Communication device, estimation method for line delay time, and estimation program for line delay time

Abstract

To properly estimate one-way line delay time.SOLUTION: A communication device 2 transmits a communication packet to an opposing device. The communication device 2 includes a transmission buffer 13 that accumulates the communication packets, a buffer data amount monitor 15 that monitors the data amount of the communication packets accumulated in the transmission buffer, an input data amount monitor 10 that monitors the data amount of the communication packets input to the transmission buffer in a predetermined period, and a delay time estimation unit 12 for estimating a retention time in the transmission buffer of the communication packets input to the transmission buffer as an upstream buffer delay time which goes from an own device to the opposing device based on the data amount of the communication packets accumulated in the transmission buffer at a first time, the data amount of the communication packets input to the transmission buffer in a period from the first time to a second time, and the data amount of the communication packets accumulated in the transmission buffer at the second time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a communication device, a line delay time estimation method, and a line delay time estimation program. [Background technology]

[0002] In packet communication, a communication device transmits a communication packet to a counterpart device, and when the counterpart device receives the communication packet from the communication device, it transmits a delivery confirmation packet for the communication packet to the communication device. For example, Patent Document 1 discloses a technology in which a communication device calculates a round-trip time (hereinafter referred to as RTT (Round-Trip Time)) based on a transmission queue length, a transmission delay, and a receiving time of the delivery confirmation packet, and calculates the queue length of the entire communication network. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 8,923,270 Summary of the Invention [Problem to be solved by the invention]

[0004] In the method disclosed in Patent Document 1, the queue length of the entire communication network is calculated, but the upstream buffer delay time from the communication device to the opposite device and the downstream buffer delay time from the opposite device to the communication device cannot be estimated separately. In addition, the timing at which the communication device calculates the RTT is after receiving a delivery confirmation packet from the opposite device, and the RTT can be calculated only after receiving a delivery confirmation packet from the opposite device. Therefore, when the communication network is a cellular line, it takes several tens to several hundreds of milliseconds from the transmission of a communication packet until the RTT is calculated. As a result, for example, assuming a situation in which the communication device is mounted on a vehicle and moves at high speed, the time required to calculate the RTT becomes approximately the same as the fluctuation period of the line state, which causes a problem of unstable feedback control.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a communication device, a line delay time estimation method, and a line delay time estimation program that can appropriately estimate one-way line delay time. [Means for solving the problem]

[0006] According to the invention described in claim 1, a communication device (2) transmits a communication packet to an opposing device. A transmission buffer (13) accumulates the communication packet. A buffer data amount monitor (15) monitors the data amount of the communication packet accumulated in the transmission buffer. An input data amount monitor (10) monitors the data amount of the communication packet input to the transmission buffer in a predetermined period. A delay time estimation unit (12) estimates a retention time for which the communication packet input to the transmission buffer is retained in the transmission buffer as an upstream buffer delay time from the communication device to the opposing device, based on the data amount of the communication packet accumulated in the transmission buffer at a first time, the data amount of the communication packet input to the transmission buffer in a period from the first time to a second time, and the data amount of the communication packet accumulated in the transmission buffer at a second time.

[0007] Based on the amount of data of communication packets stored in the transmission buffer at the first time, the amount of data of communication packets input to the transmission buffer during the period from the first time to the second time, and the amount of data of communication packets stored in the transmission buffer at the second time, the residence time of the communication packets input to the transmission buffer is estimated as the upstream buffer delay time. It is possible to appropriately estimate the one-way line delay time from the communication device to the opposing device. [Brief description of the drawings]

[0008] [Figure 1] A functional block diagram showing the overall configuration of one embodiment. [Diagram 2] FIG. 1 shows upstream buffer delay time and downstream buffer delay time. [Diagram 3] A diagram showing the transition of the amount of data stored in the transmission buffer [Figure 4] Diagram explaining the upstream communication path [Diagram 5] FIG. 1 is a diagram for explaining how an upstream wireless line affects the rate of the entire communication line. [Figure 6] Diagram explaining the upstream communication path [Figure 7] FIG. 1 is a diagram for explaining a state in which an upstream wireless line does not affect the rate limit of the entire communication line. [Figure 8] Flowchart showing the process of estimating upstream buffer delay time [Figure 9] Flowchart showing the process of estimating downstream buffer delay time [Figure 10] Flowchart showing influence determination processing of an uplink wireless line DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment in which the present invention is applied to a communication node mounted on a vehicle, for example, will be described with reference to the drawings. As shown in FIG. 1, a communication system 1 is configured so that a communication node 2 (corresponding to a communication device) and a corresponding node 3 (corresponding to a corresponding device) can communicate data via a base station 4. The communication node 2 and the base station 4 communicate data via a wireless line. The corresponding node 3 and the base station 4 communicate data via a wired line between the communication node 2 and the corresponding node 3 via the base station 4, and the data communication is in accordance with the TCP / IP (Transmission Control Protocol / Internet Protocol) communication protocol. The communication node 2 transmits a communication packet to the base station 4 via a wireless line. The base station 4 transmits the communication packet received from the communication node 2 to the corresponding node 3 via the wired line. The corresponding node 3 transmits a delivery confirmation packet for the communication packet to the base station 4 via the wired line. The base station 4 transmits the delivery confirmation packet received from the corresponding node 3 to the communication node 2 via a wireless line.

