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

Abstract

A communication device that transmits a communication packet to a counterpart device is provided with: a transmission buffer that stores the communication packet; a buffer data volume monitoring unit that monitors the data volume of the communication packets stored in the transmission buffer; an input data volume monitoring unit that monitors the data volume of the communication packets input to the transmission buffer during a predetermined period; and a delay time estimation unit. On the basis of the amount of data of the communication packets stored in the transmission buffer at a first time, and the amount of data of the communication packets input to the transmission buffer during a period from the first time to a second time, the amount of data of the communication packets stored in the transmission buffer at a second time. And estimating, as an upstream buffer delay time from the device to the counterpart device, a residence time during which the communication packet inputted to the transmission buffer is resident in the transmission buffer, by the amount of data stored in the transmission buffer at a second time.

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 Art

[0002] In packet communication, a communication device sends a communication data packet to a counterpart device, and when the counterpart device receives the communication data packet from the communication device, it sends a delivery confirmation data packet for the communication data packet to the communication device. For example, Patent Document 1 discloses a technology for calculating the queue length of the entire communication network by calculating the round-trip time (hereinafter referred to as RTT) based on the length of the sending queue, the transmission delay, and the reception time of the delivery confirmation data packet in the communication device.

[0003] Patent Document 1: U.S. Patent No. 8923270

[0004] In the method disclosed in Patent Document 1, although the queue length of the entire communication network is calculated, it is impossible to estimate the uplink buffer delay time from the communication device to the other device and the downlink buffer delay time from the other device to the communication device separately. In addition, the communication device calculates the RTT after receiving the delivery confirmation packet from the other device, and the RTT can only be calculated after receiving the delivery confirmation packet from the other device. Therefore, in the case where the communication network is a cellular line, it takes tens of milliseconds to hundreds of milliseconds from the time the communication data packet is sent before the RTT is calculated. As a result, for example, when it is assumed that the communication device is moving at high speed by being mounted on a vehicle, the time required to calculate the RTT is the same as the change cycle of the line state, and there is a problem of unstable feedback control. Summary of the invention

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

[0006] According to one aspect of the present disclosure, a communication device sends a communication data packet to a counterpart device. A sending buffer accumulates the communication data packet. A buffer data volume monitoring unit monitors the data volume of the communication data packet accumulated in the sending buffer. An input data volume monitoring unit monitors the data volume of the communication data packet input to the sending buffer during a specified period. A delay time estimation unit estimates the retention time of the communication data packet input to the sending buffer in the sending buffer as an uplink buffer delay time from the present device to the counterpart device, based on the data volume of the communication data packet already accumulated in the sending buffer at a first moment, the data volume of the communication data packet input to the sending buffer during a period from the first moment to a second moment, and the data volume of the communication data packet being accumulated in the sending buffer at a second moment.

[0007] Based on the data volume of the communication data packets already accumulated in the transmission buffer at the first time, the data volume of the communication data packets input to the transmission buffer during the period from the first time to the second time, and the data volume of the communication data packets currently accumulated in the transmission buffer at the second time, the retention time of the communication data packets input to the transmission buffer is estimated as the uplink buffer delay time. The one-way line delay time from the communication device to the other device can be appropriately estimated. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a functional block diagram showing the overall structure of one embodiment.

[0009] Figure 2 It is a diagram showing the uplink buffer delay time and the downlink buffer delay time.

[0010] Figure 3 This is a diagram showing the change in the amount of data accumulated in the transmission buffer.

[0011] Figure 4 This is a diagram for explaining a communication path in the uplink direction.

[0012] Figure 5 This is a diagram for explaining how the rate limitation of the uplink wireless line affects the entire communication line.

[0013] Figure 6 This is a diagram for explaining a communication path in the uplink direction.

[0014] Figure 7 This is a diagram for explaining a method of rate limitation in which the uplink wireless line does not affect the entire communication line.

[0015] Figure 8 This is a flowchart showing the estimation process of the uplink buffering delay time.

[0016] Fig. 9 This is a flowchart showing the process of estimating the downlink buffer delay time.

