JP2021192502A - Transmission server, transmitter, receiver and program - Google Patents

Abstract

To provide: a transmission server which allows for data retransmission, efficiently by using communication, in response to a retransmission request from a receiving side based on coded data of error correction code used in digital broadcasting; a transmitter and a receiver related to digital broadcasting; and a program.SOLUTION: A transmission server 6 of the present invention receives code data related to digital broadcasting formed in a transmitter 2 (3) and saves the data of predetermined time; and retransmits the data to a receiver 5 when receiving a retransmission request packet, via an IP network 8. The transmitter 2 (3) of the present invention outputs the coded data sequentially to the transmission server 6. When it is determined that bit errors remain in subjecting the coded data obtained through the retransmission request to decoding processing, the receiver 5 of the present invention repeats, for a first predetermined time, the decoding processing again to share one with the larger absolute value of a post-LLR or pre-LLR via a broadcast transmission line and an IP network. Nevertheless, if bit errors cannot be corrected, then decoding processing through the retransmission request is again repeated for a second predetermined time.SELECTED DRAWING: Figure 1

Description

The present invention relates to the technical fields of satellite broadcasting, terrestrial broadcasting, fixed communication, and mobile communication, and in particular, it is possible to link broadcasting and communication and retransmit data in response to a retransmission request from the receiving side using communication. It relates to a transmission server, a transmission device and a reception device related to digital broadcasting, and a program.

In the digital broadcasting system of satellite broadcasting and terrestrial broadcasting, an error correction code is used as a technique for improving transmission performance under white noise. For example, in advanced broadband satellite digital broadcasting, the LDPC (Low Density Parity Check) code, which is a powerful error correction code with performance approaching the Shannon limit, which is the theoretical upper limit of utilization efficiency for the signal-to-noise ratio, is used ( For example, see Non-Patent Documents 1 and 2). However, in satellite digital broadcasting, attenuation due to rainfall, fading in terrestrial digital broadcasting, etc., in digital broadcasting, the transmission conditions may deteriorate to the extent that the signal cannot be recovered only by the error correction code.

On the other hand, in digital wireless communication, data retransmission control by ARQ (Automatic Repeat reQuest) is known as a data compensation technique other than an error correction code (see, for example, Patent Documents 1 and 2). In digital wireless communication, improvement of transmission performance can be realized by using Hybrid ARQ that combines an error correction code and ARQ, the number of retransmissions is smaller than that using ARQ alone, and conditions that cannot be compensated by the error correction code alone. Data transmission is possible. However, the conventional prior art using Hybrid ARQ is limited to two-way communication such as FPU and mobile phone base station communication, and cooperates with communication in one-way broadcasting such as broadcasting, and data is transmitted by Hybrid ARQ. No compensation technique has been established.

Although it does not constitute a Hybrid ARP, when the transmission conditions of digital broadcasting deteriorate, the ARQ is directed from the receiving side to the transmitting side via the IP (Internet Protocol) network, which is a communication path capable of bidirectional communication. (For example, see Patent Document 3).

A general IP network is assumed to be a binary erasure channel (PEC: Packet Erasure Channel) in which information is lost due to some kind of failure such as congestion of lines. Therefore, in Hybrid ARQ in digital wireless communication, LDPC-CC (Convolutional Codes) (see, for example, Patent Document 4) and LDGM (Low-Density Generator Matrix) codes (for example, Patent Document 5) are used as error correction codes for data compensation. An error correction code dedicated to IP communication, which is a lost communication path such as (see), is used. These LDPC-CC and LDGM codes are error correction codes based on the LDPC code as in the case of advanced broadband satellite digital broadcasting, but are designed in consideration of only IP communication, which is a loss communication path. It is necessary to prepare an error correction code encoder and decoder dedicated to IP communication.

Japanese Unexamined Patent Publication No. 2014-050034 International Publication No. 2007/069406 International Publication No. 2015/048569 International Publication No. 2010/001610 International Publication No. 2015/022910

R. G. Gallager, “Low-Density Parity-Check Codes,” in Research Monograph series Cambridge, MIT Press, December 1963 "Transmission method for advanced broadband satellite digital broadcasting (ISDB-S3) standard ARIB STD-B44 2.1 version", [online], revised on March 25, 2016, ARIB, [search on April 13, 2016] , Internet <URL: https://www.arib.or.jp/kikaku/kikaku_hoso/std-b44.html>

As described above, in digital wireless communication, improvement of transmission performance can be realized by using Hybrid ARQ that combines an error correction code and ARQ, and the number of retransmissions is smaller than that using only ARQ, and only the error correction code is used. Data can be transmitted under conditions that cannot be compensated for.

However, a technique for coordinating with communication in one-way broadcasting such as broadcasting and compensating for data with Hybrid ARQ has not been established.

Therefore, also in digital broadcasting, a technique of compensating for data by Hybrid ARQ, which is a fusion of digital broadcasting and communication in which an error correction code and an ARQ are combined, is desired in cooperation with communication. For example, when the transmission conditions of digital broadcasting deteriorate, by constructing a transmission system that performs ARP from the receiving side to the transmitting side via the IP network, which is a communication path capable of bidirectional communication, and retransmits data from the transmitting side. , Transmission performance can be improved. In other words, since the current digital broadcasting only assumes data compensation using an error correction code, by compensating the data related to digital broadcasting with Hybrid ARQ, it is possible to deal with the deterioration of transmission conditions that cannot be corrected by the error correction code. .. Further, even when the ARP system is configured only by IP communication, the number of retransmissions related to ARQ can be reduced by configuring Hybrid ARP that combines the error correction code related to broadcasting and communication.

However, in order to construct a transmission system using Hybrid ARQ by fusing broadcasting and communication, an error dedicated to IP communication disclosed in Patent Documents 4, 5 and the like in the system using ARQ disclosed in Patent Document 3 and the like. When the correction code is applied and configured, a mechanism is required to prepare and cooperate with an error correction code encoder and decoder for digital broadcasting and an IP communication encoder and decoder, respectively. The scale of equipment will increase.

Therefore, it is required to efficiently combine the "error correction code used in digital broadcasting" and the ARQ, and then construct a transmission system using the Hybrid ARQ by fusing broadcasting and communication.

That is, without increasing the encoder of the transmitting device and the decoder of the receiving device related to digital broadcasting, the digital broadcasting and the communication by the IP network are linked, for example, the concatenated code and IP for error correction of the LDPC code and the BCH code. It is desired to improve the error correction capability related to digital broadcasting by constructing a transmission system that realizes Hybrid ARQ that combines retransmission requests using communication.

Further, in a general IP network, the probability of packet disappearance, the appearance of packet disappearance, and the like vary depending on the time zone used, the line, and the like, such as when the line is congested. Therefore, when realizing hybrid ARQ in digital broadcasting and communication networks without increasing the scale of equipment, pay attention to the block code among the error correction codes used in digital broadcasting, and digitally broadcast the data retransmitted via the IP network. It is required to use the coded data in the block code of the above, and to realize variable control according to the communication quality of the IP network to improve the transmission efficiency via the IP network.

Further, for the receiving device that makes a retransmission request, even if the line condition of the IP line deteriorates to the extent that the correction performance of the error correction coded signal is exceeded, high correction performance is achieved and the number of retransmission requests is suppressed. It is desired to efficiently realize the decoding process of the error correction code.

Therefore, without increasing the encoder of the transmitting device and the decoder of the receiving device related to digital broadcasting, the communication by the digital broadcasting and the IP network is linked, for example, by the concatenated code of error correction of the LDPC code and the BCH code. By constructing a transmission system that realizes a Hybrid ARP that combines a block code and a retransmission according to the communication quality of the IP network in response to a retransmission request using IP communication, the error correction capability related to digital broadcasting is improved, and moreover, First, a technique for suppressing the number of retransmission requests and realizing efficient Broadcast ARQ is desired.

In view of the above-mentioned problems, an object of the present invention is to efficiently use communication to communicate with an IP network in response to a retransmission request from a receiving side based on coded data of an error correction code used in digital broadcasting. It is an object of the present invention to provide a transmission server capable of retransmitting data according to quality, a transmission device and a reception device related to digital broadcasting, and a program.

The transmission server of the present invention digitally modulates the encoded data encoded by using the error correction code related to digital broadcasting, and transmits the digitally modulated encoded data to the receiving device via the broadcasting transmission path. A transmission server that stores a predetermined amount of the coded data from the device and enables transmission to the receiving device via the IP (Internet Protocol) network, and sequentially inputs the coded data generated by the transmitting device. , While managing in time series by a synchronization signal based on the frame number or time information of the error correction code frame constituting the code length of the error correction code, and updating the predetermined time of the coded data managed in time series. The retransmission request packet generated when the bit error of the coded data cannot be corrected by the receiving device using the error correction code is received via the storage unit and the IP network, and the retransmission request packet is received. The communication quality information measured by the receiving device stored in the receiver and the retransmission request information indicating the coded data of the error correction code frame related to the retransmission request are extracted, and the coding is predetermined based on the communication quality information. Based on the rate change criterion, it is determined whether or not to retransmit the coded data generated by the transmitting device by changing the coding rate of the block code, and based on the retransmitting request information according to the determination result. Retransmission request processing that reads out the coded data related to the retransmission request from the storage unit, configures the coded data in which the coding rate is changed, and controls the retransmission of the coded data toward the receiving device. When the coding rate of the block code of the coded data generated by the transmitting device is changed or not changed by the control of the unit and the retransmission request processing unit, and the coding rate is changed. In addition, among the predetermined number of coding rates that are based on the same coding method as the error correction coding method used in the transmission device and that can be used by the transmission device, the transmission device transmitted on the broadcast transmission line. Control by the coding rate adaptive change unit that performs error correction coding processing that changes the coding rate by distinguishing whether it is higher or lower than the coding rate of the generated coded data, and the retransmission request processing unit. It is provided with an IP packet generation unit that generates an IP packet format coded data packet for storing the coded data related to the retransmission request configured through the process and transmits the coded data packet to the receiving device via the IP network, and the coding rate. When the adaptive change unit changes the coding rate of the coded data generated by the transmission device under the control of the retransmission request processing unit, When converting to a coding rate higher than the coding rate before the change, a padding bit known on the receiving device side is added to the information bit of the coded data according to the coded rate to be changed. The parity of the block code whose coding rate is changed obtained by performing the error correction coding process is replaced with the parity added to the coded data generated by the transmission device and added, and the padding bit is removed. When the coded data for retransmission is generated and converted to a coding rate lower than the coding rate before the change, the information bit of the coded data is divided between transmission and reception by a predetermined division method. A block code in which the coding rate obtained by adding a padding bit known to the receiving device side to each of the information bits divided according to the coding rate to be changed and performing the error correction coding process is changed. It is characterized in that the parity is replaced with the parity added to the coded data generated by the transmission device and added, and the coded data for retransmission is generated by removing the padding bit.

Further, in the transmission server of the present invention, the retransmission request processing unit uses either one or both of the delay information of the communication line and the packet loss rate information measured by the receiving device as the communication quality information. It is characterized in that it determines whether or not to change the coding rate of the coded data generated by the transmission device and retransmit it according to the predetermined coding rate change standard.

Further, in the transmission server of the present invention, the code rate adaptive change unit changes the code rate of the coded data generated by the transmission device under the control of the retransmission request processing unit. In addition to changing the code rate of the above, further having a means for changing the correction capability of the error correction code connected to the block code while maintaining the frame length of the error correction code frame after the change of the code rate. It is characterized by.

Further, in the transmission server of the present invention, the IP packet generation unit is obtained by forming an interleave frame using the plurality of error correction code frames and performing interleaving so as to longitudinally cross each error correction code frame. An identification header for making the interleaved frame identifiable, a sequence number for specifying which bit is represented in each error correction code frame, and an IP header which is a header of the coded data packet are added to the payload. It is characterized by having an interleaved portion for generating an encoded data packet of an IP packet string.

Further, the transmitting device of the present invention is a transmitting device related to digital broadcasting, and is a means for sequentially outputting coded data encoded by using the error correction code related to the digital broadcasting to the transmitting server of the present invention. It is characterized by having.

Further, the transmitting device of the present invention is a transmitting device related to digital broadcasting, and is characterized in that the transmitting server of the present invention is provided inside the device.

Further, the receiving device of the present invention is a receiving device that digitally modulates the coded data encoded by the transmitting device using the error correction code related to digital broadcasting and receives the modulated wave signal transmitted via the broadcasting transmission path. The error correction code frame is reconstructed from the demodulation unit that receives and demolishes the modulated wave signal and the error correction code frame that constitutes the code length of the error correction code from the coded data obtained by demodulation. An error-correcting decoding unit that performs decoding processing corresponding to Error correction related to retransmission request for requesting In response to the retransmission request packet, an IP packet format encoded data packet storing the encoded data retransmitted in response to the retransmission request is received from the transmission server, and the encoding is retransmitted in response to the retransmission request. A predetermined period of either one or both of the delay related to the communication between the IP packet receiving unit for extracting data and the transmitting server and the packet loss rate based on the amount of packet loss generated in the communication with the transmitting server. The retransmission request packet is generated so that the communication quality information including one or both of the delay information and the packet loss rate information of the communication line is sequentially included in the retransmission request packet while being measured and updated in units. The error correction / decoding unit includes a communication quality measurement unit that outputs to the unit, and the error correction / decoding unit can determine whether or not error correction / decoding is possible for the coded data obtained from the transmission device, and can correct bit errors in the coded data. When it is determined that the packet cannot be decoded, the decodeability determination unit having a function of generating the retransmission request packet for the retransmission request packet generation unit and the encoding obtained from the transmission device by the decoding possibility determination unit. When it is determined that the bit error correction cannot be corrected for the data and decoding is not possible, the LLR storage that temporarily holds the post-log likelihood ratio after the decoding process including the bit error of the coded data or the pre-log likelihood ratio before the decoding process. The coding rate is changed by the coding rate of the coded data obtained by demodulating the part and the coded data retransmitted in response to the retransmission request when the coding rate is not changed. When, a padding bit according to the coding rate is added and decrypted. When the coded data complement section that attempts the decoding process through the complement process related to the replacement of the likelihood ratio required for the retransmission request, and when the coded data related to the retransmission request is changed to a lower coding rate and the information bits are divided. Retransmitted by a data combining unit that recombines the divided information bits after decoding with the transmission server according to a predetermined division method to generate received data, and a decoding process in the coded data complement unit. If the bit error cannot be completely corrected for the coded data retransmitted in response to the request, the posterior log likelihood ratio or the pre-log likelihood ratio obtained via the broadcast transmission line and temporarily held in the LLR storage unit and the IP. The posterior logarithmic ratio obtained by the decoding process of the coded data acquired by the retransmission request via the network or the pre-logous likelihood ratio before the decoding process are synchronized using the synchronization signal, and the posterior logarithmic of both. Compare the likelihood ratios or the prior log likelihood ratios and select the posterior log likelihood ratio or the prior log likelihood ratio with the larger absolute value as the one with the highest reliability, and select the posterior log likelihood ratio or the prior log likelihood ratio. The degree ratio is shared between the block codes of the respective coded data obtained via the broadcast transmission line and the IP line, and the decoding process of the respective coded data is attempted, and at least one of the respective coded data is used. The decoding possibility determination unit has an LLR sharing unit that repeats the decoding process for a first predetermined time while performing a process of selecting and sharing the logarithmic likelihood ratio having the larger absolute value until decoding is possible. In the decoding process within the first predetermined time by the LLR sharing unit, it is determined whether or not the error-corrected decoding of each coded data obtained via the broadcast transmission line and the IP line is possible, and the first predetermined time. If it is determined in the decryption process that bit errors still remain in both the coded data obtained via the broadcast transmission line and the IP line, the retransmission request packet generation unit is again subjected to. The retransmission request packet is generated so as to request retransmission, and a series of processes of the encoded data complement unit and the LLR sharing unit are repeated for a second predetermined time until at least one of the respective encoded data can be decoded. It is characterized by having a function to make it.

Further, in the receiving device of the present invention, the error correction code is a concatenated code in which an LDPC code is concatenated as an internal code and a BCH code is concatenated as an external code, and the decoding possibility determination unit is a coding obtained from the transmitting device. It is characterized in that it is determined that the bit error of the coded data could not be corrected when the data is not error-free in the decoding process of the BCH code.

Further, the receiving device of the present invention further includes a reception quality measuring unit for measuring the reception quality of the received modulated wave signal, and the receiving quality measuring unit can obtain the coded data decoded by the error correction decoding unit. When the receiving path at the time of generating the received data is the receiving path for broadcasting and receiving instead of via the IP network, the receiving path for broadcasting and receiving is maintained, and the coded data that can be decoded by the error correction decoding unit is used as the basis. When the reception route at the time of generating the received data is via the IP network, it is determined whether or not the reception quality is equal to or higher than the predetermined value, and if the reception quality is equal to or higher than the predetermined value, only broadcast reception is performed. If the reception quality is less than a predetermined value, the reception path is set to both broadcast reception and via the IP network, and the error correction / decoding unit is continuously requested to retransmit the coded data via the IP network. It is characterized by having a means for instructing the next encoded data to be retransmitted and acquired.

Further, in the receiving device of the present invention, the IP packet receiving unit receives a coded data packet of an IP packet string that stores coded data retransmitted in response to a retransmission request from the transmitting server in response to the retransmission request packet. It is characterized by having a deinterleave unit that receives the data, performs reverse processing of the interleave by the transmission server, and extracts the encoded data retransmitted in response to the retransmission request.

Further, the program of the present invention is configured as a program for operating the computer as the transmission server of the present invention.

Further, the program of the present invention is configured as a program for operating the computer as the receiving device of the present invention.

According to the present invention, for data loss that cannot be prevented only by broadcast reception, a retransmission request is made from the receiving side to the transmitting side via the IP network, and the data can be retransmitted from the transmitting side, so that the data can be retransmitted on the receiving side. Can be complemented. In particular, the data retransmitted by the transmitting side via the IP network is used as the coded data in the block code of digital broadcasting, and the coded data is variably controlled to the coding rate according to the communication quality of the IP network to retransmit. It is possible to reduce the number of requests, improve the transmission efficiency via the IP network, and enhance the resistance to packet loss. Further, by making both the error correction code used for broadcast reception and the error correction code used for transmission via the IP network the same as the code format of the error correction code standardized by the broadcasting standard, one error correction decoding is performed on the receiving side. This can be achieved simply by preparing a vessel, and the scale of the equipment can be reduced. Further, according to the receiving device according to the present invention, the coded data received via the IP line is decoded, and if the bit error cannot be completely corrected, the coded data received via the broadcast transmission path is decoded. The posterior log-likelihood ratio (broadcast) that is the result (including bit errors) or the pre-log-likelihood ratio (broadcast) before the decoding process and the posterior log-likelihood ratio that is the result of the decoding process (including bit errors) via the IP line. Synchronize the (IP) or the pre-log-likelihood ratio (IP) before the decoding process with each other to obtain a highly reliable post-log-likelihood ratio or pre-log-likelihood ratio (high absolute value of the log-likelihood ratio). By sharing and performing decryption processing again, it is possible to reduce the number of retransmission requests to the IP line, and to achieve high correction performance even if there is a packet loss that exceeds the correction performance of the coded data via the IP line. become.

