Re-multiplexing device and program

Abstract

To reduce the processing time of a modulation device.SOLUTION: A re-multiplexing device 12 outputs a program transmission signal that has been re-multiplexed with a plurality of pieces of data to a modulation device compatible with hierarchical transmission using time division multiplexing. The re-multiplexing device includes: a re-multiplex packet generation unit 123 that divides hierarchical and subframe-specific data into fixed-length data units; and a transmission schedule unit 121 that continuously transmits the data units in a hierarchical manner for each subframe section and keeps the transmission interval of the data unit constant in all subframe sections.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a remultiplexing device and a program. [Background technology]

[0002] Research, development, and demonstration of an advanced terrestrial broadcasting system that will improve frequency utilization efficiency compared to the current terrestrial digital broadcasting system, ISDB-T (Integrated Services Digital Broadcasting-Terrestrial), is underway as the next-generation terrestrial digital broadcasting system, and was submitted to the Information and Communications Technology Subcommittee of the Information and Communications Council of the Ministry of Internal Affairs and Communications in July 2023 as a "Technical Requirements for Broadcasting Systems." The advanced terrestrial broadcasting system is compatible with the Internet Protocol (IP) as a multiplexing format, and is compatible with hierarchical transmission technology that multiplexes multiple programs with different transmission tolerances and capacities, such as for mobile and fixed reception, and transmits them on a single modulated wave, making it a system that aims to be multifunctional (see, for example, Non-Patent Document 1).

[0003] In current terrestrial broadcasting, multiple program components, including video, audio, and data, are remultiplexed into one by a remultiplexing device and transmitted to the transmitting station in the form of a program transmission signal to which the synchronization control information required for modulation is added. A similar mechanism is being considered for the advanced terrestrial broadcasting standard, and two new IP-format program transmission signals have been developed: the fixed-length, fixed-rate XMI (eXtensible Modulator Interface) and the variable-length, variable-rate STLP (Studio to Transmitter Link Protocol).

[0004] The program transmission methods that have been considered up until now have been designed assuming only the use of frequency division multiplexing (FDM) as a hierarchical transmission technology. However, the proposed terrestrial broadcasting enhancement method revise the Orthogonal Frequency Division Multiplexing (OFDM) frame structure and makes it possible to apply time division multiplexing (TDM) to hierarchical transmission. It also makes it possible to apply FTDM, which combines FDM and TDM, to hierarchical transmission.

[0005] Fig. 6A shows an example of an OFDM frame configuration using FDM for hierarchical transmission, Fig. 6B shows an example of an OFDM frame configuration using TDM for hierarchical transmission, and Fig. 6C shows an example of an OFDM frame configuration using FTDM for hierarchical transmission. Fig. 6B and Fig. 6C show an example where the number of subframes is 2. The Advanced Terrestrial Broadcasting Standard specifies that the maximum number of subframes is 8, and the maximum number of layers per subframe is 8. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Ministry of Internal Affairs and Communications, "Report of the Broadcasting System Committee, Information and Communications Technology Subcommittee, Information and Communications Council," [online], [Retrieved January 22, 2024], Internet<URL: https: / / www.soumu.go.jp / main_content / 000892616.pdf> Summary of the Invention [Problem to be solved by the invention]

[0007] The first problem will be explained. In TDM, an OFDM frame is divided into multiple subframes, and programs with different transmission tolerances and transmission capacities are transmitted in different subframes. There is no remultiplexing device that supports the FTDM structure (see Figure 6C), which combines FDM and TDM.

[0008] As shown in Figure 7, previously considered program transmission methods involve scheduling the transmission of data packets for each layer alternately, with the number of packets depending on the ratio of the number of FEC (Forward Error Correction) blocks for each layer within one OFDM frame. This conventional transmission rule is suitable for FDM (see Figure 6A), which requires simultaneous modulation of multiple layers, but when a TDM layered structure is used, it takes time to accumulate the data required to modulate the first subframe.

