Communication device, communication method, and computer program

Abstract

A communication device or the like capable of converging a transmission rate to an available bandwidth even in an environment where feedback delay is large. [Solution] A communications device comprising: a convergence determination means for determining whether the transmission rate has converged to a certain bandwidth using time series data indicating the time series progression of the data transmission rate to the opposing communications device and the round-trip delay time between the device itself and the opposing communications device over a certain period of time; a convergence determination means for estimating an available bandwidth, which is the communication bandwidth available to the opposing communications device, using the time series data when it is determined that the transmission rate has converged to a certain bandwidth; and a transmission rate calculation means for calculating a new transmission rate using a calculation formula having an increase term and a decrease term, wherein the decrease term has a larger value as the value obtained by subtracting the transmission rate from the available bandwidth increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases.

Description

[Technical Field]

[0001] The present disclosure relates to a communication device, a communication method, and a computer program. [Background technology]

[0002] A technique is known that dynamically adjusts the transmission rate of a communication device in accordance with the network communication load, thereby controlling the transmission rate so that it converges near the available bandwidth of the network. The available bandwidth is the communication bandwidth that a communication device can use with an opposing communication device. One such technique is disclosed in Patent Document 1. In the technique described in Patent Document 1, the equation for determining the transmission rate has a first term that acts to increase the transmission rate, and a second term that multiplies the difference between the minimum RTT (Round Trip Time) and the current RTT by the value of the transmission rate, and the difference between the first and second terms determines the amount by which the transmission rate is increased or decreased. According to the technique described in Patent Document 1, when the difference between the current RTT and the minimum RTT is small, i.e., when congestion does not occur, the value of the first term increases, and the transmission rate increases. On the other hand, when the difference between the current RTT and the minimum RTT is large, i.e., when congestion occurs, the value of the second term increases, and the transmission rate decreases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4407700 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in Patent Document 1 does not take into account feedback delays that occur in environments where the connection distance between communication terminals is long. Generally, when feedback delays are long, it takes time for changes in network conditions to be reflected in the RTT value. The technology described in Patent Document 1 controls the transmission rate based on the difference between the current RTT and the minimum RTT, so in environments with long feedback delays, adjustment of the transmission rate is delayed, causing the transmission rate to be over-increased or over-suppressed relative to the available bandwidth. As a result, the transmission rate does not converge to near the available bandwidth, reducing network utilization efficiency.

[0005] An object of the present disclosure is to provide a communication device, a communication method, and a computer program that can converge the transmission rate to the available bandwidth even in an environment with a large feedback delay. [Means for solving the problem]

[0006] A communication device according to one aspect of the present disclosure comprises: a convergence determination means for determining whether the transmission rate has converged to a certain bandwidth using time series data showing the time series progression of the data transmission rate to the opposing communication device and the round-trip delay time between the device and the opposing communication device over a certain period of time; an available bandwidth estimation means for estimating an available bandwidth, which is a communication bandwidth available to the opposing communication device, using the time series data when it is determined that the transmission rate has converged to a certain bandwidth; and a transmission rate calculation means for calculating a new transmission rate using a calculation formula having an increase term for increasing the transmission rate and a decrease term for decreasing the transmission rate, wherein the decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases.

[0007] In one aspect of the communication method of the present disclosure, a computer installed in a communication device uses time series data showing the time series progression of the data transmission rate to the opposing communication device and the round-trip delay time between the device and the opposing communication device over a certain period of time to determine whether the transmission rate has converged to a certain bandwidth, and if it is determined that the transmission rate has converged to a certain bandwidth, uses the time series data to estimate an available bandwidth, which is the communication bandwidth available to the opposing communication device, and calculates a new transmission rate using a calculation formula having an increase term that increases the transmission rate and a decrease term that decreases the transmission rate, with the decrease term having a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases.

[0008] A computer program according to one aspect of the present disclosure causes a computer installed in a communication device to perform the following processes: determine whether the transmission rate has converged to a certain bandwidth using time series data showing the time series trends over a certain period of time of the transmission rate of data to the opposing communication device and the round-trip delay time between the device and the opposing communication device; estimate an available bandwidth, which is the communication bandwidth available to the opposing communication device, using the time series data if it is determined that the transmission rate has converged to a certain bandwidth; and calculate a new transmission rate using a calculation formula having an increase term that increases the transmission rate and a decrease term that decreases the transmission rate; the decrease term has a characteristic that the larger the value obtained by subtracting the available bandwidth from the transmission rate, the larger its value, and the smaller the value obtained by subtracting the available bandwidth from the transmission rate, the smaller its value. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a communication device, a communication method, and a computer program that can converge the transmission rate to the available bandwidth even in an environment where feedback delay is large. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a conceptual diagram for explaining an overview of a communication system according to the present disclosure. [Figure 2] FIG. 1 is a conceptual diagram for explaining time-series data in the present disclosure. [Figure 3] FIG. 1 is a conceptual diagram for explaining measurement of RTT in the present disclosure. [Figure 4] 10 is a graph showing the transition of the transmission rate and RTT in a communication device according to the present disclosure. [Figure 5] 10 is a graph for explaining the processing of a convergence determination unit in the present disclosure. [Figure 6] 10 is a graph for explaining the processing of a convergence determination unit in the present disclosure. [Figure 7] 10 is a graph for explaining the processing of an available bandwidth estimation unit in the present disclosure. [Figure 8] 10 is a graph showing an example of an increasing direction parameter calculated by an increasing function in the present disclosure. [Figure 9] 10 is a graph showing an example of a jitter-derived decrease direction parameter calculated by a jitter-derived decrease function in the present disclosure. [Figure 10] 10 is a graph illustrating an example of a transmission rate-derived decrease direction parameter calculated by a transmission rate-derived decrease function in the present disclosure. [Figure 11] 10 is a graph illustrating an example of a transmission rate-derived decrease direction parameter calculated by a transmission rate-derived decrease function in the present disclosure. [Figure 12] 10 is a flowchart illustrating an example of an operation of a communication device according to the present disclosure. [Figure 13] 10 is a flowchart illustrating an example of an operation of a communication device according to the present disclosure. [Figure 14] 10 is a flowchart illustrating an example of an operation of a communication device according to the present disclosure. [Figure 15] 10 is a flowchart illustrating an example of an operation of a communication device according to the present disclosure. [Figure 16] 1 is a block diagram illustrating an example of a configuration of a communication device according to the present disclosure. [Figure 17] 10 is a flowchart illustrating an example of an operation of a communication device according to the present disclosure. [Figure 18] FIG. 1 is a diagram illustrating an example of a hardware configuration in which a communication device according to the present disclosure is realized by a computer device including a processor. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below are limited in a manner that is technically preferable for implementing the present disclosure, but the scope of the invention is not limited to the following. In all drawings used to describe the following embodiments, the same reference numerals are used for similar parts unless otherwise specified. In the following embodiments, repeated explanations of similar configurations and operations may be omitted.

