JP2023146913A - Re-multiplexing apparatus, modulation device, and program - Google Patents

Abstract

To prevent a buffer underflow in a modulation device.SOLUTION: A re-multiplexing apparatus 12 comprises: a XMI packetized part 107 that generates a XMI packet housing a content signal in each hierarchy; and a packet transmission schedular part 112 that repeatedly outputs a first packet set that is formed by the XMI packet of one first hierarchy in the case where the number of XMI packets of the first hierarchy and a second hierarchy is K and L (K<L) in 1O FDM frames and the XMI packet of the second hierarchy of ceil (L/K), and a second packet set formed by the XMI packet of one first hierarchy and the XMI packet of the second hierarchy of a floor(L/K).SELECTED DRAWING: Figure 2

Description

The present invention relates to a remultiplexing device, an OFDM (Orthogonal Frequency Division Multiplexing) frame generation device, and a program.

In the next-generation advanced method of digital terrestrial television broadcasting (hereinafter referred to as the "advanced method"), the IP (Internet Protocol)-based XMI ( The use of eXtensible Modulator Interface (eXtensible Modulator Interface) packets is being considered (for example, see Patent Document 1).

In the advanced method, similar to conventional terrestrial digital broadcasting, multiple layers (services) such as a layer for mobile reception (mobile reception service) and a layer for fixed reception (fixed reception service) are multiplexed and transmitted. A method is being considered. A remultiplexing device is a device that multiplexes these multiple services and the control signals of the modulation device of the broadcasting station and sends it out to the broadcasting station as one program transmission signal stream. In conventional terrestrial digital broadcasting, TS (Transport Stream) is multiplexed and broadcast TS is output, but in the advanced method, MMT (MPEG Media Transport)/TLV (Type Length Value) is multiplexed and XMI packets are output. We are considering ways to do this.

XMI, which is currently being considered for broadcast TS and sophistication, has a one-to-one correspondence with OFDM frames in advance in the re-multiplexing device in order to make it easier to form the same OFDM waveform in the modulation devices of multiple broadcasting stations. Multiplexed frames are formed, divided into fixed-length frames for ease of assembly at broadcasting stations, and modulator control information is added for transmission at a fixed rate.

A modulation device at a broadcasting station constructs an OFDM frame from the received broadcast TS packet or XMI packet, emits it as a radio wave, and delivers the radio wave to each home.

JP2018-78552A

In the remultiplexing device described in Patent Document 1, depending on specific parameters, the output ratio of XMI packets for each layer is not constant at the end, and the output ratio of A buffer underflow occurs when the number of input packets is insufficient compared to the required packets, and the modulation device may not operate.

An object of the present invention, made in view of the above circumstances, is to provide a remultiplexing device, a modulation device, and a program that can prevent buffer underflow.

A remultiplexing device according to an embodiment is a remultiplexing device that transmits packets to a modulation device, and includes an XMI packetization unit that generates an When the number of XMI packets of the first layer and the second layer in a frame are K and L (K<L), respectively, one XMI packet of the first layer and ceil (L/K) number of A first packet set consisting of two-layer XMI packets and a second packet set consisting of one first-layer XMI packet and floor (L/K) second-layer XMI packets are repeatedly output. A packet transmission scheduler section.

Further, the remultiplexing device according to one embodiment is a remultiplexing device that transmits packets to a modulation device, and includes an XMI packetization unit that generates an , the number of XMI packets in the first layer, the second layer, and the third layer in one OFDM frame are K, L, and M (K<M<L), respectively. A first packet set consisting of an XMI packet, ceil (L/K) second layer XMI packets, and ceil (M/K) third layer XMI packets, and one first layer XMI packet , a second packet set consisting of ceil(L/K) second layer XMI packets and floor(M/K) third layer XMI packets, one first layer XMI packet, floor A packet transmission scheduler unit that repeatedly outputs (L/K) second layer XMI packets and a third packet set consisting of floor (M/K) third layer XMI packets.

Further, the modulation device according to one embodiment is a modulation device that receives an STLP packet storing a content signal for each layer in the form of a TLV packet, and converts the received STLP packet into an FEC block by converting the content signal for each layer into an FEC block. a packet receiving unit that converts the FEC block into an XMI packet stored in the format, a data processing unit that performs error correction encoding processing and interleaving processing on the FEC block, and a TMCC signal and a pilot signal to the data processed by the data processing unit. and an OFDM frame configuring section that configures an OFDM frame by inserting the .

Further, a program according to an embodiment causes a computer to function as the remultiplexing device.

Further, a program according to an embodiment causes a computer to function as the modulation device.

According to the present invention, it is possible to prevent buffer underflow in a modulation device.