[0009] Next, we will explain the second problem. According to the conventional transmission standard shown in Figure 7, layer-specific data in subframes with an FDM structure is transmitted in data units. However, the packet size of the program transmission signal is equal to or smaller than the maximum transmission unit (MTU) size of 1,500 bytes. This is smaller than the FEC block size of 8,640 bytes constituting the LDPC code, an error-correcting code used in the advanced system, or the number of bytes in the main signal area excluding the parity area (redundant bits). Therefore, an FEC block cannot be formed from one data unit. Meanwhile, a modulation device that receives and modulates the program transmission signal cannot perform error correction coding unless it can receive data for an FEC block. In particular, when a modulated signal is composed of multiple layers with different transmission rates, the modulation device must wait until it receives data units for an FEC block in a layer with a lower transmission rate and generates an FEC block that has been subjected to error correction coding, which increases the delay time of the modulation process.

[0010] In view of the above circumstances, the object of the present invention is to provide a remultiplexing device and a program that can shorten the processing time of a modulation device that supports hierarchical transmission using FDM, TDM, or FTDM. [Means for solving the problem]

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

[0012] (1) A remultiplexing device that transmits a program transmission signal in which multiple data are remultiplexed to a modulation device compatible with hierarchical transmission using time division multiplexing, comprising: a remultiplexing packet generation unit that divides data for each layer and subframe into fixed-length data units; and a transmission schedule unit that continuously transmits the data units for each layer for each subframe interval and keeps the transmission intervals of the data units constant in all subframe intervals.

[0013] (2) A remultiplexing device that transmits a program transmission signal in which multiple data are remultiplexed to a modulation device compatible with hierarchical transmission using frequency division multiplexing, comprising: a remultiplexing packet generation unit that divides layer-specific data into fixed-length data units; and a transmission scheduler that transmits the data units in hierarchical order for each period, and sets the number of periods to the minimum value of the number of FEC blocks for each layer in an OFDM frame section.

[0014] (3) A remultiplexing device that transmits a program transmission signal in which multiple data are remultiplexed to a modulation device that supports hierarchical transmission using both frequency division multiplexing and time division multiplexing, comprising: a remultiplexing packet generation unit that divides data for each layer and subframe into fixed-length data units; and a transmission scheduler that keeps the transmission intervals of the data units constant in all subframe sections, transmits the data units in hierarchical order for each period in a subframe section that has a frequency division multiplexing structure, and sets the number of periods to the minimum value of the number of FEC blocks for each layer in the subframe section.

[0015] (4) A program for causing a computer to function as the remultiplexing device according to any one of (1) to (3). [Effects of the Invention]

[0016] According to the present invention, it is possible to reduce the processing time of a modulation device that supports hierarchical transmission using FDM, TDM, or FTDM. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a distribution system according to an embodiment; [Figure 2] 1 is a block diagram showing a schematic configuration of a remultiplexing device according to an embodiment; [Figure 3] FIG. 10 is a diagram showing the order in which data units are sent out, corresponding to the TDM structure. [Figure 4] 10 is a diagram illustrating the difference between the transmission order of data units in a conventional method and the transmission order of data units in a remultiplexing device according to an embodiment. [Figure 5] FIG. 10 is a diagram showing the order in which data units are sent, corresponding to the FTDM structure. [Figure 6A] FIG. 1 is a diagram illustrating an example of an OFDM frame configuration using FDM for hierarchical transmission. [Figure 6B] FIG. 1 is a diagram illustrating an example of an OFDM frame configuration using TDM for hierarchical transmission. [Figure 6C] FIG. 1 is a diagram illustrating an example of an OFDM frame configuration using FTDM for hierarchical transmission. [Figure 7] FIG. 1 is a diagram illustrating a conventional data unit transmission order. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] <Distribution system> Fig. 1 is a diagram showing an example of the configuration of a distribution system 1 according to one embodiment. The distribution system 1 shown in Fig. 1 comprises a performance studio 10 and a broadcasting station 20. The performance studio 10 comprises a plurality (n units) of multiplexing devices 11 (11-1 to 11-n) and a re-multiplexing device 12. The broadcasting station 20 comprises a modulation device 21 and a transmission device 22. The performance studio 10 and the broadcasting station 20 are connected via a network 30.

[0020] The studio 10 performs hierarchical transmission, transmitting data for multiple layers and subframes over a single channel. The studio 10 may also transmit auxiliary data, such as emergency earthquake alerts, over a single channel.

[0021] In this embodiment, the transmission path between the multiplexer 11 and the remultiplexer 12 is an IP transmission path, and the multiplexer 11 outputs data IP packets to the remultiplexer 12 .

