JP5086980B2 - Transmitting terminal, receiving terminal and transmission system used in one-way transmission path - Google Patents

Description

  The present invention relates to a transmission technique for packetizing and transmitting a file in a one-way transmission path from a transmission terminal to a reception terminal.

  Conventionally, a service for downloading content using a unidirectional transmission path such as a broadcast transmission path is known. In such a content download service, a file is divided and stored in a plurality of packets for transmission. In this file transmission method, a transmission terminal generates and transmits a redundant packet based on a packet generated by dividing a file by an error correction method called FEC (Forward Error Correction). Then, the receiving terminal receives the redundant packet transmitted by the transmitting terminal and restores the missing packet. Thereby, it is possible to maintain a certain file transmission quality in the one-way transmission path without using a return channel (uplink from the receiving terminal to the transmitting terminal).

  As an error correction method of FEC, for example, there is a block encoding method in which block encoding is performed on a certain number of packets to generate redundant packets. In this block coding method, the size of the block to be coded varies, so the transmission quality varies greatly depending on the file size and the block coding method. Examples of block coding schemes include Raptor code shown in RFC 5053, LDPC code shown in RFC5170, Reed-Solomon code, and “Forward Error Correction for Real-Time Video Transport Audio / Audio Transport IP” shown in SMPTE Specification 2022-1. Etc. are known.

  In this way, in a system that divides a file into packets and transmits the packets via a one-way transmission path, the FEC error correction technique is used to restore the lost packets and to maintain a certain file transmission quality. Is maintained.

  By the way, FLUTE is known as a file transmission method using a unidirectional transmission path (see Non-Patent Document 1 and Patent Document 1). FLUTE is to transmit file attribute information and a file body as one object each time a file is packetized and transmitted. The attribute information of the file is described as FDT (File Delivery Table), and is handled as one object like the file body. That is, the transmitting terminal transmits a FLUTE packet of file attribute information as an object, and subsequently transmits a FLUTE packet of the file body as an object.

  Also in the broadcast transmission path, IP packets can be multiplexed using a new multiplexing method for storage-type broadcasting service (see Non-Patent Document 2). Thus, conventionally, a mechanism for dividing a content file into IP packets and transmitting it has been studied.

“FLUTE-File Delivery over Unidirectional Transport”, RFC 3926 "Information and Communication Council, Information and Communication Technology Subcommittee (60th) Report of the 60-1-2 Broadcasting System Committee", [online], July 29, 2008, Information and Communication Council, [November 2008] Search on May 12], Internet <URL: http://www.soumu.go.jp/joho_tsusin/policyreports/joho_tsusin/bunkakai/080729_1.html> US Patent Application Publication No. 2004/0153468

  When the FLUTE file transmission method is used, as described above, the file attribute information is handled as one object in the same way as the file body, and therefore, at least two objects need to be transmitted when transmitting one file. . For this reason, since it is necessary to identify the attribute information of the file and the file body by the object ID, in the FLUTE packet, in addition to the object ID for identifying the object, information for identifying the session in which the object is transmitted ( It was necessary to add a TSI (Transport Session Identifier) for each packet. In this case, the individual FLUTE packet includes, in its header, at least information for identifying a session (TSI), information for identifying an object (TOI: Transport Object Identifier), a block number (Source Block Number), And it is necessary to provide a number (Encoding Symbol ID) for identifying data in the block. However, it is desirable that the header has a data amount as small as possible from the viewpoint of improving the transmission efficiency and reducing the processing load.

  Here, a block refers to a set of packets or a set of data units when packets are arranged in the order of transmission when a file is divided into a plurality of data units and packets of the data units are transmitted.

  Also, since the block size (data amount of all data units in one block) differs depending on the application and transmission medium, the number of blocks in one file also differs, and as a result, a number (block number) for specifying the block The number of bits in the field for storing data also varies depending on the application and the transmission medium. However, when the FLUTE file transmission method is used, the block size is fixed (16 bits), and thus it has not been possible to flexibly cope with various block sizes. For example, when a file is transmitted by satellite broadcasting, since the quality of the transmission path is relatively good, the number of redundant packets generated by the FEC error correction method may be small, or the FEC error correction method may be used. No need. Therefore, the amount of data in the file that can be transmitted in one block increases (the number of data units increases), and there is no need to increase the number of blocks in one file, so the number of bits in the block number field is small. That's it. On the other hand, when a file is transmitted by a cellular phone, the quality of the transmission path is not relatively good, so it is necessary to generate a large number of redundant packets by FEC error correction. Therefore, the amount of data that can be transmitted in one block is reduced (the number of data units is reduced), and the number of blocks in one file needs to be increased. Therefore, the number of bits in the block number field needs to be increased. As described above, when the FLUTE file transmission method is used, there is no flexibility to cope with an appropriate block size according to the application and the transmission medium.