1 is a block diagram showing a configuration example of a distribution system according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration example of a remultiplexing device according to an embodiment of the present invention. FIG. 3 is a diagram showing the structure of a TLV packet generated by the TLV packetizer shown in FIG. 2. FIG. FIG. 3 is a diagram illustrating a configuration example of an FEC block configured by the FEC block configuration section illustrated in FIG. 2; FIG. 3 is a diagram illustrating an example of the structure of a hierarchical multiplex frame configured by a hierarchical frame configuration section shown in FIG. 2; FIG. 2 is a diagram showing an example of the configuration of an XMI packet used in a distribution system according to an embodiment of the present invention. 3 is a diagram illustrating an example of division of frames by layer by the XMI packetization unit illustrated in FIG. 2. FIG. FIG. 7 is a diagram showing an example of outputting an XMI packet by a conventional packet transmission scheduler section when the number of layers is two. FIG. 7 is a diagram showing an example of outputting an XMI packet by a conventional packet transmission scheduler section when the number of layers is three. FIG. 3 is a diagram showing an example of output of an XMI packet by the packet transmission scheduler section shown in FIG. 2 when the number of layers is two. FIG. 3 is a diagram showing an example of outputting an XMI packet by the packet transmission scheduler section shown in FIG. 2 when the number of layers is three. 1 is a block diagram showing a configuration example of a modulation device according to an embodiment of the present invention. FIG. FIG. 3 is a diagram showing an FEC block and an OFDM frame. FIG. 7 is a diagram showing a configuration example of an STLP packet used in a distribution system according to a modification of the present invention.

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

(Distribution system)
FIG. 1 is a diagram showing a configuration example of a distribution system 1 according to an embodiment of the present invention. The distribution system 1 shown in FIG. 1 includes a performance hall 10 and a broadcasting hall 20. The performance hall 10 includes a multiplexing device 11 (11a, 11b) and a re-multiplexing device 12. The broadcasting station 20 includes a modulation device 21 and a transmission device 22. The performance hall 10 and the broadcasting hall 20 are connected via a content transmission line 30 as a network.

The performance hall 10 performs hierarchical transmission in which data of a plurality of hierarchies is transmitted through one channel. In FIG. 1, data in two layers, A layer and B layer, is transmitted, but the number of layers in layer transmission is not limited to two layers. In addition, the performance hall 10 uses a low-latency channel (LLch), which does not perform processing such as time interleaving, in order to deliver highly immediate information such as emergency earthquake early warnings to viewers with low latency. A delay transmission channel is provided, and LLch data is transmitted on the same channel as the A layer and the B layer.

The multiplexing device 11a multiplexes content signals for layer A (video/audio signals and subtitle signals) input from the outside, packetizes them into packets in a predetermined format, and sends them to the remultiplexer 12 as a package for layer A. Output.

Similarly, the multiplexer 11b multiplexes content signals for the B layer input from the outside, packetizes them into packets in a predetermined format, and outputs them to the remultiplexer 12 as a package for the B layer.

In this embodiment, it is assumed that the multiplexing device 11 packetizes the data into MMTP (MMT Protocol) packets, which are MMT (MPEG Media Transport) format packets. The transmission path between the multiplexer 11 and the re-multiplexer 12 is an IP (Internet Protocol) transmission path, and the multiplexer 11 stores MMTP packets in IP packets and re-multiplexes them as MMTP/IP packets. Output to device 12.

The re-multiplexing device 12 generates XMI packets from the MMTP/IP packets input from the multiplexing devices 11a and 11b and the MMTP/IP packets of the LLch signal, and further multiplexes the XMI packets into one system and sends them as content transmission signals to the broadcasting station. Output to 20.

The modulator 21 modulates the XMI packet input from the remultiplexer 12 to configure an OFDM frame, and outputs the OFDM frame to the transmitter 22.

The transmitting device 22 generates broadcast waves according to the packets input from the modulating device 21, and transmits them to the outside of the broadcasting station 20 via an antenna.

(remultiplexer)
Next, a remultiplexing device 12 according to an embodiment of the present invention will be described. Remultiplexer 12 need not be dedicated hardware, but may be in the form of computer software.

FIG. 2 is a block diagram showing a configuration example of the remultiplexing device 12 when the number of layers is two. The remultiplexing device 12 shown in FIG. 2 includes a packet filter 101 (101a to 101c), an IP header compression section 102 (102a to 102d), a TLV (Type Length Value) packetization section 103 (103a to 103d), FIFO (First in, First Out) buffer 104 (104a to 104d), FEC (Forward Error Correction) block configuration unit 105 (105a, 105b), hierarchical frame configuration unit 106 (106a, 106b), and XMI packetization 107, an L0 symbol configuration unit 108, an L1 symbol configuration unit 109, a synchronization control XMI packet configuration unit 110, a stuff XMI packet configuration unit 111, and a packet transmission scheduler unit 112.

The packet filter 101a, the IP header compression unit 102a, the TLV packetization unit 103a, the FIFO buffer 104a, the FEC block configuration unit 105a, and the hierarchical frame configuration unit 106a are provided corresponding to the A layer.

The packet filter 101a receives an MMTP/IP packet containing a content signal for layer A from the multiplexer 11a. The packet filter 101a determines which packets to transmit based on the source IP address, destination IP address, protocol type, source port number, destination port number, etc. of the IP header of the input MMTP/IP packet. (packet filtering) and outputs the selected MMTP/IP packet to the IP header compression unit 102a.

The IP header compression unit 102a compresses the IP header of the MMTP/IP packet input from the packet filter 101a as needed, and outputs it to the TLV packetization unit 103a.

The TLV packetizer 103a encapsulates the MMTP/IP packet input from the IP header compressor 102a into a variable-length TLV packet, generates a TLV packet, and outputs the TLV packet to the FIFO buffer 104a.

FIG. 3 is a diagram showing an example of the structure of a TLV packet. In addition, below, the number attached to each field (area) indicates an example of the number of bits of each field.

