generator 16.

[0069] As a result, packet k with N added to descriptor m is output to the receiver from the STL transmission packet generator 18. By acquiring N from descriptor m, the receiver can grasp the value of N designated by the user on the transmitting side, and can demodulate every N times.

[0070] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0071] 10, 10A multiplexer 11 Period generator 12 N-times counting section 13 Time generator 14 NTP packet generator 15 TLV packet generator 15a NULL TVL generation section 16 FEC block generator 17 OFDM frame generator 18 STL transmission packet generator 19 Descriptor Generator a Modulation parameters b FEC block generation cycle c OFDM frame generation period d NTP packet generation signal e Current time f IP packets g MMTP packets h TLV packet i FEC block j OFDM frame k packets m Descriptor

Claims

1. a period generating unit that generates a forward error correction (FEC) block generation period and an orthogonal frequency division multiplexing (OFDM) frame generation period based on preset modulation parameters; an N-times counting unit that generates a Network Time Protocol (NTP) packet generation signal every N FEC block generation periods, where N is an integer equal to or greater than 1 and is derived from the preset modulation parameters; an NTP packet generating unit that generates an IP (Internet Protocol) packet in an NTP format based on a current time every time the NTP packet generation signal is generated; a TLV (Type Length Value) packet generating unit that converts an input MMTP (MPEG Media Transport) packet into a TLV packet and, when the NTP packet generation signal is generated, converts the NTP format IP packet into a TLV packet; an FEC block generator that inserts the TLV packet from the TLV packet generator into a main signal area of ​​an FEC block and outputs the FEC block; an OFDM frame generator that inserts the FEC blocks from the FEC block generator into an OFDM frame and outputs the OFDM frame; A multiplexing device comprising:

2. The multiplexing device according to claim 1, wherein the TLV packet generation unit includes a NULL TLV generation unit that performs stuffing with a NULL TLV packet so that the TLV packet is completed at the end of a main signal area of ​​the FEC block immediately before receiving the NTP packet generation signal from the NTP packet generation unit.

3. 2. The multiplexing device according to claim 1, further comprising a transmission packet generator that acquires the OFDM frame from the OFDM frame generator, converts the acquired OFDM frame into a packet format for IP transmission, and outputs the packet format.

4. the FEC block generator and the OFDM frame generator are provided for each layer, The multiplexing device according to claim 1 , wherein the TLV packet generation unit determines a layer to which the TLV packet belongs, and outputs the TLV packet to the FEC block generation unit provided for the determined layer.

5. the value of N is specified by a user instead of being derived from the preset modulation parameters; A descriptor generating unit that outputs a descriptor including the value of N designated by the user as additional information to the TLV packet generating unit, The multiplexing device according to claim 1 , wherein the TLV packet generating unit converts the IP packet into a TLV packet so as to include the descriptor.

6. 1. A multiplexing method implemented by a processor of a multiplexing device, comprising: generating a forward error correction (FEC) block generation period and an orthogonal frequency division multiplexing (OFDM) frame generation period based on preset modulation parameters; generating a Network Time Protocol (NTP) packet generation signal for every N FEC block generation periods, the N being an integer equal to or greater than 1, derived from the preset modulation parameters; generating an Internet Protocol (IP) packet in NTP format based on a current time by the processor each time the NTP packet generation signal is generated; a step of the processor packetizing an input MPEG Media Transport (MMTP) packet into a Type Length Value (TLV) packet and, when the NTP packet generation signal is generated, packetizing an IP packet in the NTP format into a TLV packet; the processor putting the TLV packet into a main signal area of ​​an FEC block and outputting the FEC block; the processor putting the FEC blocks into an OFDM frame and outputting the OFDM frame; A multiplexing method comprising:

7. The multiplexing method according to claim 6, further comprising a step of stuffing the TLV packet with a NULL TLV packet so that the TLV packet is completed at the end of the main signal area of ​​the FEC block immediately before the processor receives the NTP packet generation signal.

8. The multiplexing method according to claim 6 , further comprising the step of: said processor acquiring said OFDM frame, converting said acquired OFDM frame into a packet format for IP transmission, and outputting said packet format.

9. the value of N is specified by a user instead of being derived from the preset modulation parameters; 7. The multiplexing method according to claim 6, further comprising the step of: said processor packetizing said IP packets into TLV packets so as to include a descriptor with an N value specified by said user.

10. A function of generating a forward error correction (FEC) block generation period and an orthogonal frequency division multiplexing (OFDM) frame generation period based on preset modulation parameters; a function of generating a Network Time Protocol (NTP) packet generation signal every N FEC block generation periods, where N is an integer equal to or greater than 1, derived from the preset modulation parameters; a function of generating an IP (Internet Protocol) packet in an NTP format based on a current time every time the NTP packet generation signal is generated; A function of packetizing an input MMTP (MPEG Media Transport) packet into a TLV (Type Length Value) packet, and, when the NTP packet generation signal is generated, packetizing the NTP format IP packet into a TLV packet; A function of inserting the TLV packet into a main signal area of ​​an FEC block and outputting the FEC block; a function of inserting the FEC block into an OFDM frame and outputting the OFDM frame; A program that makes things happen on a computer.

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