[0012] [First embodiment]

[0013] (composition) First, the configuration of a communication system in the first embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a communication system in the present disclosure. The communication system 1 is a system for transmitting and receiving data between a plurality of communication terminals via a network. The communication system 1 includes a communication device 10 and an opposite communication device 80. The communication device 10 is an information processing device that functions as a data sending side. The opposite communication device 80 is an information processing device that functions as a data receiving side. The communication device 10 and the opposite communication device 80 are realized by general-purpose information processing devices such as a desktop terminal device, a notebook terminal device, or a server device.

[0014] As shown in FIG. 1, the communication device 10 includes a memory unit 11, a time series data observation unit 12, a transmission rate calculation unit 13, a transmission control unit 14, a transmission data generation unit 15, a transmission data output unit 16, a received data acquisition unit 17, a received data analysis unit 18, an output unit 19, and a communication interface 95.

[0015] The storage unit 11 includes a time-series data storage unit 111 and a parameter storage unit 112. The time-series data storage unit 111 stores time-series data. The time-series data is a memory block that stores the transmission rate R and the round-trip time RTT for a certain period of time in the past.

[0016] FIG. 2 is a conceptual diagram for explaining time-series data in the present disclosure. Time-series data will be further described with reference to FIG. 2. As shown in FIG. 2, the time-series data is configured as a FIFO (First In, First Out) queue. The length L of the FIFO queue is predetermined by a user. Values ​​of a transmission rate R and a round-trip time RTT are written in time series to the time-series data queue. The transmission rate R and round-trip time RTT written to the time-series data are periodically acquired. When a new value is stored in the time-series data, it is stored at the end of the block. If data is stored up to the beginning of the block at the time of writing, i.e., if all L pieces of data have been stored, the data at the beginning address is evicted and new data is stored at the end. In the following description, when simply referred to as RTT, it refers to the RTT stored at the end of the time-series data, i.e., the most recently acquired RTT. The time-series data storage unit 111 stores the minimum value of the RTTs stored in a block as the minimum RTT. In the following description, the minimum RTT will also be referred to as minRTT or minimum round-trip time.

[0017] The RTT stored in the time-series data is measured by receiving an acknowledgement (ACK). FIG. 3 is a conceptual diagram for explaining the measurement of RTT in the present disclosure. The measurement of RTT will be further described with reference to FIG. 3. The transmission data output unit 16 transmits a packet with sequence number N (Seq #N) to the opposite communication device 80 via the communication interface 95. The packet transmitted by the transmission data output unit 16 is generated by the transmission data generation unit 15. The transmission data output unit 16 holds t_N_send, which is the transmission time of the packet. Furthermore, when the packet arrives at the opposite communication device 80, the opposite communication device 80 transmits an ACK packet indicating that the packet has been received, to the communication device 10. The reception data acquisition unit 17 acquires the ACK packet. Furthermore, the reception data acquisition unit 17 acquires t_N_ACK, which is the arrival time of the ACK packet. The reception data analysis unit 18 calculates the difference between t_N_send and t_N_ACK as the RTT value. The received data analyzer 18 stores the measured RTT at the end of the memory block of the time series data. The received data analyzer 18 also stores the transmission rate at the time the RTT was measured at the end of the memory block of the time series data. The series of measurement processes described above is performed periodically.

[0018] The parameter storage unit 112 stores various parameters required for controlling the transmission rate, including the operation mode m and the determination threshold value.

[0019] The operation mode m is a flag for switching the operation of the communication device 10. The operation mode m consists of an available bandwidth estimation mode and an available bandwidth convergence mode. In the present disclosure, when the value of the operation mode m is 0, it is the available bandwidth estimation mode, and when the value of the operation mode m is 1, it is the available bandwidth convergence mode.

[0020] The available bandwidth estimation mode is a mode that is set when the transmission rate has not converged to a certain bandwidth. In the available bandwidth estimation mode, a process of repeatedly increasing or decreasing the transmission rate is performed until the transmission rate converges to a certain bandwidth. Once the transmission rate converges to a certain bandwidth, the available bandwidth estimation mode performs a process of estimating the rate at which congestion occurs, i.e., the target rate, which is the available bandwidth. The available bandwidth convergence mode is a mode that is set when the transmission rate has converged to a certain bandwidth. The available bandwidth convergence mode is a mode that prevents excessive increase or suppression of the transmission rate and converges to the available bandwidth. Figure 4 is a graph showing trends in the transmission rate and RTT in a communication device disclosed herein. As shown in Figure 4, the communication device 10 controls the transmission rate by repeatedly switching between the available bandwidth estimation mode and the available bandwidth convergence mode.

[0021] The determination thresholds are a threshold for the total amount of change in the transmission rate, a threshold for the total amount of change in the RTT, a threshold for the RTT, and a threshold for the number of times the transmission rate is obtained. The determination thresholds are, for example, determined in advance by a user and stored in the parameter storage unit 112.

[0022] The time-series data observation unit 12 has an available bandwidth estimation unit 121 and a convergence determination unit 122. The convergence determination unit 122 determines at regular time intervals whether the transmission rate R has converged to a constant bandwidth. When the convergence determination unit 122 determines that the transmission rate R has converged to a constant bandwidth, it transmits a convergence determination notification to the available bandwidth estimation unit 121. When the convergence determination unit 122 transmits the convergence determination notification, it sets a convergence determination notification transmission flag to True. The convergence determination notification transmission flag is a flag indicating whether a convergence determination notification has been transmitted to the available bandwidth estimation unit 121. When the convergence determination notification transmission flag is True, it indicates that a determination notification has been transmitted to the available bandwidth estimation unit 121. When the convergence determination notification transmission flag is False, it indicates that a determination notification has not been transmitted to the available bandwidth estimation unit 121. When the convergence determination notification transmission flag is False, it indicates that a determination notification has not been transmitted to the available bandwidth estimation unit 121. When the available bandwidth estimation unit 121 receives the convergence determination notification, it estimates a target rate, which is the available bandwidth.

[0023] The convergence determination unit 122 determines whether the transmission rate has converged to a constant bandwidth. When the operating mode m is 0, i.e., in the available bandwidth estimation mode, the convergence determination unit 122 determines whether the transmission rate has converged to a constant bandwidth using the average increase and decrease of the transmission rate. When the transmission rate converges to a constant bandwidth, the transmission rate hardly fluctuates. In other words, when the transmission rate converges to a constant bandwidth, the average increase and decrease of the transmission rate becomes close to 0. When the available bandwidth estimation mode is in the available bandwidth estimation mode, the convergence determination unit 122 refers to the time-series data and calculates a total change in the transmission rate, which is the sum of the changes in the transmission rate. For example, for each block of the time-series data, the convergence determination unit 122 calculates the difference between the transmission rate at time n and the transmission rate at time n-1, and sets the sum of these values ​​as the total change in the transmission rate. When the absolute value of the total change in the transmission rate is equal to or less than a threshold, the convergence determination unit 122 determines that the transmission rate has converged to a constant bandwidth. When the convergence determination unit 122 determines that the transmission rate has converged to a certain band, it transmits a convergence determination notification to the available band estimation unit 121. Note that the above-described method is an example, and the convergence determination unit 122 may determine that the transmission rate is substantially unchanged by other methods.