[0010] As shown in FIG. 2, the transmission of a communication packet from the communication node 2 to the correspondent node 3 via the base station 4 is an upstream data transmission. The speed at which the communication packet is transmitted from the communication node 2 to the wireless line depends on the wireless environment, and the time the communication packet is held in the communication node 2 occurs as an upstream buffer delay time (corresponding to the upstream line delay time). The transmission of a delivery confirmation packet from the correspondent node 3 to the communication node 2 via the base station 4 is a downstream data transmission. The speed at which the delivery confirmation packet is transmitted from the base station 4 to the wireless line depends on the wireless environment, and the time the delivery confirmation packet is held in the base station 4 occurs as a downstream buffer delay time (corresponding to the downstream line delay time). These upstream buffer delay time and downstream buffer delay time vary depending on the wireless environment, and are relatively short when the wireless environment is relatively good, and relatively long when the wireless environment is relatively poor.

[0011] The communication node 2 transmits driving control data relating to driving control such as vehicle speed, acceleration / deceleration, sharp turns, driving route, fuel consumption, etc. to the opposing node 3. The opposing node 3 is capable of data communication with multiple communication nodes 2 via wireless lines, and is, for example, a server having a function of statistically processing driving control data for an unspecified number of vehicles. When the opposing node 3 receives driving control data from each communication node 2 mounted on an unspecified number of vehicles, it statistically processes the received driving control data. Note that the data transmitted and received between the communication node 2 and the opposing node 3 may be data other than the above-mentioned driving control data, or may be data used for other purposes.

[0012] The communication node 2 includes a control unit 5 that controls the operation of the entire node. The control unit 5 is mainly configured with a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and I / O (Input / Output), etc. The functions provided by the control unit 5 can be provided by software recorded in a physical memory device and a computer that executes the software, software only, hardware only, or a combination of these. For example, when the control unit 5 is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a large number of logic circuits or an analog circuit. When the control unit 5 executes a program stored in a non-transitive physical recording medium, a process corresponding to the program is executed, and a method corresponding to the program is executed.

[0013] The control unit 5 includes, for each function, a packet generation unit 6, a vehicle inside communication interface unit 7, a vehicle outside communication interface unit 8, a transfer unit 9, an input data amount monitoring unit 10, a storage unit 11, and a delay time estimation unit 12. The vehicle outside communication interface unit 7 includes a transmission buffer 13, a transmission / reception unit 14, and a buffer data amount monitoring unit 15. Each of these units 6 to 15 executes a line delay time estimation program and performs a line delay time estimation method.

[0014] The packet generation unit 6 generates a communication packet in accordance with the execution of the application by the control unit 5, and outputs the generated communication packet to the transfer unit 9. When the vehicle inside communication interface unit 7 receives a communication packet from an external node 16 (corresponding to an external device), it outputs the received communication packet to the transfer unit 9. When the transfer unit 9 inputs a communication packet from the packet generation unit 6 or the vehicle inside communication interface unit 7, it transfers the input communication packet to the vehicle outside communication interface unit 8.

[0015] In the vehicle exterior communication interface unit 8, when a communication packet is transferred from the transfer unit 9, the transmission buffer 13 stores the transferred communication packet. The transmission / reception unit 14 transmits the communication packet stored in the transmission buffer 13 to the opposing node 3 via the base station 4, and receives a delivery confirmation packet for the communication packet from the opposing node 3 via the base station 4. The buffer data amount monitoring unit 15 monitors the data amount of the communication packets stored in the transmission buffer 13, and outputs the accumulated data amount indicating the data amount of the communication packets stored in the transmission buffer 13 to the delay time estimation unit 12.

