An object of the present disclosure is to provide a transmitting-side relay apparatus, a system, a method, and a program, each adapted to reduce congestions in a network while appropriately using a communication resource for a network-based communication. A transmitting-side relay apparatus according to the present disclosure includes a request rate calculation unit configured to calculate, based on a transmission rate of an input packet, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in a receiving-side relay apparatus, a request rate of the encoded packet; a permissible rate calculation unit configured to calculate, based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet.

This application is a National Stage Entry of PCT/JP2020/036122 filed on Sep. 24, 2020, which claims priority from Japanese Patent Application 2019-175433 filed on Sep. 26, 2019, the contents of all of which are incorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present disclosure relates to a transmitting-side relay apparatus, a system, a method, and a program, in particular, a transmitting-side relay apparatus, a system, a method, and a program, each adapted to reduce congestion in a network while appropriately using a communication resource for a network-based communication.

BACKGROUND ART

A rateless code is known as an encoding scheme used for leased lines such as wired networks, satellite channels, and the like. In a communication (transfer) method using a rateless code, the transmitting-side apparatus generates an encoded packet by combining a plurality of packets selected randomly from the input packets and transmits the generated encoded packet. The receiving-side apparatus transmits, when the encoded packet can be decoded, ACK for notifying that transmission has been completed to the receiving-side apparatus. The transmitting-side apparatus continues to transmit the encoded packet to the receiving-side apparatus until ACK is received from the receiving-side apparatus. In these leased lines, bandwidth is not limited and so the transmitting-side apparatus generates an unlimited number of encoded packets and transmits the generated encoded packets. This configuration has been causing a congestion in the network.

Here, a case where the rateless code is used in an environment in which the leased lines are not used, for instance, a case where it is applied to a radio network shared by a plurality of users (terminal apparatuses) is studied. In this case, since bandwidth is not limited on the transmitting-side, the transmitting-side apparatus raises the transmission rate of the rateless code until the network gets congested. Then, the transmitting-side apparatus lowers the transmission rate after the network congestion is detected. Further, even when the input rate (the reception rate) of the input packets is low, the transmitting-side apparatus continues to transmit a plurality of encoded packets until the network gets congested, thus using more communication resources (the network resources) than necessary.

Patent Literature 1 discloses, in paragraph 0024, that based on the information on the calculated RTT (Round Trip Time) and the acquired error rate, determination is made as to whether congestions have occurred in the period corresponding to the received feedback information. Further, Patent Literature 1 discloses, in paragraph 0028, that the encoding rate and the FEC rate are determined using the result of determination of the occurrence of congestions and the information on the error rate and the RTT. Patent Literature 1 does not disclose calculating a predetermined transmission rate for transmitting the encoded packets based on the two rates of the request rate of the encoded packets and the permissible rate of the encoded packets.

Patent Literature 2 discloses, in paragraph 0032, that an additional distribution server distributes, using the encoded symbol set B different from the encoded symbol set A which was used in the distribution in phase1, the encoded symbols of the encoded symbol set B by the number of additional distributions. Further, Patent Literature 2 discloses, in paragraph 0054, that by inserting encoding parameters into each packet and the like, the encoding parameters are changed for each distribution or during distribution. Patent Literature 2 does not disclose that the predetermined transmission rate for transmitting the encoded packets based on the two rates of the request rate of the encoded packets and the permissible rate of the encoded packets is calculated.

Patent Literature 3 discloses, in paragraph 0059, that the packet loss rate and the round trip transmission delay (RTT: Round Trip Time) is calculated. Further, Patent Literature 3 discloses, in paragraph 0070, that the parameter calculation unit finds the probability distribution of the delay time and finds the “number of source packets to be encoded at once”, which is the parameter of the rateless code, by substituting the “maximum delay allowance” and the “assurance establishment” input by the user. Patent Literature 3 does not disclose that the predetermined transmission rate for transmitting the encoded packets based on the two rates of the request rate of the encoded packets and the permissible rate of the encoded packets is calculated.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2009-278521Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2007-166469Patent Literature 3: International Patent Publication No. WO 2015/060297

SUMMARY OF INVENTION

Technical Problem

As described above, there has been a problem that the transmission rate of the rateless code is raised until the network gets congested. Further, there has been a problem that more communication resources (the network resources) than necessary are used.

An object of the present disclosure is to provide a transmitting-side relay apparatus, a system, and a method, and a program each configured to solve any one of the aforementioned problems.