It is a block diagram which shows the schematic structure of the transmission system including the transmission server, the transmission device and the receiving device of one embodiment according to the present invention. It is a block diagram which shows the schematic structure of the transmission server and the transmission apparatus of one Embodiment by this invention. It is a flowchart which shows the control flow which concerns on the retransmission request packet between the transmission server and the receiving apparatus of one Embodiment by this invention. Each of (a) to (d) is when the coding rate is changed by the coding rate adaptation changing unit in the transmission server of one embodiment according to the present invention (when the coding data related to the retransmission request is changed to a higher coding rate). It is a figure which shows the generation method of the coded data of. Each of (a) to (e) is when the coding rate is changed by the coding rate adaptation changing unit in the transmission server of one embodiment according to the present invention (when the coding data related to the retransmission request is changed to a lower coding rate). It is a figure which shows the generation method of the coded data of. It is explanatory drawing about the interleave processing of the IP packet generation part in the transmission server of one Embodiment by this invention. It is a block diagram which shows the schematic structure of the receiving device of one Embodiment by this invention. It is a flowchart which shows the reception control flow in the receiving apparatus of one Embodiment by this invention. It is a block diagram which shows the schematic structure of the transmission system including the transmission server, the transmission device and the receiving device of one Embodiment by this invention. It is a flowchart which shows the reception control flow in the receiving apparatus of the advanced broadband satellite digital broadcasting of one Example by this invention. Each of (a) to (e) is when the coding rate is changed by the coding rate adaptation changing unit in the transmission server of one embodiment according to the present invention (when the coding data related to the retransmission request is changed to a lower coding rate). It is a figure which shows the generation method of the coded data of. It is explanatory drawing about the interleaving process of the IP packet generation part in the transmission server of one Example by this invention. In each of (a) to (f), when the coding rate is changed by the coding rate adaptation changing unit in the transmission server of the application example according to the present invention (when the coding data related to the retransmission request is changed to a lower coding rate). It is a figure which shows the generation method of the coded data. It is a block diagram which shows the schematic structure of the receiving device of the modified example by this invention. It is a flowchart which shows the reception control flow in the receiving apparatus of the modification of a modification by this invention. It is a figure which illustrates the operation outline at the time of transmitting the coded data packet which changed the coded data which concerns on a retransmission request to a lower code rate by the transmission server of one Example of this invention to a receiving apparatus.

[Transmission system]
FIG. 1 is a block diagram showing a schematic configuration of a transmission system 1 including a transmission server 6, transmission devices 2 and 3, and a reception device 5 according to an embodiment of the present invention. The transmission system 1 shown in FIG. 1 includes transmission devices 2, 3 and reception devices 5, one or a plurality of transmission servers 6, and a load balancer 7 provided when configuring a plurality of transmission servers 6. ..

The transmission device 2 generates coded data by performing error correction coding processing on the transmission data related to digital broadcasting and imparting error correction code parity, and digitally modulates the coded data by a predetermined modulation method. This is a device that generates a modulated wave signal and radiates radio waves related to digital broadcasting via a satellite broadcasting transmission line including a broadcasting satellite 4 via a transmitting antenna 2a. For example, the transmitting device 2 can be a transmitting device for advanced wideband satellite digital broadcasting. Further, the transmission device 2 manages the sequentially generated coded data as an error correction code frame, assigns a frame number or time information that functions as a synchronization signal, and supplies one or a plurality of coded data via the local area network. It has a function of transmitting to the transmission server 6.

The transmission device 3 generates coded data by performing error correction coding processing on the transmission data related to digital broadcasting and imparting error correction code parity, and digitally modulates the coded data by a predetermined modulation method. This is a device that generates a modulated wave signal and radiates radio waves related to digital broadcasting via a transmission antenna 3a and a terrestrial broadcasting transmission line. For example, the transmitting device 3 can be a transmitting device for current or next-generation terrestrial digital broadcasting. Further, the transmission device 3 manages the sequentially generated coded data as an error correction code frame, assigns a frame number or time information that functions as a synchronization signal, and supplies one or a plurality of coded data via the local area network. It has a function of transmitting to the transmission server 6.

The receiving device 5 receives and demodulates the modulated wave signal radiated from the transmitting device 2 via the receiving antenna 5a, reconstructs the error correction code frame constituting the code length of the error correction code, and reconstructs the error correction code frame in the transmitting device 2. A function that performs decoding processing corresponding to error correction coding processing to generate received data and make it reproducible, and receives and demodulates a modulated wave signal radiated from the transmitting device 3 via the receiving antenna 5b. It is a device having a function of reconstructing an error correction code frame constituting the code length of the error correction code and performing a decoding process corresponding to the error correction coding process in the transmission device 3 to generate received data and make it playable.

Further, the receiving device 5 determines whether or not the coded data obtained from the transmitting device 2 (or the transmitting device 3) can be error-corrected and decoded, and if it is determined that the coded data can be decoded, the coded data is decoded as it is to generate the received data. If it is determined that the bit error of the coded data cannot be corrected and cannot be decoded, the post-log probability ratio after the decoding process including the bit error of the coded data via the broadcast transmission path or the pre-log probability before the decoding process. The ratio (LLR: Log-Likelihood Ratio, "log-like likelihood ratio") is temporarily held, a retransmission request packet in the form of an IP packet requesting retransmission of the corresponding encoded data is generated, and the retransmission request packet is communicated. It has a function of transmitting the quality information to the transmission server 6 via the IP network 8. Further, the receiving device 5 receives the encoded data retransmitted in response to the retransmission request from the transmission server 6 in response to the retransmission request packet (encoding data transmitted on the broadcast transmission line on the transmission server 6 side according to the communication quality information). (Reconstructed by changing the coding rate adaptively by distinguishing whether it is higher or lower than the coding rate of), the encoded data packet in the IP packet format is received, and the retransmission request is made. The encoded data retransmitted according to the above is extracted, complemented according to the coding rate so as to be used for the decoding process, and the decoding process is attempted.

Then, when the bit error cannot be completely corrected for the coded data retransmitted in response to the retransmission request, the receiving device 5 obtains the coded data via the broadcast transmission line and temporarily holds the post-LLR or the pre-LLR (hereinafter, "post-event" respectively. It is also referred to as "LLR (broadcast)" and "pre-LLR (broadcast)", and is also referred to as "post-or pre-LLR (broadcast)") and the decoding process of the coded data acquired by the retransmission request via the IP network. The post-LLR or pre-LLR obtained in (hereinafter, also referred to as "post-LLR (IP)" and "pre-LLR (IP)", respectively, and also referred to as "post-or pre-LLR (IP)"). , Synchronize using a synchronization signal, compare the two post- or pre-LLRs, select the LLR with the larger absolute value as having high reliability, and obtain the selected LLR via the broadcast transmission line and the IP line. The LLR having the larger absolute value is used until at least one of the respective coded data can be decoded by sharing between the block codes of the respective coded data and attempting the decoding process of the respective coded data. It has a function of repeating the decoding process for the first predetermined time while performing the process of selecting and sharing. Further, the receiving device 5 determines whether or not error-correcting and decoding of each coded data obtained via the broadcast transmission line and the IP line is possible in the decoding process within the first predetermined time, and the first If it is determined that bit errors still remain in both the coded data obtained via the broadcast transmission line and the IP line in the decoding process within the predetermined time, the retransmission request for the coded data is performed again. Of the respective coded data, a series of processing of decoding processing in which the packet is transmitted to the transmission server 6 and complemented with the coded data obtained by the retransmission request and decoding processing by sharing the logarithmic likelihood ratio is performed. It has a function of repeating for a second predetermined time until at least one of them can be decoded. The second predetermined time is a time limit determined for the entire decoding process based on the retransmission request, and includes the first predetermined time described above. Further, the receiving device 5 is divided when the coded data related to the retransmission request is changed to a lower coding rate and the information bits are divided (divided into two equal parts in the example described in detail later). It has a function of recombining the decoded information bit with the transmission server 6 according to a predetermined division method to generate received data. If the receiving device 5 cannot decode the data within the second predetermined time by the decoding process, the receiving device 5 generates the received data in a state including a bit error.

Each of one or a plurality of transmission servers 6 digitally modulates the coded data encoded by using the error correction code related to digital broadcasting and transmits the encoded data to the receiving device 5 via the broadcasting transmission line (transmitting device 2 (). Alternatively, the coding rate of the coded data transmitted on the broadcast transmission line according to the communication quality information for the coded data requested to be retransmitted from the receiving device 5 after storing the predetermined time of the coded data from the transmitting device 3). Is modified to reconstruct the coded data, and in this example, it is configured as a computer that can generate a coded data packet of an interleaved IP packet string and transmit it to the receiving device 5 via the IP network 8. To.

That is, the transmission server 6 sequentially inputs the coded data generated by the transmission device 2 (or the transmission device 3) via the local area network, and the frame number of the error correction code frame constituting the code length of the error correction code. Or, error correction used in the transmitting device 2 (or transmitting device 3) in the receiving device 5 via the IP network 8, which is a function of managing in time series by a synchronization signal based on time information and saving while updating a predetermined time. When the bit error of the coded data cannot be corrected by using the code, the retransmission request packet related to the coded data is received together with the communication quality information, and the communication quality information is directed to the receiving device 5 on the broadcast transmission line. A function that distinguishes whether the coding rate of the transmitted coded data is higher or lower than the coding rate and adaptively changes the coding rate to control the retransmission of the coded data, and synchronization related to the retransmission request. The error correction code frame of m frames having a continuous synchronization signal (frame number or time information) starting from the error correction code frame constituting the coded data having a signal (frame number or time information) is related to the retransmission request. An interleaved frame is constructed by forming an interleaved frame with the same coding rate as the coded data having a synchronization signal (frame number or time information), and the interleaved frame is interleaved in a direction orthogonal to the error correction code frame of the m frame. It has a function of generating a coded data packet of an IP packet string and transmitting it to the receiving device 5 via the IP network 8.

In particular, when the transmission server 6 changes the coding rate of the coded data generated by the transmitting device 2 (or the transmitting device 3) and retransmits the data, the transmission server 6 converts the coded data to a higher coding rate than the coding rate before the change. In the case, a padding bit known on the receiving device 5 side was added to the information bit of the coded data according to the coded rate to be changed, and the coded rate obtained by performing the error correction coding process was changed. The parity of the block code is replaced with the parity added to the coded data generated by the transmission device 2 (or the transmission device 3), and the padding bit is removed to generate the coded data for retransmission. Has a function. Further, when the transmission server 6 changes the coding rate of the coded data generated by the transmitting device 2 (or the transmitting device 3) and retransmits the data, the transmission server 6 converts the coded data into a code rate lower than the code rate before the change. In this case, the information bit of the coded data is divided between transmission / reception (between the transmission server 6 and the reception device 5) by a predetermined division method (divided into two equal parts in the example described in detail later), and the code is changed. A padding bit known on the receiving device 5 side is added to each of the information bits divided according to the conversion rate, and the parity of the block code obtained by performing the error correction coding process and changing the coding rate is transmitted. It has a function of replacing and adding the parity added to the coded data generated by the device 2 (or the transmitting device 3) and generating the coded data for retransmission from which the padding bit is removed.

Although the transmission system 1 illustrated in FIG. 1 has been described as including the transmission device 2 and the transmission device 3, only one of the transmission device 2 and the transmission device 3 may be used. In the transmission system 1 illustrated in FIG. 1, the transmission device 2 (or the transmission device 3) and the transmission server 6 are described as separate bodies, but the transmission device 2 (or the transmission device 3) is provided with the transmission server 6. As one or a plurality of transmission devices 2 (or transmission devices 3), instead of connecting with a local area network, a simple signal cable may be used for connection.

When a plurality of transmission servers 6 are configured, the load distribution device 7 is provided between the plurality of transmission servers 6 and the IP network 8, and is a retransmission request packet from many reception devices 5 via the IP network 8. Is a device that distributes the processing load of each of the plurality of transmission servers 6 and divides and transmits the coded data packet related to the retransmission request. In the transmission system shown in FIG. 1, a plurality of receiving devices 5 registered in advance as users are targeted, and by interposing a load balancing device 7, it is sufficient to add a transmitting server 6 even when the number of registered users increases. It becomes a thing. However, when the transmission servers 6 corresponding to the number of user registrations allowed in advance are individually arranged, the installation of the load balancer 7 may be omitted, and the transmission server 6 and the IP network 8 may be directly connected. good.

Hereinafter, the transmitting device 2 (or the transmitting device 3), the transmitting server 6, and the receiving device 5 will be described more specifically in this order.

[Transmitter]
FIG. 2 is a block diagram showing a schematic configuration of a transmission server 6 and a transmission device 2 (or a transmission device 3) according to an embodiment of the present invention. The transmission device 2 (or transmission device 3) shown in FIG. 2 shows only the main components according to the present invention, and the description of other components such as energy (electric power) diffusion processing will be omitted.

The transmission device 2 and the transmission device 3 adopt an error correction coding process and a modulation method suitable for each broadcast transmission line (satellite broadcast transmission line or terrestrial broadcast transmission line), but as shown in FIG. 2, an error occurs. It will be comprehensively described as including the correction coding unit 21 and the modulation unit 22.

The error correction coding unit 21 is a encoder that generates coded data by performing error correction coding processing on transmission data related to digital broadcasting and imparting error correction code parity, and outputs the coded data to the modulation unit 22. be. Further, the error correction coding unit 21 manages the sequentially generated coded data as an error correction code frame, assigns a frame number or time information that functions as a synchronization signal, to the transmission server 6 via the local area network. It has a function to send.

The modulation unit 22 digitally modulates the coded data obtained from the error correction coding unit 21 by a predetermined modulation method to generate a modulated wave signal, and radiates radio waves related to digital broadcasting via a broadcast transmission line.

The transmission data related to digital broadcasting can be, for example, MPEG2-TS described in ARIB STD-B31 and used in terrestrial digital broadcasting when transmitted via a terrestrial broadcasting transmission path, for example, a satellite broadcasting transmission path. When transmitting via, it can be TLV (Type Length Value) format data described in ARIB STD-B44 and used in advanced wideband satellite digital broadcasting.

In the current terrestrial digital broadcasting, error correction coding processing is performed using a convolutional code as an internal code and a connected code in which a Reed-Solomon code is connected as an external code. In the next-generation terrestrial digital broadcasting, it is considered to perform error correction coding processing with a concatenated code in which an LDPC code is concatenated as an internal code and a BCH (Bose-Chaudhuri-Hocquenghem) code is concatenated as an external code. Further, in advanced broadband satellite digital broadcasting, error correction coding processing is performed using a concatenated code in which an LDPC code is concatenated as an internal code and a BCH code is concatenated as an external code.

[Sending server]
The transmission server 6 shown in FIG. 2 digitally modulates the coded data encoded by using the error correction code related to digital broadcasting and transmits the encoded data to the receiving device 5 via the broadcasting transmission line (or the transmitting device 3). ), Sequentially input from), save while updating for a predetermined time, and of the coded data, the coded data requested to be retransmitted from the receiving device 5 is coded data transmitted on the broadcast transmission line according to the communication quality information. It is configured as a computer that can be transmitted to the receiving device 5 via the IP network 8 by selectively changing and reconfiguring the coding rate by distinguishing whether it is higher or lower than the coding rate of the storage unit. It includes 61, an IP packet generation unit 62, a retransmission request processing unit 63, a coding rate adaptation change unit 64, and a communication quality control unit 65.

The storage unit 61 sequentially inputs the coded data generated by the transmission device 2 (or the transmission device 3) based on the synchronization signal (frame number or time information) via the local area network, and the code of the error correction code. It is a functional unit that manages error correction code frames constituting the length in time series with a synchronization signal (frame number or time information) and saves them while updating a predetermined time. The coded data obtained from the transmission device 2 (or the transmission device 3) includes a frame number identified by a TMCC (Transmission and Multiplexing Configuration Control) signal, which is a control signal in a digital broadcast used in a broadcast transmission line. Time information is attached as a synchronization signal. For example, in the data transmission method using a broadcast transmission line, the storage unit 61 embeds time information (also embeds time information in the main signal) included in the TMCC signal transmitted together with the coded data in the error correction code frame unit. The coded data of the error correction code frame unit sequentially obtained from the transmission device 2 (or the transmission device 3) by receiving the coded data in units of the error correction code frame, and the frame number associated with the time information is used as a synchronization signal, and the synchronization signal is used. It can be managed with. Further, the coded data managed in time series by the storage unit 61 by the synchronization signal (frame number or time information) may be notified from the transmission server 6 via the IP network 8 while being received during digital broadcasting. That is, in the transmission system 1 shown in FIG. 1, by using the time information and the frame number contained in the TMCC signal or the main signal as the synchronization signal, the transmission devices 2, 3 and the reception devices 5, one or a plurality of units can be used. It is possible to secure the synchronization of the transmission server 6 and the load balancer 7 provided when a plurality of transmission servers 6 are configured.

The IP packet generation unit 62 is a functional unit that generates an IP packet format encoded data packet that stores the encoded data related to the retransmission request from the receiving device 5 and transmits the encoded data packet to the receiving device 5 via the IP network 8. Is. This coded data packet is generated when it is determined in the receiving device 5 that the bit error of the coded data cannot be corrected by using the error correction code used in the transmitting device 2 (or the transmitting device 3). Although the details will be described later, the IP packet generation unit 62 represents an identification header for making each interleave frame related to the interleave processing identifiable on the receiving device 5 side, and a bit number in each error correction code frame. After assigning a sequence number that specifies whether or not, the bits are rearranged so as to traverse each error correction code frame based on a predetermined rule that the bits of the coded data related to the retransmission request are separated by a predetermined value or more. It has an interleaving unit 621 that executes the interleaving process to be performed.

When the retransmission request processing unit 63 receives the retransmission request packet from the receiving device 5 via the IP network 8, the communication quality information measured by the receiving device 5 stored in the retransmission request packet and the error correction related to the retransmission request. The retransmission request information indicating the coded data of the code frame is extracted. Then, the retransmission request processing unit 63 encodes the coded data transmitted on the broadcast transmission line based on the communication quality information received this time according to a predetermined coding rate change standard managed by the communication quality management unit 65. Determine whether to resend by changing the rate. Then, the retransmission request processing unit 63 searches for the location of the coded data related to the retransmission request from the storage unit 61 based on the retransmission request information received this time according to the determination result, and constitutes the encoded data. The storage unit 61 is controlled so as to read m frames of error correction code frames having continuous synchronization signals (frame numbers or time information) starting from the error correction code frame and output them to the code rate adaptation change unit 64. The code rate adaptive change unit 64 is controlled so that the code rate of the read coded data is adaptively changed and reconstructed and output to the IP packet generation unit 62. A control example related to the retransmission request processing unit 63 will be described later with reference to FIG.

The code rate adaptation change unit 64 is controlled by the retransmission request processing unit 63, and switches between when the code rate of the coded data generated by the transmission device 2 (or the transmission device 3) is changed and when it is not changed. The switching units 641 and 642 are based on the same coding method as the error correction coding method used in the transmission device 2 (or transmission device 3) when the coding rate is changed, and the transmission device 2 (or transmission device 3) is used. Of the predetermined number of coding rates that can be used in 3), the coding rate is distinguished by distinguishing whether the coding rate is higher or lower than the coding rate of the coded data generated by the transmission device transmitted on the broadcast transmission line. An error correction coding unit 643 that performs an error correction coding process for changing the rate is provided.