  Therefore, the present invention has been made to solve the above-mentioned problems, and its object is to reduce the amount of header information and to reduce the amount of header information when a file is packetized and transmitted via a one-way transmission path. An object of the present invention is to provide a transmission terminal, a reception terminal, and a transmission system that can flexibly cope with various block sizes according to a medium.

  In order to solve the above problems, a transmitting terminal according to the present invention generates file attribute information, generates a unit by dividing a file body, stores the attribute information in a packet, transmits the unit, and transmits a plurality of the units. The number of bits of a field to which a block number for identifying the block is assigned and attribute information stored in the packet in a transmission terminal used for a one-way transmission path that stores and transmits the unit in a packet for each block consisting of And an attribute information generating unit for generating attribute information including data defining the number of bits of a field to which a sequence number for specifying a unit is assigned, and generating header information including the block number and the sequence number. A header information adding unit for adding information to the attribute information and the unit. And wherein the door.

  The transmission terminal according to the present invention is characterized in that the header information adding unit generates header information having a block number and a sequence number of 0, and adds the header information to the attribute information.

  In the transmission terminal according to the present invention, the attribute information generation unit generates attribute information including the number of bits of the field to which the block number is assigned and the number of bits of the field to which the sequence number is assigned, or When the number of bits of the field to which both the block number and sequence number are assigned is fixed, the attribute information including the number of bits of the field to which either the block number or the sequence number is assigned is generated. It is characterized by.

  In addition, when the transmitting terminal according to the present invention divides the attribute information, and stores and transmits the divided attribute information in a packet, the attribute information generation unit further determines the number of the attribute information divided. Attribute information including data for specifying is generated.

  The transmission terminal according to the present invention further includes a header information adding unit that generates header information in which a number subsequent to the sequence number of the attribute information is a unit sequence number, and the same attribute information between the blocks is transmitted to each block. It transmits before the unit which comprises.

  In addition, the transmitting terminal according to the present invention, when transmitting the attribute information before the units constituting the block, adds header information for generating header information in which the number subsequent to the sequence number of the attribute information is the unit sequence number. And the attribute information is transmitted before a unit constituting at least the first block among all the blocks.

  In the transmitting terminal according to the present invention, the attribute information generating unit generates attribute information including a file name and length in addition to data for specifying the number of bits of the block number and sequence number. It is characterized by.

  The receiving terminal according to the present invention receives a packet storing attribute information of a file and a packet storing a unit for each block obtained by dividing the file body by one-way transmission, and transmits the original file. In the receiving terminal that restores to the above, the attribute information is assigned a bit number of a field to which a block number for specifying the block is assigned, and attribute information stored in the packet and a sequence number for specifying a unit. Data for determining the number of bits of a field to be included, header information including the block number and sequence number is added to the attribute information and unit, and header information based on the attribute information is added. Analyzes the block number and sequence number included in, and obtains attribute information and unit A header information analysis unit, and a file restoration unit that aligns and combines the units acquired by the header information analysis unit based on the block number and sequence number, and restores the original file. And

  The receiving terminal according to the present invention is characterized in that the header information analysis unit acquires attribute information when the block number and sequence number included in the header information are zero.

  The receiving terminal according to the present invention is characterized in that the file restoring unit restores the unit after the attribute information is acquired by the header information analyzing unit to the original file.

  The transmission system according to the present invention is characterized by comprising the transmitting terminal and the receiving terminal.

  As described above, according to the present invention, header information including a block number and a sequence number is added to attribute information and a unit. Thereby, attribute information and a unit can be distinguished by a block number and a sequence number. Therefore, it is not necessary to add dedicated information for identifying the attribute information and the file body, and the amount of header information can be reduced compared to the FLUTE header. That is, improvement in transmission efficiency and reduction in processing load can be realized. In addition, regarding the number of bits in the header information to which the block number and the sequence number are assigned, data for specifying the number of bits is handled as part of the attribute information. Thereby, the number of bits allocated to the block number and sequence number can be changed for each file. Accordingly, since the number of bits defines the block size, various block sizes can be flexibly supported according to the application and the transmission medium.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
[Transmission system]
FIG. 1 is a diagram illustrating a schematic configuration of a transmission system including a transmission terminal and a reception terminal according to an embodiment of the present invention. This transmission system is, for example, a system that realizes a download service in advanced BS digital broadcasting, and includes a transmission terminal 1 and a reception terminal 2. The transmission terminal 1 and the reception terminal 2 are connected by a one-way transmission path 3.