Solution to Problem

A transmitting-side relay apparatus according to the present disclosure includes:a request rate calculation unit configured to calculate, based on a transmission rate of an input packet input to the transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in a receiving-side relay apparatus, a request rate of the encoded packet;a permissible rate calculation unit configured to calculate, based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate, a permissible rate of the encoded packet; anda transmission rate calculation unit configured to calculate a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate.

A system according to the present disclosure includes:a transmission terminal apparatus;a transmitting-side relay apparatus for receiving an input packet from the transmission terminal apparatus and transmitting an encoded packet;a receiving-side relay apparatus for receiving the encoded packet and transmitting an output packet; anda reception terminal apparatus for receiving the output packet,the transmitting-side relay apparatus including:a request rate calculation unit configured to calculate a request rate of the encoded packet based on a transmission rate of the input packet input to the transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in the receiving-side relay apparatus;a permissible rate calculation unit configured to calculate a permissible rate of the encoded packet based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate; anda transmission rate calculation unit configured to calculate a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate,the receiving-side relay apparatus including:an encoded packet receiving unit configured to receive the encoded packet from the transmission-side relay apparatus;a decoding unit configured to decode the encoded packet to generate the output packet;a packet transmitting unit configured to transmit the output packet to the reception terminal apparatus; andan ACK transmitting unit configured to transmit the delay time and the packet loss rate to the transmitting-side relay apparatus.

A method according to the present disclosure includes:calculating, based on a transmission rate of an input packet input to the transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in the receiving-side relay apparatus, a request rate of the encoded packet;calculating a permissible rate of the encoded packet based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate; andcalculating a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate.

A program according to the present disclosure for causing a computer to execute the processes of:calculating, based on a transmission rate of an input packet input to a transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in the receiving-side relay apparatus, a request rate of the encoded packet;calculating a permissible rate of the encoded packet based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate; andcalculating a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide a transmitting-side relay apparatus, a system, a method, and a program, each adapted to reduce congestions in a network while appropriately using a communication resource for a network-based communication.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, example embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the identical reference symbols denote identical structural elements and the redundant explanations thereof are omitted where appropriate to clarify the explanation.

Example Embodiment

Configurations of a transmitting-side relay apparatus and a system according to an example embodiment will be described.

FIG.1is a block diagram illustrating a transmitting-side relay apparatus according to the example embodiment.

FIG.2is a block diagram illustrating a system according to the example embodiment.

As shown inFIG.1, a transmitting-side relay apparatus11according to the example embodiment includes a rate calculation unit11a. The rate calculation unit11aincludes a request rate calculation unit111, a permissible rate calculation unit112, and a transmission rate calculation unit113.

As shown inFIG.2, the system10according to the example embodiment includes a transmission terminal apparatus13, the transmitting-side relay apparatus11, a receiving-side relay apparatus12, and a reception terminal apparatus14.

The transmission terminal apparatus13transmits input packets to the transmitting-side relay apparatus11.

The transmitting-side relay apparatus11receives the input packets from the transmission terminal apparatus13, encodes the input packets to thereby generate encoded packets, and transmits the generated encoded packets to the receiving-side relay apparatus12via a network.

An encoding scheme is, for example, a rateless encoding scheme.

The request rate calculation unit111of the transmitting-side relay apparatus11calculates the reception rate of the input packets input to the transmitting-side relay apparatus11. The reception rate is, for example, the number of input packets that have arrived per unit time.

The request rate calculation unit111calculates an encoding loss rate when the input packets are encoded to generate encoded packets. The encoding loss rate is calculated, for example, from the number of packets that are encoded all at once. Further, the encoding loss rate may be calculated from the number of redundant codes that are necessary in decoding the encoded packets.

The request rate calculation unit111calculates the packet loss rate of the encoded packets in the receiving-side relay apparatus12. The packet loss rate may be calculated, for instance, from a sequence number of each encoded packet included in ACK for notifying completion of decoding transmitted from the receiving-side relay apparatus12. The request rate calculation unit111performs, for instance, determination that the encoded packet corresponding to the sequence number of the packet for which ACK could not be received has been lost (a loss) when the encoded packet is transmitted to the receiving-side relay apparatus12. Then, the request rate calculation unit111may determine (the number of encoded packets lost per unit time/the total number of transmitted packets per unit time) as the packet loss rate.