More specifically, when the switching units 641 and 642 retransmit the coded data (encoded data transmitted on the broadcast transmission line) related to the retransmission request read from the storage unit 61 without changing the coding rate. When the data is output to the IP packet generation unit 62 as it is, the code rate is changed and retransmitted, the coded data reconstructed by changing the code rate by the error correction coding unit 643 is output to the IP packet generation unit 62. It is a functional part that switches so as to.

For example, when the coding rate of the transmission via the broadcast transmission line and the transmission via the IP line 8 are the same, the coding rate adaptation changing unit 64 is the transmission device 2 (or the transmission device 3) read from the storage unit 61. The coded data of the corresponding error correction code frame transmitted in 1 is output to the IP packet generation unit 62 as it is.

On the other hand, when the code rate adaptation change unit 64 retransmits the coded data whose code rate has been changed from the transmission via the broadcast transmission line, the error correction coding unit 643 changes the code rate.

When the error correction coding unit 643 changes the coding rate of the coded data (coded data transmitted on the broadcast transmission line) related to the retransmission request and retransmits the data, the storage unit 61 determines the coded data in the coded data. Only the information bits (that is, the main signal in the block code) excluding the parity of are read. Subsequently, the error correction coding unit 643 uses the information bit of the coded data as it is when converting to a coding rate higher than the coding rate before the change, and the coding rate is lower than the coding rate before the change. When converting to a rate, the information bit of the coded data is divided into two by a predetermined division method between transmission and reception, and it is known between the transmission server 6 and the reception device 5 according to the coding rate to be changed. A padding bit consisting of bits (all "0" or "1" bits, or a regular bit pattern of "0" and "1") is added to a known insertion position between transmission and reception. Then, the error correction coding unit 643 is the same as the error correction coding method used by the error correction coding unit 21 in the transmission device 2 (or the transmission device 3) for the predetermined information bit to which the padding bit is added. The error correction coding process is performed based on the coding method of the above and at a coding rate different from the coding rate transmitted on the broadcasting transmission line that can be used by the transmitting device 2 (or the transmitting device 3) related to broadcasting. Finally, the error correction coding unit 643 encodes the parity of the block code whose coding rate is changed for the coded data transmitted on the broadcast transmission line by the transmission device 2 (or the transmission device 3). Encoded data for retransmission is generated by replacing the parity added to the data with the information bit and removing the padding bit. Error correction of the code rate adaptive change unit 64 The method of generating coded data when the code rate is changed by the code rate unit 643 will be described later with reference to FIGS. 4 and 5.

The communication quality control unit 65 is controlled by the retransmission request processing unit 63, and is used to determine a coding rate according to the communication quality information stored in the retransmission request packet received from the receiving device 5. It is a functional unit that holds and manages rate change criteria as information. The standard for changing the coding rate will be described later with some examples. Further, this communication quality information is generated by the receiving device 5, and includes one or both of the delay information of the communication line and the packet loss rate information.

The delay information of the communication line is the time difference between the transmission time of the retransmission request packet transmitted from the receiving device 5 to the transmitting server 6 and the receiving time of the coded data packet retransmitted from the transmitting server 6 correspondingly. Information indicating the estimated transmission delay.

The packet loss rate information considers that packet loss has occurred when the corresponding encoded data packet cannot be received from the transmission server 6 even after a predetermined time has elapsed from the transmission time of the retransmission request packet, and the transmission server in units of a predetermined period. This is information indicating the packet loss rate measured based on the communication record with 6.

(Control flow related to retransmission request packet)
FIG. 3 is a flowchart showing a control flow relating to a retransmission request packet between the transmitting server 6 and the receiving device 5 according to the embodiment of the present invention.

First, the transmission server 6 stores the coded data transmitted on the broadcast transmission line by the storage unit 61 while updating the coded data for a predetermined time (step S50). The coded data transmitted on the broadcast transmission line is error-corrected coded data, and is composed of an error-correcting code frame of a block code such as the LDPC code described in ARIB STD-B44.

The receiving device 5 receives and demodulates the digital broadcast transmitted on the broadcast transmission line, and attempts to correct the bit error of the coded data. If the transmission environment is good and the data can be received without error, or if the influence of white noise or the like is within the range that can be decoded by the error correction code, the received data that has been error-corrected and decoded is output reproducibly. When the transmission environment is bad such as rainfall attenuation and the bit error of the coded data received via the broadcast transmission line cannot be corrected, the receiving device 5 is after the decoding process including the bit error of the coded data via the broadcast transmission line. Post-LLR (broadcast) or pre-LLR (broadcast) before decryption processing is temporarily held, a retransmission request packet is generated for the corresponding coded data through the IP network 8, and a retransmission request is made to the transmission server 6 (step). S51). As described above, the retransmission request packet includes the retransmission request information and the communication quality information.

Therefore, when the transmission server 6 receives the retransmission request packet from the receiving device 5 by the retransmission request processing unit 63 (step S52), the transmission server 6 extracts the retransmission request information and the communication quality information from the retransmission request packet (step S53).

Subsequently, the retransmission request processing unit 63, based on the communication quality information received this time, encodes the coded data transmitted on the broadcast transmission line according to a predetermined coding rate change standard managed by the communication quality management unit 65. It is determined whether or not to change the conversion rate and retransmit (step S54). The standard for changing the coding rate will be described later with some examples.

Then, when the retransmission request processing unit 63 determines that the encoding data transmitted on the broadcast transmission line is to be retransmitted without changing the coding rate (step S54: No), the retransmission request processing unit 63 saves the data based on the retransmission request information received this time. The storage unit 61 and the coding rate adaptation change so that the location of the coded data related to the retransmission request is searched for and read from the unit 61 and retransmitted at the same coding rate as the coding rate of the coded data transmitted on the broadcast transmission line. The unit 64 is controlled (step S55).

On the other hand, when the retransmission request processing unit 63 changes the coding rate of the coded data transmitted on the broadcast transmission line and determines that the data is to be retransmitted (step S54: Yes), the storage unit 63 is based on the retransmission request information received this time. The location of the coded data related to the retransmission request is searched from 61, and only the information bits (that is, the main signal in the block code) excluding the predetermined parity in the coded data are read out. Then, the retransmission request processing unit 63 changes the coding rate by distinguishing whether the coding rate is higher or lower than the coding rate of the coded data transmitted on the broadcast transmission line. That is, the retransmission request processing unit 63 uses the information bit of the coded data as it is when converting to a code rate higher than the code rate before the change, and sets the code rate lower than the code rate before the change. When converting, the information bit of the coded data is divided into two by a predetermined division method between transmission and reception. That is, when converting to a coding rate lower than the coding rate before the change, the number of the information bits is larger than the number of information bits with respect to the changed coding rate. Therefore, the information bits are divided into two. Process so that the same code format of the error correction code specified in the broadcasting standard can be applied. After that, the information bits are undivided when converting to a coding rate higher than the coding rate before the change, and divided into two when converting to a coding rate lower than the coding rate before the change. For retransmission in which the padding bit known on the receiving device 5 side is added, the parity of the block code whose coding rate is changed from the coding rate of the coded data transmitted on the broadcast transmission line is added, and then the padding bit is removed. The storage unit 61 and the coding rate adaptation change unit 64 are controlled so as to generate the coded data of (step S56).

Finally, the transmission server 6 configures an interleaved frame by the IP packet generation unit 62 using the error correction code frame for m frames, and interleaves in the direction of longitudinally crossing (orthogonal) the error correction code frame for m frames. It processes to generate an IP packet string (encoded data packet), and when the encoding rate is changed, a coding rate change notification packet is generated and transmitted as a notification to that effect, and then the encoded data packet is received. Transmission to the device 5 (step S57). It should be noted that the transmission server 6 may be in a form of forming a coded data packet including the code rate information and transmitting the coded data packet to the receiving device 5. In this example, in order to improve the transmission efficiency of the coded data packet, when the coding rate is changed, the receiving device 5 is notified in advance of the coding rate change notification packet as a notification to that effect. ..

Further, the transmission server 6 may be configured to transmit the coding rate change notification packet a plurality of times, or may be configured to obtain a reception confirmation response of the coding rate change notification packet, and receive a reception confirmation response from the receiving device 5. The code rate change notification packet may be repeatedly transmitted until it is received. When the coding rate of the coded data transmitted via the IP network 8 is the same as the coding rate of the coded data transmitted on the broadcast transmission line, the receiving device 5 has only information on the coding rate on the broadcast transmission line. The transmission server 6 may omit the advance notification of the code rate change notification packet as long as it can be grasped, but the coded data packet may be retransmitted every time the code rate is changed regardless of whether or not the code rate is changed. The code rate change notification packet may be transmitted.

Here, the communication quality information acquired from the receiving device 5 includes either one or both of the delay information of the communication line and the packet loss rate information, and which coding rate is based on these information. Whether to change to is performed according to a predetermined coding rate change standard managed by the communication quality control unit 65.

The coding rate change standard is based on the same coding method as the error correction coding method used by the error correction coding unit 21 in the transmission device 2 (or transmission device 3), and is based on the transmission device 2 (or transmission device 3) related to broadcasting. Of the predetermined number of coding rates that can be used in 3), the coding rate is changed by distinguishing whether the coding rate is higher or lower than the coding rate of the coded data transmitted on the broadcast transmission line. It has established.

For example, one of the following (1) to (9) can be used as the coding rate change criterion.
(1) Considering only the delay, when the delay obtained from the receiving device 5 is within the predetermined range of the predetermined default value, the data is retransmitted at the coding rate of the coded data transmitted on the broadcast transmission line. When the delay obtained from the receiving device 5 is less than the predetermined range of the predetermined default value, the code of the coded data transmitted on the broadcast transmission line among the multi-step coding rates determined according to the arbitrary delay. Change to the coding rate corresponding to the corresponding delay within the range higher than the conversion rate to improve the transmission efficiency, and if the delay obtained from the receiving device 5 exceeds the predetermined range of the predetermined default value, an arbitrary delay Of the multi-step coding rates determined according to the above, the delay is changed to the coding rate corresponding to the corresponding delay within the range lower than the coding rate of the coded data transmitted on the broadcast transmission line. Try to prevent resistance to packet loss due to it in advance.
(2) Considering only the packet loss rate, when the packet loss rate obtained from the receiving device 5 is within a predetermined range of a predetermined default value, the data is retransmitted with the coding rate of the coded data transmitted on the broadcast transmission line. When the packet loss rate obtained from the receiving device 5 is less than the predetermined range of the predetermined default value, the broadcast transmission line is among the multi-step coding rates determined according to the arbitrary packet loss rate. The packet loss rate obtained from the receiving device 5 is predetermined by changing to a coding rate corresponding to the corresponding packet loss rate within a range higher than the coding rate of the coded data transmitted in 1 to improve the transmission efficiency. When it exceeds the predetermined range of the default value, it corresponds within the range of the multi-step coding rate determined according to the arbitrary packet loss rate, which is lower than the coding rate of the coded data transmitted on the broadcast transmission line. Change the coding rate to correspond to the packet loss rate to increase the resistance to packet loss.
(3) Considering both the delay and the packet loss rate, the delay obtained from the receiving device 5 is within a predetermined range of a predetermined default value, or the packet loss rate obtained from the receiving device 5 is predetermined. When it is within the predetermined range of the default value, it shall be retransmitted with the coding rate of the coded data transmitted on the broadcast transmission line, and the delay obtained from the receiving device 5 is less than the predetermined range of the predetermined default value and the reception is received. When the packet loss rate obtained from the device 5 is less than the predetermined range of the predetermined default value, the coding transmitted on the broadcast transmission line among the multi-step coding rates determined according to the arbitrary packet loss rate. The transmission efficiency is improved by changing to the coding rate corresponding to the corresponding packet loss rate within the range higher than the data coding rate, and the delay obtained from the receiving device 5 exceeds the predetermined range of the predetermined default value. When the packet loss rate obtained from the receiving device 5 exceeds a predetermined range of a predetermined default value, the data is transmitted on the broadcast transmission line among the multi-step coding rates determined according to the arbitrary packet loss rate. Change to the coding rate corresponding to the corresponding packet loss rate within the range lower than the coding rate of the coded data to increase the resistance to packet loss.
(4) Considering only the delay, when the delay obtained from the receiving device 5 is within the predetermined range of the predetermined default value, the data is retransmitted at the coding rate of the coded data transmitted on the broadcast transmission line. When the delay obtained from the receiving device 5 is less than the predetermined range of the predetermined default value, the coding is increased by a predetermined step (for example, one step) within a range higher than the coding rate of the coded data transmitted on the broadcast transmission line. The transmission efficiency is increased by changing to a rate, and when the delay obtained from the receiving device 5 exceeds a predetermined range of a predetermined default value, it is within a range lower than the coding rate of the coded data transmitted on the broadcast transmission line. The coding rate is changed to a predetermined stage (for example, one stage) lower so as to prevent the resistance to packet loss due to the delay in advance.
(5) Considering only the packet loss rate, when the packet loss rate obtained from the receiving device 5 is within a predetermined range of a predetermined default value, the data is retransmitted with the coding rate of the coded data transmitted on the broadcast transmission line. When the packet loss rate obtained from the receiving device 5 is less than a predetermined range of a predetermined default value, a predetermined stage (for example, a predetermined stage) within a range higher than the coding rate of the coded data transmitted on the broadcast transmission line. 1 step) Change to a higher coding rate to improve transmission efficiency, and when the packet loss rate obtained from the receiving device 5 exceeds the predetermined range of the predetermined default value, the code of the coded data transmitted on the broadcast transmission line. The coding rate is changed to a predetermined step (for example, one step) lower within the range lower than the conversion rate to increase the resistance to packet loss.
(6) Considering both the delay and the packet loss rate, the delay obtained from the receiving device 5 is within a predetermined range of a predetermined default value, or the packet loss rate obtained from the receiving device 5 is predetermined. When it is within the predetermined range of the default value, it shall be retransmitted with the coding rate of the coded data transmitted on the broadcast transmission line, and the delay obtained from the receiving device 5 is less than the predetermined range of the predetermined default value and the reception is received. When the packet loss rate obtained from the device 5 is less than the predetermined range of the predetermined default value, the code is one step higher (for example, one step) higher than the coding rate of the coded data transmitted on the broadcast transmission line. The transmission efficiency is improved by changing to the conversion rate, the delay obtained from the receiving device 5 exceeds the predetermined range of the predetermined default value, and the packet loss rate obtained from the receiving device 5 is the predetermined default value. When the range is exceeded, the coding rate is changed to a predetermined step (for example, one step) lower within the range lower than the coding rate of the coded data transmitted on the broadcast transmission line to increase the resistance to packet loss.
(7) Considering only the delay, when the delay obtained from the receiving device 5 is within the predetermined range of the predetermined default value, the data is retransmitted at the coding rate of the coded data transmitted on the broadcast transmission line. When the delay obtained from the receiving device 5 is less than the predetermined range of the predetermined default value, the maximum value code that can be used by the transmitting device 2 (or the transmitting device 3) relating to the coded data transmitted on the broadcast transmission line. When the delay obtained from the receiving device 5 exceeds a predetermined range of a predetermined default value, the transmission device 2 (or the transmitting device) related to the coded data transmitted on the broadcast transmission line is changed to the conversion rate to improve the transmission efficiency. The coding rate is changed to the minimum value that can be used in 3) so as to prevent the resistance to packet loss due to the delay in advance.
(8) Considering only the packet loss rate, when the packet loss rate obtained from the receiving device 5 is within a predetermined range of a predetermined default value, the data is retransmitted with the coding rate of the coded data transmitted on the broadcast transmission line. When the packet loss rate obtained from the receiving device 5 is less than the predetermined range of the predetermined default value, it can be used by the transmitting device 2 (or the transmitting device 3) related to the coded data transmitted on the broadcast transmission line. When the packet loss rate obtained from the receiving device 5 exceeds the predetermined range of the predetermined default value, the coded data transmitted on the broadcast transmission line is used. The coding rate is changed to the minimum value that can be used by the transmission device 2 (or the transmission device 3) so as to increase the resistance to packet loss.
(9) Considering both the delay and the packet loss rate, the delay obtained from the receiving device 5 is within a predetermined range of a predetermined default value, or the packet loss rate obtained from the receiving device 5 is predetermined. When it is within the predetermined range of the default value, it shall be retransmitted with the coding rate of the coded data transmitted on the broadcast transmission line, and the delay obtained from the receiving device 5 is less than the predetermined range of the predetermined default value and the reception is received. When the packet loss rate obtained from the device 5 is less than the predetermined range of the predetermined default value, the maximum value that can be used by the transmission device 2 (or the transmission device 3) related to the coded data transmitted on the broadcast transmission line. The coding rate is changed to improve the transmission efficiency, the delay obtained from the receiving device 5 exceeds the predetermined range of the predetermined default value, and the packet loss rate obtained from the receiving device 5 is the predetermined default value. When it exceeds a predetermined range, the coding rate is changed to the minimum value that can be used by the transmitting device 2 (or the transmitting device 3) related to the coded data transmitted on the broadcast transmission line to improve the resistance to packet loss. ..

(Generation method of coded data when changing the code rate: When changing to a higher code rate)
With reference to FIG. 4, when the coded data related to the retransmission request is changed to a higher code rate, the retransmission request processing unit 63 changes the code rate adaptation to the storage unit 61 and the code rate according to the coding rate change standard exemplified above. An example of controlling the unit 64 to generate coded data when the code rate is changed will be described. 4 (a) to 4 (d) show higher codes for the coded data related to the retransmission request when the code rate is changed by the code rate adaptive change unit 64 in the transmission server 6 of the embodiment according to the present invention, respectively. It is a figure which shows the generation method of the coded data (at the time of changing to the conversion rate).

First, FIG. 4A is a diagram showing a configuration of an error correction code frame of a block code showing coded data transmitted on a broadcast transmission line. Usually, in digital broadcasting, a plurality of types of selectable coding rates are predetermined. For example, in ARIB STD-B44, among the LDPC codes which are block codes, 41/120 (≈1/3), 49/120 (≈2/5), 61/120 (≈1/2), 73/120 (≈) 3/5), 81/120 (≈2/3), 89/120 (≈3/4), 93/120 (≈7/9), 97/120 (≈4/5), 101/120 (≈ Eleven types of coding rates of 5/6), 105/120 (≈7/8), and 109/120 (≈9 / 10) are specified.

Information on the coding rate of the coded data transmitted on the broadcast transmission line is usually transmitted as a TMCC (Transmission and Multiplexing Configuration Control) signal, which is a transmission control signal in digital broadcasting, but is transmitted from the transmission server 6. It may be configured to notify in advance via the IP network 8. Further, as described above, regarding the information on the coding rate of the coded data to be retransmitted in response to the retransmission request, the transmission server 6 indicates that when the coding rate is changed by the IP packet generation unit 62. A code rate change notification packet is generated and transmitted as a notification, or the coded data packet including the code rate information is transmitted to the receiving device 5. Here, when the coding rate of the coded data transmitted via the IP network 8 is the same as the coding rate of the coded data transmitted on the broadcast transmission line, the receiving device 5 has information on the coding rate on the broadcast transmission line. Since it is only necessary to know, the transmission server 6 may omit the advance notification of the coding rate change notification packet.