[0016] The input data amount monitoring unit 10 monitors the amount of data of communication packets input from the transfer unit 9 to the transmission buffer 13, and outputs the input data amount indicating the amount of data of communication packets input from the transfer unit 9 to the transmission buffer 13 to the memory unit 11 and the delay time estimation unit 12.

[0017] The storage unit 11, upon receiving the input data amount from the input data amount monitoring unit 10, manages and stores the input data amount in chronological order. The delay time estimation unit 12, upon receiving the accumulated data amount from the buffer data amount monitoring unit 15 and the input data amount from the input data amount monitoring unit 10, estimates the retention time during which a communication packet input to the transmission buffer 13 is retained in the transmission buffer 13 as an upstream buffer delay time based on the received accumulated data amount and input data amount.

[0018] As shown in FIG. 3, assuming that the data amount of communication packets stored in the transmission buffer 13 at time t1 is data amount b(t1), the data amount of communication packets input to the transmission buffer 13 during the period from time t1 to time t2 is data amount P, and the data amount of communication packets stored in the transmission buffer 13 at time t2 is data amount b(t2), the delay time estimation unit 12 estimates the retention time for which the communication packets input to the transmission buffer 13 are retained in the transmission buffer as the upstream buffer delay time using the following formula. Upstream buffer delay time = (t2-t1) × b(t1) / {b(t1)-b(t2)-P}

[0019] Where: Wireless link transmission rate = {b(t1)-b(t2)-P} / (t2-t1) If the transmission buffer 13 does not become empty between time t1 and time t2, Wireless line transmission rate = line bandwidth It is.

[0020] In addition to estimating the uplink buffer delay time, the delay time estimation unit 12 also estimates the downlink buffer delay time. That is, the delay time estimation unit 12 obtains the RTT, which is the sum of the uplink delay and the downlink delay. Here, if the delay time that is not affected by the fluctuation of the wireless environment in the communication line is the default delay time, RTT = upstream buffer delay + downstream buffer delay + default delay Since the above equation holds, the delay time estimation unit 12 estimates the downstream buffer delay time by the following equation. Downstream buffer delay = RTT - (Upstream buffer delay + Default delay)

[0021] The default delay time is Predefined delay time = time required for data processing in the uplink direction at the base station 4 + data communication time from the base station 4 to the correspondent node 3 + time required for data processing in the correspondent node 3 + data communication time from the correspondent node 3 to the base station 4, time required for data processing in the downlink direction at the communication node 2 This time can be calculated by measuring in advance based on the processing capabilities of the base station 4, the correspondent node 3, and the communication node 2, etc.

[0022] Furthermore, the delay time estimation unit 12 compares the fluctuation of the uplink buffer delay time with the fluctuation of the RTT to determine whether or not the uplink wireless line affects the rate limiting of the entire communication line. The delay time estimation unit 12 determines that the uplink wireless line affects the rate limiting of the entire communication line during a period in which the fluctuation of the RTT follows the fluctuation of the uplink buffer delay time. That is, the delay time estimation unit 12 determines that the uplink wireless line is a bottleneck section of the entire communication line. By determining that the uplink wireless line is a bottleneck section of the entire communication line, the delay time estimation unit 12 can determine that suppressing the delay of the transmission buffer 13 is effective in improving the RTT. In this case, the delay time estimation unit 12 can determine that the RTT can be adjusted by adjusting the data amount of the communication packets input to the transmission buffer 13 and adjusting the input rate to the transmission buffer 13. The delay time estimation unit 12 can reduce the uplink buffer delay time and reduce the RTT by reducing the input rate to the transmission buffer 13.

[0023] On the other hand, in a period in which the RTT fluctuation does not follow the upstream buffer delay time fluctuation, the delay time estimation unit 12 determines that the upstream wireless line does not affect the rate limit of the entire communication line. That is, the delay time estimation unit 12 determines that the upstream wireless line is not a bottleneck section of the entire communication line. By determining that the upstream wireless line is not a bottleneck section of the entire communication line, the delay time estimation unit 12 can determine that suppressing delay in the transmission buffer 13 is not effective in improving the RTT. In this case, the delay time estimation unit 12 can determine that the RTT cannot be adjusted even if the data amount of the communication packets input to the transmission buffer 13 is adjusted, and it is possible to prevent a situation in which the RTT is adjusted meaninglessly.