[0024] When the operation mode m is 1, i.e., when the available bandwidth convergence mode is selected, the convergence determination unit 122 determines whether the transmission rate has converged to a certain bandwidth using the RTT value. The convergence determination unit 122 determines whether the transmission rate has converged to a certain bandwidth based on the amount of change in the RTT over a certain period of time or the result of comparing the RTT with a threshold.

[0025] First, details of the process for determining whether the transmission rate has converged to a certain bandwidth based on the amount of change in RTT over a certain period of time will be described. FIG. 5 is a graph illustrating the process performed by the convergence determination unit in the present disclosure. In the graph in FIG. 5, the vertical axis represents the transmission rate or RTT, and the horizontal axis represents time. In the graph shown in FIG. 5, the target rate increases at time t_change. When the target rate increases, the RTT stops increasing for a certain period of time. In other words, the average increase or decrease in RTT over a certain period of time approaches zero. For example, when the operating mode m is 1, i.e., the available bandwidth convergence mode, the convergence determination unit 122 refers to the time-series data and calculates the total RTT change, which is the sum of the changes in RTT. For example, for each block of the time-series data, the convergence determination unit 122 calculates the difference between the RTT at time n and the RTT at time n-1, and sets the sum of these values ​​as the total RTT change. When the absolute value of the total RTT change is equal to or less than a threshold, the convergence determination unit 122 determines that the transmission rate has not converged to the target rate. If the convergence determination unit 122 determines that the transmission rate has not converged to the target rate, it switches the operation mode m to 0, i.e., to the available bandwidth estimation mode. When the convergence determination unit 122 rewrites the operation mode m to 0, it sets the convergence determination notification transmission flag to False. Note that the above-described method is an example, and the convergence determination unit 122 may determine that the target rate has increased by other methods.

[0026] Next, details of the process for determining whether the transmission rate has converged to a certain bandwidth based on the comparison result between the RTT and the threshold will be described. FIG. 6 is a graph illustrating the process of the convergence determination unit in the present disclosure. In the graph in FIG. 6, the vertical axis represents the transmission rate or RTT, and the horizontal axis represents time. In the graph shown in FIG. 6, the target rate decreases at time t_change. When the target rate decreases, the RTT begins to increase. For example, when the operation mode m is 1, i.e., in the available bandwidth convergence mode, the convergence determination unit 122 refers to the RTT at the end of the time-series data, i.e., the latest RTT value, and determines that the transmission rate has not converged to a certain bandwidth if the RTT is equal to or greater than the threshold. When the convergence determination unit 122 determines that the transmission rate has not converged to a certain bandwidth, it switches the operation mode m to 0, i.e., to the available bandwidth estimation mode. When the convergence determination unit 122 rewrites the operation mode m to 0, it sets the convergence determination notification transmission flag to False. The above-described method is merely an example, and the convergence determination unit 122 may determine that the target rate has decreased by other methods. That is, in the available bandwidth convergence mode, the convergence determination unit 122 determines whether the target rate has changed, and if the target rate has changed, performs processing to switch the operation mode to the available bandwidth estimation mode.

[0027] The available bandwidth estimation unit 121 estimates a target rate, which is the available bandwidth. The available bandwidth estimation unit 121 executes its processing in the available bandwidth estimation mode, i.e., when the operation mode m is 0. When the available bandwidth estimation unit 121 receives a convergence determination notification from the convergence determination unit 122, it starts estimating the target rate. If the RTT is greater than the threshold, the available bandwidth estimation unit 121 refers to the time-series data storage unit and acquires the transmission rate from the current time to the minimum RTT before.

[0028] The reason why the available bandwidth estimation unit 121 acquires the transmission rate from the current time to the minimum RTT will be described with reference to FIG. 7. FIG. 7 is a graph for explaining the processing of the available bandwidth estimation unit in the present disclosure. In the graph of FIG. 7, the vertical axis represents the transmission rate or RTT, and the horizontal axis represents time. In the graph shown in FIG. 7, the time when the transmission rate R exceeds the target rate R_target is designated as t_over. Referring to FIG. 7, the RTT has not increased at t_over. The RTT begins to increase at least at a time after t_over+minRTT, which is the minimum RTT after t_over. In other words, it can be estimated that the transmission rate R at t-minRTT, which is the time t when the RTT begins to increase minRTT minus the time t when the RTT begins to increase, is the target rate R_target. For this reason, the available bandwidth estimation unit 121 acquires the transmission rate from the current time to the minimum RTT.

[0029] When the number of times the transmission rate before the minimum RTT is acquired exceeds a threshold, the available bandwidth estimation unit 121 calculates the average value of each transmission rate before the minimum RTT. For example, assume that the threshold for the number of acquisitions is 2. In this case, when the number of times the transmission rate before the minimum RTT is acquired exceeds 2, the available bandwidth estimation unit 121 calculates the average value of each transmission rate. For example, in the example shown in FIG. 4, when the available bandwidth estimation unit 121 acquires the transmission rate at the minimum RTT at time t3, it calculates the average value of the transmission rate at the minimum RTT at time t1, the transmission rate at the minimum RTT at time t2, and the transmission rate at the minimum RTT at time t3. Note that the threshold may be any value equal to or greater than 0. The reason for acquiring the transmission rate before the minimum RTT multiple times and calculating the average value is to improve the accuracy of estimating the target rate by taking measurement error into consideration. The available bandwidth estimation unit 121 stores the calculated value in the time-series data storage unit 111 as an estimate of the target rate. Furthermore, upon completing the estimation of the target rate, the available bandwidth estimation unit 121 switches the operation mode m to 1, that is, the available bandwidth convergence mode.

[0030] The transmission rate calculation unit 13 calculates a new transmission rate. The transmission rate calculation unit 13 calculates the increase direction parameter of the transmission rate, the decrease direction parameter derived from jitter, and the decrease direction parameter derived from the transmission rate, and uses these to calculate a new transmission rate. The new transmission rate is calculated, for example, using equation (1). In the following equation, Rnew is the new transmission rate, R is the current transmission rate, and R_target is the estimated target rate. Furthermore, RTT is the latest RTT, i.e., the RTT stored at the end of the time-series data, and minRTT is the minimum RTT held by the time-series data storage unit 111. α is an increase constant, β is a decrease constant derived from jitter, and γ is a decrease constant derived from the transmission rate. f is an increase function, g is a decrease function derived from jitter, and h is a decrease function derived from the transmission rate. In the following description, the increase direction parameter calculated using the increase function f is referred to as inc. Similarly, in the following description, the decrease direction parameter derived from jitter calculated using the decrease function g derived from jitter is referred to as dec_jitter. Similarly, in the following description, the decrease direction parameter derived from the transmission rate calculated by the decrease function h derived from the transmission rate will be referred to as dec_rate. Details of each function will be described later.