As shown in FIG. 4 (a), when the coding rate of the coded data in the block code having a code length N bits transmitted by the broadcast transmission path to F _b, the information bits of the encoded data (i.e., the block code The main signal) is composed of N × F _b bits, and the parity is composed of N × (1-F _b ) bits. Normally, when a block code is used in a broadcast transmission line, the number of bits of the code length of the error correction code frame is often constant regardless of the coding rate so that it can be easily handled in the broadcast transmission line. For example, in ARIB STD-B44, the code length N of the LDPC code, which is a block code, is constant at N = 44880 bits regardless of the LDPC coding rate. Here, the coding rate of the coded data to be retransmitted via the IP network 8 When F _i, the encoded data transmitted by the broadcast transmission channel as coding rate F _i of the coded data to be retransmitted over IP rope 8 when changing higher than the coding rate, the information bits transmitted by the broadcast transmission path used as it is, into a coding rate F _i.

Therefore, the transmission server 6 that has received the retransmission request packet from the receiving device 5 extracts the communication quality information included in the retransmission request packet by the retransmission request processing unit 63, and based on the communication quality information, the communication quality management unit 65. It is determined whether or not to change the coding rate by referring to the coding rate change standard managed in.

Then, the retransmission request processing section 63, when it is determined to change the coding rate F _b of the transmission encoded data in a broadcast transmission path to the coding rate F _i is (F b _{<F i),} First, FIG. 4 ( Of the coded data of N bits of code length related to the retransmission request shown in a), _{only the information bit of N × F b} bits (that is, the main signal in the block code) is read out from the storage unit 61 (FIG. 4 (b). )reference).

Subsequently, the retransmission request processing unit 63 controls the coding rate adaptation change unit 64, and the N × F _b bit information bit (that is, in the block code) read from the storage unit 61 by the error correction coding unit 643. with respect to the main signal), it is added to a known value (e.g., insertion location to known between transmission and reception of N × (F i _{-F b)} bits with all zero bits) as padding bits between transmission and reception, this It applies error correction coding processing as a coding rate F _i to the information bits and padding bits, generates parity of N × (1-F _i) bits (see FIG. 4 (c)). For example, error correction coding unit 643, a coding rate F _i, N × F _b information bits (i.e., main signal in the block code) while using a transmission apparatus 2 (or transmitted from the coding rate F _b Change to the maximum code rate that can be used in the device 3). In this example, although the padding bit is shown as being added after the information bit, the padding bit may be added before the information bit, that is, the insertion position of the padding bit is a code after the change. it is sufficient to set in advance as known between transmission and reception by the value of the ratio F _i.

Then, the error correction coding unit 643 removes the padding bit and reconstructs the coded data for retransmission in which the parity of the N × (1- _{Fi ) bit is added to the information bit of the N × F b bit.} , Is output to the IP packet generation unit 62 (see FIG. 4D). Since the frame length of the reconstructed coded data for retransmission is shorter than the original code length N bits, the transmission efficiency is higher than when the coded data for the code length N bits is retransmitted to the receiving device 5. It gets higher.

(Generation method of coded data when changing the code rate: When changing to a lower code rate)
Next, referring to FIG. 5, when the coded data related to the retransmission request is changed to a lower coding rate, the retransmission request processing unit 63 encodes the storage unit 61 and the code rate according to the coding rate change standard exemplified above. An example of controlling the rate adaptation change unit 64 to generate coded data when the code rate is changed will be described. 5 (a) to 5 (e) show a lower code for the coded data related to the retransmission request when the code rate is changed by the code rate adaptive change unit 64 in the transmission server 6 of the embodiment according to the present invention, respectively. It is a figure which shows the generation method of the coded data (at the time of changing to the conversion rate).

As shown in FIG. 5 (a), when the coding rate of the coded data in the block code having a code length N bits transmitted by the broadcast transmission path to F _b, the information bits of the encoded data (i.e., the block code The main signal) is composed of N × F _b bits, and the parity is composed of N × (1-F _b ) bits. Normally, when a block code is used in a broadcast transmission line, the number of bits of the code length of the error correction code frame is often constant regardless of the coding rate so that it can be easily handled in the broadcast transmission line. For example, in ARIB STD-B44, the code length N of the LDPC code, which is a block code, is constant at N = 44880 bits regardless of the LDPC coding rate. Here, if the coding rate of the coded data to be retransmitted via the IP network 8 to F _i, the information bits of the coding rate F _i Ordinarily N × F _i, parity, N × (1-F _i) becomes a bit, to become excessive relative to the coding length of the error correction code standards broadcasting standards, broadcast code rate F _i of the coded data to be retransmitted over IP rope 8 in this embodiment When changing the coding rate of the coded data transmitted on the transmission line to _{less than F b} , the original information bit is divided into two equal parts so that the code is stored in the coded length of the error correction code specified by the broadcasting standard. Reconfigure and reconstruct the coded data.

More specifically, first, the transmission server 6 that has received the retransmission request packet from the receiving device 5 extracts the communication quality information included in the retransmission request packet by the retransmission request processing unit 63, and based on the communication quality information. , It is determined whether or not to change the coding rate with reference to the coding rate change standard managed by the communication quality management unit 65.

For example, assuming that the code rate change criterion of (9) above is followed, the retransmission request processing unit 63 has a delay obtained from the receiving device 5 less than a predetermined default value, or a packet loss rate obtained from the receiving device 5. If is less than the predetermined default value, it is determined that there is no change in the coding rate of the coded data transmitted on the broadcast transmission line (F _b = _Fi ), and the retransmission request shown in FIG. 5 (a) is concerned. The code rate adaptation change unit 64 is controlled so that the coded data having a code length of N bits is read from the storage unit 61 and output to the IP packet generation unit 62 as it is.

On the other hand, when the delay obtained from the receiving device 5 is equal to or higher than a predetermined default value and the packet loss rate obtained from the receiving device 5 is equal to or higher than a predetermined default value, the retransmission request processing unit 63 performs a broadcast transmission line. in determining the coding rate F _b of the transmission encoded data to change the coding rate _{F i (F b> F i} ), first, the code length N-bit code according to the retransmission request shown in FIG. 5 (a) Of the converted data, only the N × F _b bit information bit (that is, the main signal in the block code) is read out from the storage unit 61 (see FIG. 5 (b)).

Subsequently, the retransmission request processing unit 63 controls the coding rate adaptation change unit 64, and _{the information bit of N × F b} bits read from the storage unit 61 by the error correction coding unit 643 (that is, in the block code). The main signal) is divided into two between transmission and reception by a predetermined division method ((N × F _b ) / 2). Here, an example is made in which the first half and the second half of the information bit position are divided into two equal parts (see FIG. 5C), but even if other division methods are used, such as dividing into two by odd-numbered bits and even-numbered bits. good.

Subsequently, the retransmission request processing unit 63 controls the coding rate adaptation change unit 64, and for each of the information bits ((N × F _b ) / 2) divided into two, a value known between transmission and reception ( For example, N × _Fi − ((N × F _b ) / 2) bits (all 0 bits) are added as padding bits to the insertion positions known between transmission and reception, and the information bits and padding bits are used. applies error correction coding processing as a coding rate _{F i,} to generate the parity of N × _{(1-F i)} bits (see FIG. 5 (d)). For example, error correction coding unit 643, a coding rate F _i, N × F _b information bits (i.e., main signal in the block code) while using a transmission apparatus 2 (or transmitted from the coding rate F _b Change to the minimum code rate that can be used in the device 3). In this example, although the padding bit is shown as being added after the information bit, the padding bit may be added before the information bit, that is, the insertion position of the padding bit is a code after the change. it is sufficient to set in advance as known between transmission and reception by the value of the ratio F _i.

Then, the error correction coding unit 643 removes the padding bit and adds the parity of N × (1- _{Fi ) bit to the information bit of (N × F b} ) / 2 bit, and encodes the data for retransmission. Is reconstructed and output to the IP packet generation unit 62 (see FIG. 5E). The frame length of the reconstructed coded data for retransmission is shorter than the original code length N bits, does not exceed the coded length of the error correction code specified by the broadcasting standard, and the retransmission request. The coded data according to the above can be changed to a lower coding rate, and the correction capability is higher than in the case of retransmitting without changing the coding rate.

In this way, when the transmission server 6 receives the retransmission request packet, it is encoded by adaptively changing the coding rate of the encoded data related to the retransmission request based on the communication quality information included in the retransmission request packet. A data packet is generated and transmitted to the receiving device 5.

(How to generate a coded data packet)
The transmission server 6 is an IP packet generation unit in order to achieve high correction performance even for burst packet loss caused by the IP line 8 when transmitting the encoded data requested to be retransmitted to the receiving device 5 through the IP network 8. With reference to FIG. 6, an interleave frame of n × m, which will be described later, is constructed according to FIG. 6, an IP packet sequence with an identification header, a sequence number, and an IP header is generated, and the transmission order of IP packets is interleaved according to the sequence number. Then, it is preferable to transmit the coded data packet to the receiving device 5.

More specifically, with reference to FIG. 6, a method of generating an IP packet of the IP packet generation unit 62 in the transmission server 6 will be described. 6 (a) to 6 (d) are explanatory views of an IP packet generation method of the IP packet generation unit 62 in the transmission server 6 of the embodiment according to the present invention, respectively.

First, IP packet generating unit 62, a coding rate adaptively changing unit 64, respectively constituted by code length n bits of the same code rate F _i, the synchronization signal related to the retransmission request (frame number or time information) Error correction code frames constituting the coded data included The error correction code frames for m frames having continuous synchronization signals (frame numbers or time information) starting from the code frames are input to form an n × m interleaved frame. Although m is a fixed value, it can be variably set from the outside and is a value shared between transmission and reception. Further, an n = N when code length n bits of code rate F _i has not changed since the code length N bits of encoded rate F _b used in the broadcast transmission path, the code length of the code rate F _b When changed from N bits, n <N.

Therefore, the IP packet generation unit 62 temporarily stores the error correction code frames of m frames including the error correction code frames as the coded data related to the retransmission request in the storage unit (not shown) so as to be arranged in the vertical direction (not shown). See FIG. 6 (a)).

Subsequently, the IP packet generation unit 62 reads each bit from the beginning into the error correction code frame of the m frame by the interleaving unit 621, and n-packets the m-bit IP payload as the packet length excluding the header of the generated IP packet. Minutes are generated (see FIG. 6 (b)). That is, of the 1 to n bits of each error correction code frame, the same bit of each bit is collected by 1 bit to form an m bit, which is used as an IP payload.

Subsequently, the IP packet generation unit 62 has an identification header for making each interleave frame related to the interleave processing identifiable on the receiving device 5 side in the IP payload for n packets generated by the interleave unit 621, and each error. A sequence number for specifying which bit is represented in the correction code frame and an IP header are added as headers of the coded data packet to generate IP packets for n packets (see FIG. 6 (c)). In this example, the sequence numbers are represented as 1 to n for easy understanding, but the expression form can be used to identify which bit of the error correction code frame each IP packet represents for the receiving device 5. Is optional.

Further, as shown in FIG. 6B, one interleaved frame is composed of IP payloads for n packets generated from a plurality of error correction code frames. Therefore, if the IP packet generation unit 62 assigns, for example, ID = "1" to the identification header added to a certain interleave frame, ID = "2" is assigned to the identification header added to the next interleave frame. The identification header to be added to the next interleaved frame is assigned while incrementing ID = "3" so that the interleaved frame to which the ID = "3" belongs can be identified by the value of the identification header. Therefore, as shown in FIG. 6 (c), the identification header is added so as to have the same value in one interleaved frame. Therefore, on the receiving device 5 side, by referring to the identification header, it becomes possible to identify which interleaved frame the IP payload of the received coded data packet belongs to.

Subsequently, the IP packet generation unit 62 interleaves the generated n packets of IP packets by the interleaving unit 621 in the order of transmission to the IP network 8 according to the sequence number (for example, in ascending order of the sequence number). It may be transmitted in the transmission order of another sequence number determined between transmission and reception.), And it is transmitted to the receiving device 5 as a coded data packet.

The IP packet generation unit 62 in the present embodiment needs m (m is an integer of 1 or more) error correction code frames including the error correction code frames as the coded data related to the retransmission request. For example, the interleaving unit 621 cannot execute the interleaving process until the error correction code frames for m frames are aligned. Therefore, when time loss becomes a problem, only n1 (<n) for a predetermined number of bits as the sequence number among the n-bit error correction code frames related to the retransmission request, and m (m is an integer of 1 or more) are used. The total number of IP packets holding the corresponding sequence number may be reduced by extracting from the error correction code frame. Then, m and n are fixed values but can be variably set from the outside, so that the packet length of each IP packet can be adjusted.

Further, although the IP packet is generated by collecting one bit from each error correction code frame, it is also possible to collect a plurality of bits from each error correction code frame. Conversely, it is possible to treat two frames of error correction code frames as one frame, or to generate 2n m-bit packets. The IP payload for n packets generated in this way is regarded as one interleaved frame, and an identification header for making each interleaved frame identifiable on the receiving device 5 side and a sequence number for identifying each IP payload are assigned. That is, other interleaving techniques should be applied if the transmission order of each bit of the error correction code frame is rearranged so that the packet loss in the IP network 8 can be assumed in advance and alleviated. Is possible. Generally, the longer the period (signal length) targeted for interleaving processing, the more resistant to burst packet loss. Therefore, the optimum interleaving processing should be executed within an acceptable period for the entire transmission system 1. It constitutes an interleaved portion 621.

[Receiver]
FIG. 7 is a block diagram showing a schematic configuration of the receiving device 5 according to the embodiment of the present invention. The receiving device 5 includes a demodulation unit 51, an error correction decoding unit 52, a retransmission request packet generation unit 53, an IP packet reception unit 54, a communication path connection switch unit 55, and a communication quality measurement unit 56.

The demodulation unit 51 receives a modulated wave signal radiated from the transmission device 2 (or the transmission device 3) via the broadcast transmission line (satellite broadcast transmission line or terrestrial broadcast transmission line), demodulates the signal, and obtains the demodulation process. The coded data to be output is output to the error correction decoding unit 52.

The error correction decoding unit 52 calculates the log-likelihood ratio (LLR) of each bit of the coded data obtained from the demodulation unit 51 in advance of the error correction code decoding process, and the error correction decoding unit 52 calculates the log-likelihood ratio (LLR). Using the degree ratio (preliminary LLR), the error correction code frame constituting the code length of the error correction code is reconstructed, and the decoding process corresponding to the error correction coding process in the transmission device 2 (or the transmission device 3) is performed. It is a decoder that generates received data and outputs it to the outside for reproducibility.

Here, the error correction decoding unit 52 includes a decoding possibility determination unit 521, a coded data complement unit 522, a data combination unit 523, an LLR storage unit 524, and an LLR sharing unit 525.

The decoding possibility determination unit 521 determines whether or not error correction decoding is possible for the coded data constituting the error correction code frame, and when it is determined that the decoding is possible, decodes the coded data as it is to generate received data, and bit error of the coded data. If it is determined that the data cannot be corrected and cannot be decoded, the retransmission request information for the coded data constituting the error correction code frame is output to the retransmission request packet generation unit 53, and the data is retransmitted to the retransmission request packet generation unit 53. It has a function to generate a request packet. In the data transmission method using the broadcast transmission line, the coded data of the error correction code frame unit obtained by the receiving device 5 sequentially receiving via the demodulator 51 is included in the TMCC signal or the main signal transmitted together. Since it can be identified based on the time information to be transmitted and can be managed by a synchronization signal (frame number or time information) like the transmission server 6, this retransmission request information is an error correction code for retransmitting as a synchronization signal. It may include time information that makes the frame identifiable, or it may include the frame number.

The coded data complementing unit 522 extracts the coded data related to the retransmission request from the coded data packet received from the transmission server 6 in response to the transmission of the retransmission request packet by the retransmission request packet generation unit 53, and the error. It is a functional unit that attempts the decoding process by complementing it so that it can be used for the decoding process of the coded data in the correction code frame.

When the coded data related to the retransmission request is changed to a lower coding rate and the information bits are divided, the data coupling unit 523 previously transfers the divided information bits after decoding to the transmission server 6. It is a functional unit that generates received data by recombining according to the specified division method.

When the LLR storage unit 524 determines that the coded data obtained from the transmitting device 2 (or the transmitting device 3) cannot be decoded because the bit error correction cannot be corrected by the decoding possibility determination unit 521, the coded data of the coded data is determined. The post-LLR (broadcast) after the decoding process including the bit error or the pre-LLR (broadcast) before the decoding process is combined with the synchronization signal (frame number or time information), and the bit error of the coded data is retransmitted by the retransmission request. Temporarily hold while attempting the decryption process.

The LLR sharing unit 525 is obtained via the broadcast transmission line and is obtained via the broadcast transmission line when the bit error cannot be completely corrected for the coded data retransmitted in response to the retransmission request in the decoding process in the coded data complement unit 522. Post-LLR (broadcast) or pre-LLR (broadcast) temporarily held at 524 and post-LLR (IP) or pre-LLR before decryption processing obtained by decryption processing of coded data acquired by retransmission request via IP network ( IP) is synchronized using the synchronization signal, the LLRs of both are compared, the LLR having the larger absolute value is selected as having high reliability, and the selected LLR is routed via the broadcast transmission line and the IP line. The block code of each coded data obtained in the above is shared between the block codes to try to decode each coded data, and the larger absolute value is obtained until at least one of the coded data can be decoded. It has a function of repeating the decoding process for the first predetermined time while performing the process of selecting and sharing the LLR.

Therefore, the decoding possibility determination unit 521 determines whether or not the error correction decoding of each coded data obtained via the broadcast transmission line and the IP line is possible in the decoding process within the first predetermined time by the LLR sharing unit 525. Then, when it is determined that a bit error remains in both the coded data obtained via the broadcast transmission line and the IP line in the decoding process within the first predetermined time, the retransmission request packet is obtained. A retransmission request packet is generated so that the generation unit 53 again requests retransmission, and a series of processes of the coded data complement unit 522 and the LLR sharing unit 525 can be decoded until at least one of the respective coded data can be decoded. It has a function of repeating for a second predetermined time.

If the error correction decoding unit 52 cannot decode the data within the second predetermined time by the decoding process, the error correction decoding unit 52 generates the received data in a state including a bit error.

Further, in this example, when the transmission server 6 changes the coding rate of the coded data to be retransmitted, the code rate change notification packet is generated as a notification to that effect, and after transmission, the coded data packet is received. It transmits to the device 5. Therefore, the error correction decoding unit 52 uses the function of the coded data complementing unit 522 to determine the coding rate of the coded data obtained via the IP network 8 based on the presence or absence of the code rate change notification when the broadcast is received. It is determined whether or not the data is different from the above, padding bits are added as appropriate according to the coding rate, and complementary processing for replacement of the likelihood ratio required for decoding is performed.

When the retransmission request packet generation unit 53 determines that the decoding is not possible by the decoding possibility determination unit 521, the retransmission request packet generation unit 53 requests the transmission server 6 to retransmit the encoded data in the error correction code frame, so that the encoded data is used. A retransmission request packet in the form of an IP packet including a retransmission request information indicating that a retransmission request is made and communication quality information obtained from the communication quality measurement unit 56 is generated and transmitted to the transmission server 6 via the IP network 8. It is a functional part.

The IP packet receiving unit 54 receives the coded data packet of the IP packet string storing the coded data retransmitted in response to the retransmission request packet from the transmission server 6, and receives the coded data related to the retransmission request. This is a functional unit that acquires data and outputs it to the error correction / decoding unit 52 via the communication path connection switch unit 55. The IP packet receiving unit 54 uses the identification header and the sequence number to perform reverse processing of the interleaving unit 621 on the transmission server 6 side to reconstruct the encoded data retransmitted in response to the retransmission request. It has a part 541.