[0017] Fig.10 This is a flowchart showing the influence determination process of the uplink wireless line. DETAILED DESCRIPTION

[0018] Hereinafter, with reference to the accompanying drawings, an embodiment in which the present invention is applied to a communication node mounted on a vehicle, for example, will be described. Figure 1 As shown, the communication system 1 is configured so that the communication node 2 (equivalent to the communication device) and the counterpart node 3 (equivalent to the counterpart device) can perform data communication by relaying the base station 4. The communication node 2 and the base station 4 perform data communication via a wireless line. The data communication performed by the counterpart node 3 and the base station 4 by relaying the base station 4 between the communication node 2 and the counterpart node 3 via a wired line is data communication conforming to the communication protocol of TCP / IP (Transmission Control Protocol / Internet Protocol). The communication node 2 sends a communication data packet to the base station 4 via a wireless line. The base station 4 sends the communication data packet received from the communication node 2 to the counterpart node 3 via a wired line. The counterpart node 3 sends a delivery confirmation data packet for the communication data packet to the base station 4 via a wired line. The base station 4 sends the delivery confirmation data packet received from the counterpart node 3 to the communication node 2 via a wireless line.

[0019] like Figure 2 As shown, the transmission of a communication data packet from the communication node 2 to the counterpart node 3 via the relay base station 4 is data transmission in the uplink direction. The speed of transmitting a communication data packet from the communication node 2 to the wireless line depends on the wireless environment, and the time the communication data packet stays in the communication node 2 is generated as an uplink buffer delay time (equivalent to the uplink line delay time). The transmission of a delivery confirmation data packet from the counterpart node 3 to the communication node 2 via the relay base station 4 is data transmission in the downlink direction. The speed of transmitting a delivery confirmation data packet from the base station 4 to the wireless line depends on the wireless environment, and the time the delivery confirmation data packet stays in the base station 4 is generated as a downlink buffer delay time (equivalent to the downlink line delay time). These uplink buffer delay times and downlink buffer delay times vary according to the wireless environment, and are relatively short when the wireless environment is relatively good, and relatively long when the wireless environment is relatively bad.

[0020] The communication node 2 sends the driving control data related to driving control, such as vehicle speed, acceleration and deceleration, sharp turns, driving route, fuel consumption, etc., to the counterpart node 3. The counterpart node 3 can communicate data with multiple communication nodes 2 via wireless lines, and is, for example, a server having the function of performing statistical processing on driving control data for many non-specific vehicles. When the counterpart node 3 receives driving control data from each communication node 2 mounted on many non-specific vehicles, it performs statistical processing on the received driving control data. In addition, the data sent and received between the communication node 2 and the counterpart node 3 may also be data other than the above-mentioned driving control data, or may be data used for other purposes.

[0021] The communication node 2 is provided with a control unit 5 for controlling the overall operation of the node. The control unit 5 is mainly composed of a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an I / O (Input / Output). 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 thereof. For example, in the case where the control unit 5 is provided by an electronic circuit as hardware, the control unit 5 can be provided by a digital circuit or an analog circuit including many logic circuits. The control unit 5 executes a program stored in a non-transitional physical recording medium to perform processing corresponding to the program, and executes a method corresponding to the program.

[0022] The control unit 5 includes a data packet generating unit 6, an in-vehicle communication interface unit 7, an out-vehicle communication interface unit 8, a forwarding unit 9, an input data amount monitoring unit 10, a storage unit 11, and a delay time estimating unit 12, respectively, for each function. The out-vehicle communication interface unit 7 includes a transmission buffer 13, a signal transceiver unit 14, and a buffered data amount monitoring unit 15. Each of these units 6 to 15 executes a line delay time estimation program to perform a line delay time estimation method.

[0023] The packet generation unit 6 generates a communication packet according to the execution of the application by the control unit 5, and outputs the generated communication packet to the transfer unit 9. When the in-vehicle communication interface unit 7 receives a communication packet from the external node 16 (equivalent to an external device), it outputs the received communication packet to the transfer unit 9. When the transfer unit 9 receives a communication packet from the packet generation unit 6 and the in-vehicle communication interface unit 7, it transfers the input communication packet to the in-vehicle communication interface unit 8.