[0031]

number

[0032] The transmission rate-derived decrease function h has the characteristic that, regardless of the RTT value, the greater the transmission rate value exceeds the estimated target rate, the more the transmission rate decreases. That is, according to equation (1), regardless of the RTT value, when the difference between the current transmission rate and the estimated target rate is large, the transmission rate decreases. This makes it possible to throttle the transmission rate before the RTT starts to extend. The transmission rate calculation unit 13 stores the new transmission rate Rnew calculated using equation (1) in the time-series data storage unit 111. The transmission rate calculation unit 13 also notifies the transmission control unit 14 of the new transmission rate Rnew.

[0033] FIG. 8 is a graph showing an example of an increase direction parameter calculated by an increase function in the present disclosure. The increase function will be described in detail with reference to FIG. 8. In the graph shown in FIG. 8, the vertical axis represents the increase direction parameter inc. The horizontal axis represents the value obtained by subtracting the minimum RTT from the RTT. The increase direction parameter inc of the transmission rate is calculated, for example, by an increase function f as shown in the following equation (2). The increase direction parameter inc calculated by the increase function f is the amount of change in the increase direction of the transmission rate. Furthermore, b is a parameter for preventing over-suppression of the transmission rate. By setting b, it is guaranteed that the transmission rate will increase above a certain value, thereby preventing over-suppression of the transmission rate.

[0034]

number

[0035] As shown in FIG. 8, according to equation (2), when congestion occurs, i.e., when the difference between the RTT and the minimum RTT increases, the value of the increase direction parameter inc decreases. That is, according to equation (2), the value of the increase direction parameter inc can be increased when congestion does not occur, and decreased when congestion occurs. Furthermore, in equation (2), when the RTT is large, i.e., when the connection distance between communication terminals is long, the base value in equation (2) increases. In the example shown in FIG. 8, the solid line graph is a graph with a base value of 2, and the dashed dotted line graph is a graph with a base value of 4. As the base value increases, as shown in FIG. 8, the increase in the transmission rate decreases in a shorter time. This makes it possible to suppress the increase in the transmission rate when the connection distance between communication terminals is long, thereby suppressing the increase in jitter caused by an excessive increase in the transmission rate. That is, the increase direction parameter inc calculated by equation (2) has the characteristic that the value decreases as the difference between the RTT and the minimum RTT increases, and the time it takes for the value to decrease as the RTT increases. Note that the formula (2) for calculating the increase direction parameter inc is merely an example and is not limiting. The formula for calculating the increase direction parameter inc may be any formula as long as it satisfies the above-described characteristics of formula (2).

[0036] FIG. 9 is a graph showing an example of a jitter-induced decrease direction parameter calculated using a jitter-induced decrease direction function according to the present disclosure. The jitter-induced decrease direction function will be described in detail with reference to FIG. 9. In the graph shown in FIG. 9, the vertical axis represents the jitter-induced decrease direction parameter dec_jitter. The horizontal axis represents the value obtained by subtracting the minimum RTT from the RTT. The jitter-induced decrease direction parameter dec_jitter is calculated, for example, using a decrease function g as shown in the following equation (3). As shown in FIG. 9, equation (3) has the characteristic that the larger the difference between the RTT and the minimum RTT, i.e., the more congestion occurs, the larger the value of the decrease direction parameter dec_jitter becomes. Note that equation (3), which is the calculation formula for the jitter-induced decrease direction parameter dec_jitter, is merely an example and is not limiting. The calculation formula for the jitter-induced decrease direction parameter dec_jitter may be any formula that satisfies the above-described characteristics of equation (3).

[0037]

number

[0038] 10 and 11 are graphs showing an example of a transmission rate-derived decrease direction parameter calculated using a transmission rate-derived decrease function according to the present disclosure. The transmission rate-derived decrease function will be described in detail with reference to FIGS. 10 and 11. In the graphs shown in FIGS. 10 and 11, the vertical axis represents the transmission rate-derived decrease direction parameter dec_rate. The horizontal axis represents the value obtained by subtracting the estimated target rate from the current transmission rate. The transmission rate-derived decrease direction parameter dec_rate is calculated, for example, using a decrease function h as shown in Equation (4) below. In the following equation, m is a coefficient representing the operation mode. When the operation mode m is 0, the mode is the available bandwidth estimation mode, and when the operation mode m is 1, the mode is the available bandwidth convergence mode. In other words, according to Equation (4), the value of the transmission rate-derived decrease direction parameter is 0 in the available bandwidth estimation mode. As shown in FIG. 10, the transmission rate-derived decrease direction parameter dec_rate increases in value in proportion to the value obtained by subtracting the target rate from the current transmission rate. According to equation (4), the decrease direction parameter derived from the transmission rate acts in a direction that decreases the transmission rate as the value of the transmission rate exceeds the estimated target rate. Furthermore, equation (4) has a characteristic that no decrease component occurs when the transmission rate is below the target rate. Note that equation (4), which is a formula for calculating the decrease direction parameter derived from the transmission rate, is an example and is not limited to this. For example, the decrease direction parameter derived from the transmission rate may be calculated using equation (5). As shown in FIG. 11, according to equation (5), the decrease direction parameter derived from the transmission rate acts in a direction that decreases the transmission rate as the value of the transmission rate exceeds the estimated target rate.

[0039]

number

[0040]

number

[0041] When the transmission control unit 14 receives notification of the new transmission rate calculated by the transmission rate calculation unit 13, it issues an instruction to the transmission data output unit 16 to transmit packets at the new transmission rate.

[0042] The transmission data generation unit 15 generates packets, which are transmission data. The transmission data generation unit 15 outputs the generated packets to the transmission data output unit 16. The transmission data output unit 16 outputs the packets at the transmission rate notified by the transmission control unit 14. The packets output by the transmission data output unit 16 are transmitted to the opposite communication device 80 via the communication interface 95. The reception data acquisition unit 17 acquires the packets transmitted from the opposite communication device 80 via the communication interface 95. The reception data analysis unit 18 calculates the RTT value. Furthermore, the reception data analysis unit 18 stores the calculated RTT value in the time-series data storage unit 111. The processing of the transmission data generation unit 15 to the reception data analysis unit 18 is as described with reference to FIG. 3, and therefore detailed description thereof will be omitted.

[0043] The output unit 19 generates and outputs output information including time-series data. For example, the output information includes changes in the transmission rate and RTT included in the time-series data stored in the time-series data storage unit 111. In another example, the output information includes a graph showing changes in the transmission rate and RTT over time, as shown in FIG. 4. In this case, the output unit 19 references the time-series data in the time-series data storage unit 111 and generates a graph such as that shown in FIG. 4. The output information generated by the output unit 19 is transmitted to, for example, a management device 70. The management device 70 is an information processing device operated by an administrator of the communication device 10, for example.

