US-12627611-B2 - Communication device, line delay time estimation method, and line delay time estimation program

US12627611B2US 12627611 B2US12627611 B2US 12627611B2US-12627611-B2

Abstract

By a communication device, a line delay time estimation method, a non-transitory computer-readable storage medium storing a line delay time estimation program, a communication packet is accumulated, a data amount of the communication packet is monitored, and a residence time, which is a duration and for which the communication packet remains in a transmission buffer, is estimated as an upstream buffer delay time from the communication device to a counterpart device.

Inventors

Tsuneo Nakata

Assignees

DENSO CORPORATION

Dates

Publication Date: 20260512
Application Date: 20240705
Priority Date: 20230711

Claims (10)

1 . A communication device configured to transmit a communication packet to a counterpart device, the communication device comprising: a transmission buffer configured to accumulate the communication packet; and at least one of (i) a circuit and (ii) a processor with a memory storing computer program code executable by the processor or the circuit, the at least one of the circuit and the processor configured to cause the communication device to: monitor a data amount of the communication packet accumulated in the transmission buffer; monitor the data amount of the communication packet input to the transmission buffer in a predetermined period; and estimate, as an upstream buffer delay time from the communication device to the counterpart device, a residence time, which is a duration for which the communication packet input to the transmission buffer remains in the transmission buffer, based on a data amount of the communication packet accumulated in the transmission buffer at a first time, a data amount of the communication packet input to the transmission buffer during a period from the first time to a second time, and a data amount of the communication packet accumulated in the transmission buffer at the second time.
2 . The communication device according to claim 1 , wherein the at least one of the circuit and the processor is configured to estimate a downstream buffer delay time from the counterpart device to the communication device based on the upstream buffer delay time.
3 . The communication device according to claim 2 , wherein the at least one of the circuit and the processor is configured to acquire: a round-trip time that is a sum of an upstream line delay and a downstream line delay; and a default delay time, and estimate the downstream buffer delay time by subtracting a sum of the upstream buffer delay time and the default delay time from the acquired round-trip time.
4 . The communication device according to claim 1 , wherein the at least one of the circuit and the processor is configured to acquire a round-trip time that is a sum of an upstream line delay and a downstream line delay, compare fluctuation of the upstream buffer delay time and fluctuation of the round-trip time, and determine whether an upstream wireless line is affecting a rate limit of an entire communication line.
5 . The communication device according to claim 4 , wherein the at least one of the circuit and the processor is configured to determine 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 at least one of the circuit and the processor is configured to determine that the upstream wireless line is not affecting the rate limit of the entire communication line during a period in which the fluctuation of the round-trip time does not follow the fluctuation of the upstream buffer delay time.
7 . A line delay time estimation method comprising causing a communication device, which is configured to transmit a communication packet to a counterpart device, to: acquire a data amount of the communication packet accumulated in a transmission buffer at a first time; acquire a data amount of the communication packet input to the transmission buffer during a period from the first time to a second time; acquire a data amount of the communication packet accumulated in the transmission buffer at the second time; and estimate, as an upstream buffer delay time from the communication device to the counterpart device, a residence time, which is a duration for which the communication packet input to the transmission buffer remains in the transmission buffer, based on the data amount of the communication packet accumulated in the transmission buffer at the first time, the data amount of the communication packet input to the transmission buffer during the period from the first time to the second time, and the data amount of the communication packet accumulated in the transmission buffer at the second time.
8 . The line delay time estimation method according to claim 7 , further causing the communication device to: acquire a round-trip time that is a sum of an upstream line delay and a downstream line delay; acquire a default delay time that is not affected by fluctuation of a wireless environment in a communication line; and estimate a downstream buffer delay time from the counterpart device to the communication device, based on the upstream buffer delay time, the acquired round-trip time, and the acquired default delay time.
9 . A non-transitory computer-readable storage medium storing a line delay time estimation program causing a controller of a communication device, which is configured to transmit a communication packet to a counterpart device, to: acquire a data amount of the communication packet accumulated in a transmission buffer at a first time; acquire a data amount of the communication packet input to the transmission buffer during a period from the first time to a second time; acquire a data amount of the communication packet accumulated in the transmission buffer at the second time; and estimate, as an upstream buffer delay time from the communication device to the counterpart device, a residence time, which is a duration for which the communication packet input to the transmission buffer remains in the transmission buffer, based on the data amount of the communication packet accumulated in the transmission buffer at the first time, the data amount of the communication packet input to the transmission buffer during the period from the first time to the second time, and the data amount of the communication packet accumulated in the transmission buffer at the second time.
10 . The non-transitory computer-readable storage medium storing the line delay time estimation program according to claim 9 , the program further causing the controller to: acquire a round-trip time that is a sum of an upstream line delay and a downstream line delay; acquire a default delay time that is not affected by fluctuation of a wireless environment in a communication line; and estimate a downstream buffer delay time from the counterpart device to the communication device, based on the upstream buffer delay time, the acquired round-trip time, and the acquired default delay time.