  The transmission terminal 1 is a device that packetizes a file constituting content and metadata, stores file attribute information and a file body in the packet, and transmits the packet to the reception terminal 2 via the one-way transmission path 3. The receiving terminal 2 is a device that receives the packet transmitted by the transmitting terminal 1 via the one-way transmission path 3 and restores the original file. The one-way transmission path 3 is a broadcast transmission path, for example.

[Sending terminal / configuration]
Next, the transmission terminal 1 of the transmission system shown in FIG. 1 will be described. First, the configuration of the transmission terminal 1 will be described. FIG. 2 is a block diagram illustrating a configuration of the transmission terminal 1. The transmission terminal 1 includes a storage unit 11, an attribute information generation unit 12, a unit generation unit 13, a download header addition unit (header information addition unit) 14, and a packet transmission unit 15.

  The storage unit 11 stores content and metadata files transmitted to the receiving terminal 2 using the unidirectional transmission path 3. The attribute information generation unit 12 reads a file from the storage unit 11 and generates attribute information including the name of the file body and the length of the file for the file.

  The unit generation unit 13 reads a file from the storage unit 11, divides the file body into data units of a certain size, and generates a plurality of data units. The unit generation unit 13 generates a parity unit based on the generated plurality of data units, and generates a block including the data unit and the parity unit.

  The download header adding unit 14 adds a download header to the attribute information generated by the attribute information generating unit 12. Also, a download header is added to the data unit and parity unit generated by the unit generator 13.

  The packet transmission unit 15 generates a packet by adding an IP header and a UDP header to the attribute information, data unit, and parity unit to which the download header is added by the download header addition unit 14, or adds a compression header to the packet. It is generated and transmitted to the receiving terminal 2.

  In this way, the transmission terminal 1 generates file attribute information and adds a download header, generates a parity unit from the data unit obtained by dividing the file body, and adds a download header to each of the data unit and the parity unit. . Then, the transmission terminal 1 generates a packet and transmits it to the reception terminal 2 via the one-way transmission path 3.

[Sending terminal / Process]
Next, processing of the transmission terminal 1 will be described. FIG. 3 is a flowchart showing the processing of the transmission terminal 1, and shows a flow of packetizing a file when the transmission terminal 1 transmits a packet via the one-way transmission path 3. FIG. 4 is a schematic diagram for explaining a generation flow of attribute information, units, and blocks.

  First, the attribute information generation unit 12 of the transmission terminal 1 reads a file from the storage unit 11, and generates attribute information including at least the name of the file body and the length of the file (step S1). In this case, the attribute information generation unit 12 divides the generated attribute information into the data unit size when the size of the attribute information to be generated is larger than the size of the data unit described later (preset).

  FIG. 5 is a diagram showing a configuration of attribute information. As shown in FIG. 5, the attribute information is used to specify “the number of bits in the Block Number (block number BN) field in the download header”, “the number of packets in the block”, “the last sequence number of the attribute information packet”, and “FEC system”. “URI (file body name)” “File Length (file length)” “Content Type (content type)” “Final block number and final sequence number of the final block” “Storage destination” Directory structure ”“ Content Encoding (content encoding) ”“ Transfer Length (transmission length) ”“ Content MD5 (content MD5) ”.

  The attribute information generation unit 12 sets each component shown in FIG. 5 based on the read file, and generates attribute information. Specifically, the attribute information generation unit 12 sets a bit length preset according to the type and characteristics of the one-way transmission path 3 to “the number of bits of the block number BN field in the download header”. Details of the number of bits of the block number BN field and the block number BN will be described later.

  The attribute information generation unit 12 sets the preset number of packets in the block to “number of packets in block”. The “number of packets in a block” is the number of packets that can be transmitted in the block in a block that is an aggregate of data units separated from the file body and parity units generated from the data units.

  When the attribute information generation unit 12 divides the generated attribute information, the attribute information generation unit 12 sets the number of divided attribute information to “the last sequence number of the attribute information packet”. If the size of the attribute information is equal to or smaller than the size of the data unit, the “last sequence number of the attribute information packet” is 0.

  The attribute information generation unit 12 sets the file size to “File Length (file length)” and the content type to “Content Type (content type)”. Further, the attribute information generation unit 12 calculates the number of blocks and the number of sequences based on the number of data units and parity units generated by the unit generation unit 13 described later, the size of the data unit set in advance, and the like. These are set to “the last block number for transmitting the file and the last sequence number of the last block”.