[0044] (operation) Next, the operation of the communication device 10 in this embodiment will be described with reference to Fig. 12 to Fig. 15. Fig. 12 to Fig. 15 are flowcharts showing an example of the operation of the communication device in the present disclosure. The processing of the communication device 10 includes a convergence determination process shown in Fig. 12, a target rate estimation process shown in Fig. 13, a transmission rate calculation process shown in Fig. 14, and an RTT measurement process shown in Fig. 15.

[0045] [Convergence determination process] First, the operation of the convergence determination process by the convergence determination unit 122 will be described with reference to Fig. 12. For example, the convergence determination process shown in Fig. 12 is periodically called and executed.

[0046] First, the convergence determination unit 122 checks the flag of the operation mode m by referring to the parameter storage unit 112 (step S101). If the value of the operation mode m is 0, the convergence determination unit 122 executes the processes of steps S102 to S106, and if the value of the operation mode m is 1, the convergence determination unit 122 executes the processes of steps S107 to S113.

[0047] First, we will explain the operation of the convergence determination process when the value of the operation mode m is 0. When the operation mode m is 0 and the transmission rate converges to a certain band, the convergence determination unit 122 executes a process of notifying the available band estimation unit 121 of the convergence determination.

[0048] First, the convergence determination unit 122 checks the value of the convergence determination notification transmission flag (step S102). If the convergence determination notification transmission flag is True (Yes in step S102), the convergence determination unit 122 ends the convergence determination process.

[0049] If the convergence determination notification transmission flag is False (No in step S102), the convergence determination unit 122 refers to the time-series data and calculates the total amount of change in the transmission rate, which is the total value of the amount of change in the transmission rate (step S103).If the total amount of change in the transmission rate is greater than the threshold (No in step S104), the convergence determination unit 122 determines that the transmission rate has not converged to a certain band, and ends the convergence determination process.

[0050] If the total amount of change in the transmission rate is equal to or less than the threshold value (Yes in step S104), the convergence determination unit 122 determines that the transmission rate has converged to a constant band, and transmits a convergence determination notification to the available band estimation unit 121 (step S105). Then, the convergence determination unit 122 rewrites the value of the convergence determination notification transmission flag to True (step S106), and ends the convergence determination process.

[0051] Next, we will explain the convergence determination process when the value of operation mode m is 1. When the operation mode m is 1 and the transmission rate does not converge to a constant band, the convergence determination unit 122 executes a process of switching the operation mode m to 0.

[0052] First, the convergence determination unit 122 acquires the latest RTT (step S107). The convergence determination unit 122 also refers to the time-series data and calculates the total RTT change amount, which is the total value of the RTT change amount (step S108). The processing of steps S107 and S108 may be performed in reverse order.

[0053] The convergence determination unit 122 checks whether the latest RTT value is equal to or greater than a threshold (step S109). If the latest RTT value is less than the threshold (No in step S109), the convergence determination unit 122 proceeds to the processing of step S111. If the latest RTT value is equal to or greater than the threshold (No in step S109), the convergence determination unit 122 determines whether the absolute value of the total RTT change amount is equal to or less than a threshold (step S110). If the absolute value of the total RTT change amount is greater than the threshold (No in step S110), the convergence determination unit 122 determines that the transmission rate has converged to a certain bandwidth, and ends the processing. Note that the processing of steps S109 and S110 may be performed in reverse order.

[0054] If the absolute value of the RTT total change amount is equal to or less than the threshold (Yes in step S110) or if the latest RTT value is less than the threshold (No in step S109), the convergence determination unit 122 determines that the transmission rate has not converged to a constant band, and updates the value of the operation mode m to 0 (step S111). Then, the convergence determination unit 122 stores the value of the operation mode m in the parameter storage unit 112 (step S112). Next, the convergence determination unit 122 rewrites the value of the convergence determination notification transmission flag to False (step S113), and ends the convergence determination process.

[0055] [Target rate estimation process] Next, the operation of the available bandwidth estimation unit 121 will be described with reference to Fig. 13. The target rate estimation process shown in Fig. 13 is started when a convergence determination notification is received from the convergence determination unit 122.

[0056] First, the available bandwidth estimation unit 121 refers to the time-series data storage unit 111 and acquires the time-series data and the minimum RTT (step S120).

[0057] Next, the available bandwidth estimation unit 121 determines whether the latest RTT is greater than a threshold (step S121). If the latest RTT is equal to or less than the threshold (No in step S121), the available bandwidth estimation unit 121 waits for a certain period of time (step S122) and then returns to the process of step S120.

[0058] If the RTT is greater than the threshold (Yes in step S121), the available bandwidth estimation unit 121 acquires the transmission rate from the current time to the minimum RTT before (step S123). The available bandwidth estimation unit 121 repeats the processes of steps S120 to S124 until the number of times the transmission rate has been acquired exceeds a certain number (No in step S124).

[0059] When the number of times that the transmission rate has been acquired exceeds a certain number (Yes in step S124), the available bandwidth estimation unit 121 calculates the average value of the acquired transmission rates before the minimum RTT, and estimates the average value as the target rate value (step S125).

[0060] Next, the available bandwidth estimation unit 121 stores the target rate in the time-series data storage unit 111 (step S126). Next, the available bandwidth estimation unit 121 rewrites the value of the operation mode m to 1 (step S127). The available bandwidth estimation unit 121 stores the value of the operation mode m in the parameter storage unit 112 (step S128). After completing the process of step S128, the available bandwidth estimation unit 121 ends the target rate estimation process.

[0061] [Transmission rate calculation process] Next, the operation of the transmission rate calculation unit 13 will be described with reference to Fig. 14. For example, the transmission rate calculation process shown in Fig. 14 is periodically called and executed.

[0062] First, the transmission rate calculation unit 13 refers to the time-series data storage unit 111 and acquires the time-series data and the minimum RTT (step S130). Next, the transmission rate calculation unit 13 determines whether the latest RTT is smaller than the minimum RTT (step S131). If the latest RTT is equal to or larger than the minimum RTT (No in step S131), the transmission rate calculation unit 13 executes the processes from step S133 onward.

[0063] If the latest RTT is smaller than the minimum RTT (Yes in step S131), the transmission rate calculation unit 13 updates the value of the minimum RTT stored in the time-series data storage unit 111 to the value of the latest RTT (step S132).

[0064] If step S131 is No, or after completing the process of step S132, the transmission rate calculation unit 13 calculates the increase direction parameter inc, the jitter-derived decrease direction parameter dec_jitter, and the transmission rate-derived decrease direction parameter dec_rate (steps S133 to S135). The increase direction parameter inc is calculated, for example, by equation (2). The jitter-derived decrease direction parameter dec_jitter is calculated, for example, by equation (3). The transmission rate-derived decrease direction parameter dec_rate is calculated, for example, by equation (4) or equation (5).

[0065] Next, the transmission rate calculation unit 13 calculates a new transmission rate R_new using the increase direction parameter inc, the jitter-derived decrease direction parameter dec_jitter, and the transmission rate-derived decrease direction parameter dec_rate (step S136). The transmission rate calculation unit 13 stores the calculated new transmission rate R_new in the time-series data storage unit 111 (step S137). Furthermore, the transmission rate calculation unit 13 notifies the calculated new transmission rate R_new to the transmission control unit 14 (step S138). After completing the process of step S138, the transmission rate calculation unit 13 ends the transmission rate calculation process.