As shown in FIG. 3, the TLV packet includes a reserved area, a packet type area, a data length area, and a data area. The packet type indicates the type of TLV packet. Depending on the packet type, it is specified whether the TLV packet is IPv4, IPv6, or compressed IP. The data length indicates the size of data stored in the data area. The TLV packetizer 103a stores the IP packet input from the IP header compressor 102a in a data area. Note that for the reserved area, all bits may be set to "1", for example.

Referring again to FIG. 2, the FIFO buffer 104a stores the TLV packets input from the TLV packetization unit 103a, and outputs the stored TLV packets to the FEC block configuration unit 105a in the order in which they were stored.

The FEC block configuration unit 105a configures FEC blocks at regular intervals from the TLV packets input from the FIFO buffer 104a, and outputs the FEC blocks to the hierarchical frame configuration unit 106a.

FIG. 4 is a diagram showing an example of the configuration of the FEC block. As shown in FIG. 4, the FEC block includes an FEC block header area, a main signal area, a BCH parity area, an LDPC (Low Density Parity Check) parity area, and may further include a stuff bit area. Note that although FIG. 4 shows one main signal area and one BCH parity area, each may be divided into a plurality of areas.

The main signal area stores TLV packets output from the FIFO buffer 104a. The FEC block header area contains the beginning position of the first TLV packet stored in the main signal area of the FEC block, specifically, the position of the first byte of the first TLV packet stored in the FEC block. Information indicated by the number of bytes from the beginning of the FEC block excluding the header is stored. Bit “1” is stored in all of the BCH parity area, stuff bit area, and LDPC parity area.

Note that three types of FEC block sizes are set according to the code length (Short, Middle, Long) of LDPC encoding performed by the modulation device 21. Furthermore, the sizes of the main signal area, stuff bit area, and LDPC parity area are determined according to the coding rate. The BCH parity area is fixed at 24 bytes.

The FEC block configuration unit 105a concatenates the TLV packets input from the FIFO buffer 104a in output order and stores them in the main signal area, and sets the value of the first TLV instruction field for each FEC block. Note that when the TLV packet to be stored in the main signal area does not exist in the FIFO buffer 104a, the FEC block configuration unit 105a stores a null type TLV packet in the main signal area.

Referring again to FIG. 2, the hierarchical frame configuration unit 106a configures a hierarchical frame from the FEC block input from the FEC block configuration unit 105a, and outputs it to the XMI packetization unit 107.

FIG. 5 is a diagram showing the structure of a hierarchical frame. As shown in FIG. 5, the hierarchical frame is composed of FEC block areas. The FEC block area stores concatenated FEC blocks output from the FEC block configuration unit 105a and fragments of FEC blocks. Note that the size of each hierarchical frame is determined according to the modulation method, FFT size, guard interval ratio, pilot signal ratio, and number of segments.

The hierarchical frame configuration unit 106a concatenates the FEC blocks input from the FEC block configuration unit 105a in the order of input, and stores them in the FEC block area.

Referring to FIG. 2 again, the packet filter 101b, the IP header compression unit 102b, the TLV packetization unit 103b, the FIFO buffer 104b, the FEC block configuration unit 105b, and the hierarchical frame configuration unit 106b are provided corresponding to the B layer. ing. Since the configuration corresponding to the A hierarchy and the configuration corresponding to the B hierarchy are the same, the description of the configuration corresponding to the B hierarchy will be omitted.

The XMI packetization unit 107 generates an XMI packet in which content signals for each layer are stored in an FEC block format.

FIG. 6 shows the packet structure of the XMI packet. The XMI packet includes a header and a data unit area. The header of the XMI packet includes an IPv4 header, a UDP header, a header of an MMTP packet (MMTP header), and an XMI header. The XMI packet includes an XMI packet whose data unit area contains synchronization control information (Fig. 6 (a)), an XMI packet whose data unit area contains a data unit (Fig. 6 (b)), and a data unit. There are four types of XMI packets: an XMI packet whose area includes a data unit and stuff bits (FIG. 6(c)), and an XMI packet whose data unit area includes stuff bits (FIG. 6(d)).

The synchronization control information is information indicating parameters for configuring an OFDM frame, timing for transmitting an OFDM frame, TMCC (Transmission and Multiplexing Configuration and Control) information, and the like. A data unit is data obtained by dividing a hierarchical frame into predetermined sizes. Furthermore, in FIGS. 6(b), 6(c), and 6(d), an LLch information area for storing L0 symbols and L1 symbols is provided.

The XMI header includes data unit type information indicating the type of object to be stored in the data unit area of the XMI packet. Therefore, when configuring the XMI packet, the synchronous control XMI packet configuration unit 110 sets the data unit type information to a value (for example, '0') that corresponds to the synchronous control XMI packet. Furthermore, when configuring the XMI packet, the XMI packetization unit 107 sets the data unit type information to a value (for example, '1') corresponding to the XMI packet of the A layer or a value (for example, '1') corresponding to the XMI packet of the B layer. 2'). Furthermore, when configuring the XMI packet, the stuff XMI packet configuration unit 111 sets a value corresponding to the stuff XMI packet (for example, '4' or '15') in the data unit type information. By doing so, it is possible to specify the type of object to be stored in the XMI packet.