[0024] In the vehicle external communication interface unit 8, when the communication data packet is forwarded from the forwarding unit 9, the transmission buffer 13 accumulates the forwarded communication data packet. The signal transceiver unit 14 transmits the communication data packet accumulated in the transmission buffer 13 to the counterpart node 3 via the relay base station 4, and receives the delivery confirmation data packet for the communication data packet from the counterpart node 3 via the relay base station 4. The buffer data amount monitoring unit 15 monitors the data amount of the communication data packet accumulated in the transmission buffer 13, and outputs the accumulated data amount indicating the data amount of the communication data packet accumulated in the transmission buffer 13 to the delay time estimation unit 12.

[0025] The input data amount monitoring unit 10 monitors the data amount of communication packets input from the transfer unit 9 to the transmission buffer 13 , and outputs the input data amount indicating the data amount of communication packets input from the transfer unit 9 to the transmission buffer 13 to the storage unit 11 and the delay time estimation unit 12 .

[0026] When the input data volume is input from the input data volume monitoring unit 10, the storage unit 11 manages and stores the input data volume in time series. When the accumulated data volume is input from the buffered data volume monitoring unit 15 and the input data volume is input from the input data volume monitoring unit 10, the delay time estimation unit 12 estimates the retention time of the communication data packet input to the transmission buffer 13 in the transmission buffer 13 as the uplink buffer delay time based on the input accumulated data volume and the input data volume.

[0027] like Figure 3 As shown, when it is assumed that the data amount of the communication data packets accumulated in the sending buffer 13 at time t1 is the data amount b(t1), the data amount of the communication data packets input to the sending buffer 13 during the period from time t1 to time t2 is the data amount P, and the data amount of the communication data packets being accumulated in the sending buffer 13 at time t2 is the data amount b(t2), the delay time estimation unit 12 estimates the retention time of the communication data packets input to the sending buffer 13 in the sending buffer as the uplink buffer delay time through the following calculation formula.

[0028] Uplink buffer delay time = (t2-t1) × b(t1) / {b(t1)-b(t2)-P}

[0029] here,

[0030] The transmission rate of the wireless link = {b(t1)-b(t2)-P} / (t2-t1). If the transmission buffer 13 is not empty during the period from time t1 to time t2, then

[0031] The transmission rate of the wireless line = line bandwidth.

[0032] In addition, the delay time estimation unit 12 estimates the downlink buffer delay time in addition to the uplink buffer delay time. That is, the delay time estimation unit 12 obtains the RTT which is the sum of the uplink line delay and the downlink line delay. Here, when the delay time in the communication line that is not affected by the change of the wireless environment is set as the predetermined delay time,

[0033] RTT=uplink buffer delay time+downlink buffer delay time+predetermined delay time holds, and therefore the delay time estimation unit 12 estimates the downlink buffer delay time using the following calculation formula.

[0034] Downlink buffer delay time = RTT - (uplink buffer delay time + predetermined delay time)

[0035] The established delay times are:

[0036] The predetermined delay time = the time required for data processing in the uplink direction in the base station 4 + the data communication time from the base station 4 to the other node 3 + the time required for data processing in the other node 3 + the data communication time from the other node 3 to the base station 4, the time required for data processing in the downlink direction in the communication node 2 is established, and can be calculated by pre-determining the time based on the processing capabilities of the base station 4, the other node 3 and the communication node 2.

[0037] Furthermore, the delay time estimation unit 12 compares the change of the uplink buffer delay time with the change of the RTT, and determines whether the uplink wireless line affects the rate limit of the entire communication line. The delay time estimation unit 12 determines that the uplink wireless line affects the rate limit of the entire communication line during the period when the change of the RTT follows the change of the uplink buffer delay time. That is, the delay time estimation unit 12 determines that the uplink wireless line is the bottleneck section of the entire communication line. By determining that the uplink wireless line is the bottleneck section of the entire communication line, the delay time estimation unit 12 can determine that the delay suppression of the sending buffer 13 is effective for 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 data packet input to the sending buffer 13 and adjusting the input rate to the sending buffer 13. The delay time estimation unit 12 can reduce the uplink buffer delay time by reducing the input rate to the sending buffer 13, and can reduce the RTT.