[0066] [RTT measurement process] Next, the operation of the RTT measurement process will be described with reference to Fig. 15. For example, the RTT measurement process shown in Fig. 15 is periodically called and executed.

[0067] First, the transmission data generating unit 15 generates a packet, which is transmission data (step S140).

[0068] Next, the transmission data output unit 16 transmits the transmission data generated in step S140 to the opposite communication device 80. At this time, the transmission data output unit 16 transmits the transmission data at the new transmission rate R_new (step S141).

[0069] Next, the received data acquisition unit 17 receives received data from the opposite communication device 80 as a response to the transmitted data (step S142).

[0070] Next, the received data analysis unit 18 calculates the RTT (step S143). The RTT is calculated by subtracting the time when the transmission data is transmitted from the time when the reception data is received.

[0071] Next, the received data analyzer 18 stores the RTT and the transmission rate R_new at the end of the time-series data (step S144). After completing the process of step S144, the communication device 10 ends the RTT measurement process.

[0072] As described above, the communication device of this embodiment includes a convergence determination unit, an available bandwidth estimation unit, and a transmission rate calculation unit. The convergence determination unit determines whether the transmission rate has converged to a certain bandwidth using time-series data indicating the time-series transition of the data transmission rate to the opposite communication device and the round-trip delay time between the device and the opposite communication device over a certain period of time. The available bandwidth estimation unit, when it is determined that the transmission rate has converged to a certain bandwidth, estimates the available bandwidth, which is the communication bandwidth available to the opposite communication device, using the time-series data. The transmission rate calculation unit calculates a new transmission rate using a calculation formula having an increase term that increases the transmission rate and a decrease term that decreases the transmission rate. The decrease term has a characteristic that the larger the value obtained by subtracting the available bandwidth from the transmission rate, the larger its value becomes, and the smaller the value obtained by subtracting the available bandwidth from the transmission rate, the smaller its value becomes.

[0073] With the above configuration, the communication device of this embodiment can converge the transmission rate to the available bandwidth even in an environment with a large feedback delay. This is because the decrease term has a characteristic that the value increases as the value obtained by subtracting the available bandwidth from the transmission rate increases, and decreases as the value obtained by subtracting the available bandwidth from the transmission rate decreases. In other words, the decrease term increases as the transmission rate exceeds the estimated available bandwidth, regardless of the value of the round-trip delay time. This allows the communication device of this embodiment to reduce the transmission rate before the round-trip delay time begins to increase. Generally, when the feedback delay is large, it takes time for changes in the network status to be reflected in the value of the round-trip delay time. However, because the communication device of this embodiment can reduce the transmission rate before the round-trip delay time begins to increase, the transmission rate can converge to near the available bandwidth even in an environment with a large feedback delay.

[0074] In a communication device according to an aspect of the present embodiment, the calculation formula further includes a second decrease term. The second decrease term has a characteristic that the value increases as the difference between the round-trip delay time and a minimum round-trip delay time, which is the minimum value of the round-trip delay time, increases, and decreases as the difference between the round-trip delay time and the minimum round-trip delay time decreases. In other words, the value of the second decrease term decreases as congestion does not occur, and increases as congestion occurs. The communication device according to an aspect of the present embodiment can adjust the amount of reduction in the transmission rate depending on the congestion state. This allows the communication device according to an aspect of the present embodiment to more quickly converge the transmission rate to the available bandwidth. Therefore, the communication device according to an aspect of the present embodiment can converge the transmission rate to near the available bandwidth even in an environment with a large feedback delay.

[0075] In a communication device according to an aspect of this embodiment, the available bandwidth estimation unit estimates the available bandwidth as the transmission rate at the time when the round trip time in the time series data exceeds a predetermined threshold minus the minimum round trip time, which is the minimum value of the round trip time. As shown in Fig. 7, the RTT starts to increase at least at a time after t_over+minRTT, which is the time after the minimum RTT has elapsed from t_over. In a communication device according to an aspect of this embodiment, the available bandwidth is estimated as the transmission rate at the time when the RTT value in the time series data exceeds a predetermined threshold minus the minimum RTT, which is the minimum value of the RTT stored in the time series data. This makes it possible to estimate the available bandwidth value more accurately.

[0076] In a communication device according to an aspect of this embodiment, the value of the increase term decreases as the difference between the round-trip time and the minimum round-trip time increases, and the time it takes for the value to decrease decreases as the round-trip time increases. A state in which the RTT value is large corresponds to a state in which the feedback delay is large. As described above, when the feedback delay is large, it takes time for changes in the network status to be reflected in the RTT value. Therefore, in an environment with a large feedback delay, it takes time for the difference between the RTT and the minimum RTT to increase, and the value of the increase term in the transmission rate calculation formula becomes larger than the value of the decrease term, which may result in an excessive increase in the transmission rate. In a communication device according to an aspect of this embodiment, the time it takes for the increase term to decrease as the RTT value increases. Therefore, in an environment with a large feedback delay, the time it takes for the value of the increase term to become smaller than the value of the decrease term is shorter, preventing an excessive increase in the transmission rate. In other words, according to a communication device according to an aspect of this embodiment, the transmission rate can converge to the available bandwidth even in an environment with a large feedback delay.

[0077] In a communication device according to one aspect of the present embodiment, when the transmission rate does not converge to a certain bandwidth, the decrement term takes on a value of 0. As a result, when the transmission rate falls below the available bandwidth, no decrement component due to this decrement term occurs in the calculation formula, and the transmission rate can be increased to the available bandwidth more quickly.

[0078] A communication device according to an aspect of the present embodiment further includes a storage unit that stores time-series data and an operation mode, which is a flag for switching between operations. The operation modes include an available bandwidth estimation mode, which is set when the transmission rate has not converged to a constant bandwidth, and an available bandwidth convergence mode, which is set when the transmission rate has converged to a constant bandwidth. In the available bandwidth estimation mode, the convergence determination unit determines whether the transmission rate has converged to a constant bandwidth based on whether a total transmission rate change, which is the sum of changes in the transmission rate over a certain period of time, is equal to or less than a predetermined threshold. When it is determined that the transmission rate has converged to a constant bandwidth, the convergence determination unit changes the operation mode to the available bandwidth convergence mode. In the available bandwidth convergence mode, the convergence determination unit determines whether the available bandwidth has fluctuated using an RTT value. When it is determined that the available bandwidth has fluctuated, the convergence determination unit changes the operation mode to the available bandwidth estimation mode. As described above, the communication device according to an aspect of the present embodiment can appropriately control the transmission rate even when the available bandwidth fluctuates midway.