  In addition, the attribute information generation unit 12 sets the method to “Content Encoding” when encoding and transmitting a file, and when the file is encoded and transmitted, the length of the original file and the transmission time Since the file lengths of the files are different, the file length “Transfer Length (transmission length)” at the time of transmission is set. Also, a checksum “Content MD5 (content MD5)” for checking whether or not the receiving side has received the file correctly is set. Furthermore, “an identifier for specifying the FEC method”, “URI (name of file body)”, and “directory configuration of storage destination” are also set.

  Returning to FIG. 3, the unit generation unit 13 reads a file from the storage unit 11 (reads the same file as the file read by the attribute information generation unit 12), and stores the file body in a preset data unit of a certain size. Divide (step S2, FIG. 4 (1)). The size of the data unit can be freely set, for example, 1344 bytes and 4032 bytes.

  The unit generator 13 divides the data unit divided into a plurality of L × D pieces and aligns them in two dimensions of L columns and D rows (step S3, FIG. 4 (2)). This collection of two-dimensional data units is the source of the block.

  In addition, the unit generation unit 13 generates a parity unit from each data unit in the column direction and the row direction in the aligned two-dimensional data units (step S4, FIG. 4 (3)). For example, the unit generation unit 13 adds mod 2 for all data units for each column direction to generate a parity unit for each column direction. Similarly, mod2 is added to all data units in the row direction to generate parity units in the row direction.

  The unit generation unit 13 generates a block using the two-dimensional data unit array arranged in step S3 and the column-direction and row-direction parity units generated in step S4 (step S5, FIG. 4 (3)).

  The download header adding unit 14 adds a download header to the attribute information generated by the attribute information generating unit 12, and also downloads the data header and the parity unit generated by the unit generating unit 13. Is added (steps S6 and S7).

(Add download header)
FIG. 6 is a diagram showing the configuration of the download header. As shown in FIG. 6, the download header is a 64-bit header composed of three fields, “Transport File ID (Transport File ID: TFID)”, “Block Number (block number BN)”, “Sequence Number” (sequence) Number SN) ". The number of bits (field width) of the “TFID” field is 32. The total number of bits in the “block number BN” and “sequence number SN” fields is 32, but each has a variable length, depending on the type and characteristics of the one-way transmission path 3 or the file to be transmitted. It is set in advance. Further, during transmission of one file, these field widths are not changed and fixed values are used.

  “TFID” serves as a label for uniquely identifying a file to be transmitted. Therefore, the download header adding unit 14 sets the same “TFID” for the attribute information, data unit, and parity unit of the same file. On the other hand, different “TFIDs” are set for attribute information of different files. In the above-mentioned FLUTE, this “TFID” corresponds to “Transport Object Identifier (TOI)”. For details, refer to the aforementioned Non-Patent Documents 1 and 2.

  “Block number BN” indicates the block number in the file to be transmitted. “Sequence number SN” indicates the number of attribute information (each attribute information when divided) and the number of a unit in a block (hereinafter, a data unit and a parity unit are collectively referred to as a unit). For example, BN = 0 and SN = 0 are set for the first attribute information, and an SN subsequent to the SN set for the last attribute information is set for the unit following the attribute information.

  More specifically, when one attribute information is generated by the attribute information generating unit 12, the download header adding unit 14 determines that BN = 0 and SN = 0 for the attribute information in the first block (BN = 0). Set. Then, the download header adding unit 14 sets BN = 0 and SN = 1 for the head unit of the first block, and sets BN = 0 and SN = 2 for the next unit. The sequence number SN increases by 1 according to the number of units. The download header adding unit 14 also sets BN = 0 and SN = 0 for the same attribute information as the attribute information in the first block in the next block (BN = 1). The download header adding unit 14 sets BN = 1 and SN = 1 for the head unit of the block (BN = 1), and sets BN = 1 and SN = 2 for the next unit.

  On the other hand, when the attribute information generated by the attribute information generation unit 12 is divided into a plurality of pieces, the download header addition unit 14 adds BN = 0 to the first divided attribute information in the first block (BN = 0). , SN = 0, and BN = 0, SN = 1 for the next attribute information. The sequence number SN increases by 1 in accordance with the division of the attribute information. Then, the download header adding unit 14 sets BN = 0 and SN = 2 for the head unit of the first block (BN = 0), and sets BN = 0 and SN = 3 for the next unit. . The sequence number SN increases by 1 according to the number of units. Here, when the number of attribute information generated and divided by the attribute information generation unit 12 is n, the sequence number SN of each attribute information is SN = 0, 1,..., N−1. The sequence number SN of the first unit is SN = n. The download header adding unit 14 also sets BN = 0, SN = 0, 1,... Of the same attribute information as the attribute information in the first block in the next block (BN = 1). Then, the download header adding unit 14 sets BN = 1, SN = 2 (when the number of divided attribute information is two) for the head unit of the block (BN = 1), and the next BN = 1 and SN = 3 are set for the unit. As described above, the sequence number SN increases by 1 according to the number of units, and when the final attribute information is SN = n−1, the first unit is SN = n.

