The present application claims priority to Japanese Patent Application No. 2022-154191 filed on Sep. 27, 2022, the contents of which are incorporated herein by reference in their entirety.
The present invention relates to a data transmission method and a data transmission system for transmitting data via a network with a transmission latency.
In recent years, various techniques for transmitting data to a remote location via a network have been proposed. For example, Patent Literature 1 discloses a system in which a camera captures images of a machine in a remote welding site and an operator in a local site remotely operates the machine while watching the images on a monitor. Patent Literature 2 discloses a technique for a data streaming system that divides data to be streamed and determines a destination and a delivery time in a planned way. When the system judges that a latency on a transmission line is large, the streaming is performed prior to the planned data delivery time, which eliminates the data latency on a receiving end.
Patent Literature 3 discloses a remote control system that enables a user to operate an operation device by presenting to the user a contact force detected by a contact force sensor provided on a remote robot, concurrently with displaying captured images of the remote robot on a monitor near the user. In this remote control system, if there is a time difference between displaying the images and presenting the contact force due to a transmission latency, the user develops a feeling of strangeness. To reduce the feeling of strangeness, the system delays the motion control of at least one of the robot and the operation device.
Patent Literature 4 discloses a remotely controllable automated driving system in which a remote operation device transmits a control signal to a vehicle and the vehicle returns the received control signal and transmits video footage. The remote operation device calculates movement of the vehicle based on a difference between the control signal transmitted to the vehicle and the control signal returned from the vehicle, and displays information indicating the movement of the vehicle such that the information is superimposed on the video footage received from the vehicle.
Patent Literature 1 is on the assumption that a latency time on a network connecting between the local site and the remote site is sufficiently short, and thus the technique of Patent Literature 1 cannot be applied to data transmission via a network with a relatively large transmission latency. In Patent Literature 2, since the content of data to be streamed is determined in advance, the streaming is performed prior to the scheduled delivery time when a latency on a communication path is expected, which makes it possible to realize a low-latency reception on the receiving end. However, in general communication in which the content of data to be streamed is not determined in advance, it seems impossible to use the technique of Patent Literature 2. The techniques of Patent Literature 3 and Patent Literature 4 are not intended to eliminate a data transmission latency.
The invention has been made in view of the foregoing, and an object of the invention is to provide a data transmission method and a data transmission system for realizing a low-latency data transmission.
A data transmission method according to the invention is a method for transmitting data via a network with a transmission latency. The method includes: sequentially transmitting data by a transmitting device; predicting future data after a lapse of a prediction time equivalent to a latency time on a transmission line of the network based on time-series data in a given period transmitted from the transmitting device, by a data prediction device using a prescribed prediction method; transmitting the future data by the data prediction device; and receiving the future data by a receiving device.
A data transmission system according to the invention is a system for transmitting data via a network with a transmission latency. The system includes: a transmitting device configured to sequentially transmit data; a data prediction device configured to predict future data after a lapse of a prediction time equivalent to a latency time on a transmission line of the network based on time-series data in a given period transmitted from the transmitting device, using a prescribed prediction method, and transmit the future data; and a receiving device configured to receive the future data.
According to the invention, a data prediction device predicts future data after a lapse of a prediction time equivalent to a latency time on a transmission line of a network. With this feature, it is possible to realize data transmission with almost zero latency time between transmitting and receiving ends.
Exemplary embodiments of the invention will be described below with reference to the accompanying drawings.
In some kind of real-time communication, a future data content can be predicted from a previously transmitted data content. The embodiments provide data transmission methods and systems which allow almost zero latency time on a receiving end in such data communication by installing a data prediction device on a communication path to predict future data.
A data transmission system according to a first embodiment of the invention will be described. As shown in
The network N typically has a transmission latency, and a latency time on a transmission line of the network N is assumed to be constant in the first embodiment. The data prediction device 104 predicts future data after a lapse of a prediction time equivalent to the latency time on the network N based on data sequentially transmitted from the transmitting device 102 (a data prediction method will be described later) and transmits the predicted future data to the receiving device 108. Accordingly, the receiving device 108 can receive data that has practically no transmission latency as compared to the data transmitted from the transmitting device 102.
The data prediction device 104 is a computer including a buffer. The data prediction device 104 accumulates data online after the start of data input from the transmitting device 102 until the buffer is full. When the buffer is full, the data prediction device 104 predicts future data after a lapse of a prediction time Tp from time-series data accumulated in the buffer, and outputs one piece of predicted future data. It takes a given period to accumulate data in the buffer only at the beginning, but thereafter the data in the buffer is sent in a pipeline manner and the data is output one by one. The data prediction device 104 repeats a process of discarding the oldest data in the buffer when next data is input, and predicting and outputting future data after a lapse of the prediction time Tp based on the current time-series data in the buffer. Although the prediction time Tp is the sum of a latency time T2 on the network N and a data accumulation time (buffering time) Tb (Tp=Tb+T2), once the buffer is full, the subsequent data accumulation time is negligibly small (Tp×T2).
As shown in
At the time of training, as shown in
At the time of prediction, as shown in
Next, a second embodiment of the invention will be described. In the first embodiment described above, the latency time on the transmission line of the network N is fixed, and future data after a lapse of the prediction time Tp equivalent to the latency time is predicted. However, the latency time may change dynamically depending on the situation of the transmission line. Therefore, in the second embodiment, in order to cope with a dynamically changing latency time, a means for detecting the latency time on the transmission line of the network N before transmitting data to the receiving end is provided, thereby also dynamically changing the prediction time Tp accordingly.