[0079] The communication device according to one aspect of the present embodiment further includes an output unit that outputs output information including time-series data. The output information further includes graphs showing time trends in the transmission rate and round-trip time. The output information is output to, for example, a terminal of an administrator of the communication device. This allows the administrator of the communication device to visually understand the time trends in the transmission rate and RTT of the communication device according to the present embodiment.

[0080] [Second embodiment] In this embodiment, a communication device 20 will be described, which has a simplified configuration of the communication device in the first embodiment. In the following description, the same parts as in the first embodiment will be omitted as appropriate.

[0081] (composition) The configuration of a communication device according to this embodiment will be described with reference to the drawings. Fig. 16 is a block diagram showing an example of the configuration of a communication device according to the present disclosure. The communication device 20 includes a convergence determination unit 21, an available bandwidth estimation unit 22, and a transmission rate calculation unit 23.

[0082] The convergence determination unit 21 determines whether the transmission rate has converged to a certain bandwidth using time-series data indicating the transmission rate of data to the opposite communication device and the time-series transition of the round-trip delay time between the device and the opposite communication device over a certain period of time. The available bandwidth estimation unit 22, when it is determined that the transmission rate has converged to a certain bandwidth, uses the time-series data to estimate the available bandwidth, which is the communication bandwidth available to the opposite communication device. The transmission rate calculation unit 23 calculates a new transmission rate using a calculation formula that has an increase term that increases the transmission rate and a decrease term that decreases the transmission rate. The decrease term has a characteristic that the larger the value obtained by subtracting the available bandwidth from the transmission rate, the larger its value becomes, and the smaller the value obtained by subtracting the available bandwidth from the transmission rate, the smaller its value becomes.

[0083] (operation) Next, an example of the operation of the communication device in this embodiment will be described with reference to Fig. 17. Fig. 17 is a diagram showing an example of the operation of the communication device in the present disclosure.

[0084] First, the convergence determination unit 21 determines whether the transmission rate has converged to a certain bandwidth using time series data showing the time series trends of the data transmission rate to the opposite communication device and the round-trip delay time between the device itself and the opposite communication device over a certain period of time (step S21).

[0085] Next, when it is determined that the transmission rate has converged to a certain band, the available band estimation unit 22 uses the time-series data to estimate an available band, which is a communication band available to the opposite communication device (step S22).

[0086] Next, the transmission rate calculation unit 23 calculates a new transmission rate using a calculation formula having an increase term that increases the transmission rate and a decrease term that decreases the transmission rate (step S23). The decrease term has a characteristic that the larger the value obtained by subtracting the available bandwidth from the transmission rate, the larger the value, and the smaller the value obtained by subtracting the available bandwidth from the transmission rate, the smaller the value.

[0087] The communication device of this embodiment is configured as described above. The communication device of this embodiment estimates the available bandwidth and uses a calculation formula for calculating a new transmission rate that has a decreasing term whose value increases as the value obtained by subtracting the available bandwidth from the transmission rate increases, and whose value decreases as the value obtained by subtracting the available bandwidth from the transmission rate decreases. The communication device of this embodiment can reduce the transmission rate before the round-trip delay time begins to increase, so that the transmission rate can converge to near the available bandwidth even in an environment with a large feedback delay.

[0088] (Hardware configuration) The functions of each of the components in each of the embodiments of the present disclosure described above can be realized not only as hardware but also as a computer device or firmware under program control.

[0089] 18 is a diagram showing an example of a hardware configuration in which a communication device according to the present disclosure is realized by a computer device 90 including a processor. The communication device according to each embodiment is realized by the computer device 90. As shown in FIG. 17, the computer device 90 includes a processor 91, a memory 92, a storage device 93 such as a hard disk for storing programs, an input / output interface 94 for connecting input devices and output devices, and a communication interface 95 for connecting to a network.

[0090] The processor 91 loads a program (instructions) stored in a storage device 93 or the like into the memory 92. For example, the program is a software program for executing the control and processing in the present disclosure. The processor 91 executes the program loaded into the memory 92. The processor 91 executes the program to execute the control and processing in the present disclosure.

[0091] The storage device 93 may be, for example, an optical disk, a flexible disk, a magneto-optical disk, an external hard disk, or a semiconductor memory. Some storage media in the storage device are non-volatile storage devices, and the programs are recorded therein. The programs may also be downloaded from an external computer (not shown) connected to a communication network.

[0092] The input device connected to the input / output interface 94 is realized by, for example, a mouse or a keyboard, and is used for input operations. Similarly, the output device connected to the input / output interface 94 is realized by, for example, a display, and is used for displaying and checking output results.

[0093] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0094] Some or all of the above embodiments can also be described as follows:

[0095] (Appendix 1) a convergence determination means for determining whether the transmission rate has converged to a certain bandwidth using time series data indicating a time series transition of a data transmission rate to an opposite communication device and a round-trip delay time between the device itself and the opposite communication device over a certain period of time; an available bandwidth estimation means for estimating an available bandwidth, which is a communication bandwidth available to the opposite communication device, using the time series data when it is determined that the transmission rate has converged to a certain bandwidth; a transmission rate calculation means for calculating a new transmission rate using a calculation formula having an increasing term for increasing the transmission rate and a decreasing term for decreasing the transmission rate, The decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases. (Appendix 2) The formula further includes a second decreasing term, The communication device described in Appendix 1, characterized in that the second decreasing term has a larger value as the difference between the round trip delay time and a minimum round trip delay time, which is the smallest value of the round trip delay time, becomes larger, and has a smaller value as the difference between the round trip delay time and the minimum round trip delay time becomes smaller. (Appendix 3) The communication device according to claim 1 or 2, wherein the available bandwidth estimation means estimates the available bandwidth to be the transmission rate at a time obtained by subtracting a minimum round-trip delay time, which is the minimum value of the round-trip delay time, from the time at which the round-trip delay time in the time series data exceeds a predetermined threshold. (Appendix 4) The communication device described in Appendix 1, characterized in that the value of the increase term becomes smaller as the difference between the round-trip delay time and a minimum round-trip delay time, which is the smallest value of the round-trip delay time, becomes larger, and the time it takes for the value to decrease becomes shorter as the value of the round-trip delay time becomes larger. (Appendix 5) 2. The communication device according to claim 1, wherein the decreasing term has a value of 0 when it is determined that the transmission rate has converged to a constant bandwidth. (Appendix 6) further comprising a storage means for storing the time series data and an operation mode which is a flag for switching the operation of the convergence determination means; the operation modes include an available bandwidth estimation mode, which is a mode that is set when the transmission rate has not converged to a constant bandwidth, and an available bandwidth convergence mode, which is a mode that is set when the transmission rate has converged to a constant bandwidth; The convergence determination means In the available bandwidth estimation mode, it is determined whether the transmission rate has converged to a certain bandwidth depending on whether a total value of changes in the transmission rate over a certain period of time is equal to or less than a predetermined threshold, and when it is determined that the transmission rate has converged to the certain bandwidth, the operation mode is changed to the available bandwidth convergence mode; The communication device described in Appendix 1, wherein in the available bandwidth convergence mode, the value of the round-trip delay time is used to determine whether the available bandwidth has changed, and if it is determined that the available bandwidth has changed, the operation mode is changed to the available bandwidth estimation mode. (Appendix 7) 2. The communication device according to claim 1, further comprising an output unit that outputs output information including the time-series data. (Appendix 8) 8. The communication device according to claim 7, wherein the output information further includes graphs showing changes over time in the transmission rate and the round-trip delay time. (Appendix 9) A computer installed in a communication device determining whether the transmission rate to the opposite communication device has converged to a certain bandwidth using time series data indicating a time series transition of a data transmission rate to the opposite communication device and a round trip delay time between the own device and the opposite communication device over a certain period of time; When it is determined that the transmission rate has converged to a certain bandwidth, an available bandwidth that is a communication bandwidth available to the opposite communication device is estimated using the time series data; calculating the new transmission rate using a calculation formula having an increasing term for increasing the transmission rate and a decreasing term for decreasing the transmission rate; The communication method is characterized in that the decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and has a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases. (Appendix 10) The computer installed in the communication device a process of determining whether or not the transmission rate to the opposite communication device has converged to a certain bandwidth using time series data indicating a time series transition of the data transmission rate to the opposite communication device and a round trip delay time between the device itself and the opposite communication device over a certain period of time; a process of estimating an available bandwidth, which is a communication bandwidth available to the opposite communication device, using the time-series data when it is determined that the transmission rate has converged to a certain bandwidth; calculating a new transmission rate using a calculation formula having an increasing term for increasing the transmission rate and a decreasing term for decreasing the transmission rate; The computer program is characterized in that the decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and has a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases.