[0038] On the other hand, during the period when the change of RTT does not follow the change of the uplink buffer delay time, the delay time estimation unit 12 determines that the uplink wireless line does not affect the rate limit of the entire communication line. That is, the delay time estimation unit 12 determines that the uplink wireless line is not the bottleneck section of the entire communication line. By determining that the uplink wireless line is not the bottleneck section of the entire communication line, the delay time estimation unit 12 can determine that the delay suppression of the transmission buffer 13 is not effective for improving the RTT. In this case, the delay time estimation unit 12 can determine that even if the data amount of the communication data packet input to the transmission buffer 13 is adjusted, the RTT cannot be adjusted, and the situation of meaninglessly adjusting the RTT can be avoided in advance.

[0039] like Figure 4 as well as Figure 5 As shown in FIG. 1 , if the bandwidth of the uplink path other than the uplink wireless line in the communication path in the uplink direction is larger than the bandwidth of the uplink wireless line (B2>B1), the change of RTT follows the change of the uplink buffer delay time, so the delay time estimation unit 12 determines that the uplink wireless line is the bottleneck section of the entire communication line during the period when the change of RTT follows the change of the uplink buffer delay time. In the section (t11 to t12) where the bandwidth of the uplink wireless line increases, the uplink buffer delay time and RTT are inclined in the direction of decrease, and in the section (t12 to t14) where the bandwidth of the uplink wireless line decreases, the uplink buffer delay time and RTT are inclined in the direction of increase.

[0040] On the other hand, Figure 6 as well as Figure 7 As shown in FIG. 1 , if the bandwidth of the uplink path other than the uplink wireless line in the uplink communication path is smaller than the bandwidth of the uplink wireless line (B3<B1), the change of RTT does not follow the change of the uplink buffer delay time. Therefore, the delay time estimation unit 12 determines that the uplink path other than the uplink wireless line in the uplink communication path is the bottleneck section of the entire communication path during the period when the change of RTT does not follow the change of the uplink buffer delay time. In this case, the uplink buffer delay time and RTT are inclined to the decreasing direction in the section (t21-t22) in which the bandwidth of the uplink wireless line increases, and the uplink buffer delay time and RTT are inclined to the increasing direction in the section (t22-t25) in which the bandwidth of the uplink wireless line decreases. In addition, if the size of the bandwidth of the uplink path other than the uplink wireless line and the bandwidth of the uplink wireless line are reversed, and the bandwidth of the uplink path other than the uplink wireless line becomes larger than the bandwidth of the uplink wireless line (t24), then from then on, the change of RTT follows the change of the uplink buffer delay time.

[0041] Next, refer to Figures 8 to 10Here, the uplink buffer delay time estimation process of estimating the uplink buffer delay time, the downlink buffer delay time estimation process of estimating the downlink buffer delay time, and the uplink wireless line influence determination process of determining the influence of the uplink wireless line are described.

[0042] (1) Estimation of uplink buffering delay time (see Figure 8 )

[0043] When the control unit 4 starts the estimation process of the uplink buffer delay time, the control unit 4 sets the predetermined time as time t1, and obtains the data volume of the communication data packets accumulated in the transmission buffer 13 at time t1 (S1, equivalent to the first accumulated data volume obtaining step). The control unit 4 sets the time after the predetermined time from time t1 as time t2, and obtains the data volume of the communication data packets input to the transmission buffer 13 during the period from time t1 to time t2 (S2, equivalent to the input data volume obtaining step). The control unit 4 obtains the data volume of the communication data packets being accumulated in the transmission buffer 13 at time t2 (S3, equivalent to the second accumulated data volume obtaining step).

[0044] Based on the acquired data volume of the communication data packets accumulated in the sending buffer 13 at time t1, the data volume of the communication data packets input to the sending buffer 13 during the period from time t1 to time t2, and the data volume of the communication data packets being accumulated in the sending buffer 13 at time t2, the control unit 4 estimates the uplink buffer delay time (S4, equivalent to the uplink buffer delay time estimation step) using the above-mentioned calculation formula, and ends the uplink buffer delay time estimation process.