  As described above, the download header adding unit 14 adds a download header including the TFID, the block number BN, and the sequence number SN to the attribute information and the unit. In this case, the download header addition unit 14 assigns the same attribute information to a plurality of blocks generated by the unit generation unit 13, and BN is assigned to the first attribute information among the attribute information corresponding to one block. = 0 and SN = 0 are unified and set. As a result, the receiving terminal 2 determines whether or not the 32-bit data obtained by concatenating both the block number BN and sequence number SN fields in the download header is 0x0000 for the received packet. If it is determined that the packet number is 0x00000000, a packet having such a download header includes a packet containing the attribute information of the file (initially) regardless of the setting of the bit number of the block number BN field and the bit number of the sequence number SN field. Can be recognized.

  FIG. 7 is a diagram illustrating a configuration example of the download header. In FIG. 7, (1) is a configuration example when the block size is large. When the block size is set to be large, since a large number of units are included in the block, the number of allocated bits in the sequence number SN field is increased and the number of allocated bits in the block number BN field is decreased.

  (2) is a configuration example when the block size is small. When the block size is set to be small, since many units are not included in the block, the number of assigned bits in the sequence number SN field is reduced and the number of assigned bits in the block number BN field is increased.

  (3) is a configuration example of a download header added to file attribute information, and the block number BN and the sequence number SN are BN = 0 and SN = 0. When the attribute information generated by the attribute information generation unit 12 is divided into a plurality of pieces, a download header added to the first attribute information is shown.

  As described above, the number of bits allocated to the block number BN and sequence number SN field of the download header can be changed according to the setting of “number of bits of the block number BN field in the download header” included in the attribute information shown in FIG. Therefore, the number of bits according to the type and characteristics of the one-way transmission path 3 or the file to be transmitted can be set, and the number of bits can be flexibly dealt with.

(Packet generation)
Returning to FIG. 3, the packet transmission unit 15 adds a header to the attribute information and the unit to which the download header is added by the download header addition unit 14, and generates a packet (step S8). Then, the packet transmission unit 15 transmits the generated packet (step S9).

  FIG. 8 is a diagram illustrating a packet configuration. (1) shows a packet configuration when the unidirectional transmission path 3 shown in FIG. 1 is a transmission path based on an IP network. The packet transmission unit 15 stores the attribute information and unit to which the download header is added in the UDP payload, adds the IP header and the UDP header, and generates and transmits the packet shown in (1).

  (2) shows a packet configuration when the unidirectional transmission path 3 is, for example, a transmission path for advanced BS digital broadcasting. The packet transmission unit 15 stores the attribute information and unit with the download header added in the UDP payload, generates a compressed header instead of the IP header and the UDP header, adds the compressed header, and the packet shown in (2) Generate and send.

(Compressed header)
Next, a usage example of the compressed header will be briefly described. As for the format of the compressed header of advanced BS digital broadcasting, the supplementary proposal page 31 “2.3.2.2” of the above-mentioned Non-Patent Document 2 Document 60-1-2 “Broadcasting System Committee Report”. Refer to “IP packet header compression method”.

  In general, an IP header compression format is used as a technique for compressing a packet header. As this IP header compression format, RFC2508 (Compressing IP / UDP / RTP Headers for Low-Speed Serial Links) and RFC3095 (Robust Header Compression, RODP): Framework and future ProP: What is specified is known.

  These header compression techniques utilize the property that the information described in the packet header is the same or predictable in the same flow in which a plurality of packets are continuous. In the header of the header-compressed packet, a context ID (CID) for specifying a flow is described in addition to the minimum header information.

  As a specific example of header compression technology, all packets belonging to the same flow are not included in all header information, but some packets include all header information and CID, and other packets Includes a part of header information and a CID. A header including all of the header information and the CID is called a full header, and a packet to which the full header is added is called a full header packet. A header including a part of header information and a CID is called a compressed header, and a packet to which the compressed header is added is called a compressed header packet. FIG. 8B is a compressed header packet.

  In this header compression technique, a CID table in which a CID and a part of header information are associated in advance is shared between the transmission terminal 1 and the reception terminal 2. Then, the full header packet and the compressed header packet are transmitted from the transmission terminal 1 to the reception terminal 2. Thereby, all the header information can be shared between the transmission terminal 1 and the reception terminal 2 using the CID as a key.