[0022] The multiplexing device 11 multiplexes externally input program signals (video signals, audio signals, and subtitle signals), packetizes them into IP packets, and outputs them to the remultiplexing device 12 as layer / subframe data IP packets.

[0023] The re-multiplexer 12 generates re-multiplexed IP packets by further re-multiplexing the layer / subframe data IP packets input from the multiplexer 11 into a single system, and sends the re-multiplexed IP packets to a modulator 21 that supports hierarchical transmission using FDM, TDM, or FTDM as a program transmission signal. The re-multiplexer 12 will be described in detail later.

[0024] The modulator 21 modulates the layer / subframe data units as the main signal based on the control information contained in the re-multiplexed IP packets input from the re-multiplexer 12, constructs an OFDM frame using FDM, TDM, or FTDM for hierarchical transmission, and outputs the generated OFDM signal by OFDM modulation to the transmitter 22.

[0025] The transmitter 22 generates a broadcast wave according to the OFDM signal input from the modulator 21 and transmits it outside the broadcast station 20 via an antenna.

[0026] <Remultiplexer> Fig. 2 is a diagram showing a schematic configuration of a remultiplexing device according to one embodiment. The remultiplexing device 12 shown in Fig. 2 includes a transmission scheduler 121, a synchronization control information packet generator 122, a plurality of layer / subframe re-multiplexing packet generators 123 (123-1 to 123-n), and a GPS reference signal generator 125.

[0027] The synchronization control information packet generation unit 122 generates a synchronization control information packet including frame synchronization information, which is information related to the control of transmission timing, and TMCC (Transmission and Multiplexing Configuration and Control), which is control information corresponding to the advanced method, and outputs the packet to the transmission schedule unit 121.

[0028] The layer / subframe re-multiplexed packet generator 123 generates FEC blocks or pseudo FEC blocks by excluding the parity area from the FEC blocks based on the input layer / subframe data IP packets. The layer / subframe re-multiplexed packet generator 123 then sequentially concatenates the FEC blocks or pseudo FEC blocks to generate a multiplexed frame or pseudo multiplexed frame corresponding to one OFDM frame, divides the multiplexed frame into data units of a fixed length (e.g., 1080 bytes), generates layer / subframe re-multiplexed packets with a predetermined header added, and outputs the re-multiplexed packets to the transmission scheduler 121. Note that if subframes do not exist, "layer / subframe" can be read as "layer".

[0029] The GPS reference signal generating unit 125 generates a GPS reference signal based on the input GPS signal and outputs it to the transmission scheduling unit 121 .

[0030] The transmission schedule unit 121 schedules the transmission timings of the synchronization control information packet input from the synchronization control information packet generation unit 122 and the hierarchical / subframe-based multiplexed packet input from the hierarchical / subframe-based multiplexed packet generation unit 123, and transmits them at fixed intervals based on the clock generated based on the GPS reference signal input from the GPS reference signal generation unit 125. Hereinafter, the scheduling function of the transmission schedule unit 121 will be described.

[0031] <Scheduling Function for TDM Structure> The scheduling function for the TDM structure shown in FIG. 6B will be described below.

[0032] The transmission schedule unit 121 continuously transmits hierarchical data units for each subframe interval to the modulation device 21 corresponding to hierarchical transmission using TDM, and makes the transmission interval of the data units constant in all subframe intervals.

[0033] FIG. 3 is a diagram showing the transmission order of data units corresponding to the TDM structure. The square with cross hatching indicates the data unit of the synchronization control information, the square with slanting lines indicates the data unit of subframe #1, and the white square indicates the data unit of subframe #2. The number of data units (the number of data units constituting the subframe) Ns of subframe number s is determined by the following formula (1). Here, N data is the number of data carriers in the subframe, Vs is the modulation order [bits] of subframe number s, L FECB is the length [bits] of the FEC block, Ms is the number of data units constituting the FEC block unit transmitted by the program transmission signal in subframe number s, and ceil() is an operation that rounds up the decimal part of the value inside ().