FIG. 7 is a diagram showing an example of division of frames by layer by the XMI packetization unit 107. As shown in FIG. 7, the XMI packetizer 107 divides the hierarchical frame into predetermined sizes (10,448 bits in FIG. 7) to form data units. The XMI packetizer 107 stores the data unit in the data unit area of the XMI packet. Note that, as shown in FIG. 7, the last data unit may be less than a predetermined size (in FIG. 7, less than 10448 bits). In this case, the XMI packetizer 107 adds predetermined bits (stuff bits) to a data unit that is less than a predetermined size to make it a predetermined size, and stores it in the data unit area.

The packet filter 101c, the IP header compression units 102c and 102d, the TLV packetization units 103c and 103d, the FIFO buffers 104c and 104d, the L0 symbol configuration unit 108, and the L1 symbol configuration unit 109 are provided corresponding to the LLch.

LLch MMTP/IP packets are input to the packet filter 101c. The packet filter 101c selects packets to be transmitted (packet filtering) based on the source IP address, destination IP address, protocol type, source port number, destination port number, etc. of the IP header of the input IP packet. , outputs the selected MMTP/IP packet to the IP header compression section 102c or the IP header compression section 102d.

The IP header compression unit 102c compresses the IP header of the MMTP/IP packet input from the packet filter 101c as needed, and outputs it to the TLV packetization unit 103c. The IP header compression unit 102d compresses the IP header of the MMTP/IP packet input from the packet filter 101c as necessary, and outputs the compressed IP header to the TLV packetization unit 103d.

The TLV packetizer 103c encapsulates the MMTP/IP packet input from the IP header compressor 102c into a TLV packet, generates a TLV packet, and outputs the TLV packet to the FIFO buffer 104c. The TLV packetizer 103d encapsulates the MMTP/IP packet input from the IP header compressor 102d into a TLV packet, generates a TLV packet, and outputs the TLV packet to the FIFO buffer 104d.

The FIFO buffer 104c stores the TLV packets input from the TLV packetization unit 103c, and outputs the stored TLV packets to the L0 symbol configuration unit 108 in the order in which they were stored. The FIFO buffer 104d stores the TLV packets input from the TLV packetization unit 103d, and outputs the stored TLV packets to the L1 symbol configuration unit 109 in the order in which they were stored.

L0 symbol configuration section 108 configures a symbol (L0 symbol) from the TLV packet input from FIFO buffer 104c, and outputs it to XMI packetization section 107. The L1 symbol configuration section 109 configures symbols (L1 symbols) from the TLV packets input from the FIFO buffer 104d, and outputs them to the XMI packetization section 107.

For example, the L0 symbol is transmitted in 9 segments for partial reception, and the L1 symbol is transmitted in the other 24 or 26 segments. Therefore, packet filtering by the packet filter 101c is also performed according to such allocation.

Note that the number of bits of the L0 symbol and L1 symbol per 1 OFDM frame, where the number of segments is N, is 4 x N x 223 bits for 8K FFT, 8 x N x 111 bits for 16K FFT, and 16 x 55 for 32K FFT. ×N bits. That is, when 9 segments are allocated to the L0 symbol and 24 segments are allocated to the L1 symbol, in the case of 16K FFT, the L0 symbol per OFDM frame has a size of 7992 bits and the L1 symbol has a size of 21312 bits. The L0 symbol configuration unit 108 configures the L0 symbol by allocating each byte of the TLV packet input from the FIFO buffer 104c in MSB (Most Significant Bit) first to the L0 symbol having such a size, and outputs the L0 symbol to the packet transmission scheduler unit 112. do. Similarly, the L1 symbol configuration section 109 configures the L1 symbol by allocating each byte of the TLV packet inputted from the FIFO buffer 104d, MSB first, to the L1 symbol having such a size, and outputs the L1 symbol to the packet transmission scheduler section 112. Here, MSB first refers to forming a string of bits starting with the most significant bit of each byte constituting the TLV packet.

The synchronization control XMI packet configuration unit 110 stores synchronization control information indicating information regarding transmission control such as transmission parameters for the modulation device 21 to configure the OFDM frame, timing for transmitting the OFDM frame, and TMCC information in the data unit area. An XMI packet (synchronous control XMI packet) is generated and output to the packet transmission scheduler section 112. Note that if the synchronization control information does not meet the predetermined size for dividing the hierarchical frame, the synchronization control Store.

The stuff XMI packet configuration section 111 configures an XMI packet (stuff XMI packet) in which only stuff bits of the same size as the data unit are stored in the data unit area, and outputs it to the packet transmission scheduler section 112. The stuff XMI packets are used to keep the number of XMI packets output by the remultiplexer 12 constant every second even when modulation methods and coding rates differ.

The packet transmission scheduler unit 112 receives an XMI packet input from the XMI packetization unit 107 , an XMI packet (synchronous control XMI packet) input from the synchronous control XMI packet configuration unit 110 , and an XMI packet ( stuff XMI packet) is output to the modulation device 21.

The packet transmission scheduler unit 112 outputs one synchronous control XMI packet at the beginning of the OFDM frame. Subsequently, the packet transmission scheduler unit 112 outputs the XMI packets of each layer (layer A XMI packet and layer B XMI packet). After outputting all the XMI packets of each layer, the packet transmission scheduler unit 112 outputs stuffed XMI packets so that the number of XMI packets configuring the OFDM frame becomes a constant number. Note that the packet transmission scheduler unit 112 may output, for example, at least one stuff XMI packet to indicate the end of outputting the XMI packet in the OFDM frame.

(Conventional XMI packet sending algorithm)
For comparison with the present invention, the XMI packet sending algorithm of the conventional packet sending scheduler section will be described.