Description

CROSS REFERENCE TO RELATED APPLICATION The present application claims the benefit of priority from Japanese Patent Application No. 2023-113756 filed on Jul. 11, 2023. The entire disclosure of the above application is incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a communication device, a line delay time estimation method, and a non-transitory computer-readable storage medium storing a line delay time estimation program. BACKGROUND In packet communication, a communication device transmits a communication packet to a counterpart device, and upon receiving the communication packet from the communication device, the counterpart device transmits a reception confirmation packet for the communication packet to the communication device. For example, according to a technology of a comparative example, a communication device calculates a round-trip time (hereinafter referred to as RTT) based on a transmission queue length, a transmission delay, and a reception time of a reception confirmation packet, and calculates the queue length of the entire communication network. SUMMARY By a communication device, a line delay time estimation method, a non-transitory computer-readable storage medium storing a line delay time estimation program, a communication packet is accumulated, a data amount of the communication packet is monitored, and a residence time, which is a duration and for which the communication packet remains in a transmission buffer, is estimated as an upstream buffer delay time from the communication device to a counterpart device. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram showing an overall configuration according to an embodiment. FIG. 2 is a diagram showing upstream buffer delay time and downstream buffer delay time. FIG. 3 is a diagram showing a transition of the amount of data stored in a transmission buffer. FIG. 4 is a diagram illustrating an upstream communication path. FIG. 5 is a diagram illustrating a state in which an upstream wireless line affects a rate limit of the entire communication line. FIG. 6 is a diagram illustrating the upstream communication path. FIG. 7 is a diagram illustrating a state in which the upstream wireless line does not affect the rate limit of the entire communication line. FIG. 8 is a flowchart showing an estimation process of the upstream buffer delay time. FIG. 9 is a flowchart showing an estimation process of the downstream buffer delay time. FIG. 10 is a flowchart showing an influence determination process of an upstream wireless line. DETAILED DESCRIPTION In a method of the comparative example, although the queue length of the entire communication network is calculated, it is not possible to separately estimate an upstream buffer delay time from the communication device to the counterpart device or a downstream buffer delay time from the counterpart device to the communication device. Further, the timing at which the communication device calculates the RTT is after receiving a reception confirmation packet from the counterpart device, and the RTT can be calculated only after receiving the reception confirmation packet from the counter device. Therefore, when the communication network is a cellular line, it takes several tens to several hundreds of milliseconds from the transmission of the communication packet until the RTT is calculated. As a result, for example, a situation is assumed 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 condition. As the result, a feedback control becomes unstable. Examples of the present disclosure provide a communication device, a line delay time estimation method, a non-transitory computer-readable storage medium storing a line delay time estimation program capable of appropriately estimating one-way line delay time. According to one example embodiment, a communication device is configured to transmit a communication packet to a counterpart device. A transmission buffer is configured to accumulate the communication packet. A buffer data amount monitoring unit is configured to monitor a data amount of the communication packet accumulated in the transmission buffer. An input data amount monitoring unit is configured to monitor the data amount of the communication packet input to the transmission buffer in a predetermined period. A delay time estimation unit is configured to estimate, as an upstream buffer delay time from the communication device to the counterpart device, a residence time, which is a duration and for which the communication packet input to the transmission buffer remains in the transmission buffer, based on a data amount of the communication packet accumulated in the transmission buffer at a first time, a data amount of the communication packet input to the transmission buffer during a period from the first time to