[0034]

Equation

[0035] When sending data units for each sub-frame interval, if the transmission interval is defined along the time width of the sub-frame in the OFDM frame, the ratio of the number of data units Ns is not the same as the ratio of the time widths. As a result, the transmission interval of the data units varies for each sub-frame interval, and the transmission rate changes for each sub-frame interval. Therefore, the transmission scheduler 121 makes the transmission interval of the data units constant (fixed rate) by sending the data units at a time interval ΔT obtained by dividing the OFDM frame length T by the sum of the number of data units of the synchronization control information and the number of data units of all sub-frames. ΔT can be expressed by the following equation (2). However, N sync is the number of data units of the synchronization control information sent for each OFDM frame, and S is the number of sub-frames in one OFDM frame. In the modulator 21, since the data required for modulation can be received in the order of the sub-frames, it is expected that the delay time required for the modulation process from the reception of the IP packet can be reduced.

[0036]

Equation

[0037] <Scheduling Function for FDM Structure> Next, the scheduling function for the FDM structure shown in FIG. 6A will be described. In this embodiment, it is assumed that data of two layers, namely layer A and layer B, are transmitted, but the number of layers for hierarchical transmission is not limited to two layers.

[0038] The transmission scheduler 121 sends data units in the order of the layers for each period to the modulator 21 corresponding to hierarchical transmission using FDM, and sets the number of periods to the minimum value of the number of FEC blocks for each layer in the OFDM frame interval.

[0039] Table 1 shows an example of transmission parameters. Here, k s,l is the number of FEC blocks of the l-th layer of the sub-frame number s. M s,lis the number of data units (DU) that make up one FEC block in the lth layer of subframe number s. In this example, the length of the FEC block is 8640 bytes, the length of the data unit is 1080 bytes, and the main signal area of the FEC block excluding the parity area is transmitted. In layer A (l=0), the coding rate is 7 / 16, so M s,0 = 8640 × (7 / 16) / 1080 = 3.5. In the B layer (l = 1), the coding rate is 9 / 16, so M s,1 = 8640 × (9 / 16) / 1080 = 4.5. In the FDM structure, the number of subframes in an OFDM frame is 1. Therefore, when the transmission scheduler 121 supports only the FDM structure, the subframe number s is not required, and k s,l, M s,l are k l, M l Furthermore, when the transmission scheduler 121 supports both the FDM structure and the FTDM structure, the subframe number s is fixed to 0 for the FDM structure, and is variable for the FTDM structure.

[0040] [Table 1]

[0041] In the FDM structure, the transmission order of data units is specified as follows: The number of periods I of the subframe number s in the FDM structure s is the minimum number of FEC blocks per layer in the OFDM frame interval. s is expressed by the following formula (3). min() is an operator that returns the minimum value among the values in (). In the example in Table 1, I s =min(23,171)=23.

[0042]

number

[0043] Here, the number of FEC blocks in the lth layer sent in one cycle is k s,l In the example of Table 1, the number of FEC blocks in layer A (l=0) in one cycle, k s,0 is K s,0 / I s = 23 / 23 = 1, and the number of FEC blocks in layer B (l = 1) in one cycle is k s,1 is K s,1 / I s =171 / 23=7.434...

[0044]

number

[0045] The number of data units S of the lth layer sent in the nth cycle n l In the example of Table 1, the number of data units in layer A (l=0) is S n 0 is ceil(3.5×1×n)-ceil(3.5×1×(n-1)). Also, the number of data units in layer B (l=1) is S n 1 is ceil(4.5×(171 / 23)×n)-ceil(4.5×(171 / 23)×(n-1)).

[0046]

number

[0047] Table 2 shows the number of data units S according to Equation (5). n l The calculation result is shown below. The number of data units in the lth layer in the subframe with subframe number s is N s,l =ceil(K s,l ×M s,l ) is K s,l , M s,l When the value shown in Table 1 is used, the number of data units in the 0th layer, A, is N s,0It becomes ceil(23 × 3.5) = 81. Also, the number of data units in B layer which is the first layer is ceil(171 × 4.5) = 770. Since this matches the total number of data units shown in the bottom row of Table 2, it can be confirmed that all the data units to be sent according to the sending order calculated according to the above-mentioned formula have been sent.