The communication path connection switch unit 55 is a switch that is controlled by the communication path connection ON / OFF signal by the error correction decoding unit 52 whether or not reception of coded data via the IP line is necessary. That is, when the communication path connection switch unit 55 determines that the coded data obtained via the broadcast transmission path cannot be decoded by the decoding possibility determination unit 521 in the error correction decoding unit 52, the communication path connection by the error correction decoding unit 52 The coded data retransmitted via the IP network 8 and obtained from the IP packet receiving unit 54 is error-corrected until it can be decoded by the error correction code decoding process within the second predetermined time controlled by the ON / OFF signal. Input to the decoding unit 52. Further, the error correction decoding unit 52 can decode the error correction code by the decoding process of the error correction code within the second predetermined time by the communication path connection ON / OFF signal, or after the second predetermined time has elapsed. It is unnecessary to receive the coded data via the IP line (setting OFF), the reception of the coded data via the IP line is blocked, and the error correction decoding unit 52 uses only the coded data obtained via the broadcast transmission line. Decryption processing is performed.

The communication quality measurement unit 56 measures either one or both of the delay related to the communication with the transmission server 6 and the packet loss rate based on the amount of packet loss generated in the communication with the transmission server 6 in units of predetermined periods. This is a functional unit that sequentially outputs communication quality information including one or both of the delay information and the packet loss rate information of the communication line to the retransmission request packet generation unit 53.

As described above, the delay information of the communication line includes the transmission time of the retransmission request packet transmitted from the receiving device 5 to the transmitting server 6 and the reception of the encoded data packet retransmitted from the transmitting server 6 correspondingly. This is information indicating the transmission delay estimated by the time difference from the time.

Further, the packet loss rate information is regarded as a packet loss when the corresponding encoded data packet cannot be received from the transmission server 6 even after a predetermined time has elapsed from the transmission time of the retransmission request packet, and the packet loss rate information is in units of a predetermined period. This is information indicating the packet loss rate measured based on the communication record.

(Reception control flow in receiver)
FIG. 8 is a flowchart showing a reception control flow in the receiving device 5 according to the embodiment of the present invention.

First, the receiving device 5 receives and demodulates the modulated wave signal radiated from the transmitting device 2 (or the transmitting device 3) via the broadcasting transmission line (satellite broadcasting transmission line or terrestrial broadcasting transmission line) by the demodulation unit 51. Then, the coded data obtained by this demodulation process is output to the error correction / decoding unit 52 (step S1).

Subsequently, the receiving device 5 calculates the pre-LLR of each bit of the coded data obtained by the demodulation process by the error correction decoding unit 52 to reconstruct the error correction code frame, and the transmitting device 2 (or the transmitting device 5). The decoding process corresponding to the error correction coding process in 3) is executed (step S2).

Here, the error correction decoding unit 52 determines whether or not the coded data obtained from the transmission device 2 (or the transmission device 3) can be error-corrected and decoded by the decoding possibility determination unit 521 (step S3), and can be decoded. When it is determined, it is decoded as it is and the received data is reproducibly generated (step S3: No), and since the current reception path is not via the IP network 8 (step S14: No), communication is performed as it is as a reception path for broadcast reception only. The setting OFF of the route connection switch unit 55 is maintained, and the process proceeds to the demodulation / decoding process for the next coded data in chronological order. That is, the error correction decoding unit 52 attempts to decode the coded data obtained from the transmission device 2 (or the transmission device 3), and when there is no bit error or when the bit error is within the correctable range. , Decrypt as it is and generate the received data reproducibly.

On the other hand, when the error correction decoding unit 52 determines that the coded data constituting the error correction code frame cannot be decoded by the function of the decoding possibility determination unit 521 (step S3: Yes), the error correction code frame is used. It is determined whether or not the retransmission request for the constituent coded data has been made even once (step S4). When the retransmission request has not been made even once (step S4: No), the error correction decoding unit 52 performs a decoding process including a bit error of the coded data obtained via the broadcast transmission line by the function of the LLR storage unit 524. The post-post LLR (broadcast) or the pre-LLR (broadcast) before the decoding process is temporarily held together with the synchronization signal (step S5).

Subsequently, the error correction decoding unit 52 generates retransmission request information for the coded data constituting the error correction code frame by the function of the decoding possibility determination unit 521, and outputs the retransmission request information to the retransmission request packet generation unit 53. It is instructed to generate a retransmission request packet indicating a retransmission request of the encoded data (step S6). Further, the decoding possibility determination unit 521 controls the communication path connection switch unit 55 to be set ON, and switches to the reception path for inputting the coded data to the error correction decoding unit 52 via the IP network 8.

Further, in step S6, when the retransmission request packet generation unit 53 determines that the decoding is not possible by the decoding possibility determination unit 521 in response to the instruction from the decoding possibility determination unit 521, the coded data in the error correction code frame is determined. In order to request the retransmission to the transmission server 6, an IP packet format retransmission request packet including the retransmission request information and the communication quality information obtained from the communication quality measurement unit 56 is generated, and the retransmission request packet is generated via the IP network 8. It transmits to the transmission server 6. Here, the communication quality information includes one or both of the delay information of the communication line and the packet loss rate information.

Therefore, when the transmission server 6 receives the retransmission request packet from the receiving device 5, the transmission server 6 extracts the retransmission request information and the communication quality information from the retransmission request packet, and changes the coding rate predetermined based on the communication quality information. According to the standard, it is decided whether or not to change the coding rate, and if so, which coding rate to change. As described above, the coding rate change standard is based on the same coding method as the error correction coding method used by the error correction coding unit 21 on the transmitting side, and is predetermined to be usable in the transmitting device 2 related to broadcasting. Among the code rates of the number of types, it is stipulated that the code rate is changed by distinguishing whether the code rate is higher or lower than the code rate of the coded data transmitted on the broadcast transmission line. Further, the transmission server 6 has a continuous synchronization signal (frame number or time information) starting from the error correction code frame constituting the coded data having the synchronization signal (frame number or time information) related to the retransmission request. Frame error correction A code frame is formed with the same coding rate as the coded data having the synchronization signal (frame number or time information) related to the retransmission request to construct an interleaved frame, and the interleaved frame is m-frame error. Interleaving processing is performed in a direction orthogonal to the correction code frame to generate a coded data packet of an IP packet string, which is transmitted to the receiving device 5 via the IP network 8. Further, when the coding rate is changed, the transmission server 6 generates a coding rate change notification packet as a notification to that effect, transmits the coded data packet, and then transmits the coded data packet. Therefore, the receiving device 5 determines whether or not the coding rate of the coded data obtained via the IP network 8 is different from that at the time of broadcasting reception by the IP packet receiving unit 54 and the error correction decoding unit 52. can.

Therefore, the receiving device 5 transmits the retransmission request packet to the transmitting server 6, and then the error correction code for m frames including the coded data to be decoded retransmitted from the transmitting server 6 in response to the retransmission request packet. Upon receiving the coded data packet (IP packet string) of the frame, the deinterleave unit 541 performs reverse processing of the interleave unit 621 on the transmission server 6 side by using the identification header and the sequence number assigned to the IP packet. Then, the encoded data resent in response to the retransmission request is reconstructed and output to the error correction decoding unit 52 (step S7).

Subsequently, the receiving device 5 determines whether or not the coding rate of the coded data obtained via the IP network 8 is different from that at the time of broadcasting reception by the coded data complementing unit 522 in the error correction decoding unit 52 (). In step S8), when the coding rate of the coded data obtained via the IP network 8 is different from that at the time of receiving the broadcast (step S8: Yes), the code rate shown in FIG. 4D or FIG. In order to restore the changed error correction code frame, a padding bit known between transmission and reception according to the coding rate is added to the insertion position known between transmission and reception (step S9).

On the other hand, when the coding rate of the coded data obtained via the IP network 8 is the same as that at the time of broadcasting reception (step S8: No), the coded data complementing unit 522 does not need to add a padding bit.

Subsequently, the coded data complementing unit 522 complements the coded data acquired via the IP network 8 so as to be used for the decoding process of the coded data in the error correction code frame (step S10). More specifically, the error correction / decoding unit 52 is configured as an error correction / decoding unit for the block code, and is acquired by the coded data complement unit 522 via the IP network 8 in order to perform decoding using the logarithmic likelihood ratio. For the coded data, the log-like likelihood ratio when the bit value is 0 is + ∞ (the maximum value as the probability that it is "0"), and the log-like likelihood ratio when the bit value is 1 is-. ∞ (maximum value as the probability of being “1”), If packet loss occurs and non-reachable bits occur, the logarithmic probability ratio is supplemented by replacing it with 0.

Then, the error correction decoding unit 52 performs a decoding process using the coded data received via the IP rope in response to the retransmission request (step S2). In this decoding process, if the bit error of the coded data cannot be completely corrected even if the decoding process is attempted after the first retransmission request (step S3: Yes, step S4: Yes), the next step is as follows. After the fact, the LLR sharing unit 525 is made to function.

That is, when the LLR sharing unit 525 cannot completely correct the bit error in the coded data retransmitted in response to the retransmission request in the decoding process in the coded data complementing unit 522 (step S3: Yes, step). S4: Yes), obtained by the post-LLR (broadcast) or pre-LLR (broadcast) obtained via the broadcast transmission line and temporarily held in the LLR storage unit 524, and the decoding process of the coded data acquired by the retransmission request via the IP network. The post-LLR (IP) performed and the pre-LLR (IP) before the decoding process are synchronized using the synchronization signal (step S11).

Next, the LLR sharing unit 525 compares the post-or pre-LLR (broadcast) with the post-or pre-LLR (IP) and selects and selects the LLR having the larger absolute value in bit units as having high reliability. The LLR is shared between the block codes of the respective coded data obtained via the broadcast transmission line and the IP line (step S12), the decoding process of the respective coded data is attempted, and the respective coded data is obtained. Until at least one of them can be decoded, the LLR with the larger absolute value is selected and shared, and the LLR is obtained via the updated broadcast transmission line and the IP network for the first predetermined time. The process of decoding the block code of the coded data is repeated (step S13: steps S2, S3, S4, S11, S12 via No). By the way, "comparison between post-or pre-LLR (broadcast) and post-or pre-LLR (IP)" means "comparison between post-lLR (broadcast) and post-LLR (IP)" and "post-LLR (broadcast) and pre-. Any of four methods may be used: "comparison with LLR (IP)", "comparison between pre-LLR (broadcast) and post-LLR (IP)", and "comparison between pre-LLR (broadcast) and pre-LLR (IP)". ..

In the post-shared or pre-LLR shared by the LLR sharing unit 525, if the coding rate of the coded data obtained via the IP network related to the retransmission request is changed, the coded data is included in the block code of the coded data. Only the post-or pre-LLR corresponding to the information bit is used, and the post-or pre-LLR corresponding to the parity bit is not shared because it differs between the broadcast transmission line and the IP network. On the other hand, if the coding rate of the coded data obtained via the IP network related to the retransmission request is not changed from that of the coded data obtained via the broadcast transmission line, the entire block code including the information bit and the parity bit is used. Post-or pre-LLR can be shared for each coded data via its broadcast transmission line and IP network.

By interposing the function of this LLR sharing unit 525, the post-or pre-LLR (broadcast) that was temporarily held and the post-or pre-LLR (IP) of the coded data obtained via the IP line by one retransmission request. By repeating the decoding process by sharing and repeatedly updating in bit units while selecting the one with the larger absolute value, the likelihood gradually increases and there is a possibility that bit errors in the encoded data can be corrected. That is, the respective coded data obtained via the broadcast transmission line and the IP line should be decoded regardless of whether or not the coding rate shown in FIG. 4D or FIG. 5E has been changed. Has an information bit of. Then, when the post-or pre-LLR (IP) and the post-or pre-LLR (broadcast) are shared so as to be repeatedly updated in bit units while selecting the one having the larger absolute value and the decoding process is repeated, the accuracy of the likelihood determination is correct. Will gradually improve. In order to avoid infinitely performing the decoding process based on the function of the LLR shared unit 525, the above-mentioned first predetermined time is set.

Then, the error correction decoding unit 52 obtains each coding via the broadcast transmission line and the IP line in the decoding process within the first predetermined time by the LLR sharing unit 525 from the function of the decoding possibility determination unit 521. Error correction of data Although it is determined whether or not the data can be decrypted, bit errors still remain in both the coded data obtained via the broadcast transmission line and the IP line in the decoding process within the first predetermined time. If it is determined to be present (step S13: Yes), the function of the retransmission request packet generation unit 53 generates a retransmission request packet so as to request retransmission again (step S6).

That is, the decodeability determination unit 521 performs a series of processes of the coded data complement unit 522 based on the above-mentioned steps S6 to S10 and a series of processes of the LLR shared unit 525 based on the steps S11 to S13 of the respective coded data. It is repeated for a second predetermined time until at least one of them can be decoded.

Finally, after the error correction decoding unit 52 generates the received data based on the encoded data that can be decoded (step S3: No), the communication path connection switch unit 55 is set ON and the current reception path. When the IP network 8 is also possible (step S14: Yes), the communication path connection switch unit 55 is set to OFF so as to return only to reception via the broadcast transmission line (step S15), and in chronological order, It shifts to the demodulation / decoding process for the next coded data. If the error correction decoding unit 52 cannot decode the data by the decoding process within the second predetermined time, the error correction decoding unit 52 generates the received data in a state including the bit error, proceeds to step S14, and switches to the communication path connection switch. The unit 55 is controlled to be set to OFF, and the reception path is switched only to reception via the broadcast transmission line.

When the coded data related to the retransmission request is changed to a lower coding rate and the information bits are divided, the error correction decoding unit 52 obtains both of the coded data of the divided information bits. The request for retransmitting the coded data transmitted on the broadcast transmission line is repeated until the error correction code can be decoded by the decoding process within the second predetermined time. Then, when the error correction decoding unit 52 can decode both of the coded data of the divided individual information bits, the function of the data combining unit 523 transmits the divided decoded information bits. Received data is generated by recombining with the server 6 according to a predetermined division method.

By the way, as the retransmission request packet, a non-delivery notification packet generally used in the IP packet format can be used, and the encoded data packet is configured to perform retransmission in response to the non-delivery notification packet. Therefore, the error correction decoding unit 52 can replace the coded data obtained from the demodulation unit 51 with the coded data obtained by retransmission, and perform decoding again for the second predetermined time. By repeatedly requesting retransmission until the received data can be restored, the data can be reproducibly output.

As described above, in the transmission system 1 shown in FIG. 1, when the transmission condition deteriorates to the extent that data restoration by the error correction code becomes impossible due to attenuation due to rainfall, fading, or the like, the receiving device 5 sends the transmission server 6 through the IP network 8. Requests the retransmission of the coded data corresponding to. The transmission server 6 relates to the coded data encoded by the same error correction code encoder (that is, the error correction coding unit 21) as when transmitted by the transmission device 2 (or the transmission device 3) via the broadcast transmission line. , The coding rate is adaptively changed according to the communication quality information, and transmitted to the receiving device 5 via the IP network 8.

The receiving device 5 complements the code bits acquired via the IP network 8 for the coded data that could not be decoded by the decoder (that is, the error correction decoding unit 52) having the same error correction code as when it was received by radio waves. Then try decrypting again to restore the received data. Even when there is a lot of data lost via radio waves, or when the IP network 8 is also considered to be a lost communication path and some data is lost, the receiving device 5 decodes the coded data received via the broadcast transmission path. And by combining the decoding result of the coded data received via the IP line 8, the performance of restoring the coded data is improved, and if the coded data cannot be restored, the retransmission request is made again. By doing so, it is possible to reproduce the data.

In particular, the data retransmitted by the transmission server 6 via the IP network 8 is used as coded data in the block code of digital broadcasting, and the coded data is variably controlled to a coding rate according to the communication quality of the IP network 8. This makes it possible to reduce the number of retransmission requests and further improve the transmission efficiency via the IP network 8. Further, by using the same standardized code for the error correction code used for broadcasting and the error correction code used for transmission via the IP network 8, the receiving device 5 can be realized by preparing only one error correction decoder. The equipment scale can be reduced. In particular, according to the receiving device 5 according to the present invention, the coded data received via the IP line 8 is decoded, and when the bit error cannot be completely corrected, the coded data received via the broadcast transmission line is decoded. Post-LLR (broadcast) that is the result of the decoding process (including bit errors) or pre-LLR (broadcast) before the decryption process and post-LLR (IP) or before the decryption process that is the result of the decoding process (including bit errors) via the IP line. By synchronizing the pre-LLRs (IPs) of the above with each other, sharing the highly reliable LLR (high absolute value of LLR) with both parties, and performing the decryption process again, it is possible to reduce the number of retransmission requests to the IP line. High correction performance can be achieved even when there is a packet loss that exceeds the correction performance of the coded data via the IP line.

<Example>
Hereinafter, a more specific embodiment in which the transmission system 1 is configured for high-wideband satellite digital broadcasting will be described.

FIG. 9 is a block diagram showing a schematic configuration of a transmission system 1 including a transmission server 6, a transmission device 2, and a reception device 5 according to an embodiment of the present invention. The same components will be described with the same reference numbers.

The transmission system 1 of the embodiment shown in FIG. 9 is an example of the advanced wideband satellite digital broadcasting described in ARIB STD-B44 as an example, and the transmission server 6, the transmission device 2 and the transmission device 2 of the embodiment according to the present invention. A receiving device 5 is provided. Here, one transmission server 6 is used, and the installation of the load balancer 7 is omitted. However, as described above, a plurality of transmission servers 6 are used and connected to the IP network 8 via the load balancer 7. It may be in the form of

Further, in the transmission system 1 illustrated in FIG. 9, an example in which the transmission device 2 and the transmission server 6 are connected separately via a local area network will be described, but the transmission device 2 is provided with the transmission server 6 in a local area. Instead of connecting with a network, it may be configured to connect with a simple signal cable.

The transmission device 2 exemplified in FIG. 9 is configured in the same manner as in FIG. 2 described above, and performs error correction coding processing on the transmission data related to digital broadcasting to impart error correction code parity (LDPC parity and BCH parity). By doing so, coded data is generated, the coded data is digitally modulated by a predetermined modulation method to generate a modulated wave signal, and a broadcast transmission path of an advanced broadband satellite digital broadcast including a broadcast satellite 4 via a transmission antenna 2a. It emits radio waves related to digital broadcasting via. In the advanced broadband satellite digital broadcasting, the number of bits for one frame of coded data is 44880 bits, and the LDPC code is used as the internal code and the BCH code is used as the external code as the error correction coding process. Further, the transmission device 2 manages the sequentially generated coded data as an error correction code frame, assigns a synchronization signal (frame number or time information), and transmits the coded data to the transmission server 6.

The receiving device 5 exemplified in FIG. 9 is configured in the same manner as in FIG. 7 described above, receives a modulated wave signal radiated from the transmitting device 2 via the receiving antenna 5a, demodulates the signal, and corrects an error in the transmitting device 2. Decoding processing corresponding to the coding processing is performed to generate received data so that it can be played back.