[0024] As shown in FIGS. 4 and 5, if the bandwidth of the upstream path excluding the upstream wireless link among the upstream communication paths is larger than the bandwidth of the upstream wireless link (B2 > B1), since the variation of the RTT follows the variation of the upstream buffer delay time, the delay time estimation unit 12 identifies that the upstream wireless link is the bottleneck section of the entire communication link during the period when the variation of the RTT follows the variation of the upstream buffer delay time. In the section where the bandwidth of the upstream wireless link increases (t11 to t12), the upstream buffer delay time and the RTT slope downward, and in the section where the bandwidth of the upstream wireless link decreases (t12 to t14), the upstream buffer delay time and the RTT slope upward.

[0025] On the other hand, as shown in FIGS. 6 and 7, if the bandwidth of the upstream path excluding the upstream wireless link among the upstream communication paths is smaller than the bandwidth of the upstream wireless link (B3 < B1), since the variation of the RTT does not follow the variation of the upstream buffer delay time, the delay time estimation unit 12 identifies that the upstream path excluding the upstream wireless link among the upstream communication paths is the bottleneck section of the entire communication link during the period when the variation of the RTT does not follow the variation of the upstream buffer delay time. Also in this case, in the section where the bandwidth of the upstream wireless link increases (t21 to t22), the upstream buffer delay time and the RTT slope downward, and in the section where the bandwidth of the upstream wireless link decreases (t22 to t25), the upstream buffer delay time and the RTT slope upward. Note that if the magnitude relationship between the bandwidth of the upstream path excluding the upstream wireless link and the bandwidth of the upstream wireless link is reversed and the bandwidth of the upstream path excluding the upstream wireless link becomes larger than the bandwidth of the upstream wireless link (t24), thereafter, the variation of the RTT follows the variation of the upstream buffer delay time.

[0026] Next, the operation of the above-described configuration will be described with reference to FIGS. 8 to 10. Here, the estimation process of the upstream buffer delay time for estimating the upstream buffer delay time, the estimation process of the downstream buffer delay time for estimating the downstream buffer delay time, and the influence determination process of the upstream wireless link for determining the influence of the upstream wireless link will be described.

[0027] (1) Estimation process of upstream buffer delay time (see FIG. 8), When the control unit 4 starts the estimation process of the upstream buffer delay time, the control unit 4 sets a predetermined time as time t1, and acquires the data amount of communication packets accumulated in the transmission buffer 13 at time t1 (S1, corresponding to the first accumulated data amount acquisition procedure). The control unit 4 sets a time when a predetermined time has elapsed from time t1 as time t2, and acquires the data amount of communication packets input to the transmission buffer 13 during the period from time t1 to time t2 (S2, corresponding to the input data amount acquisition procedure). The control unit 4 acquires the data amount of communication packets accumulated in the transmission buffer 13 at time t2 (S3, corresponding to the second accumulated data amount acquisition procedure).

[0028] The control unit 4 estimates the upstream buffer delay time using the above-mentioned formula based on the amount of data of communication packets stored in the transmission buffer 13 at the acquired time t1, the amount of data of communication packets input to the transmission buffer 13 during the period from time t1 to time t2, and the amount of data of communication packets stored in the transmission buffer 13 at time t2 (S4, corresponding to the upstream buffer delay time estimation procedure), and terminates the upstream buffer delay time estimation process.

[0029] (2) Estimation of downstream buffer delay time (see Figure 9) When the control unit 4 starts the process of estimating the downlink buffer delay time, it acquires the RTT, which is the sum of the uplink delay and the downlink delay (S11, which corresponds to the RTT acquisition step). The control unit 4 acquires a preset delay time that is not affected by fluctuations in the wireless environment that has been measured in advance (S12, which corresponds to the preset delay time acquisition step). The control unit 4 estimates the uplink buffer delay time in the downlink direction using the above-mentioned arithmetic expression based on the uplink buffer delay time acquired by the above-mentioned process of estimating the uplink buffer delay time, the acquired RTT, and the preset delay time (S13, which corresponds to the downlink buffer delay time estimation step), and ends the process of estimating the downlink buffer delay time.