The request rate calculation unit111calculates the request rate of the encoded packets based on the reception rate, the encoding loss rate, and the packet loss rate. The specific formula for calculating the request rate will be described later.

Note that the packet loss may sometimes be referred to as a network loss (NW loss).

The permissible rate calculation unit112calculates a delay time indicating the time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus12. The permissible rate calculation unit112receives, for instance, the packet number, the generation time of the packet, and the reception time at which the packet is received by the receiving-side relay apparatus12from the receiving-side relay apparatus12via an ACK receiving unit118to be described later. The permissible rate calculation unit112may, then, calculate the delay time based on these information. The permissible rate calculation unit112calculates the permissible rate of the encoded packet based on at least one of the calculated delay time and the packet loss rate calculated by the request rate calculation unit111.

Note that the permissible rate calculation unit112may calculate the permissible rate (the frequency band) at which the network does not get congested from the reception of ACK.

The transmission rate calculation unit113calculates the predetermined transmission rate for transmitting the encoded packets based on the request rate calculated by the request rate calculation unit111and the permissible rate calculated by the permissible rate calculation unit112. The predetermined transmission rate is, for instance, the number of encoded packets to be transmitted per unit time.

Specifically, the transmission rate calculation unit113sets the request rate or the permissible rate whichever is smaller as the predetermined transmission rate.

Further, the transmitting-side relay apparatus11further includes a packet receiving unit114, an encoding unit115, a transmission rate control unit116, and an encoded packet transmitting unit117, and the ACK receiving unit118.

The packet receiving unit114receives input packets. The encoding unit115encodes the input packets based on the predetermined transmission rate to generate encoded packets. The transmission rate control unit116performs control so that the transmission rate of the encoded packets is set to be the predetermined transmission rate. The encoded packet transmitting unit117transmits the encoded packets to the receiving-side relay apparatus12.

Instead of the request rate calculation unit111, the receiving-side relay apparatus12may calculate the packet loss rate, and the ACK receiving unit118may receive, from the receiving-side relay apparatus12, the delay time indicating the time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus12.

The receiving-side relay apparatus12receives the encoded packet from the transmitting-side relay apparatus11and transmits an output packet obtained by decoding the encoded packet to the reception terminal apparatus14.

The receiving-side relay apparatus12includes an encoded packet receiving unit127, a decoding unit125, a packet transmitting unit124, and an ACK transmitting unit128.

The encoded packet receiving unit127receives the encoded packets from the transmitting-side relay apparatus11. The decoding unit125decodes the encoded packets and generates the output packets. The packet transmitting unit124transmits the output packets to the reception terminal apparatus14.

The receiving-side relay apparatus12may calculate the packet loss rate instead of the request rate calculation unit111, and the ACK transmitting unit128may transmit, to the transmitting-side relay apparatus11, the delay time and the packet loss rate.

The reception terminal apparatus14receives the output packets from the receiving-side relay apparatus12.

Here, an operation of a rateless code will be described.

FIG.3is a schematic diagram illustrating an operation of a rateless code.

As shown inFIG.3, the transmitting-side relay apparatus11transmits, to the receiving-side relay apparatus12, the encoded packets in the order of an encoded packet (a+b), an encoded packet (a+b+c), an encoded packet (b+c), an encoded packet (a+c), and an encoded packet (a). Here, the symbol “+” refers to excusive OR (XOR). For instance, the encoded packet (a+b) indicate exclusive or of the input packet a and the input packet b.

In this example, it is assumed that the encoded packet (a+b) and the encoded packet (b+c) are lost in the course of the transmission. In this case, the number of input packets that are unknown is three, the input packet a, the input packet b, and the input packet c. Therefore, the receiving-side relay apparatus12can obtain the input packet a, the input packet b, and the input packet c based on the encoded packet (a+b+c), the encoded packet (a+c), and the encoded packet (a) that are the three received encoded packets. As described above, in the rateless code, by receiving the number of packets equal to the untimed number, the packets can be decoded.

A transmitting-side relay apparatus according to the example embodiment will be described.

FIG.4is a block diagram illustrating an operation of a request rate calculation unit according to the example embodiment.

As shown inFIG.4, the request rate calculation unit111acquires reception rate of the input packets input to the transmitting-side relay apparatus11from the packet receiving unit114. The request rate calculation unit111acquires, from the encoding unit115, the encoding loss rate when the input packets are encoded to generate encoded packets. The request rate calculation unit111acquires the packet loss rate of the encoded packets in the receiving-side relay apparatus12from the ACK receiving unit118.