Further, the receiving device 5 determines whether or not the coded data obtained from the transmitting device 2 can be corrected and decoded, and if it is determined that the coded data can be decoded, the coded data is decoded as it is to generate the received data, and the bit error of the coded data is obtained. If it is determined that the data cannot be corrected and cannot be decoded, the posterior log-like likelihood ratio after the decoding process including the bit error of the coded data via the broadcast transmission line or the pre-logous likelihood ratio before the decoding process (post-or pre-LLR). (Broadcast)) is temporarily held, a retransmission request packet in the form of an IP packet requesting retransmission of the corresponding encoded data is generated, the retransmission request packet includes communication quality information, and the data is passed through the IP network 8. It has a function of transmitting data to the transmission server 6. Further, the receiving device 5 receives the encoded data retransmitted in response to the retransmission request from the transmission server 6 in response to the retransmission request packet (encoding data transmitted on the broadcast transmission line on the transmission server 6 side according to the communication quality information). (Reconstructed by changing the coding rate adaptively by distinguishing whether it is higher or lower than the coding rate of), the encoded data packet in the IP packet format is received, and the retransmission request is made. The encoded data retransmitted according to the above is extracted, complemented according to the coding rate so as to be used for the decoding process, and the decoding process is attempted.

Then, when the bit error cannot be completely corrected for the coded data resent in response to the retransmission request, the receiving device 5 obtains the coded data via the broadcast transmission line and temporarily holds the coded data after or in advance LLR (broadcasting) and the IP network. The post-or pre-LLR (IP) obtained by the decoding process of the coded data acquired by the retransmission request via the channel is synchronized using a synchronization signal, and the LLRs of the two are compared and the LLR having the larger absolute value is compared. Is selected as having high reliability, and the selected LLR is shared between the block codes of the respective coded data obtained via the broadcast transmission line and the IP line to attempt the decoding process of the respective coded data. It has a function of repeating the decoding process for the first predetermined time while performing the process of selecting and sharing the LLR having the larger absolute value until at least one of the encoded data can be decoded. Further, the receiving device 5 determines whether or not error-correcting and decoding of each coded data obtained via the broadcast transmission line and the IP line is possible in the decoding process within the first predetermined time, and the first If it is determined that bit errors still remain in both the coded data obtained via the broadcast transmission line and the IP line in the decoding process within the predetermined time, the retransmission request for the coded data is performed again. Of the respective coded data, a series of processing of decoding processing in which the packet is transmitted to the transmission server 6 and complemented with the coded data obtained by the retransmission request and decoding processing by sharing the logarithmic likelihood ratio is performed. It has a function of repeating for a second predetermined time until at least one of them can be decoded. Further, the receiving device 5 is divided when the coded data related to the retransmission request is changed to a lower coding rate and the information bits are divided (divided into two equal parts in the example described in detail later). It has a function of recombining the decoded information bit with the transmission server 6 according to a predetermined division method to generate received data. If the receiving device 5 cannot decode the data within the second predetermined time by the decoding process, the receiving device 5 generates the received data in a state including a bit error.

The transmission server 6 is configured in the same manner as in FIG. 2 described above, sequentially inputs the coded data generated by the transmission device 2, and manages the coded data in chronological order by the synchronization signal (frame number or time information) of the error correction code frame. Generates a coded data packet in the IP packet format that stores the coded data related to the retransmission request in response to the retransmission request packet received from the receiving device 5 via the IP network 8 with the function of saving while updating the predetermined time. It also has a function of transmitting data to the receiving device 5 via the IP network 8.

Therefore, in the present embodiment, the transmitting device 2 generates a modulated wave signal after performing error correction coding processing of the advanced wideband satellite digital broadcasting on the transmission data related to the digital broadcasting, and the broadcasting satellite 4 passes through the transmitting antenna 2a. Send via. The receiving device 5 first demodulates the modulated wave signal of the advanced broadband satellite digital broadcast received from the receiving antenna 5a, and attempts to restore the received data by error correction / decoding processing. The receiving device 5 restores the received data from the coded data and makes it playable as it is when the transmission environment is good and the reception can be performed without error, or when the influence of white noise or the like is within the range that can be decoded by the error correction code. .. When the transmission environment is poor such as rainfall attenuation and the coded data deteriorates to the extent that it cannot be decoded by the error correction code, the receiving device 5 operates in cooperation with the transmitting device 2 for the corresponding coded data through the IP network 8. At the same time as making a retransmission request to the data, the post-LLR (broadcast) including a bit error and the pre-LLR (broadcast) before the decoding process is temporarily held.

When a retransmission request is made from the receiving device 5 to the transmitting server 6 through the IP network 8, the transmitting server 6 variably controls the coding rate of the coded data after the error correction coding process according to the communication quality information, and the IP network. Retransmit to the receiving device 5 via 8. The receiving device 5 generates coded data that complements the coded data obtained from the IP network 8, executes an error correction / decoding process, and restores the received data to make it playable. When the received data cannot be completely restored due to the retransmission request and the bit error remains, the receiving device 5 is the result of decoding the coded data received via the IP line 8 after the temporary holding or in advance LLR (broadcasting) or after. The decryption process is performed again by combining the preliminary LLR (IP). In the combination of the post-LLR via the broadcast transmission line and the IP network 8, the absolute values of both are compared, and the LLR having the larger value is decoded by the respective coded data via the broadcast transmission line and the IP network 8. Share to process. The receiving device 5 repeats the process of sharing and decoding the LLR to try to restore the received data, and if the bit error cannot be corrected even after that, the receiving device 5 makes a retransmission request again, and the LLR sharing, decoding, and the retransmission request are performed. The received data can be decoded by repeating the decoding within a predetermined time.

(Example: Reception control flow in a receiver of advanced broadband satellite digital broadcasting)
FIG. 10 is a flowchart showing a reception control flow in the receiving device 5 of the advanced broadband satellite digital broadcasting of one embodiment shown in FIG. The same step numbers as those in FIG. 8 are assigned the same numbers.

First, the receiving device 5 receives and demodulates the modulated wave signal radiated from the transmitting device 2 via the broadcast transmission path of the advanced broadband satellite digital broadcasting by the demodulation unit 51, and the coded data obtained by this demodulation processing. Is output to the error correction / decoding unit 52 (step S1).

Subsequently, the receiving device 5 first performs the pre-LLR of each bit of the coded data from the likelihood table in order to execute the decoding process corresponding to the error correction coding process in the transmitting device 2 by the error correction decoding unit 52. Calculate and reconstruct the error correction code frame (step S2A). In advanced broadband satellite digital broadcasting, the number of bits for one frame of coded data is 44880 bits, and the LDPC code is used as the internal code and the BCH code is used as the external code for error correction coding processing. The degree table is used to calculate the probability that the bit is "0" and the pre-log likelihood ratio that indicates the probability that the bit is "1".

Subsequently, the receiving device 5 performs LDPC decoding using the sum-product algorithm based on the log-likelihood ratio by the error correction decoding unit 52 (step S2B), and then performs power despreading processing and BCH code decoding processing. Carry out (step S2C). In ARIB STD-B44, when the error of the bit error cannot be corrected completely in the decoding process of the BCH code of the external code and it is not error-free, the data is replaced with a null packet, a flag with an error is added, and so on. It stipulates.

Therefore, the error correction decoding unit 52 determines whether or not the coded data obtained from the transmission device 2 can be error-corrected and decoded by the decoding possibility determination unit 521, so that the bit error error is corrected in the BCH code decoding process. It is determined whether or not the error could not be completed or the error could be corrected by decoding but the predetermined number of BCH errors was reached (step S3'). That is, in this embodiment, paying attention to the fact that the correction ability of the LDPC code is uncertain and the correction ability of the BCH code is definite, the presence or absence of error-free of the BCH code connected to the LDPC code is used. Therefore, it is intended to realize an efficient retransmission request in Hybrid ARQ.

Here, the error correction decoding unit 52 determines whether or not the coded data obtained from the transmission device 2 can be error-corrected and decoded by the decoding possibility determination unit 521. Since the data is reproducibly generated (step S3': No) and the current reception path is not via the IP network 8 (step S14: No), the setting OFF of the communication path connection switch unit 55 is set as the reception path for receiving the broadcast as it is. Maintaining this, the process shifts to the demodulation / decoding process for the next coded data in chronological order.

On the other hand, when the error correction decoding unit 52 determines that the coded data constituting the error correction code frame cannot be decoded by the function of the decoding possibility determination unit 521 (step S3': Yes), the error correction code frame It is determined whether or not the retransmission request for the coded data constituting the above is performed even once (step S4). When the retransmission request has not been made even once (step S4: No), the error correction decoding unit 52 performs a decoding process including a bit error of the coded data obtained via the broadcast transmission line by the function of the LLR storage unit 524. The post-post LLR (broadcast) or the pre-LLR (broadcast) before the decoding process is temporarily held together with the synchronization signal (step S5). The LLR temporarily held is an LLR corresponding to each of the 44880 bits of each LDPC block, and at the same time, a synchronization signal based on time information or the like is also stored.

Subsequently, the error correction decoding unit 52 generates retransmission request information for the coded data constituting the error correction code frame by the function of the decoding possibility determination unit 521, and outputs the retransmission request information to the retransmission request packet generation unit 53. It is instructed to generate a retransmission request packet indicating a retransmission request of the encoded data (step S6). That is, when the error correction / decoding unit 52 cannot restore the received data from the encoded data due to deterioration of transmission conditions or the like, the retransmission request packet generation unit 53 requests the transmission server 6 to make a retransmission request by RQ. To instruct. Further, the decoding possibility determination unit 521 controls the communication path connection switch unit 55 to be set ON, and switches to the reception path for inputting the coded data to the error correction decoding unit 52 via the IP network 8.

Further, in step S6, in response to the instruction from the decoding possibility determination unit 521, the retransmission request packet generation unit 53 indicates that the encoding data determined by the decoding possibility determination unit 521 that cannot be decoded is requested to be retransmitted. An IP packet format retransmission request packet including the retransmission request information and the communication quality information obtained from the communication quality measurement unit 56 is generated and transmitted to the transmission server 6 via the IP network 8. Here, the communication quality information includes one or both of the delay information of the communication line and the packet loss rate information.

Therefore, when the transmission server 6 receives the retransmission request packet from the receiving device 5, the transmission server 6 extracts the retransmission request information and the communication quality information from the retransmission request packet, and changes the coding rate predetermined based on the communication quality information. According to the standard, it is decided whether or not to change the coding rate, and if so, which coding rate to change. As described above, the coding rate change standard is based on the same coding method as the error correction coding method used by the error correction coding unit 21 on the transmitting side, and is predetermined to be usable in the transmitting device 2 related to broadcasting. Among the code rates of the number of types, it is stipulated that the code rate is changed by distinguishing whether the code rate is higher or lower than the code rate of the coded data transmitted on the broadcast transmission line.

Then, the transmission server 6 has a continuous synchronization signal (frame number or time information) starting from the error correction code frame constituting the coded data having the synchronization signal (frame number or time information) related to the retransmission request. Frame error correction A code frame is formed with the same coding rate as the coded data having the synchronization signal (frame number or time information) related to the retransmission request to construct an interleaved frame, and the interleaved frame is m-frame error. Interleaving processing is performed in a direction orthogonal to the correction code frame to generate a coded data packet of an IP packet string, which is transmitted to the receiving device 5 via the IP network 8. Further, when the coding rate is changed, the transmission server 6 generates a coding rate change notification packet as a notification to that effect, transmits the coded data packet, and then transmits the coded data packet. Therefore, the receiving device 5 determines whether or not the coding rate of the coded data obtained via the IP network 8 is different from that at the time of broadcasting reception by the IP packet receiving unit 54 and the error correction decoding unit 52. can. An example of changing the code rate by the transmission server 6 (typically described when the coded data related to the retransmission request is changed to a lower code rate) will be described later with reference to FIG. 11. Further, for an example of a method of generating an IP packet format retransmission request packet by the transmission server 6 (when the coded data related to the retransmission request is changed to a lower coding rate, which will be described as a representative), refer to FIG. Will be described later.

Therefore, the receiving device 5 transmits the retransmission request packet to the transmitting server 6, and then the error correction code for m frames including the coded data to be decoded retransmitted from the transmitting server 6 in response to the retransmission request packet. Upon receiving the coded data packet (IP packet string) of the frame, the deinterleave unit 541 performs reverse processing of the interleave unit 621 on the transmission server 6 side by using the identification header and the sequence number assigned to the IP packet. Then, the encoded data resent in response to the retransmission request is reconstructed and output to the error correction decoding unit 52 (step S7).

Subsequently, the receiving device 5 determines whether or not the coding rate of the coded data obtained via the IP network 8 is different from that at the time of broadcasting reception by the coded data complementing unit 522 in the error correction decoding unit 52 (). In step S8), when the coding rate of the coded data obtained via the IP network 8 is different from that at the time of receiving the broadcast (step S8: Yes), the code rate shown in FIG. 4D or FIG. In order to restore the changed error correction code frame, a padding bit known between transmission and reception according to the coding rate is added to the insertion position known between transmission and reception (step S9).

On the other hand, when the coding rate of the coded data obtained via the IP network 8 is the same as that at the time of broadcasting reception (step S8: No), the coded data complementing unit 522 does not need to add a padding bit.

Subsequently, the coded data complementing unit 522 complements the coded data acquired via the IP network 8 so as to be used for the decoding process of the coded data in the error correction code frame (step S10'). Assuming that the IP network 8 has a lost communication path, the error correction decoding unit 52 determines the correct bit value for the coded data received via the IP network 8, and packets in the communication path in the middle of the IP network 8. The correct bit value is unknown for packets lost due to loss or the like. More specifically, the error correction / decoding unit 52 is configured as an error correction / decoding unit for the block code, and is acquired by the coded data complement unit 522 via the IP network 8 in order to perform decoding using the logarithmic likelihood ratio. For the coded data, the log-like likelihood ratio when the bit value is 0 is + ∞ (the maximum value as the probability that it is "0"), and the log-like likelihood ratio when the bit value is 1 is-. ∞ (maximum value as the probability of being “1”), If packet loss occurs and non-reachable bits occur, the logarithmic probability ratio is supplemented by replacing it with 0.

Then, the error correction decoding unit 52 performs LDPC decoding processing and BCH decoding processing using the coded data received via the IP rope in response to the retransmission request (steps S2B and S2C). In this LDPC decoding process, when the bit error of the coded data cannot be completely corrected even if the LDPC decoding process and the BCH decoding process are attempted after the first retransmission request (step S3': Yes, step S4: Yes. ), As the next step, the LLR sharing unit 525 is made to function.

That is, the LLR sharing unit 525 could not completely correct the bit error in the BCH code decoding process for the encoded data retransmitted in response to the retransmission request in the decoding process in the coded data complement section 522. Or, if the error can be corrected by decoding but the predetermined number of BCH errors is reached (step S3': Yes, step S4: Yes), it is obtained via the broadcast transmission line and temporarily held in the LLR storage unit 524 after or in advance. The LLR (broadcast) and the post-or pre-LLR (IP) obtained by the decoding process of the coded data acquired by the retransmission request via the IP network are synchronized using the synchronization signal (step S11).

Next, the LLR sharing unit 525 compares the post-or pre-LLR (broadcast) with the post-or pre-LLR (IP) and selects and selects the LLR having the larger absolute value in bit units as having high reliability. The LLR is shared between the block codes of the respective coded data obtained via the broadcast transmission line and the IP line (step S12), the decoding process of the respective coded data is attempted, and the respective coded data is obtained. Until at least one of them can be decoded, the LLR with the larger absolute value is selected and shared, and the LLR is obtained via the updated broadcast transmission line and the IP network for the first predetermined time. The process of decoding the block code of the coded data is repeated (step S13: steps S2B, S2C, S3', S4, S11, S12 via No).

Then, the error correction decoding unit 52 obtains each coding via the broadcast transmission line and the IP line in the decoding process within the first predetermined time by the LLR sharing unit 525 from the function of the decoding possibility determination unit 521. Error correction of data Although it is determined whether or not the data can be decrypted, bit errors still remain in both the coded data obtained via the broadcast transmission line and the IP line in the decoding process within the first predetermined time. If it is determined to be present (step S13: Yes), the function of the retransmission request packet generation unit 53 generates a retransmission request packet so as to request retransmission again (step S6).

That is, the decoding possibility determination unit 521 performs the processing of the coded data complementing unit 522 based on the above-mentioned steps S6 to S10'and the series of processing of the LLR sharing unit 525 based on the steps S11 to S13, respectively. It is repeated for a second predetermined time until at least one of them can be decoded.

Finally, after the error correction decoding unit 52 generates the received data based on the encoded data that can be decoded (step S3: No), the communication path connection switch unit 55 is set ON and the current reception path. When is via the IP network 8 (step S14: Yes), the communication path connection switch unit 55 is set to OFF to return to the reception processing via the broadcast transmission line (step S15), and the following is performed in chronological order. It shifts to the demodulation / decoding process for the coded data of. If the error correction decoding unit 52 cannot decode the data by the decoding process within the second predetermined time, the error correction decoding unit 52 generates the received data in a state including the bit error, proceeds to step S14, and switches to the communication path connection switch. The unit 55 is controlled to be set to OFF, and the reception path is switched only to reception via the broadcast transmission line.

When the coded data related to the retransmission request is changed to a lower coding rate and the information bits are divided, the error correction decoding unit 52 obtains both of the coded data of the divided individual information bits. The request for retransmitting the coded data transmitted on the broadcast transmission line is repeated until the code can be decoded by the error correction code decoding process within the second predetermined time, and the error correction decoding unit 52 is divided into individual pieces. When both of the coded data of the information bits can be decoded, the divided decoded information bits are recombined with the transmission server 6 according to a predetermined division method by the function of the data combination unit 523. To generate received data.

By the way, as the retransmission request packet, a non-delivery notification packet generally used in the IP packet format can be used, and the encoded data packet is configured to perform retransmission in response to the non-delivery notification packet. Therefore, the error correction decoding unit 52 can replace the coded data obtained from the demodulation unit 51 with the coded data obtained by retransmission, and perform decoding again for the second predetermined time. By repeatedly requesting retransmission until the received data can be restored, the data can be reproducibly output.

(Method of generating coded data when changing the code rate of one embodiment: when changing to a lower code rate)
As described with reference to FIGS. 4 and 5, the transmission server 6 has a higher coding rate for the coded data related to the retransmission request than the coding rate of the coded data transmitted on the broadcast transmission line according to the communication quality information. It is reconstructed by changing the coding ratio adaptively by distinguishing between low and low.

That is, for the coded data related to the retransmission request generated by the transmission server 6, only the difference is that the information bit is undivided when changing to a higher coding rate and the information bit is divided when changing to a lower coding rate. Therefore, here, with reference to FIG. 11 as an example of changing the coded data related to the retransmission request to a lower coding rate as a representative, ARIB STD is performed by the retransmission request processing unit 63 in the transmission server 6. Within the range of the number of types of LDPC coding rate conforming to −B44, in this example, the storage unit 61 and the code rate adaptation changing unit 64 are controlled and coded according to the coding rate changing standard of (9) above. An example of generating coded data when the rate is changed will be described.

In the example shown in FIGS. 11 (a) to 11 (e), the transmission server 6 has the highest LDPC coding rate (109/120) within the range of the number of types of LDPC coding rates conforming to ARIB STD-B44. The coded data (≈9/10) is received, stored in the storage unit 61, and the coded data requested to be retransmitted from the receiving device 5 via the IP network 8 when the radio wave reception condition deteriorates. This is an example of retransmitting by changing the coding rate to 61/120 (≈1/2).