The latency time detection device 210 is a computer that calculates a latency time on the transmission line of the network N from a round-trip time of data between the transmitting and receiving ends using a command called “ping”, and outputs the data of the calculated latency time to the data prediction device 204.
As in the first embodiment, the data prediction device 204 includes the neural network 105 (see
At the time of data transmission, the latency time detection device 210 detects the latency time on the transmission line of the network N before one data packet is sent. The neural network 105 of the data prediction device 204 reads out the trained parameters d3 by referring to the table 212 using the latency time detected by the latency time detection device 210 as a key so as to prepare for the prediction process. Then, the neural network 105 predicts future data after a lapse of the prediction time Tp that is equal to the detected latency time based on the trained parameter d3 corresponding to current time-series data d4 in the buffer, and outputs the predicted future data d5. The predicted future data d5 is transmitted via the network N. Consequently, the receiving device 208 can receive the data with almost no transmission latency.
Note that
Next, as an example of application of the data transmission systems according to the first and second embodiments, a remote control system for operating a machine in a remote location using a controller will be described.
The camera 514 captures images of the machine 508, and the captured images of the machine 508 are transmitted via the network N and displayed on the display 516. An operator OP operates the controller 502 while watching the images of the machine 508 on the display 516, and operating information is sequentially transmitted from the controller 502. The operating information of the controller 502 is, for example, data of three-dimensional coordinate values (X, Y, Z) of a handle portion of the controller 502 according to the operation of the controller 502 (operation in an operable range such as up and down, right and left, and back and forth).
The data prediction device 504 includes the neural network 105 (
In the remote control system 500 shown in
Specific examples of the remote control system 500 shown in
Since the controller is voluntarily operated by the operator (human), it is difficult to predict a timing at which the controller starts moving by data prediction using only operating information acquired from the controller. It is known that when a human operates a controller manually, his/her muscle is activated before the controller actually starts moving. By taking advantage of this property, it is possible to predict a timing at which the controller starts moving by using not only the operating information of the controller but also electromyographic information of a person who operates the controller at the same time.
The controller 602a and the electromyography sensor 602b constitute a transmitting device. The electromyography sensor 602b is attached to near the biceps, triceps, shoulder muscle, or forearm muscle of the operator who grasps a handle of the controller 602a.
The data prediction device 604 includes the neural network 105 (see
At the time of prediction, the neural network 105 predicts a future coordinate value after a lapse of the prediction time Tp based on the time-series data of coordinate values and muscle activity in the given period Tb (time-series data d4 in
In the example of
Note that a plurality of electromyography sensors 602b may be attached to a plurality of areas on the operator's arm and shoulder, and the data prediction may be performed using three-dimensional operating information and a plurality of pieces of electromyographic information.
As shown in
Since the controller 602a moves from right to left, the X and Z coordinates show little change, but the Y coordinates change from about +0.18 in right position to about −0.2 in left position. Focusing on the Y coordinates, while the measured value Ym starts changing from a lapse of about 1.5 seconds, the predicted value Yp starts changing from a lapse of around 1.0 second, which means that 0.5 seconds future prediction is realized. In addition, curves of the predicted value Yp and the expected value Ye almost coincide with each other, which means that the prediction of Y coordinates is realized not only around the start of operating the controller 602a, but also in the entire region.
The prediction of the operating information using the electromyographic information shown in
When T3<T2, it is possible to employ the data prediction method using the neural network 105 in which only time-series data of operating information is used as input data as described above. Other data prediction methods for T3<T2 include a linear prediction method, an autoregressive (AR) model for predicting current data from a plurality of pieces of past data, a moving average (MA) model, and an autoregressive integrated moving average (ARIMA) model.
As an example of the data prediction methods, the linear prediction method will be briefly described below with reference to
Xp(t+1)=Xm(t)+(Xm(t)−Xm(t−1))
Yp(t+1)=Ym(t)+(Ym(t)−Ym(t−1))
Zp(t+1)=Zm(t)+(Zm(t)−Zm(t−1))
In this way, the position at the future time t+1 can be predicted from the measured values of the positions at time t−1 and time t (that is, time-series data of the positions) using the linear prediction method.
As described above, according to the embodiments of the invention, in data transmission via the network N with a transmission latency, the data prediction device predicts future data after a lapse of a prediction time equivalent to a latency time on a transmission line of the network N. This makes it possible to realize transmission with almost zero latency time between transmitting and receiving ends.
Especially in the remote control system 600 shown in
The following non-patent literature reveals that, in vehicle remote control, a latency time on a transmission line up to 600 msec does not significantly affect a steering maneuver, whereas an actual vehicle trajectory greatly deviates from an intended trajectory when the latency time exceeds 600 msec. By using the data prediction methods according to the embodiments, reduction from an actual latency time by about 500 msec can be expected. Therefore, even when the latency time exceeds 600 msec, the operation can be performed more accurately than ever before.
The invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. Other embodiments and variations made by those skilled in the art are intended to be embraced within the scope of the invention.
Number | Date | Country | Kind |
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2022-154191 | Sep 2022 | JP | national |