[0096] In addition, in the above appendices, some or all of the configurations described in appendices 2 to 8 that are dependent on appendices 1 may also be dependent on appendices 9 and 10 in the same dependent relationship as appendices 2 to 8. Furthermore, not limited to appendices 1, 9, and 10, some or all of the configurations described as appendices may be made dependent on various hardware or systems in the same manner, within the scope of each of the above-mentioned embodiments. [Explanation of symbols]

[0097] 10, 20 Communication equipment 11 Storage section 111 Time series data storage unit 112 Parameter storage unit 12 Time series data observation section 121, 22 Available bandwidth estimation unit 122, 21 Convergence judgment section 13, 23 Transmission rate calculation section 14 Transmission control section 15 Transmission data generation unit 16 Transmission data output section 17 Received data acquisition unit 18 Received data analysis unit 19 Output section 70 Management device 80 Opposite communication device 90 Computer Equipment 91 processors 92 memory 93 Storage device 94 Input / Output Interface 95 Communication Interface

Claims

1. a convergence determination means for determining whether the transmission rate has converged to a certain bandwidth using time series data indicating a time series transition of a data transmission rate to an opposite communication device and a round trip delay time between the device itself and the opposite communication device over a certain period of time; an available bandwidth estimation means for estimating an available bandwidth, which is a communication bandwidth available to the opposite communication device, using the time series data when it is determined that the transmission rate has converged to a certain bandwidth; a transmission rate calculation means for calculating a new transmission rate using a calculation formula having an increasing term for increasing the transmission rate and a decreasing term for decreasing the transmission rate, the decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases, The available bandwidth estimation means estimates the available bandwidth as the transmission rate at the time obtained by subtracting a minimum round-trip delay time, which is the minimum value of the round-trip delay time, from the time at which the round-trip delay time in the time series data exceeds a predetermined threshold.

2. The formula further includes a second decreasing term, 2. The communication device according to claim 1, wherein the second decreasing term has a larger value as the difference between the round trip delay time and a minimum round trip delay time that is the smallest value of the round trip delay time increases, and has a smaller value as the difference between the round trip delay time and the minimum round trip delay time decreases.

3. The communication device according to claim 1, characterized in that the value of the increase term decreases as the difference between the round-trip delay time and a minimum round-trip delay time that is the smallest value of the round-trip delay time increases, and the time it takes for the value to decrease decreases as the value of the round-trip delay time increases.

4. The communication device according to claim 1 , wherein the decreasing term has a value of 0 when it is determined that the transmission rate has converged to a constant bandwidth.

5. further comprising a storage means for storing the time series data and an operation mode which is a flag for switching the operation of the convergence determination means; the operation modes include an available bandwidth estimation mode, which is a mode that is set when the transmission rate has not converged to a constant bandwidth, and an available bandwidth convergence mode, which is a mode that is set when the transmission rate has converged to a constant bandwidth; The convergence determination means In the available bandwidth estimation mode, it is determined whether the transmission rate has converged to a certain bandwidth depending on whether a total value of changes in the transmission rate over a certain period of time is equal to or less than a predetermined threshold, and when it is determined that the transmission rate has converged to the certain bandwidth, the operation mode is changed to the available bandwidth convergence mode; 2. The communication device according to claim 1, wherein in the available bandwidth convergence mode, the value of the round-trip delay time is used to determine whether the available bandwidth has changed, and when it is determined that the available bandwidth has changed, the operation mode is changed to the available bandwidth estimation mode.

6. The communication device according to claim 1 , further comprising an output unit that outputs output information including the time-series data.

7. The communication device according to claim 6 , wherein the output information further includes graphs showing the transmission rate and the round trip delay time over time.

8. A computer installed in a communication device determining whether the transmission rate to the opposite communication device has converged to a certain bandwidth using time series data indicating a time series transition of a data transmission rate to the opposite communication device and a round trip delay time between the own device and the opposite communication device over a certain period of time; When it is determined that the transmission rate has converged to a certain bandwidth, an available bandwidth that is a communication bandwidth available to the opposite communication device is estimated using the time series data; calculating the new transmission rate using a calculation formula having an increasing term for increasing the transmission rate and a decreasing term for decreasing the transmission rate; the decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases, In estimating the available bandwidth, the communication method estimates the transmission rate at the time when the round-trip delay time in the time series data exceeds a predetermined threshold minus the minimum round-trip delay time, which is the smallest value of the round-trip delay time, as the available bandwidth.

9. The computer installed in the communication device a process of determining whether or not the transmission rate to the opposite communication device has converged to a certain bandwidth using time series data indicating a time series transition of the data transmission rate to the opposite communication device and a round trip delay time between the device itself and the opposite communication device over a certain period of time; a process of estimating an available bandwidth, which is a communication bandwidth available to the opposite communication device, using the time-series data when it is determined that the transmission rate has converged to a certain bandwidth; calculating a new transmission rate using a calculation formula having an increasing term for increasing the transmission rate and a decreasing term for decreasing the transmission rate; the decrease term has a larger value as the value obtained by subtracting the available bandwidth from the transmission rate increases, and a smaller value as the value obtained by subtracting the available bandwidth from the transmission rate decreases, In the process of estimating the available bandwidth, the computer program estimates the available bandwidth as the transmission rate at the time when the round-trip delay time in the time series data exceeds a predetermined threshold minus the minimum round-trip delay time, which is the smallest value of the round-trip delay time.

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