FIG. 8 is a diagram showing an example of an output of an XMI packet by a conventional packet transmission scheduler section when the number of layers is two. The numbers of XMI packets in layer A and layer B in one OFDM frame are K and L, respectively. The conventional packet transmission scheduler unit ceils (L /K) output. Here, ceil(x) is a ceiling function and represents the smallest integer greater than or equal to argument x. When the parameters of OFDM transmission are the values shown in Table 1, as shown in FIG. 8, K=311, L=1050, and ceil(L/K)=4.

As described above, in the example shown in FIG. 8, the conventional packet transmission scheduler section repeatedly outputs a packet set consisting of one layer A XMI packet and four layer B XMI packets 262 times. If L/K is not an integer as in this example, a fraction is generated at the end. In order to send the fractional number of XMI packets, the conventional packet transmission scheduler unit subsequently outputs one XMI packet of the A layer and two XMI packets of the B layer, and then outputs the last remaining XMI packet of the A layer. Outputs 48 pieces.

FIG. 9 is a diagram showing an example of output of an XMI packet by a conventional packet transmission scheduler unit when the number of layers is three. The numbers of XMI packets in layer A, layer B, and layer C in one OFDM frame are K, L, and M, respectively. The conventional packet transmission scheduler unit ceils (L /K) and outputs ceil (M/K) C layer XMI packets. Here, when the parameters of OFDM transmission are the values shown in Table 2, as shown in FIG. 9, K=311, L=1050, M=388, ceil(L/K)=4, ceil M/K)=2.

In the example shown in FIG. 9, the conventional packet transmission scheduler unit generates a packet set consisting of one layer A XMI packet, four layer B XMI packets, and two layer C XMI packets. Output repeatedly 194 times. If L/K and M/K are not integers as in this example, a fraction is generated at the end. The conventional packet transmission scheduler unit subsequently repeats a packet set consisting of one layer A XMI packet and four layer B XMI packets 68 times in order to send the fractional number of XMI packets. Subsequently, one XMI packet of layer A and two XMI packets of layer B are output, and finally the remaining 48 XMI packets of layer A are output.

By outputting XMI packets in this manner, the output ratio of XMI packets for each layer is constant, except when fractions are sent. However, at the end of the transmission, the XMI packets of layer A are consecutively transmitted, resulting in a biased transmission, and the number of input packets is insufficient compared to the packets required for the buffer area of the input stage of the modulation device that receives the packets. This causes an operation called buffer underflow, which may cause the modulation device to malfunction.

(XMI packet sending algorithm according to the present invention)
Therefore, the packet transmission scheduler unit 112 according to the present invention changes the XMI packet transmission algorithm.

First, a case where the number of layers is two will be explained. In one OFDM frame, the number of XMI packets in the first layer (layer A) is K, and the number of XMI packets in the second layer (layer B), which has more XMI packets than the first layer, is L. That is, K<L. The packet transmission scheduler unit 112 sends a first packet set consisting of one A-layer XMI packet and ceil (L/K) B-layer XMI packets, one A-layer XMI packet, and the floor ( A second packet set consisting of L/K) B layer XMI packets is repeatedly output. Here, floor(x) is a floor function and represents the largest integer less than or equal to the argument x.

The packet transmission scheduler section 112 outputs the first packet set and the second packet set a predetermined number of times. For example, the packet transmission scheduler unit 112 may repeat one of the first packet set and the second packet set one or more times and then repeatedly output the other one or more times, or repeatedly output the first packet set together and then repeatedly output the other one or more. The second packet set may be collectively and repeatedly output, or the second packet set may be collectively and repeatedly output, and then the first packet set may be collectively and repeatedly output. Furthermore, in each packet set, the position of the first layer XMI packet is not limited to the beginning, but may be placed at any position.

FIG. 10 is a diagram showing an example of output of an XMI packet by the packet transmission scheduler section 112 according to the present invention when the number of layers is two. Here as well, as in the example shown in FIG. /K)=3.

In the example shown in FIG. 10, the packet transmission scheduler unit 112 repeatedly outputs the first packet set consisting of one A layer XMI packet and four B layer XMI packets 117 times, and then outputs one A layer XMI packet. A second packet set consisting of a layer XMI packet and three B layer XMI packets is repeatedly output 194 times.

Note that the number of repetitions K* of the second packet set and the number of repetitions K** of the first packet set are expressed by the following formula.
K*=(K×floor(L/K))+K−L=194
K**=K-K*=117

Next, a case where the number of layers is three will be explained. In one OFDM frame, the number of XMI packets in the first layer (layer A) is K, the number of XMI packets in the second layer (layer B) where the number of XMI packets is greater than the first layer is L, and the number of XMI packets is Let M be the number of XMI packets in the third layer (layer C), which is larger than the first layer and smaller than the second layer. That is, K<M<L. The packet transmission scheduler unit 112 generates a first packet set consisting of one A-layer XMI packet, ceil (L/K) B-layer XMI packets, and ceil (M/K) C-layer XMI packets. and a second packet set consisting of one A-layer XMI packet, ceil (L/K) B-layer XMI packets, and floor (M/K) C-layer XMI packets, and one A third packet set consisting of an A-layer XMI packet, floor(L/K) B-layer XMI packets, and floor(M/K) C-layer XMI packets is repeatedly output. The packet transmission scheduler unit 112 outputs each of the first packet set, the second packet set, and the third packet set a predetermined number of times.