The request rate calculation unit111calculates, using the reception rate, the encoding loss rate, and the packet loss rate, the request rate in which the encoding loss rate and the packet loss rate in accordance with the reception rate of the input packets are taken into account, and notifies the transmission rate calculation unit113of the calculated request rate.

The specific formula of the request rate is as follows.
Request rate=Reception rate×(1+encoding loss rate+packet loss rate)

Here, (1+encoding loss rate+packet loss rate) is referred to as the redundancy rate.

That is, the request rate calculation unit111calculates the redundancy rate by adding a numerical value 1, the encoding loss rate, and the packet loss rate. The request rate calculation unit111calculates the request rate by multiplying the calculated redundancy rate by the reception rate. The request rate calculation unit111notifies the transmission rate calculation unit113of the calculated request rate.

Here, the encoding loss rate is calculated from, for instance, the number of packets that have been encoded all at once by the encoding unit115. Further, the packet loss rate may, for instance, calculated from the sequence number of the packet included in ACK.

Note that the reception rate may also be referred to as an input rate or an arrival rate.

FIG.5is a block diagram illustrating a permissible rate calculation unit according to the example embodiment.

As shown inFIG.5, the permissible rate calculation unit112calculates the permissible rate permitted by the network based on the delay time and the packet loss rate. The permissible rate calculation unit112transmits the calculated permissible rate to the transmission rate calculation unit113. The permissible rate calculation unit112may receive the delay time and the packet loss rate from the ACK receiving unit118.

The permissible rate calculation unit112may include a delay time correspondence table showing the correspondence between the delay time and the permissible rate. The permissible rate calculation unit112may have a packet loss correspondence table showing the correspondence between the packet loss rate and the permissible rate. The permissible rate calculation unit112may calculate the permissible rate based on the delay time correspondence table or the packet loss rate correspondence table.

FIG.6is a block diagram illustrating a transmission rate calculation unit according to an example embodiment.

As shown inFIG.6, the transmission rate calculation unit113acquires the request rate from the request rate calculation unit111and acquires the permissible rate from the permissible rate calculation unit112. Further, the transmission rate calculation unit113acquires the predetermined relay time from the user. The transmission rate calculation unit113calculates the predetermined transmission rate for transmitting the encoded packets based on the request rate and the permissible rate.

The specific formula for calculating the predetermined transmission rate is as follows.
Predetermined transmission rate=min (request rate, permissible rate)

wherein, min (x, y) indicates a numerical value x or a numerical value y whichever is smaller.

That is, the transmission rate calculation unit113sets the request rate or the permissible rate, whichever is smaller, as the predetermined transmission rate.

Here, when the predetermined transmission rate is simply the request rate, there is a possibility that the relay time of the packets at the transmitting-side relay apparatus11may exceed the predetermined relay time set by the user. Therefore, the transmission rate calculation unit113may output, to the encoding unit115and the transmission rate control unit116, a burst transmission instruction without exceeding the predetermined relay time. Note the relay time indicates, for instance, the time period from the time of generation of the input packet to the time of transmission of the encoded packet from the transmitting-side relay apparatus11.

The encoding unit115dynamically changes the generation amount of the encoded packets generated in accordance with the instruction as regards the number of encoded packets to be generated (the burst transmission instruction) calculated by the transmission rate calculation unit113.

The transmission rate control unit116changes the transmission timing of the encoded packets in burst mode or dynamically, such as at regular intervals, in accordance with the instruction (the burst transmission instruction) of the packet transmission timing calculated by the transmission rate calculation unit113.

Note that the burst transmission instruction includes an instruction as regards the number of encoded packets to be generated and an instruction as regards the transmission timing of the encoded packets.

The transmission rate control unit116performs control so that the transmission rate of the encoded packets is equal to the predetermined transmission rate. The transmission rate control unit116performs control so that the relay time indicating the time period from the time of generation of the input packet to the time of transmission of the encoded packet from the transmitting-side relay apparatus11is set to be equal to or less than the predetermined relay time. The transmission rate control unit116performs, for instance, encoding and transmission of the encoded packet which has the relay time that is closer to the predetermined relay time in precedence over other input packets.