[0030] (3) Process for determining the influence of the upstream wireless line (see Figure 10) When the control unit 4 starts the influence judgment process of the uplink wireless line, it compares the fluctuation of the uplink buffer delay time with the fluctuation of the RTT (S21), and judges whether the fluctuation of the RTT follows the fluctuation of the uplink buffer delay time (S22). When the control unit 4 judges that the fluctuation of the RTT follows the fluctuation of the uplink buffer delay time (S22: YES), it determines that the uplink wireless line affects the rate of the entire communication line, that is, the uplink wireless line is the bottleneck section (S23), and ends the influence judgment process of the uplink wireless line. On the other hand, when the control unit 4 judges that the fluctuation of the RTT does not follow the fluctuation of the uplink buffer delay time (S22: NO), it determines that the uplink wireless line does not affect the rate of the entire communication line, that is, the uplink wireless line is not the bottleneck section (S24), and ends the influence judgment process of the uplink wireless line.

[0031] As described above, according to this embodiment, the following advantageous effects can be obtained. In the communication node 2, the residence time of the communication packets input to the transmission buffer 13 is estimated as the upstream buffer delay time based on the data amount of the communication packets stored in the transmission buffer 13 at time t1, the data amount of the communication packets input to the transmission buffer 13 during the period from time t1 to time t2, and the data amount of the communication packets stored in the transmission buffer 13 at time t2. The line delay time in the upstream direction from the communication node 2 to the opposing node 3 can be appropriately estimated.

[0032] The RTT, which is the sum of the uplink delay and the downlink delay, is obtained, a default delay time that is not affected by fluctuations in the wireless environment is obtained, and the downlink buffer delay time is estimated by subtracting the sum of the uplink buffer delay time and the default delay time from the obtained RTT. This makes it possible to appropriately estimate the downlink delay time from the remote node 3 to the communication node 2.

[0033] In the period when the RTT fluctuation follows the upstream buffer delay time fluctuation, the upstream wireless line affects the rate of the entire communication line, and the upstream wireless line is identified as the bottleneck section. It can be identified that suppressing the delay of the transmission buffer 13 is effective in improving the RTT, and the RTT can be adjusted by adjusting the input rate to the transmission buffer 13.

[0034] In a period in which the RTT fluctuation does not follow the upstream buffer delay time fluctuation, the upstream wireless line does not affect the overall communication line rate, and the upstream wireless line is determined to be not a bottleneck section. It is possible to determine that suppressing delay in the transmission buffer 13 is not effective in improving the RTT, and it is possible to avoid a situation in which the input rate to the transmission buffer 13 is adjusted unnecessarily.

[0035] In addition to the claims, the present disclosure also includes the following inventions. [1] A communication device (2) that transmits a communication packet to an opposite device, a transmission buffer (13) for storing the communication packets; a buffer data amount monitor (15) for monitoring the amount of data of the communication packets stored in the transmission buffer; an input data amount monitor (10) for monitoring the amount of data of the communication packets input to the transmission buffer in a predetermined period of time; and a delay time estimation unit (12) that estimates a residence time for which the communication packets input to the transmission buffer remain in the transmission buffer as an upstream buffer delay time from the communication device to the opposing device, based on the amount of data of the communication packets stored in the transmission buffer at a first time, the amount of data of the communication packets input to the transmission buffer during a period from the first time to a second time, and the amount of data of the communication packets stored in the transmission buffer at a second time.

[0036] [2] The communication device according to [1], wherein the delay time estimation unit estimates a downstream buffer delay time from the opposite device to the own device based on the upstream buffer delay time.

[0037] [3] The delay time estimation unit obtains a round trip time which is the sum of an uplink delay and a downlink delay, and estimates the downlink buffer delay time by subtracting the sum of the uplink buffer delay time and a default delay time from the obtained round trip time.

[0038] [4] The delay time estimation unit obtains a round trip time which is the sum of an uplink delay and a downlink delay, compares the fluctuation of the uplink buffer delay time with the fluctuation of the round trip time, and determines whether or not the uplink wireless line is affecting the rate limit of the entire communication line.

[0039] [5] The communication device described in [4], wherein the delay time estimation unit determines that the upstream wireless line is affecting the rate of the entire communication line during a period in which the fluctuations in the round trip time follow the fluctuations in the upstream buffer delay time.

[0040] [6] The communication device described in [4], wherein the delay time estimation unit determines that the upstream wireless line does not affect the rate limit of the entire communication line during a period in which fluctuations in the round trip time do not follow fluctuations in the upstream buffer delay time.

[0041] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0042] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0043] In the drawing, 1 is a communication system, 2 is a communication node (communication device), 3 is a counterpart node (counterpart device), 4 is a control unit, 10 is an input data amount monitoring unit, 12 is a delay time estimation unit, 13 is a transmission buffer, and 15 is a buffer data amount monitoring unit.