FIG. 11 is a diagram showing an example of output of an XMI packet by the packet transmission scheduler section 112 according to the present invention when the number of layers is three. Here, as in the example shown in FIG. 9, if the number of XMI packets in the A layer in one OFDM frame K = 311, the number of XMI packets in the B layer L = 1050, and the number of XMI packets in the C layer M = 388, then ceil (L/K)=4, floor(L/K)=3, ceil(M/K)=2, floor(M/K)=1.

In the example shown in FIG. 11, the packet transmission scheduler unit 112 sends the first packet set consisting of one layer A XMI packet, four layer B XMI packets, and two layer C XMI packets 77 times. After repeatedly outputting, a second packet set consisting of one A-layer XMI packet, four B-layer XMI packets, and one C-layer XMI packet is repeatedly output 40 times, and then one A third packet set consisting of an A-layer XMI packet, three B-layer XMI packets, and one C-layer XMI packet is repeatedly output 194 times.

Note that the number h of outputting ceil (L/K) B layer XMI packets per one A layer XMI packet, and the number h of outputting ceil (L/K) B layer XMI packets for one A layer XMI packet, The number i of outputting XMI packets is expressed by the following equation.
h=L-(K*floor(L/K))=117
i=Kh=194
In addition, the number j of outputting ceil (M/K) C layer XMI packets per one A layer XMI packet, and the number j of outputting ceil (M/K) C layer XMI packets per one A layer The number of times k to output XMI packets is expressed by the following equation.
j=M-(K*floor(M/K))=77
k=K-j=234

(Modulation device)
Next, a modulation device 21 according to an embodiment of the present invention will be described. The modulation device 21 does not need to be dedicated hardware, and may be in the form of computer software.

FIG. 12 is a block diagram showing a configuration example of the modulation device 21 when the number of layers is two. The modulating device 21 shown in FIG. 12 includes a packet receiving section 201, a layer separating section 202, a layer-specific frame generating section 203, an FEC block forming section 204, an energy spreading section 205, an error correction encoding section 206, Bit interleaving unit 207, mapping unit 208, layer combining unit 209, frame header adding unit 210, time/frequency interleaving unit 211, TMCC analysis unit 212, LLch frame generation unit 213, LLch modulation unit 214. , a pilot signal generation section 215, an OFDM frame configuration section 216, and an OFDM transmission processing section 217.

Packet receiving section 201 receives the content transmission signal from remultiplexing device 12 , removes the IPv4 header and UDP header from the XMI packet, and outputs it to layer separation section 202 .

The layer separation unit 202 identifies the type of each XMI packet by referring to data unit type information included in the XMI header of the XMI packet. Then, the layer separation unit 202 separates packets belonging to each layer and distributes them to the processing systems of each layer. Further, data of a channel (for example, emergency earthquake early warning) that is transmitted with a lower delay compared to each layer is output to the LLch frame generation unit 213. Furthermore, the layer separation section 202 outputs synchronization control information to the TMCC analysis section 212.

The hierarchical frame generation section 203 concatenates the data units included in the A layer XMI packet input from the layer separation section 202, generates a frame of the A layer, and outputs the frame to the FEC block forming section 204. Further, the hierarchical frame generation section 203 concatenates the data units included in the B layer XMI packet input from the layer separation section 202, generates a B layer frame, and outputs it to the FEC block forming section 204.

FEC block forming section 204 forms FEC blocks for each layer and outputs them to energy diffusion section 205 .

Energy spreading section 205 performs energy spreading processing on the FEC block input from FEC block forming section 204 and outputs it to error correction encoding section 206 .

The error correction encoding section 206 performs error correction encoding (in this embodiment, LDPC encoding) on the signal input from the energy spreading section 205 to enable correction of transmission errors on the receiving side of the OFDM signal. Generate a signal. Then, error correction encoding section 206 outputs the generated encoded signal to bit interleaving section 207.

In order to improve the performance of the error correction code, the bit interleaving unit 207 generates bit data by interleaving the encoded signal inputted from the error correction encoding unit 206 in units of bits. Then, bit interleaving section 207 outputs the generated bit data to mapping section 208.

Mapping section 208 maps the bit data input from bit interleaving section 207 onto the IQ plane, and generates carrier symbols subjected to carrier modulation according to the modulation method. Then, mapping section 208 outputs the generated carrier symbol to hierarchical combining section 209.

Layer combining section 209 combines carrier symbols input from mapping section 208 of each layer, and outputs the combined carrier symbols to frame header adding section 210 .

Frame header adding section 210 adds a frame header to the carrier symbol input from layer combining section 209 and outputs it to time/frequency interleaving section 211 .

The time/frequency interleaving unit 211 rearranges the order of carrier symbols input from the frame header adding unit 210 in the time direction and frequency direction to generate an interleaved signal subjected to interleaving processing. The time/frequency interleaving unit 211 then outputs the generated interleaved signal to the OFDM frame configuring unit 216.

TMCC analysis section 212 generates a TMCC signal from the synchronization control information input from layer separation section 202 and outputs it to OFDM frame composition section 216.

LLch frame generation section 213 generates an LLch frame by concatenating the L0 symbol and L1 symbol included in the XMI packet input from layer separation section 202, and outputs the LLch frame to LLch modulation section 214.