[0048]

Table 2

[0049] FIG. 4 is a diagram showing the difference between the sending order of conventional data units and the sending order of data units in the demultiplexing apparatus 12 according to an embodiment. The upper row shows the conventional sending order, and the lower row shows the sending order of the demultiplexing apparatus 12. According to Table 1, the number of data units M s,0 required to form one FEC block in layer A is 3.5, but in the conventional sending order, it was necessary to receive 32 data units. On the other hand, the demultiplexing apparatus 12 according to the present embodiment sends 4 data units (S1 0 = 4) of layer A in the first cycle (n = 1), and then sends 34 data units (S1 1 = 34) of layer B. Therefore, it can be seen that error correction coding processing can be started only by receiving 4 data units, and the delay time until the start of processing can be shortened.

[0050] <Scheduling function for FTDM structure> Next, the scheduling function for the FTDM structure shown in FIG. 6C will be described. For the FTDM structure shown in FIG. 6C, the transmission schedule unit 121 combines and corresponds to the scheduling function for the above-mentioned TDM structure and the scheduling function for the FDM structure.

[0051] The transmission scheduler 121 makes the transmission interval of data units constant in all subframe sections for the modulation device 21 that supports hierarchical transmission using FTDM, and in the subframe section that has an FTDM structure, transmits data units in hierarchical order for each period, and sets the number of periods to the minimum value of the number of FEC blocks for each hierarchical level in the subframe section.

[0052] Fig. 5 shows the transmission order of data units corresponding to the FTDM structure. Subframe #1 has an FDM structure. Each square in Fig. 5 indicates a group of data units required to form one FEC block, and the number of data units to be transmitted is the same as that of the S n l That is, in the example shown in Table 1, 4 packets or 3 packets are sent in layer A.

[0053] In the structure shown in FIG. 6C, the 0th subframe (subframe #1) has an FDM structure, so the number of data units N0 required to configure the 0th subframe is the sum of the number of data units in all layers, and the number of data units N 0,l Using the above, it can be expressed by the following equation (6): where L is the number of layers.

[0054]

number

[0055] In this way, the remultiplexer 12 can reduce the processing time of the modulator 21 that supports hierarchical transmission using FDM, TDM, or FTDM, by using the scheduling function of the transmission scheduler 121.

[0056] <Program> A computer capable of executing program instructions can also be used to function as the above-described remultiplexing device 12. Here, the computer may be a general-purpose computer, a special-purpose computer, a workstation, a PC (Personal Computer), etc. The program instructions may be program code, code segments, etc. for performing the necessary tasks.

[0057] 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.

[0058] 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.

[0059] The remultiplexing device 12 may be configured with one or more semiconductor chips. The semiconductor chip may include a CPU that executes a program that describes the processing to realize each function of the remultiplexing device 12.

[0060] 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]

[0061] 1. Distribution System 10 Performance hall 11 Multiplexer 12 Remultiplexer 20 Broadcasting Station 30 Network 21 Modulator 22 Transmitting device 121 Transmission Schedule Department 122 Synchronous control information packet generator 123 Layer / subframe re-multiplexing packet generator 125 GPS reference signal generator

Claims

1. A remultiplexing device that transmits a program transmission signal in which a plurality of data are remultiplexed to a modulation device that supports hierarchical transmission using time division multiplexing, a re-multiplexing packet generator that divides layer / subframe data into fixed-length data units; a transmission scheduler that continuously transmits the data units for each layer in each subframe period and keeps the transmission intervals of the data units constant in all subframe periods; A remultiplexing device comprising:

2. A remultiplexing device that transmits a program transmission signal in which a plurality of data are remultiplexed to a modulation device that supports hierarchical transmission using frequency division multiplexing, a re-multiplexing packet generator that divides layer-specific data into fixed-length data units; a transmission scheduler that transmits the data units in hierarchical order for each period, and that sets the number of periods to the minimum number of FEC blocks for each layer in an OFDM frame section; A remultiplexing device comprising:

3. A remultiplexing device that transmits a program transmission signal in which a plurality of data are remultiplexed to a modulation device that supports hierarchical transmission using both frequency division multiplexing and time division multiplexing, a re-multiplexing packet generator that divides layer / subframe data into fixed-length data units; a transmission scheduler that keeps the transmission intervals of the data units constant in all subframe sections, transmits the data units in hierarchical order for each period in a subframe section that has a frequency division multiplexing structure, and sets the number of periods to the minimum value of the number of FEC blocks for each layer in the subframe section; A remultiplexing device comprising:

4. A program for causing a computer to function as the remultiplexing device according to any one of claims 1 to 3.

Images