  Thus, the compressed header is information added to a packet of the same flow from the transmission terminal 1 to the reception terminal 2, and is used for sharing header information using the CID as a key.

(Packet transmission order)
Next, the packet transmission order will be described. FIG. 9 is a diagram illustrating an example of a packet transmission order. As shown in FIG. 9, the packet transmission unit 15 of the transmission terminal 1 transmits a packet of attribute information prior to transmission of the unit. Specifically, the packet transmission unit 15 transmits the attribute information packet (download header BN = 0, SN = 0) prior to the transmission of the unit with the block number BN = 0 in the transmission of the file 1, and continues. , The units with the block number BN = 0 are transmitted. Then, the packet transmission unit 15 transmits the same attribute information packet (the attribute information packet to which the download header of BN = 0, SN = 0 is added) prior to the transmission of the unit with the block number BN = 1, Subsequently, the packet of the unit with the block number BN = 1 is transmitted. In this way, the packet transmission unit 15 transmits the packet of the last block, and ends the transmission of the file 1.

  In FIG. 9, the packet transmission unit 15 transmits the file attribute information before transmitting the unit for each block, but only once before transmitting the unit with the block number BN = 0. You may make it transmit. Further, an even number of blocks such as block number BN = 0 and block number BN = 2 may be transmitted before being transmitted. The file attribute information may be transmitted before transmitting the block number BN = 0 and before transmitting any subsequent block. Efficient transmission can be realized in the one-way transmission path 3 by reducing the number of transmissions of file attribute information.

[Receiving terminal / configuration]
Next, the receiving terminal 2 of the transmission system shown in FIG. 1 will be described. First, the configuration of the receiving terminal 2 will be described. FIG. 10 is a block diagram showing the configuration of the receiving terminal 2. The receiving terminal 2 includes a packet receiving unit 21, a download header analysis unit (header information analysis unit) 22, a file restoration unit 23, and a storage unit 24.

  The packet receiving unit 21 receives a packet transmitted from the transmitting terminal 1, performs a receiving process such as removing an IP header and the like, and outputs file attribute information and a unit to the download header analyzing unit 22.

  The download header analysis unit 22 inputs the attribute information and unit of the file from the packet reception unit 21, analyzes the attribute information of the file and the download header added to the unit, and distinguishes the file identification processing and the attribute information from the unit The file attribute information and all the units in the file are acquired. Then, the download header analysis unit 22 outputs the identification information and all the units in the same file to the file restoration unit 23.

  The file restoration unit 23 receives the attribute information and all units in the same file from the download header analysis unit 22, restores the missing data unit based on the parity unit, and combines the data units to restore the original file. . Then, the file restoration unit 23 writes the restored file in the storage unit 24. For example, when mod 2 is added to each data unit in the column direction and the row direction to generate a parity unit, the file restoration unit 23 selects one missing data unit in one row or one column. Thus, restoration is performed by adding mod 2 to the other data units and parity units.

  Thus, the receiving terminal 2 receives the packet transmitted by the transmitting terminal 1 via the one-way transmission path 3, and distinguishes it into attribute information and all units in the same file. Then, the receiving terminal 2 restores the data unit among the distinguished units based on the parity unit, and combines the data units to restore the original file.

[Receiving terminal / processing]
Next, processing of the receiving terminal 2 will be described. FIG. 11 is a flowchart showing processing of the receiving terminal 2, and shows a flow for restoring a file when the receiving terminal 2 receives a packet from the one-way transmission path 3.

  First, the packet receiving unit 21 of the receiving terminal 2 receives a packet storing file attribute information and units, and outputs the file attribute information and unit data to the download header analyzing unit 22 after receiving processing. (Step S11).

  The download header analysis unit 22 receives file attribute information and unit data from the packet reception unit 21, refers to the attribute information and the 64-bit download header added to the unit, and constitutes a 32-bit download header. The file is identified based on “TFID” (step S12). Thereafter, the processes of steps S13 to S16 are performed for files having the same “TFID”.

  The download header analysis unit 22 determines whether or not the attribute information of the identified file has been acquired. If the download header analysis unit 22 determines that the attribute information of the identified file has not been acquired, the download header block number BN and the data input from the packet reception unit 21 are determined. It is determined whether or not the sequence number SN is BN = 0, SN = 0, and waits until data of BN = 0, SN = 0 is input. When it is determined that the download header is BN = 0, SN = 0, the data is recognized as the first attribute information, and the “bit of the block number BN field in the download header included in the first attribute information” By referring to “Number”, it is recognized what ratio the block number BN and sequence number SN fields of the next 32 bits of “TFID” included in the download header are. And about the data input after that, the block number BN and sequence number SN in case "TFID" contained in a download header are the same are specified. Then, the download header analysis unit 22 refers to the “final sequence number of the attribute information packet” included in the first attribute information, and the sequence number SN of the data input thereafter is the same as the “final sequence number of the attribute information packet” The data up to is acquired as attribute information in the same file (step S13).