LLch modulation section 214 modulates the data input from layer separation section 202 using a predetermined modulation method (for example, DBPSK) to generate symbols, and outputs the symbols to OFDM frame configuration section 216.

Pilot signal generation section 215 generates pilot signals (SP signal and CP signal) and outputs them to OFDM frame configuration section 216.

OFDM frame configuration section 216 combines the interleaved signal input from time/frequency interleaving section 211 with the TMCC signal input from TMCC analysis section 212, the symbol input from LLch modulation section 214, and the pilot signal input from pilot signal generation section 215. is inserted to construct an OFDM frame. Then, the OFDM frame configuration section 216 outputs the generated OFDM frame to the OFDM transmission processing section 217.

The OFDM transmission processing unit 217 performs OFDM modulation processing on the OFDM frame input from the OFDM frame configuration unit 216 to generate an OFDM signal, and transmits the generated OFDM signal to the receiving device. More specifically, the OFDM transmission processing unit 217 performs IFFT (Inverse Fast Fourier Transform) processing on the OFDM symbols of the OFDM frame input from the OFDM frame configuration unit 216 to obtain effective symbols in the time domain. Generate a signal. Then, the OFDM transmission processing unit 217 inserts a guard interval at the beginning of the effective symbol signal, and then performs orthogonal modulation processing and D/A conversion processing to generate an OFDM signal.

As described above, according to the present invention, it is possible to suppress bias in the output ratio of XMI packets for each layer in the remultiplexing device 12, and therefore it is possible to prevent buffer underflow in the modulation device 21. .

(Modified example)
Next, a modification of the above-described distribution system 1 will be described. As described with reference to FIG. 6, in order to maintain a fixed length of the XMI packet, stuffing is performed by adding stuff bits to synchronization control information and data units that are less than the packet length. Furthermore, if there is no data, stuff bits are sent as shown in FIG. 6(d) to maintain a constant rate. However, in this configuration, since the parity area of the FEC block is filled with nulls, unnecessary packets will be sent to the line, and there is a risk of an increase in the transmission rate and packet loss on the line.

FIG. 13 is a diagram showing an FEC block and an OFDM frame. Here, an example is shown in which the coding rate is 7/16 and the code length is Middle. In this case, the LDPC parity occupies 9/16 (4860 bytes) of the 8640 bytes of the FEC block.

Therefore, the distribution system 1 according to the modification uses STLP (Studio to Transmitter Link Protocol) packets, which are slimmed down XMI packets, instead of XMI packets for sending and receiving content transmission. The remultiplexer 12 constructs an FEC block and an OFDM frame from the TLV packet as described above (see FIGS. 4 and 5), and divides the OFDM frame into XMI packets (see FIG. 7). On the other hand, in STLP packets, TLV packets are stored without using FEC blocks. That is, the STLP packet is a packet in which content signals for each layer are stored in a TLV packet format.

The packet receiving unit 201 of the modulation device 21 according to the modification converts the received STLP packet into an XMI packet. When the modulation device 21 is capable of receiving both XMI packets and STLP packets, the packet receiving unit 201 determines whether the received packet is an XMI packet or an STLP packet. When the received packet is an XMI packet, the packet receiving unit 201 removes the IPv4 header and UDP header from the XMI packet and outputs it to the layer separation unit 202. When the received packet is an STLP packet, the packet receiving unit 201 converts the STLP packet into an XMI packet, removes an IPv4 header and a UDP header from the XMI packet, and outputs it to the layer separation unit 202. The subsequent processing is the same as that of the modulation device 21 described above.

Next, a specific example of the STLP packet will be explained. FIG. 14 is a diagram showing an example of the structure of an STLP packet. FIG. 14(a) shows a synchronization control STLP packet storing synchronization control information, FIG. 14(b) shows an example of a hierarchical data STLP packet storing a TLV packet of hierarchical data, and FIG. ) shows a null STLP packet storing a null TLV packet, and FIG. 14(d) shows a LLch data STLP packet storing a TLV packet of LLch data. Note that the structure of the STLP packet is not limited to this example.

The STLP packet includes an IPv4 header, a UDP header, packet type information, a sequence number, and a timestamp. The packet type information and sequence number are the same as those contained in the XMI header. The STLP packet may include a frame number indicating the frame number of the OFDM frame, and a frame number flag indicating the presence or absence of the frame number.

The synchronization control STLP packet shown in FIG. 14(a) includes synchronization control information. The synchronization control information includes FEC block byte offset information indicating the byte offset of the FEC block from the beginning of the OFDM frame. This makes it possible to configure an FEC block on the broadcasting station 20 side that has received the content transmission signal. Further, the synchronization control information includes TMCC information, time information indicating the time at which the next OFDM frame should be transmitted, and the like.

The layer data STLP packet shown in FIG. 14B and the null STLP packet shown in FIG. A data TLV packet or a null TLV packet. Hierarchical data TLV packets and null TLV packets can be slimmed down by transmitting input IP packets in TLV format without stuffing them to a fixed length. By placing TLV storage byte offset information in front of the TLV packet and obtaining byte offset information from the beginning of the OFDM frame, it is possible to know the beginning of the OFDM frame.

The LLch data STLP packet shown in FIG. 14(d) includes LLch offset information, a synchronization signal, and an LLch data TLV packet. There are two types of LLch data STLP packets: L0ch data STLP packets compatible with partial reception and L1ch data STLP packets compatible with fixed reception, and these are collectively referred to as LLch data STLP packets. By transmitting an input IP packet in TLV format without stuffing the LLch data TLV packet to make it a fixed length, it is possible to slim down the packet.