[0045] (2) Estimation of Downlink Buffering Delay Time (See Fig. 9 )

[0046] When the control unit 4 starts the estimation process of the downlink buffer delay time, it obtains the RTT which is the sum of the uplink line delay and the downlink line delay (S11, which corresponds to the RTT acquisition step). The control unit 4 obtains a predetermined delay time which is not affected by the change of the wireless environment and is measured in advance (S12, which corresponds to the predetermined delay time acquisition step). The control unit 4 estimates the uplink buffer delay time in the downlink direction by the above-mentioned calculation formula based on the uplink buffer delay time obtained by the above-mentioned estimation process of the uplink buffer delay time, the obtained RTT, and the predetermined delay time (S13, which corresponds to the downlink buffer delay time estimation step), and ends the downlink buffer delay time estimation process.

[0047] (3) Uplink wireless line influence determination process (refer to Fig.10 )

[0048] When the control unit 4 starts the influence determination process on the uplink wireless line, it compares the change of the uplink buffer delay time with the change of the RTT (S21), and determines whether the change of the RTT follows the change of the uplink buffer delay time (S22). When the control unit 4 determines that the change of the RTT follows the change of the uplink buffer delay time (S22: "Yes"), it determines that the uplink wireless line affects the rate limit of the entire communication line, that is, the uplink wireless line is a bottleneck section (S23), and ends the influence determination process on the uplink wireless line. On the other hand, when the control unit 4 determines that the change of the RTT does not follow the change of the uplink buffer delay time (S22: "No"), it determines that the uplink wireless line does not affect the rate limit of the entire communication line, that is, the uplink wireless line is not a bottleneck section (S24), and ends the influence determination process on the uplink wireless line.

[0049] As described above, according to this embodiment, the following effects can be obtained.

[0050] In the communication node 2, the retention time of the communication data packets input to the transmission buffer 13 is estimated as the uplink buffer delay time based on the data volume of the communication data packets already accumulated in the transmission buffer 13 at time t1, the data volume of the communication data packets input to the transmission buffer 13 during the period from time t1 to time t2, and the data volume of the communication data packets currently accumulated in the transmission buffer 13 at time t2. The line delay time in the uplink direction from the communication node 2 to the counterpart node 3 can be appropriately estimated.

[0051] The RTT is obtained as the sum of the uplink delay and the downlink delay, a predetermined delay time that is not affected by changes 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 predetermined delay time from the obtained RTT. The line delay time in the downlink direction from the counterpart node 3 to the communication node 2 can be appropriately estimated.

[0052] During the period when the change of RTT follows the change of the uplink buffer delay time, it is determined that the uplink wireless line affects the rate limit of the entire communication line and the uplink wireless line is a bottleneck section. It can be determined that the delay suppression of the sending buffer 13 is effective in improving the RTT, and the RTT can be adjusted by adjusting the input rate to the sending buffer 13.

[0053] During the period when the change of RTT does not follow the change of the uplink buffer delay time, it is determined that the uplink wireless line does not affect the rate limit of the entire communication line, and the uplink wireless line is not a bottleneck section. It is determined that the delay suppression of the sending buffer 13 is not effective for improving the RTT, and unnecessary adjustment of the input rate to the sending buffer 13 can be avoided in advance.

[0054] Although the present disclosure is described based on the embodiments, it should be understood that the present disclosure is not limited to the above-mentioned embodiments and structures. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and methods, and other combinations and methods containing only one element, above or below them, also belong to the scope and thought range of the present disclosure.

[0055] The control unit and method described in the present disclosure may also be implemented by a special-purpose computer, which is provided by a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and method described in the present disclosure may also be implemented by a special-purpose computer, which is provided by a processor composed of one or more special-purpose hardware logic circuits. Alternatively, the control unit and method described in the present disclosure may also be implemented by one or more special-purpose computers, which are composed of a combination of a processor and a memory programmed to execute one or more functions and a processor composed of one or more hardware logic circuits. In addition, a computer program may also be stored as an instruction executed by a computer in a computer-readable non-transient tangible recording medium.