As shown in FIG. 11A, here, the coding rate of the coded data in the LDPC code having a code length N = 44880 bits transmitted on the broadcast transmission line is set to F _b = 109/120 (≈9/10). do. In ARIB STD-B44, one error correction code frame has a constant code length of 44880 bits regardless of the LDPC coding rate, and is composed of slot units based on the set division method. Therefore, the LDPC code is coded. As the information bits, the "slot header", "main signal (data to be transmitted)", "BCH code parity", and "stuff bit" are power-spread, and the parity of the LDPC code is It is added to form one error correction code frame. Then, in the storage unit 61 of the transmission server 6, the coded data of one error correction code frame unit shown in FIG. 11A is attached with a synchronization signal (frame number or time information) and managed in chronological order. It is saved while updating the specified time. The LDPC code parity at the LDPC coding rate 109/120 (≈9/10) is composed of 44880 × (1-109 / 120) = 4114 bits.

Therefore, the transmission server 6 that has received the retransmission request packet from the receiving device 5 extracts the communication quality information included in the retransmission request packet by the retransmission request processing unit 63, and determines the delay and the packet loss rate included in the communication quality information. Based on each information, it is determined whether or not to change the coding rate with reference to the coding rate change standard managed by the communication quality control unit 65.

Assuming that the code rate change criterion of (9) is followed, the retransmission request processing unit 63 has a delay obtained from the receiving device 5 less than a predetermined default value, or a packet loss rate obtained from the receiving device 5 is set. If it is less than the predetermined default value, it is determined that there is no change with the LDPC coding rate of 109/120 (≈9/10) of the coded data transmitted on the broadcast transmission line, and the retransmission request shown in FIG. 11 (a). The code rate adaptation change unit 64 is controlled so that the coded data having a code length of N bits according to the above is read from the storage unit 61 and output to the IP packet generation unit 62 as it is.

On the other hand, when the delay obtained from the receiving device 5 is equal to or higher than a predetermined default value and the packet loss rate obtained from the receiving device 5 is equal to or higher than a predetermined default value, the retransmission request processing unit 63 performs a broadcast transmission line. in the LDPC coding rate of the transmission encoded data _{F b = 109/120 (≒} 9/10), determines to change the LDPC coding rate _{F i = 61/120 (≒} 1/2) (F b> F _i), First, FIG. 11 (N × _F b = 40766 bits of the LDPC code encoded subject to information bits of the code length 44880 bits of the coded data according to the retransmission request indicated in a) (i.e., the power spreading Only the completed BCH coding bit) is read from the storage unit 61 (see FIG. 11B).

Subsequently, the error correction coding unit 643 controls the coding rate adaptation change unit 64, and the error correction coding unit 643 reads out from the storage unit 61 40766 bits of information bits (that is, the power-spread BCH). The coded bit) is divided into two between transmission and reception by a predetermined division method ((N × F _b ) / 2 = 20383 bits). Here, an example is made in which the first half and the second half of the information bit position are divided into two equal parts (see FIG. 11 (c)), but even if other division methods are used, such as dividing into two by odd-numbered bits and even-numbered bits. good.

Subsequently, the retransmission request processing unit 63 controls the coding rate adaptation change unit 64, and for the first half and the second half of each of the information bits divided into two, known values between transmission and reception (for example, all 0). Bit), N × _Fi − ((N × F _b ) / 2) = 2431 bits are added as padding bits to the insertion position known between transmission and reception, and these information bits and padding bits are encoded. subjected to rate _{F i = 109/120 (≒} 9/10) to become LDPC encoding process to generate the parity of _{N × (1-F i)} = 4114 bits (see FIG. 11 (d)). In this example, although the padding bit is shown as being added after the information bit, the padding bit may be added before the information bit, that is, the insertion position of the padding bit is a code after the change. it is sufficient to set in advance as known between transmission and reception by the value of the ratio F _i.

Then, the error correction coding unit 643 removes the padding bit, reconstructs the encoded data (42449 bits) for retransmission in which 22066 bit parity is added to the 20383 bit information bit, and the IP packet generation unit 62. (See FIG. 11 (e)). The frame length of the reconstructed coded data for retransmission is 24449 bits, which is shorter than the original code length of 44880 bits, and does not exceed the coded length of the error correction code specified by the broadcasting standard. The coded data related to the retransmission request can be changed to a lower coding rate, and the correction capability is higher than in the case of retransmitting without changing the coding rate.

In this way, when the transmission server 6 of the present embodiment receives the retransmission request packet, the LDPC coding rate of the coded data related to the retransmission request is adaptively adjusted based on the communication quality information included in the retransmission request packet. It is modified to generate an encoded data packet and transmitted to the receiving device 5.

(Method of generating a coded data packet in IP packet format by the transmission server of one embodiment)
The coded data packet is configured by using one or more IP packets, and here, an example in which the packet length excluding the IP header of the IP packet is 1000 bytes and the fixed length is described will be described. However, in reality, the packet length can be arbitrarily determined to be a variable length within a range that does not exceed the assumed MTU (Maximum Transmission Unit) of the IP network 8.

As described above, regarding the coded data related to the retransmission request generated by the transmission server 6, the information bit is undivided when changing to a higher coding rate, and the information bit is divided when changing to a lower coding rate. Since there is only a difference, here, FIG. 12 is referred to as an example of changing the coded data related to the retransmission request to a lower coding rate, and an n × m interleaved frame is used for the coded data. An example of generating a coded data packet (IP packet string) and transmitting the coded data packet (IP packet string) to the receiving device 5 will be described.

12 (a) to 12 (d) are explanatory views of an IP packet generation method of the IP packet generation unit 62 in the transmission server 6 of the embodiment according to the present invention, respectively.

First, IP packet generating unit 62, a coding rate adaptively changing unit 64, respectively constituted by code length n bits of the same code rate F _i, the synchronization signal related to the retransmission request (frame number or time information) Error correction code frames constituting the coded data included The error correction code frames for m frames having continuous synchronization signals (frame numbers or time information) starting from the code frames are input to form an n × m interleaved frame. Although m is a fixed value, it can be variably set from the outside and is a value shared between transmission and reception. Further, an n = N when code length n bits of code rate F _i has not changed since the code length N bits of encoded rate F _b used in the broadcast transmission path, the code length of the code rate F _b When changed from N bits, n <N.

Therefore, the IP packet generation unit 62 stores the m-frame error correction code frames (LDPC frames) including the error correction code frames as the coded data related to the retransmission request in the storage unit (not shown) so as to be arranged in the vertical direction. Temporarily store (see FIG. 12 (a)). In FIG. 12A, the IP packet generation unit 62 has 2 information bits when the coding data obtained from the coding rate adaptation changing unit 64 is an LDPC frame whose coding rate has been changed to a lower level. Since it is divided (in this example, the first half and the second half), LDPC frame # 1 (information bit first half), LDPC frame # 2 (information bit second half), LDPC frame # 3 (information bit first half), ..., Like the LDPC frame #m (second half of the information bit), the first half and the second half of the information bit are temporarily stored in the storage unit (not shown) so as to be arranged in a vertical direction.

Hereinafter, as described above with reference to FIG. 6, the IP packet generation unit 62 reads each bit from the beginning into the error correction code frame of the m frame by the interleaving unit 621, and the packet excluding the header of the generated IP packet. An IP payload of m bits as a length is generated for n packets (see FIG. 12B), and each interleave frame related to interleave processing can be identified on the receiving device 5 side in the generated IP payload for n packets. An identification header for this purpose, a sequence number that specifies which bit is represented in each error correction code frame, and an IP header are added as the header of the coded data packet to generate an IP packet for n packets (. See FIG. 12 (c)). Then, the IP packet generation unit 62 interleaves the generated n packets of IP packets by the interleaving unit 621 in the order of transmission to the IP network 8 according to the sequence number based on a predetermined rule (for example, in ascending order of the sequence number). It may be transmitted, or it may be a transmission order of another sequence number determined between transmission and reception), and it is transmitted to the receiving device 5 as a coded data packet.

By transmitting the IP packet string of the coded data subjected to the interleave processing as a coded data packet from the transmission server 6 to the receiving device 5, the resistance to burst packet loss in the IP network 8 becomes stronger. (That is, the packet loss correction capability is improved).

(Application example: change of coding rate of LDPC code and change of correction ability of BCH code)
The error correction coding unit 643 in the coding rate adaptation changing unit 64 changes the coding rate of the coded data (coded data transmitted on the broadcast transmission line) related to the retransmission request and retransmits the LDPC code. Not only the coding ratio may be changed, but also the correction capability of the BCH code may be changed to be enhanced from 12 bits to 23 bits to reconstruct the coded data.

13 (a) to 13 (f), respectively, show lower coding of the coded data related to the retransmission request when the code rate is changed by the code rate adaptive change unit 64 in the transmission server 6 of the application example according to the present invention. It is a figure which shows the generation method of the coded data (at the time of changing to a rate). In addition, FIG. 13 shows the LDPC code having the highest value within the range of the number of types of LDPC coding rate conforming to ARIB STD-B44 by the retransmission request processing unit 63 in the transmission server 6 so as to be comparable to the example shown in FIG. Encoded data having a conversion rate (109/120 (≈9 / 10)) was received and held in the storage unit 61, and when the radio wave reception condition deteriorated from the receiving device 5, a retransmission request was made via the IP network 8. An example is shown in which the coded data is generated by changing the code rate to 61/120 (≈1/2).

First, in FIG. 13A, similarly to FIG. 11A, the coding rate of the coded data in the LDPC code having a code length N = 44880 bits transmitted on the broadcast transmission line is F _b = 109/120 (≈ It is shown as 9/10). As described above, in ARIB STD-B44, one error correction code frame has a constant code length of 44,880 bits regardless of the LDPC coding rate, and is composed of slot units based on the set division method. The information bits to be encoded are the "slot header", "main signal (data to be transmitted)", "BCH code parity", and "stuff bit", which are power-spread and LDPC codes. Parity is added to form one error correction code frame. Then, in the storage unit 61 of the transmission server 6, the coded data of one error correction code frame unit shown in FIG. 13A is attached with a synchronization signal (frame number or time information) and managed in chronological order. It is saved while updating the specified time. The LDPC code parity at the LDPC coding rate 109/120 (≈9/10) is composed of 44880 × (1-109 / 120) = 4114 bits.

Therefore, the transmission server 6 that has received the retransmission request packet from the receiving device 5 uses the retransmission request processing unit 63 to obtain the communication quality information included in the retransmission request packet, as in the embodiment described with reference to FIG. 11 described above. Whether or not to change the coding rate by referring to the coding rate change standard managed by the communication quality management unit 65 based on each information of the delay and the packet loss rate extracted and included in the communication quality information. Is determined.

Assuming that the code rate change criterion of (9) is followed, the retransmission request processing unit 63 has a delay obtained from the receiving device 5 less than a predetermined default value, or a packet loss rate obtained from the receiving device 5 is set. If it is less than the predetermined default value, it is determined that there is no change with the LDPC coding rate of 109/120 (≈9/10) of the coded data transmitted on the broadcast transmission line, and the retransmission request shown in FIG. 13 (a). The code rate adaptation change unit 64 is controlled so that the coded data having a code length of N bits according to the above is read from the storage unit 61 and output to the IP packet generation unit 62 as it is.

On the other hand, when the delay obtained from the receiving device 5 is equal to or more than a predetermined default value and the packet loss rate obtained from the receiving device 5 is less than a predetermined default value, the retransmission request processing unit 63 performs a broadcast transmission line. in the LDPC coding rate of the transmission encoded data _{F b = 109/120 (≒} 9/10), determines to change the LDPC coding rate _{F i = 61/120 (≒} 1/2) (F b> F _i ) First, of the coded data having a code length of 44880 bits according to the retransmission request shown in FIG. 13 (a), the information bits (that is, power spreading) to be encoded by the LDPC code _{having N × F b = 40766 bits.} Only the completed BCH coding bit) is read from the storage unit 61 (see FIG. 13B).

Subsequently, in this application example, the retransmission request processing unit 63 controls the coding rate adaptation change unit 64, and the error correction coding unit 643 reads out 40766 bits of information bits (that is, power) from the storage unit 61. The spread BCH coded bit) is once subjected to power despreading processing, and then the "slot header", "main signal (data to be transmitted)", "12-bit correction capability BCH code parity", and "staff". It restores to the bit array of "bits", deletes the "slot header", and allocates the deleted bit area to BCH code parity (see FIG. 13 (c)). Therefore, the bit array of "main signal (data to be transmitted)", "BCH code parity with 23-bit correction capability", and "stuff bit" is obtained without changing the entire information bit length. As a result, the 12-bit correction BCH code described in ARIB STD-B44 is corrected to the 23-bit correction BCH code while maintaining the frame length of the error correction code frame after the change of the LDPC coding rate. It can be configured to enhance the capability (for BCH code with 23-bit correction capability, for example, "Yoichi Suzuki, Specified Hashimoto, Takafumi Matsuzaki, Shoji Tanaka, Takeshi Kimura, Kenichi Tsuchida," LDPC code and BCH code. Performance improvement of set division 8PSK coded modulation to which the concatenated code of is applied, "Journal of the Society of Electronics, Information and Communication Engineers B, V0l.97, no.8, PP.648-659, August 1, 2014").

Subsequently, the error correction coding unit 643 uses the information bits of the bit array of the "signal (data to be transmitted)", the "BCH code parity of 23-bit correction capability", and the "stuff bit" shown in FIG. 13 (c). After performing the power diffusion processing again, the information bit is divided into two between transmission and reception by a predetermined division method in the same manner as in the embodiment described with reference to FIG. 11 described above ((N × F _b). ) / 2 = 20383 bits). Here, an example is made in which the first half and the second half of the information bit position are divided into two equal parts (see FIG. 13 (d)), but even if other division methods are used, such as dividing into two by odd-numbered bits and even-numbered bits. good.

Subsequently, the retransmission request processing unit 63 controls the coding rate adaptation change unit 64, and for the first half and the second half of each of the information bits divided into two, known values between transmission and reception (for example, all 0). bit) at _{N × F i - (N ×} F b) = 2431 adds bits as padding bits and an encoding rate _F i = 61/120 with respect to the information bits and padding bits (≒ 1/2) by performing LDPC encoding process becomes, and generates the parity of _{N × (1-F i)} = 22066 bits (see FIG. 13 (e)). In this example, although the padding bit is shown as being added after the information bit, the padding bit may be added before the information bit, that is, the insertion position of the padding bit is a code after the change. it is sufficient to set in advance as known between transmission and reception by the value of the ratio F _i.

Then, the error correction coding unit 643 removes the padding bit, reconstructs the encoded data (42449 bits) for retransmission in which 22066 bit parity is added to the 20383 bit information bit, and the IP packet generation unit 62. Is output to (see FIG. 13 (f)). The frame length of the reconstructed coded data for retransmission is 24449 bits, which is shorter than the original code length of 44880 bits, and does not exceed the coded length of the error correction code specified by the broadcasting standard. The coded data related to the retransmission request can be changed to a lower coding rate, and the correction capability is higher than in the case of retransmitting without changing the coding rate.

Further, by improving the correction capability of the BCH code, the packet loss tolerance in the IP network 8 can be improved. Regarding this change of BCH code, it is determined in advance between transmission and reception that the correction capability of BCH code is always changed when the LDPC code rate is changed, or it depends on either or both of the delay and the packet loss rate. In addition to the above-mentioned coding rate change criteria, the criteria for changing the correction capability of the BCH code, which is arbitrarily determined so as to switch the correction capability of the BCH code, is added to the above-mentioned coding rate change criteria, and at the same time as the notification of the coding rate change, before the transmission of the coded data to be retransmitted. In addition, the receiving device 5 may be notified in advance.

In this way, when the transmission server 6 of this application example receives the retransmission request packet, the LDPC coding rate and the BCH code of the coded data related to the retransmission request are determined based on the communication quality information included in the retransmission request packet. It is also possible to adaptively change the correction capability to generate a coded data packet and transmit it to the receiving device 5.

As described above, according to the transmission system 1 of the present embodiment, a retransmission request is made from the receiving device 5 side to the transmitting server 6 side via the IP network 8 for data loss that cannot be prevented only by broadcasting reception, and the transmitting server. By enabling data retransmission from the 6 side, the data can be complemented on the receiving device 5 side. In particular, the data retransmitted by the transmission server 6 via the IP network 8 is used as coded data in the block code of digital broadcasting, and the coded data is variably controlled to a coding rate according to the communication quality of the IP network 8. This makes it possible to reduce the number of retransmission requests and further improve the transmission efficiency via the IP network. Further, by making both the error correction code for broadcast reception and the error correction code used for transmission via the IP network the same as the code format of the error correction code standardized by the broadcasting standard, the receiving device 5 has one error correction. This can be achieved simply by preparing a decoder, and the scale of the equipment can be reduced. Further, according to the receiving device 5 according to the present invention, the coded data received via the IP line is decoded, and if the bit error cannot be completely corrected, the coded data received via the broadcast transmission line is decoded. Post-LLR (broadcast) that is the processing result (including bit error) or pre-LLR (broadcast) before decoding processing and post-LLR (IP) or pre-decoding processing that is the decoding processing result (including bit error) via the IP line. By synchronizing the pre-LLRs (IPs) with each other, sharing the highly reliable LLR (high absolute value of LLR) with both parties, and performing the decryption process again, it is possible to reduce the number of retransmission requests to the IP line and IP. High correction performance can be achieved even when there is a packet loss that exceeds the correction performance of the coded data via the line.

(Modification example)
FIG. 14 is a block diagram showing a schematic configuration of the receiving device 5 of the modified example according to the present invention. In FIG. 14, components similar to those shown in FIG. 7 are given the same reference numbers. The receiving device 5 of the modified example shown in FIG. 14 further includes a receiving quality measuring unit 57 as compared with that shown in FIG. 7, and the communication path connection switch unit 55 is from the error correction coding unit 52 as described above. The setting ON / OFF switching control is performed by the communication path connection ON / OFF signal of the above, but in this modification, the error correction coding unit 52 has its communication path based on the broadcast reception quality information from the reception quality measurement unit 57. The difference is that the setting ON / OFF switching control of the connection switch unit 55 is determined, and the other configurations are the same.

The reception quality measurement unit 57 measures the reception quality (for example, MER (Modulation Error Ratio)) of the received modulated wave signal, and outputs the broadcast reception quality information indicating the measured value to the error correction decoding unit 52.

Similar to the above-described embodiment, the communication path connection switch unit 55 is a switch that is controlled by the communication path connection ON / OFF signal by the error correction decoding unit 52 whether or not it is necessary to receive the coded data via the IP rope. Is.

That is, when the communication path connection switch unit 55 determines that the coded data obtained via the broadcast transmission path cannot be decoded by the decoding possibility determination unit 521 in the error correction decoding unit 52, the communication path connection by the error correction decoding unit 52 The coded data retransmitted via the IP network 8 and obtained from the IP packet receiving unit 54 is error-corrected until it can be decoded by the error correction code decoding process within the second predetermined time controlled by the ON / OFF signal. Input to the decoding unit 52. However, the error correction decoding unit 52 of this modification determines whether or not to block the reception of the coded data via the IP line based on the broadcast reception quality information from the reception quality measurement unit 57.

More specifically, the error correction / decoding unit 52 broadcasts from the reception quality measurement unit 57 when the communication path connection switch unit 55 is set to ON and the coded data can be received via the IP network 8. When the reception quality information indicates that the reception quality of the received modulated wave signal is equal to or higher than a predetermined value, after the decoding processing for a certain coded data is completed, the communication path connection ON / OFF signal is used for the broadcast transmission path. Control to switch to receive only via.