The synchronous control STLP packet, hierarchical data STLP packet, null STLP packet, and LLch data STLP packet may be distinguished using 3-bit packet type information. For example, as shown in Table 3, by predefining the STLP packet corresponding to the value of the packet type information, the type of the STLP packet can be determined.

The LLch offset information shown in FIG. 14(d) includes a 1-bit LLch start flag, a 1-bit LLch end flag, a 5-bit reserved area, a 9-bit LLch symbol offset, and an 8-bit LLch byte offset.

The LLch symbol offset indicates the first symbol position to which LLch data is allocated, and the LLch byte offset indicates the first carrier position to which LLch data is allocated. That is, the LLch symbol offset and LLch byte offset can specify the leading position of the carrier symbol when assigning LLch data to an OFDM frame.

The LLch start flag and the LLch end flag indicate whether the LLch data TLV packet after each division is the first part, the last part, or a part other than the first part and the last part when the LLch data TLV packet is divided. Show that. Table 4 shows specific examples of the LLch start flag and LLch end flag.

As described above, according to the modified example, content is transmitted using a slimmed packet structure, and the broadcasting station 20 (modulation device 21) generates FEC blocks and OFDM frames, so the transmission rate can be reduced. It becomes possible to transmit video and audio at a rate close to the data capacity of the original data.

(program)
In order to function as the remultiplexing device 12 or the modulating device 21 described above, it is also possible to use a computer capable of executing program instructions. The computer stores in its storage a program that describes the processing contents for realizing each function of the remultiplexing device 12 or the modulating device 21, and reads and executes this program by the processor of the computer. A part of these processing contents may be realized by hardware. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (Personal Computer), an electronic notepad, or the like. Program instructions may be program code, code segments, etc. to perform necessary tasks. The processor may be a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), or the like.

Further, this program may be recorded on a computer-readable recording medium. Using such a recording medium, it is possible to install a program 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, but may be a recording medium such as a CD-ROM or a DVD-ROM. Moreover, this program can also be provided by downloading via a network.

Although the embodiments described above have been described as representative 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 invention. Therefore, the present invention should not be construed as being limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims. For example, it is possible to integrate a plurality of configuration blocks described in the configuration diagram of the embodiment, or to divide one configuration block.

1 Distribution system 10 Performance hall 11 Multiplexing device 12 Re-multiplexing device 20 Broadcasting station 21 Modulation device 22 Transmitter 30 Content transmission line 101 Packet filter 102 IP header compression unit 103 TLV packetization unit 104 FIFO buffer 105 FEC block configuration unit 106 Hierarchical frame configuration unit 107 XMI packetization unit 108 L0 symbol configuration unit 109 L1 symbol configuration unit 110 Synchronization control XMI packet configuration unit 111 Stuff XMI packet configuration unit 112 Packet transmission scheduler unit 201 Packet reception unit 202 Layer separation unit 203 Hierarchical frame Generation unit 204 FEC block formation unit 205 Energy spreading unit 206 Error correction coding unit 207 Bit interleaving unit 208 Mapping unit 209 Hierarchical synthesis unit 210 Frame header addition unit 211 Time/frequency interleaving unit 212 TMCC analysis unit 213 LLch frame generation unit 214 LLch Modulation unit 215 Pilot signal generation unit 216 OFDM frame configuration unit 217 OFDM transmission processing unit

Claims (5)

A remultiplexer for transmitting packets to a modulator, the remultiplexer comprising:
an XMI packetization unit that generates an XMI packet storing layered content signals in an FEC block format;
When the number of XMI packets in the first layer and second layer in one OFDM frame is K and L (K<L), respectively,
a first packet set consisting of one first layer XMI packet and ceil (L/K) second layer XMI packets;
a second packet set consisting of one first layer XMI packet and floor (L/K) second layer XMI packets;
a packet transmission scheduler section that repeatedly outputs the
A remultiplexing device comprising: A remultiplexer for transmitting packets to a modulator, the remultiplexer comprising:
an XMI packetization unit that generates an XMI packet storing layered content signals in an FEC block format;
When the numbers of XMI packets in the first layer, second layer, and third layer in one OFDM frame are respectively K, L, and M (K<M<L),
a first packet set consisting of one first layer XMI packet, ceil (L/K) second layer XMI packets, and ceil (M/K) third layer XMI packets;
a second packet set consisting of one first layer XMI packet, ceil(L/K) second layer XMI packets, and floor(M/K) third layer XMI packets;
a third packet set consisting of one first layer XMI packet, floor (L/K) second layer XMI packets, and floor (M/K) third layer XMI packets;
a packet transmission scheduler section that repeatedly outputs the
A remultiplexing device comprising: A modulation device that receives an STLP packet in which layered content signals are stored in a TLV packet format, the modulation device comprising:
a packet receiving unit that converts the received STLP packet into an XMI packet storing layered content signals in an FEC block format;
a data processing unit that performs error correction encoding processing and interleaving processing on the FEC block;
an OFDM frame configuration unit that configures an OFDM frame by inserting a TMCC signal and a pilot signal into the data processed by the data processing unit;
A modulation device comprising: A program for causing a computer to function as the remultiplexing device according to claim 1 or 2. A program for causing a computer to function as the modulation device according to claim 3.

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