Claims

1. A communication device (2) that transmits a communication packet to an opposing device, a transmission buffer (13) for storing the communication packets; a buffer data amount monitor (15) for monitoring the data amount of the communication packets stored in the transmission buffer; an input data amount monitoring unit (10) for monitoring the data amount of the communication packets input to the transmission buffer in a predetermined period of time; a delay time estimation unit (12) that estimates a residence time for which the communication packets input to the transmission buffer remain in the transmission buffer as an upstream buffer delay time from the communication device to the opposing device, based on the amount of data of the communication packets stored in the transmission buffer at a first time, the amount of data of the communication packets input to the transmission buffer during a period from the first time to a second time, and the amount of data of the communication packets stored in the transmission buffer at a second time.

2. The communication device according to claim 1 , wherein the delay time estimation unit estimates a downstream buffer delay time from the opposite device to the communication device itself based on the upstream buffer delay time.

3. The communication device described in claim 2, wherein the delay time estimation unit acquires a round trip time, which is the sum of an uplink delay and a downlink delay, and a preset delay time, and estimates the downlink buffer delay time by subtracting the sum of the uplink buffer delay time and the preset delay time from the acquired round trip time.

4. The communication device described in claim 1, wherein the delay time estimation unit acquires a round trip time which is the sum of an uplink delay and a downlink delay, compares the fluctuation of the uplink buffer delay time with the fluctuation of the round trip time, and determines whether the uplink wireless line is affecting the rate limit of the entire communication line.

5. The communication device according to claim 4, wherein the delay time estimation unit determines that the upstream wireless line is affecting the rate limit of the entire communication line during a period in which the fluctuation of the round trip time follows the fluctuation of the upstream buffer delay time.

6. The communication device according to claim 4, wherein the delay time estimation unit determines that the upstream wireless line does not affect the rate limit of the entire communication line during a period in which the fluctuations in the round trip time do not follow the fluctuations in the upstream buffer delay time.

7. In a communication device (2) that transmits a communication packet to an opposing device, a first accumulated data amount acquisition step of acquiring the data amount of the communication packets accumulated in the transmission buffer at a first time; an input data amount acquisition step of acquiring the data amount of the communication packets input to the transmission buffer during a period from the first time to the second time; a second accumulated data amount acquisition step of acquiring the data amount of the communication packets accumulated in the transmission buffer at a second time; an upstream buffer delay time procedure for estimating the time that the communication packet input to the transmission buffer remains in the transmission buffer based on the amount of data acquired by the first accumulated data amount acquisition procedure, the amount of data acquired by the input data amount acquisition procedure, and the amount of data acquired by the second accumulated data amount acquisition procedure, as the upstream buffer delay time from the own device to the opposite device.

8. A round trip time acquisition procedure for acquiring a round trip time, which is the sum of an uplink delay and a downlink delay; A procedure for acquiring a predetermined delay time that is not affected by fluctuations in the wireless environment in a communication line; 8. The line delay time estimation method according to claim 7, further comprising: a downstream buffer delay time procedure for estimating a downstream buffer delay time from the opposite device to the own device based on the upstream buffer delay time, the round trip time acquired by the round trip time acquisition procedure, and the default delay time acquired by the default delay time acquisition procedure.

9. A control unit (4) of a communication device (2) that transmits a communication packet to an opposing device, a first accumulated data amount acquisition step of acquiring the data amount of the communication packets accumulated in the transmission buffer at a first time; an input data amount acquisition step of acquiring the data amount of the communication packets input to the transmission buffer during a period from the first time to the second time; a second accumulated data amount acquisition step of acquiring the data amount of the communication packets accumulated in the transmission buffer at a second time; and an upstream buffer delay time estimation procedure that estimates the residence time that the communication packet input to the transmission buffer remains in the transmission buffer as the upstream buffer delay time from the device to the opposing device based on the data amount acquired by the first accumulated data amount acquisition procedure, the data amount acquired by the input data amount acquisition procedure, and the data amount acquired by the second accumulated data amount acquisition procedure.

10. A round trip time acquisition procedure for acquiring a round trip time, which is the sum of an uplink delay and a downlink delay; A procedure for acquiring a predetermined delay time that is not affected by fluctuations in the wireless environment in a communication line; A line delay time estimation program as described in claim 9, which performs a downstream buffer delay time procedure of estimating a downstream buffer delay time from the opposing device to the own device based on the upstream buffer delay time, the round trip time acquired by the round trip time acquisition procedure, and the default delay time acquired by the default delay time acquisition procedure.

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