The transmission rate control unit116performs control so that the burst transmission of the encoded packets is performed from the one with the smaller relay time difference obtained by subtracting the relay time from the predetermined relay time. The transmission rate control unit116may perform control so that, for instance, the plurality of the encoded packets with the small relay time differences are collectively transmitted in burst mode.

Specifically, the transmission rate calculation unit113notifies the encoding unit115of the number of encoded packets to be generated (the volume of packets) to be transmitted by burst transmission. The encoding unit115outputs the encoded packets at a full rate until transmission of the notified number of the encoded packets is completed. The transmission is delayed until the next transmission timing so that an average transmission rate is achieved.

Note that a method of transmitting the encoded packets with a smaller relay time difference is, for instance, to use FIFO (First In First Out). If the encoded packets are loaded on the queue of the FIFO, the encoded packets are output in the order of their arrival and thus the encoded packets are automatically transmitted from the one with the smaller relay time difference.

Here, a function of transmitting the encoded packets from the one with the smaller relay time difference will be described taking an example in which a plurality of the transmission terminal apparatuses13are connected to one transmitting-side relay apparatus11.

FIG.7is a block diagram illustrating a plurality of transmission terminal apparatuses and a transmitting-side relay apparatus.

InFIG.7, explanation will be given taking an example in which three transmission terminal apparatuses13are connected to one transmitting-side relay apparatus11and a FIFO119is connected posterior to the packet receiving unit114. Note that inFIG.7, the stages posterior to the FIFO119are omitted for the sake of simplifying the explanation.

As shown inFIG.7, the transmitting-side relay apparatus11includes three packet receiving units114(a packet receiving unit114a, a packet receiving unit114b, and a packet receiving unit114c) to be connected to respective three transmission terminal apparatuses13(a transmission terminal apparatus13a, a transmission terminal apparatus13b, and a transmission terminal apparatus13c). The transmitting-side relay apparatus11includes the FIFOs119(a FIFO119a, a FIFO119b, and a FIFO119c) connected to the three packet receiving units114, respectively. In order to support the plurality of the transmission terminal apparatuses13, the transmission rate control unit116is connected to the FIFOs119. The queues of the three FIFOs119are present in parallel. Note that there is the encoding unit115in the stage posterior to the FIFO119, but the explanation thereof will be omitted for the sake of simplifying the description.

The time period from the time of output of the input packet from the FIFO119to the time of transmission of the encoded packet from the encoded packet transmitting unit117is the prescribed processing time. Therefore, the transmission rate control unit116can control the relay time of a packet by controlling the time of output of the packet from the FIFO119.

Specifically, the transmission rate control unit116performs control so that the input packets are sequentially output from the FIFO queues from the one with the smaller FIFO relay time difference. However, the FIFO relay time difference is the time difference obtained by subtracting the FIFO relay time from the predetermined FIFO relay time, and the FIFO relay time is the time period from the time of generation of the input packet to the time of output of the input packet from the FIFO119.

While in the present example embodiment, an explanation has been given of a case in which three transmission terminal apparatuses13are connected to the transmitting-side relay apparatus11, the present disclosure is not limited thereto. The present example embodiment can be also be implemented in the case in which only one transmission terminal apparatus13transmits a plurality of packets of different types, each packet (input packet) being received by the packet receiving unit114.

Note that when the relay time exceeds the predetermined relay time set by the user, the encoded packet exceeding the predetermined relay time is unnecessary and so the transmission rate calculation unit113notifies the encoding unit115of the packet discard instruction for discarding the unnecessary encoded packet. The encoding unit115discards the encoded packets which are retained in the encoding unit115.

Further, the transmitting-side relay apparatus11may display an error message instead of discarding the encoded packets.

Note that the predetermined relay time may sometimes be referred to as the Dead line time. Further, in the example embodiments, as an example, an explanation has been given of a rateless code, and thus the encoding unit may sometimes be referred to as a rateless code encoding unit.

An effect of a transmitting-side relay apparatus according to an example embodiment will be described.

FIG.8is a graph illustrating an operation of a transmitting-side relay apparatus according to an example embodiment.

InFIG.8, the horizontal axis represents the reception rate of the input packet and the vertical axis represents the predetermined transmission rate (the transmission rate) of the encoded packet.

InFIG.8, graph Gp1is a graph of the reception rate, graph Gp2is a graph of the request rate, graph Gp3is a graph of the permissible rate, and graph Gp4is a graph of the predetermined transmission rate.