On the other hand, the error correction / decoding unit 52 uses the broadcast reception quality information from the reception quality measurement unit 57 when the communication path connection switch unit 55 is set to ON and the coded data can be received via the IP network 8. When it is shown that the reception quality of the received modulated wave signal is less than the predetermined value, the coded data can be received as it is via the IP network 8 even after the decoding process for a certain coded data is completed. Control.

(Reception control flow in the receiving device of the modified example)
FIG. 15 is a flowchart showing a reception control flow in the receiving device 5 of the modified example according to the present invention. The same step numbers as those in FIG. 8 are assigned the same numbers.

Steps S1 to S14 shown in FIG. 15 are the same as steps S1 to S14 shown in FIG. 8, and further description thereof will be omitted.

That is, even in the receiving device 5 of this modification, when it is determined that the coded data transmitted via the broadcast transmission line and demodulated by the demodulation unit 51 can be decoded, it is decoded as it is and the received data is reproducibly generated. When it is determined that the data cannot be decoded, the processing of the coded data complementing unit 522 based on the above-mentioned steps S6 to S10 and the series of processing of the LLR sharing unit 525 based on the steps S11 to S13 are performed for a predetermined time as described above. Repeat within.

Then, the receiving device 5 of the present modification generates the received data based on the coded data that can be decoded by the error correction decoding unit 52, and then the current receiving path cannot pass through the IP network 8 and receives the broadcast. If only the reception path is used (step S14: No), the setting OFF of the communication path connection switch unit 55 is maintained as the reception path for broadcast reception only, and the demodulation / decoding process for the next coded data in chronological order is performed. Move to.

On the other hand, when the receiving device 5 of this modification generates the received data based on the coded data that can be decoded by the error correction decoding unit 52, and then the current receiving path can also be via the IP network 8 ( Step S14: Yes), the reception quality measuring unit 57 determines whether or not the reception quality of the received modulated wave signal is equal to or higher than a predetermined value (step S15A).

When the current reception path can be routed via the IP network 8 (step S14A: Yes) and the reception quality of the received modulated wave signal is equal to or higher than a predetermined value, the reception quality measurement unit 57 (step S15A: Yes). Yes), the communication path connection switch unit 55 is switched and controlled to set OFF so as to return only to reception via the broadcast transmission line, and the process proceeds to the demodulation / decoding process for the next coded data in chronological order (step S15B). ..

However, when the current reception path can be via the IP network 8 (step S14A: Yes) and the reception quality is less than a predetermined value (step S15A: No), the reception quality measurement unit 57 has a communication path. The connection switch unit 55 is maintained in the set ON state, and the next coded data in chronological order is received via the broadcast transmission path and the respective reception paths via the IP network 8.

Therefore, once the reception device 5 of the present modification shown in FIGS. 14 and 15 is switched so that the reception path can be via the IP network 8, if the reception quality of the received modulated wave signal is less than a predetermined value, Regarding the coded data to be coded by the error correction / decoding unit 52, it is predicted that the reception condition will continue to deteriorate to the extent that the bit error cannot be corrected by the error correction / decoding process in the future, until the reception quality exceeds a predetermined value. The coded data can be retransmitted and acquired even via the IP network 8.

The error correction / decoding unit 52 always indicates that the reception quality of the received modulated wave signal is less than a predetermined value as the broadcast reception quality information from the reception quality measurement unit 57, the communication path connection switch unit. It is also possible to control the setting of 55 to be ON.

Therefore, even in the transmission system 1 provided with the receiving device 5 of the present modification, the operation is performed in consideration of the reception quality of the received modulated wave signal in addition to all the advantages of the above-described embodiment. Stable digital data reception is possible.

[Outline of operation when the coded data related to the retransmission request is changed to a lower coding rate and retransmitted]
In order to further enhance understanding, in reference to FIG. 16, in the transmission system 1 of the embodiment including one embodiment and one modification shown in FIGS. 1 to 15 described above, the coded data related to the retransmission request can be obtained. An outline of the operation when changing to a low coding rate and retransmitting will be described.

FIG. 16 illustrates an outline of the operation when a coded data packet in which the coded data related to the retransmission request is changed to a lower code rate by the transmission server 6 of the embodiment according to the present invention is transmitted to the receiving device 5. It is a figure.

For example, as the coded data related to the retransmission request, the code rate (LDPC code rate) of the coded data transmitted on the broadcast transmission line conforms to ARIB STD-B44, and the code rate is 9/10 (109/120). (See FIG. 16A).

First, the transmission server 6 distinguishes whether the coding rate is higher or lower than the coding rate of the coded data transmitted on the broadcast transmission line according to the communication quality information, and adaptively changes the coding rate to the coded data. To reconstruct. Here, an example of changing the coding rate 9/10 of the coded data related to the retransmission request to a lower coding rate 1/2 will be described.

When the transmission server 6 changes the coding rate 9/10 of the coded data related to the retransmission request to a lower coding rate 1/2, the transmission server 6 transfers the information bit of the coded data related to the retransmission request between transmission and reception (transmission). The server 6 and the receiving device 5) are divided into two according to a predetermined division method (here, the first half and the second half are divided into two equal parts) (see FIG. 16B).

Subsequently, the transmission server 6 performs re-coding using the padding bit to change the coding rate to 1/2, and temporarily generates coded data to which a parity bit having a coding rate of 1/2 is added (FIG. 16). (C)).

Then, the transmission server 6 generates an error correction code frame (LDPC frame) of the coded data in which the padding bit is deleted from the coded data to which the parity bit is added, and then forms an interleaved frame to form an interleaved coded data packet (an interleaved coded data packet). An IP packet sequence) is formed and transmitted to the receiving device 5 via the IP network 8 (see FIG. 16D).

After receiving the coded data packet, the receiving device 5 performs deinterleaving as a reverse process on the transmitting server 6 side, adds a padding bit, and then decodes the coded data at a coding rate of 1/2 to obtain the packet. Erasure correction is performed (see FIG. 16 (e)).

Then, the receiving device 5 relates to the coded data requested to be retransmitted by connecting the first half of the decoded information bit of the error correction code frame # 1 and the second half of the decoded information bit of the error correction code frame # 2. Received data with the information bits restored can be generated (see FIG. 16 (f)).

Therefore, according to the transmission system 1 according to the present invention, for data loss that cannot be prevented only by broadcast reception, a retransmission request is made from the receiving device 5 to the transmitting server 6 via the IP network 8, and data retransmission is performed from the transmitting server 6. By making it possible, the data can be complemented on the receiving device 5 side. In particular, the data retransmitted by the transmission server 6 via the IP network 8 is used as coded data in the block code of digital broadcasting, and the coded data is variably controlled to a coding rate according to the communication quality of the IP network 8. This makes it possible to reduce the number of retransmission requests, improve the transmission efficiency via the IP network 8, and enhance the resistance to packet loss. Further, by making both the error correction code by broadcasting reception and the error correction code used in transmission via the IP network 8 the same as the code format of the error correction code standardized by the broadcasting standard, one on the receiving device 5 side. This can be achieved simply by preparing an error correction decoder, and the scale of the equipment can be reduced.

With respect to the above-described embodiment, a program for operating each means of the computer functioning as the transmission server 6 can be preferably used. Further, a program for operating each means of the computer functioning as the receiving device 5 can be preferably used. Specifically, at least a storage unit in which a control unit for controlling each means can be configured by a central processing unit (CPU) in a computer and a program necessary for operating each means is appropriately stored is at least. It can be configured with one memory. That is, by causing such a computer to execute the program by the CPU, the functions of the above-mentioned means can be realized. Further, a program for realizing the function of each means can be stored in a predetermined area of the above-mentioned storage unit (memory). Such a storage unit can be configured by a RAM or ROM inside the device, or can be configured by an external storage device (for example, a hard disk). Further, such a program can be configured as a part of software (stored in ROM or an external storage device) on an OS used by a computer. Further, the program for causing such a computer to function as each means can be recorded on a computer-readable recording medium. Further, each of the above-mentioned means may be configured as a part of hardware or software, and each of them may be combined and realized.

Examples, applications, and modifications of the above-described embodiment have been described as representative examples, but it is clear to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the present invention. .. For example, the transmission server 6 has described an example in which encoded data is directly input from the transmission device 2 (or transmission device 3), but in relay broadcasting or the like, reception is once received from the transmission device 2 (or transmission device 3). It may be in the form of receiving the modulated wave by the machine, demodulating it, and inputting the coded data obtained by this demodulation. Therefore, the present invention should not be construed as being limited by the above embodiments, but only by the claims.

According to the present invention, since the error correction code used in digital broadcasting and the retransmission request can be efficiently combined, it is useful for data compensation related to digital broadcasting.

1 Transmission system 2 Transmitter for satellite broadcast transmission line 2a Transmission antenna for satellite broadcast transmission line 3 Transmitter for terrestrial broadcast transmission line 3a Transmission antenna for terrestrial broadcast transmission line 4 Broadcast satellite 5 Receiver 5a Satellite broadcast transmission line Receiving antenna for 5b Receiving antenna for terrestrial broadcasting transmission line 6 Transmission server 7 Load distribution device 8 IP network 21 Error correction coding unit 22 Modulation unit 51 Demodition unit 52 Error correction decoding unit 53 Retransmission request packet generation unit 54 IP packet reception Channel 55 Communication path connection switch 56 Communication quality measurement 57 Reception quality measurement 61 Storage 62 IP packet generation 63 Retransmission request processing 64 Coding rate adaptation change 521 Decoding / rejection judgment 522 Coding data complement 523 Data Coupling part 524 LLR storage part 525 LLR common part 541 Deinterleaved part 621 Interleaved part 641,642 Switching part 643 Error correction coding part

Claims (12)

The coded data is digitally modulated using the error correction code related to digital broadcasting, and the coded data is transmitted to the receiving device via the broadcast transmission line. It is a transmission server that saves a predetermined amount of time and enables transmission to a receiving device via an IP (Internet Protocol) network.
The coded data generated by the transmission device is sequentially input, managed in time series by a synchronization signal based on the frame number or time information of the error correction code frame constituting the code length of the error correction code, and managed in time series. A storage unit that stores the coded data for a predetermined time while updating it, and a storage unit that stores the coded data for a predetermined time.
The retransmission request packet generated when the bit error of the coded data cannot be corrected by the receiving device using the error correction code is received via the IP network, and the reception is stored in the retransmission request packet. The communication quality information measured by the device and the retransmission request information indicating the coded data of the error correction code frame related to the retransmission request are extracted, and based on the coding rate change standard predetermined based on the communication quality information. , It is determined whether or not to retransmit the coded data generated by the transmission device by changing the coding rate of the block code, and according to the determination result, based on the retransmission request information, from the storage unit. A retransmission request processing unit that reads out the encoded data related to the retransmission request, configures the encoded data in which the encoding rate is changed, and controls the retransmission of the encoded data toward the receiving device.
When the code rate of the block code of the coded data generated by the transmission device is changed or not changed by the control of the retransmission request processing unit, and the code rate is changed, the code rate is changed. Based on the same coding method as the error correction coding method used in the transmission device, and among the predetermined number of coding rates that can be used by the transmission device, the code rate is generated by the transmission device transmitted on the broadcast transmission line. An error correction coding process that changes the code rate by distinguishing whether it is higher or lower than the code rate of the coded data, and a code rate adaptive change unit.
An IP packet generation unit that generates an IP packet format coded data packet that stores coded data related to a retransmission request configured through control by the retransmission request processing unit and transmits it to the receiving device via the IP network. , Equipped with
When the code rate adaptation change unit changes the code rate of the coded data generated by the transmission device under the control of the retransmission request processing unit,
When converting to a coding rate higher than the coding rate before the change, a padding bit known on the receiving device side is added to the information bit of the coded data according to the coded rate to be changed. The parity of the block code obtained by performing the error correction coding process and whose coding rate is changed is replaced with the parity added to the coded data generated by the transmission device and added, and the padding bit is removed. Generates coded data for retransmission
When converting to a coding rate lower than the coding rate before the change, the information bit of the coded data is divided between transmission and reception by a predetermined division method, and each is divided according to the coding rate to be changed. The parity of the block code obtained by adding the padding bit known on the receiving device side to the information bit of the above and changing the coding rate obtained by performing the error correction coding process is the code generated by the transmitting device. A transmission server characterized by generating encoded data for retransmission by replacing and adding the parity added to the converted data and removing the padding bit. The retransmission request processing unit has the predetermined coding rate based on either one or both of the communication line delay information and the packet loss rate information measured by the receiving device as the communication quality information. The transmission server according to claim 1, wherein the coding rate of the coded data generated by the transmission device is changed according to a change criterion to determine whether or not to retransmit. When the code rate adaptation change unit changes the code rate of the coded data generated by the transmission device under the control of the retransmission request processing unit, the code rate adaptation change unit is in addition to changing the code rate of the block code. The first aspect of the invention, claim 1, further comprising means for changing the correction capability of the error correction code connected to the block code while maintaining the frame length of the error correction code frame after the change of the coding rate. The transmission server according to 2. The IP packet generation unit constitutes an interleaved frame using the plurality of error-correcting code frames, and can identify the interleaved frame in a payload obtained by interleaving each error-correcting code frame so as to traverse. The coded data packet of the IP packet string by adding the identification header for the purpose, the sequence number that specifies which bit is represented in each error correction code frame, and the IP header that is the header of the coded data packet. The transmission server according to any one of claims 1 to 3, further comprising an interleaving unit for generating the above. A transmitter for digital broadcasting
A transmission device according to any one of claims 1 to 4, wherein the transmission server has a means for sequentially outputting coded data encoded by using the error correction code related to the digital broadcasting. .. A transmitter for digital broadcasting
A transmission device comprising the transmission server according to any one of claims 1 to 4 inside the device. A receiving device that digitally modulates coded data encoded by a transmitting device using an error correction code related to digital broadcasting and receives a modulated wave signal transmitted via a broadcasting transmission line.
A demodulation unit that receives and demodulates the modulated wave signal,
An error in which an error correction code frame constituting the code length of the error correction code is reconstructed from the coded data obtained by demodulation and a decoding process corresponding to the error correction code is performed to generate received data and make it playable. Correction and decoding section and
Retransmission request information indicating the encoded data of the error correction code frame related to the retransmission request for requesting the retransmission of the corresponding encoded data when the bit error of the encoded data cannot be corrected by using the error correction code. A retransmission request packet generation unit that generates a retransmission request packet in the form of an IP packet including the retransmission request packet and transmits the retransmission request packet to the transmission server according to any one of claims 1 to 4.
The encoded data packet in the form of an IP packet that stores the encoded data retransmitted in response to the retransmission request is received from the transmission server in response to the retransmission request packet, and the encoded data retransmitted in response to the retransmission request is received. The IP packet receiver to be extracted and
One or both of the delay related to communication with the transmitting server and the packet loss rate based on the amount of packet loss generated related to communication with the transmitting server are measured and updated and held in predetermined period units. A communication quality measuring unit that sequentially outputs communication quality information including one or both of the delay information and the packet loss rate information of the communication line to the retransmission request packet generation unit so as to be included in the retransmission request packet. Equipped with
The error correction decoding unit
When it is determined whether or not the coded data obtained from the transmission device can be error-corrected and decoded, and it is determined that the bit error of the coded data cannot be corrected and cannot be decoded, the retransmission is performed to the retransmission request packet generation unit. The coded data when it is determined by the decoding passability determination unit having a function of generating a request packet and the coded data obtained from the transmission device that bit error correction cannot be corrected and decoding is not possible. The LLR storage unit that temporarily holds the post-log likelihood ratio after the decoding process or the pre-log likelihood ratio before the decoding process, including the bit error of
The coded data retransmitted in response to the retransmission request is the coding rate of the coded data obtained by demodulating the coded data when the coding rate is not changed, and is coded when the coding rate is changed. A coded data complement unit that adds padding bits according to the conversion rate and attempts decryption processing through completion processing related to replacement of the likelihood ratio required for decoding.
When the coded data related to the retransmission request is changed to a lower code rate and the information bits are divided, the divided information bits after decoding are regenerated according to a predetermined division method with the transmission server. A data combination part that combines to generate received data,
If the bit error cannot be completely corrected for the coded data retransmitted in response to the retransmission request in the decoding process in the coded data complementing unit, it is obtained via the broadcast transmission path and temporarily held in the LLR storage unit. The log-likelihood ratio or the pre-likelihood ratio and the post-log-likelihood ratio or the pre-log-likelihood ratio before the decoding process obtained by the decoding process of the coded data acquired by the retransmission request via the IP network are described above. Synchronize using a synchronization signal, compare the posterior log-likelihood ratio or prior log-likelihood ratio of both, and select the posterior log-likelihood ratio or prior log-likelihood ratio with the larger absolute value as having high reliability. Then, the selected posterior log-likelihood ratio or pre-log-likelihood ratio is shared between the block codes of the respective coded data obtained via the broadcast transmission line and the IP line, and the decoding process of the respective coded data is performed. LLR sharing that repeats the decoding process for the first predetermined time while performing the process of selecting and sharing the log-likelihood ratio of the larger absolute value until at least one of the encoded data can be decoded. With a part,
The decoding possibility determination unit determines whether or not error correction and decoding of each coded data obtained via the broadcast transmission line and the IP line is possible in the decoding process within the first predetermined time by the LLR sharing unit. When it is determined that a bit error remains in both the coded data obtained via the broadcast transmission line and the IP line in the decoding process within the first predetermined time, the retransmission request packet is generated. The retransmission request packet is generated so as to request the retransmission again from the unit, and a series of processes of the encoded data complement unit and the LLR shared unit are performed until at least one of the respective encoded data can be decoded. A receiving device having a function of repeating 2 for a predetermined time. The error correction code is composed of a concatenated code in which an LDPC code is concatenated as an internal code and a BCH code is concatenated as an external code. The receiving device according to claim 7, wherein it is determined that the bit error of the coded data cannot be corrected when the coded data is not error-free. Further provided with a reception quality measuring unit for measuring the reception quality of the received modulated wave signal.
The reception quality measurement unit
When the reception path at the time of generating the received data based on the coded data decrypted by the error correction decoding unit is the reception path for broadcasting and receiving instead of via the IP network, the receiving path for broadcasting and receiving is maintained.
When the reception path at the time of generating the received data based on the coded data decrypted by the error correction decoding unit is via the IP network, it is determined whether or not the reception quality is equal to or higher than a predetermined value, and the above is described. If the reception quality is equal to or higher than the predetermined value, the reception path is used only for broadcasting reception, and if the reception quality is less than the predetermined value, the reception path is used for both broadcasting reception and via the IP network, and the error correction / decoding unit is encoded. The receiving device according to claim 7 or 8, further comprising means for instructing the next encoded data to be retransmitted and acquired via the IP network even after the data retransmission request. The IP packet receiving unit receives the coded data packet of the IP packet string storing the coded data retransmitted in response to the retransmission request from the transmitting server in response to the retransmission request packet, and interleaves by the transmitting server. The invention according to any one of claims 7 to 9, wherein the deinterleaved portion is provided by performing the reverse processing of the above and extracting the encoded data retransmitted in response to the retransmission request. Receiver. A program for operating a computer as a transmission server according to any one of claims 1 to 4. A program for operating a computer as a receiving device according to any one of claims 7 to 10.

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