  The download header analysis unit 22 refers to the “number of packets in the block” included in the attribute information, and can identify the last unit in the block. The download header analysis unit 22 includes “the last block number and the last block for transmitting the file” included in the attribute information. The last block can be identified by referring to the “last sequence number of the last block”, and the unit of the last block and the unit of the last sequence in the last block can be identified. And the download header analysis part 22 acquires all the units of all the blocks in the same file about the data input after acquiring all the attribute information (step S14). Then, the acquired attribute information and all units are output to the file restoration unit 23.

  On the other hand, if it is determined in step S13 that the attribute information of the identified file has been acquired, the download header analysis unit 22 performs the process of step S14 described above.

  The file restoration unit 23 inputs the attribute information and all units in the same file from the download header analysis unit 22, and based on the block number BN and sequence number SN of the download header, the data unit and the parity unit are sorted in block number order and Arrange in order of sequence number in block. Then, referring to the “identifier for specifying the FEC scheme” included in the attribute information, the FEC decoding process using the parity unit is performed, the missing data unit is restored, and the data units are combined (step S15). ). Then, the file restoration unit 23 restores the original file and writes it in the storage unit 24 (step S16).

  As described above, according to the transmission system according to the embodiment of the present invention, when the transmission terminal 1 transmits a packet with the download header including the block number BN and the sequence number SN for each attribute information and unit, For the first attribute information, the block number BN and sequence number SN of BN = 0, SN = 0 are set. Then, the receiving terminal 2 determines the block number BN = 0 and the sequence number SN = 0 included in the download header, acquires attribute information, and selects a unit based on the block number BN and the sequence number SN included in the download header. Aligned and merged to restore the original file. Accordingly, it is not necessary to separately provide dedicated information for identifying the file body and the attribute information, so that the amount of header information can be reduced compared to the FLUTE header. Therefore, improvement in transmission efficiency and reduction in processing load can be realized.

  Further, according to the transmission system according to the embodiment of the present invention, the attribute information generation unit 12 of the transmission terminal 1 “the number of bits of the block number BN field in the download header” “the number of packets in the block” “the final block for transmitting the file The number and the last sequence number of the last block ”are set in the attribute information. And the download header analysis part 22 of the receiving terminal 2 specified the block number BN and the sequence number SN, the number of units in a block, and the number of blocks based on the attribute information. As a result, the transmission terminal 1 can transmit a packet having a different block size according to the file, and the reception terminal 2 can receive the packet having a different block size and restore the file. Therefore, it is not necessary to fix the block size, and it is possible to flexibly cope with various block sizes according to the application and the transmission medium.

  Moreover, according to the transmission system by embodiment of this invention, the packet transmission part 15 of the transmission terminal 1 transmitted the attribute information of the file, respectively before transmitting the unit for every block. Thereby, when the receiving terminal 2 receives from the middle packet of the file, the subsequent unit can be received and restored to the file by acquiring the middle attribute information. Further, the transmission terminal 1 may perform transmission by thinning the attribute information by transmitting before transmitting even-numbered blocks such as block number BN = 0 and block number BN = 2. Thereby, since the number of attribute information transmissions can be reduced, efficient transmission can be realized in the one-way transmission path 3.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea thereof. For example, in the above embodiment, the unit generation unit 13 of the transmission terminal 1 generates a parity unit from each data unit for each column direction and row direction. However, depending on the transmission quality of the one-way transmission path 3, There is no need to generate a parity unit. Further, the FEC method does not need to generate a parity unit by aligning data units two-dimensionally, and a method of generating redundant data, that is, a parity unit by a Reed-Solomon code or a Raptor code may be used. The present invention is not limited to the FEC method.

  In the embodiment, the attribute information generation unit 12 of the transmission terminal 1 sets “identifier for identifying the FEC scheme” in the attribute information, and the reception terminal 2 identifies the encoding scheme based on this information. However, it is not necessarily transmitted as part of the attribute information. Since information such as the encoding method and parity unit position necessary for FEC decoding need only be consistent between the transmitting terminal 1 and the receiving terminal 2, it is not only transmitted as part of the attribute information but also fixed in advance. Or may be transmitted by another means.

  Moreover, in the said embodiment, although the attribute information generation part 12 of the transmission terminal 1 produced | generated the attribute information of the text format shown in FIG. 5, you may produce | generate the attribute information of a binary format. The present invention is not limited to the format of attribute information.