As shown inFIG.8, the transmitting-side relay apparatus11according to the example embodiment operates such that the predetermined transmission rate shown by the graph Gp4is made to be equal to the request rate shown by the graph Gp2or the permissible rate shown by the graph Gp3whichever is smaller.

FIG.9is a graph illustrating an operation of a transmitting-side relay apparatus according to an example embodiment.

InFIG.9, the horizontal axis represents time and the vertical axis represents the predetermined transmission rate (the transmission rate) of the encoded packet.

InFIG.9, graph Gp1is a graph of the reception rate, graph Gp2is a graph of the request rate, graph Gp3is a graph of the permissible rate, and graph Gp4is a graph of the predetermined transmission rate.

As shown inFIG.9, the transmitting-side relay apparatus11according to the example embodiment operates such that the predetermined transmission rate shown by the graph Gp4is made to be equal to the request rate shown by the graph Gp2or the permissible rate shown by the graph Gp3whichever is smaller.

As shown inFIGS.8and9, the transmitting-side relay apparatus11operates such that the predetermined transmission rate is made to be equal to the request rate or the permissible rate whichever is smaller. By this configuration, the likelihood that the transmission rate of the rateless code will increase until the network gets congested will be reduced. Further, no more communication resources than necessary are used. As a result, according to the example embodiment, it is possible to provide a transmitting-side relay apparatus, a system, a method, and a program, each adapted to reduce congestions in a network while appropriately using a communication resource for a network-based communication.

Note that while in the example embodiments, an explanation has been given using an example in which one transmission terminal apparatus13is connected to one transmitting-side relay apparatus11, the present disclosure is not limited thereto. In the example embodiment, a plurality of the transmission terminal apparatuses13may be connected to one transmitting-side relay apparatus11.

Further, while in the example embodiments, an explanation has been given using an example in which one reception terminal apparatus14is connected to one receiving-side relay apparatus12, the present disclosure is not limited thereto. In the example embodiment, a plurality of the reception terminal apparatuses14may be connected to one receiving-side relay apparatus12.

Further, when the transmission terminal apparatus13is connected to the transmitting-side relay apparatus11on an N-on-N basis instead on a one-on-one basis, N-number of rate calculation units11amay be arranged in parallel in one transmitting-side relay apparatus11and the predetermined transmission rate may be calculated for each pair. N is a natural number equal to or greater than two.

Further, in the example embodiment, the permissible rate and the reception rate may be set to any fixed value in advance from the outside instead of being calculated dynamically. Therefore, the transmitting-side relay apparatus11may include an external interface for performing such setting.

Further, a relay apparatus including functions of the transmitting-side relay apparatus11and the receiving-side relay apparatus12may be provided, and the relay apparatus may be used in place of the transmitting-side relay apparatus11and the receiving-side relay apparatus12.

In the above example embodiments, the present disclosure has been described as a hardware configuration, but the present disclosure is not limited thereto. It is also possible to implement processing of each structural element by causing a CPU (Central Processing Unit) to execute a computer program.

The present disclosure has been described with reference to the example embodiments. However, it should be noted that the present disclosure is not to be limited in any way by the example embodiments described above. The configuration and the details of the present disclosure can be modified in various ways that can be understood by one skilled in the art within the scope of present disclosure.

Note that the present disclosure is not limited to the aforementioned example embodiments and can be changed as appropriate without departing from the gist of the present disclosure.

A transmitting-side relay apparatus comprising:a request rate calculation unit configured to calculate, based on a transmission rate of an input packet input to the transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in a receiving-side relay apparatus, a request rate of the encoded packet;a permissible rate calculation unit configured to calculate, based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate, a permissible rate of the encoded packet; anda transmission rate calculation unit configured to calculate a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate.
(Supplementary Note 2)

The transmitting-side relay apparatus described in Supplementary note 1, wherein the transmission rate calculation unit is configured to set the request rate or the permissible rate, whichever is smaller, as the predetermined transmission rate.