Claims

1. A communication device, which is a communication device that sends a communication data packet to a counterpart device, wherein: have: A sending buffer is used to store the above communication data packets; a buffer data amount monitoring unit for monitoring the data amount of the communication data packets accumulated in the transmission buffer; An input data volume monitoring unit for monitoring the data volume of the communication data packets input to the transmission buffer within a predetermined period; as well as The delay time estimation unit estimates the retention time of the communication data packets input into the sending buffer within the sending buffer as the uplink buffer delay time from the present device to the other device, based on the data volume of the communication data packets accumulated in the sending buffer at the first moment, the data volume of the communication data packets input into the sending buffer during the period from the first moment to the second moment, and the data volume of the communication data packets being accumulated in the sending buffer at the second moment.

2. The communication device according to claim 1, wherein: The delay time estimation unit estimates a downlink buffering delay time from the counterpart device to the own device based on the uplink buffering delay time.

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

4. The communication device according to any one of claims 1 to 3, wherein: The delay time estimation unit obtains a round trip time which is a sum of an uplink delay and a downlink delay, compares a change in the uplink buffer delay time with a change in the round trip time, and determines whether the uplink wireless link affects a rate limit of the entire communication link.

5. The communication device according to claim 4, wherein: The delay time estimation unit determines that the uplink wireless link has a rate limit that affects the entire communication link while the change in the round trip time follows the change in the uplink buffering delay time.

6. The communication device according to claim 4, wherein: The delay time estimation unit determines that the uplink wireless link does not affect the rate limitation of the entire communication link while the variation of the round trip time does not follow the variation of the uplink buffering delay time.

7. A method for estimating line delay time, wherein: The following steps are performed in the communication device that sends the communication data packet to the other device: A first accumulated data amount obtaining step of obtaining the data amount of the communication data packet already accumulated in the transmission buffer at a first moment; An input data amount acquisition step of acquiring the data amount of the communication data packet input to the transmission buffer during a period from the first time to the second time; A second accumulated data amount obtaining step of obtaining the data amount of the communication data packet currently being accumulated in the transmission buffer at a second time; and Based on the amount of data obtained through the above-mentioned first accumulated data amount obtaining step, the amount of data obtained through the above-mentioned input data amount obtaining step, and the amount of data obtained through the above-mentioned second accumulated data amount obtaining step, the residence time of the above-mentioned communication data packet input into the above-mentioned sending buffer within the sending buffer is estimated as the uplink buffer delay time from the present device to the above-mentioned other device.

8. The method for estimating line delay time according to claim 7, wherein: Follow these steps: a round trip time acquisition step of acquiring a round trip time which is a sum of an uplink delay and a downlink delay; A step of obtaining a predetermined delay time in a communication line that is not affected by changes in the wireless environment; and A downlink buffer delay time step of estimating a downlink buffer delay time from the other device to the own device based on the uplink buffer delay time, the round trip time acquired in the round trip time acquisition step, and the predetermined delay time acquired in the predetermined delay time acquisition step.

9. A line delay time estimation program, which causes a control unit of a communication device that transmits a communication data packet to a counterpart device to execute the following steps: A first accumulated data amount obtaining step of obtaining the data amount of the communication data packet already accumulated in the transmission buffer at a first moment; An input data amount acquisition step of acquiring the data amount of the communication data packet input to the transmission buffer during a period from the first time to the second time; A second accumulated data amount obtaining step of obtaining the data amount of the communication data packet currently being accumulated in the transmission buffer at a second time; and Based on the amount of data obtained through the above-mentioned first accumulated data amount obtaining step, the amount of data obtained through the above-mentioned input data amount obtaining step, and the amount of data obtained through the above-mentioned second accumulated data amount obtaining step, the retention time of the above-mentioned communication data packet input to the above-mentioned sending buffer within the sending buffer is estimated as the uplink buffer delay time from the present device to the above-mentioned other device.

10. The line delay time estimation program according to claim 9, wherein: Follow these steps: a round trip time acquisition step of acquiring a round trip time which is a sum of an uplink delay and a downlink delay; A step of obtaining a predetermined delay time in a communication line that is not affected by changes in the wireless environment; and A downlink buffer delay time step of estimating a downlink buffer delay time from the other device to the own device based on the uplink buffer delay time, the round trip time acquired in the round trip time acquisition step, and the predetermined delay time acquired in the predetermined delay time acquisition step.

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