  In the above-described embodiment, the download header adding unit 14 of the transmission terminal 1 adds a download header having a total of 32 bits including the bit number of the block number BN field and the bit number of the sequence number SN field. , It is not necessarily 32 bits. Further, the attribute information generation unit 12 sets only “the number of bits of the block number BN field in the download packet” in the attribute information. Although the number of bits of the sequence number SN field can be calculated based on this attribute information, the number of bits of the sequence number SN field or the number of bits of both fields may be set in the attribute information.

It is a figure which shows schematic structure of the transmission system containing the transmission terminal and receiving terminal by embodiment of this invention. It is a block diagram which shows the structure of a transmission terminal. It is a flowchart which shows the process of a transmission terminal. It is a schematic diagram explaining the generation flow of attribute information, a unit, and a block. It is a figure which shows the structure of attribute information. It is a figure which shows the structure of a download header. It is a figure which shows the structural example of a download header. It is a figure which shows the structure of a packet. It is a figure which shows the example of the transmission order of a packet. It is a block diagram which shows the structure of a receiving terminal. It is a flowchart which shows the process of a receiving terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission terminal 2 Reception terminal 3 Unidirectional transmission line 11 Storage part 12 Attribute information generation part 13 Unit generation part 14 Download header addition part 15 Packet transmission part 21 Packet reception part 22 Download header analysis part 23 File restoration part 24 Storage part

Claims (11)

Generate attribute information of a file, generate a unit by dividing the file body, store the attribute information in a packet and send it, and store and send the unit in a packet for each block composed of a plurality of units In a transmitting terminal used for a one-way transmission line,
Attribute information including data that defines the number of bits of a field to which a block number for specifying the block is assigned, and attribute information stored in the packet and the number of bits of a field to which a sequence number for specifying a unit is assigned An attribute information generation unit for generating
A transmission terminal comprising: a header information adding unit that generates header information including the block number and sequence number, and adds the header information to the attribute information and the unit. In the transmission terminal according to claim 1,
The header information adding unit generates header information having a block number and a sequence number of 0, and adds the header information to the attribute information. In the transmission terminal according to claim 1 or 2,
The attribute information generation unit generates attribute information including the number of bits of the field to which the block number is assigned and the number of bits of the field to which the sequence number is assigned, or both the block number and the sequence number are Transmitting terminal characterized by generating attribute information including the number of bits of a field to which any one of the block number and sequence number is assigned when the number of bits of the assigned field is fixed . In the transmission terminal according to any one of claims 1 to 3,
When the attribute information is divided and the divided attribute information is stored and transmitted in a packet,
The transmission terminal characterized in that the attribute information generation unit further generates attribute information including data for specifying the number of divisions of the attribute information. In the transmission terminal according to any one of claims 1 to 4,
A header information adding unit that generates header information in which the number subsequent to the sequence number of the attribute information is a unit sequence number;
The transmission terminal characterized by transmitting the same attribute information between the blocks before the units constituting each block. In the transmission terminal according to any one of claims 1 to 4,
A header information adding unit that generates header information with the sequence number of the attribute information as the sequence number of the unit when the attribute information is transmitted before the units constituting the block;
The transmitting terminal, wherein the attribute information is transmitted before a unit constituting at least a first block among all the blocks. In the transmission terminal according to any one of claims 1 to 6,
The transmission terminal characterized in that the attribute information generation unit generates attribute information including a file name and length in addition to data for specifying the number of bits of the block number and sequence number. In the receiving terminal that receives the packet storing the attribute information of the file and the packet storing the unit for each block obtained by dividing the file body by one-way transmission and restores the original file,
The attribute information includes the number of bits of a field to which a block number for specifying the block is assigned, and the number of bits of a field to which a sequence number for specifying attribute information and a unit stored in the packet is assigned. Data for defining, header information including the block number and sequence number is added to the attribute information and unit,
Based on the attribute information, analyzing the block number and sequence number included in the header information, to obtain the attribute information and unit, header information analysis unit,
A receiving terminal comprising: a file restoration unit that arranges and combines the units acquired by the header information analysis unit based on the block number and sequence number, and restores the original file. The receiving terminal according to claim 8, wherein
The receiving terminal characterized in that the header information analysis unit acquires attribute information when a block number and a sequence number included in the header information are 0. In the receiving terminal according to claim 8 or 9,
The receiving terminal, wherein the file restoring unit restores the unit after the header information analyzing unit has acquired the attribute information to the original file.   A transmission system comprising: the transmission terminal according to any one of claims 1 to 7; and the reception terminal according to any one of claims 8 to 10.

Images