The transmitting-side relay apparatus described in Supplementary note 1 or 2, wherein the request rate calculation unit is configured tocalculate a redundancy rate by adding up a numerical value 1, the encoding loss rate, and the packet loss rate, andcalculate the request rate by multiplying the redundancy rate by the reception rate.
(Supplementary Note 4)

The transmitting-side relay apparatus described in any one of Supplementary notes 1 to 3, wherein the permissible rate calculation unithas a delay time correspondence table showing correspondence between the delay time and the permissible rate,has a packet loss rate correspondence table showing correspondence between the packet loss rate and the permissible rate, andis configured to calculate the permissible rate based on the delay time correspondence table or the packet loss rate correspondence table.
(Supplementary Note 5)

The transmitting-side relay apparatus described in any one of Supplementary notes 1 to 4, further comprising transmission rate control unit configured to perform control so that a transmission rate of the encoded packet is set to be the predetermined transmission rate, whereinthe transmission rate control unit is configured to perform control so that the relay time indicating the time period from the time of generation of the input packet to the time of transmission of the encoded packet from the transmitting-side relay apparatus is set to be equal to or less than the predetermined relay time.
(Supplementary Note 6)

The transmitting-side relay apparatus described in Supplementary note 5, wherein the transmission rate control unit is configured to perform control so that the encoded packet is transmitted from the transmitting-side relay apparatus with the smaller relay time difference obtained by subtracting the relay time from the predetermined relay time.

The transmitting-side relay apparatus described in Supplementary note 5 or 6, wherein the transmission rate calculation unit is configured to output, when the relay time exceeds the predetermined relay time, an instruction to discard the encoded packet which has exceeded the predetermined relay time.

The transmitting-side relay apparatus described in any one of Supplementary notes 1 to 7, wherein a scheme for performing the encoding is a rateless encoding scheme.

The transmitting-side relay apparatus described in any one of Supplementary notes 1 to 8, further comprising a packet receiving unit configured to receive the input packet.

The transmitting-side relay apparatus described in any one of Supplementary notes 1 to 9, further comprising an encoding unit configured to perform the encoding of the input packet and generate the encoded packet.

The transmitting-side relay apparatus according to any one of Supplementary notes 1 to 10, further comprising an encoded packet transmission unit configured to transmit the encoded packet to the receiving-side relay apparatus.

The transmitting-side relay apparatus according to any one of Supplementary notes 1 to 10, further comprising an ACK receiving unit configured to receive the delay time and the packet loss rate from the receiving-side relay apparatus.

A system comprising:a transmission terminal apparatus;a transmitting-side relay apparatus for receiving an input packet from the transmission terminal apparatus and transmitting an encoded packet;a receiving-side relay apparatus for receiving the encoded packet and transmitting an output packet; anda reception terminal apparatus for receiving the output packet,the transmitting-side relay apparatus including:a request rate calculation unit configured to calculate a request rate of the encoded packet based on a transmission rate of the input packet input to the transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in the receiving-side relay apparatus;a permissible rate calculation unit configured to calculate a permissible rate of the encoded packet based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate; anda transmission rate calculation unit configured to calculate a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate, the receiving-side relay apparatus including:an encoded packet receiving unit configured to receive the encoded packet from the transmission-side relay apparatus;a decoding unit configured to decode the encoded packet to generate the output packet;a packet transmitting unit configured to transmit the output packet to the reception terminal apparatus; andan ACK transmitting unit configured to transmit the delay time and the packet loss rate to the transmitting-side relay apparatus.
(Supplementary Note 14)

The system according to Supplementary note 13, wherein the transmission rate calculation unit is configured to set the request rate or the permissible rate, whichever is smaller, as the predetermined transmission rate.

A method comprising:calculating, based on a transmission rate of an input packet input to the transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in the receiving-side relay apparatus, a request rate of the encoded packet;calculating a permissible rate of the encoded packet based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate; andcalculating a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate.
(Supplementary Note 16)

A program for causing a computer to execute the processes of:calculating, based on a transmission rate of an input packet input to a transmitting-side relay apparatus, an encoding loss rate at the time of encoding the input packet to generate an encoded packet, and a packet loss rate of the encoded packet in the receiving-side relay apparatus, a request rate of the encoded packet;calculating a permissible rate of the encoded packet based on at least one of a delay time indicating a time period from the time of generation of the input packet to the time of reception of the encoded packet by the receiving-side relay apparatus and the packet loss rate; andcalculating a predetermined transmission rate for transmitting the encoded packet based on the request rate and the permissible rate.

The present disclosure has been described with reference to the example embodiments. However, it should be noted that the present disclosure is to be limited in any way by the example embodiments described above. The configuration and details of the present disclosure can be modified in various ways within the scope of the disclosure which can be understood by a skilled person in the art.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2019-175433, filed on Sep. 26, 2019, the entire contents of which are incorporated herein by reference.

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