KR20020039945A - A Management Method for the Shared State using Network Delay Estimation in Client-Server Based Distributed Virtual Environment - Google Patents

Abstract

PURPOSE: A method for managing a shared state using delay prediction in distributed virtual environment is provided to be suitable for client-server based distributed virtual environment and secure an impartial service to network users with inter-different bandwidths through the delay prediction. CONSTITUTION: It is confirmed whether an event is generated by an event packet received from a server or an event is generated in a client itself for judging an event type(301). If the event is generated by the event packet received from the server, maximum transmission delay from the server to an other client is extracted from the last field of the event packet and the extracted maximum transmission delay is stored in a database(320)(302). A transmission delay time from a server computer to client computers is calculated using a received time of the event packet and an event generation time in the event packet, and the calculated transmission delay time is stored(303). The calculated transmission delay time is attached to the event packet(304), and the event packet is transmitted to the server(311). If the event is generated in the client itself, a real value is obtained from a real model(305) and a prediction value is obtained from a prediction model stored in the database(320)(306). The difference between the obtained real value in the real model at current time and the prediction value in the prediction model of the client computer having the maximum transmission delay is calculated from obtaining a prediction error(307). If the prediction error is more than an other threshold value according to the various application of the client computers(308), the prediction model is corrected(309). The corrected content is attached to the event packet(310), and the event packet is transmitted to the server computer through a network(311).

Description

A Management Method for the Shared State using Network Delay Estimation in Client-Server Based Distributed Virtual Environment}

The present invention relates to a method of managing a shared state in a client-server distributed virtual environment and a computer-readable recording medium recording a program for realizing the method. More particularly, the present invention provides a fair service to network users having different bandwidths. In order to guarantee the state change of distributed shared objects in each client to other clients, the shared state management method using the state change propagation method in consideration of the transmission delay of the network, and the computer recording the program for realizing the method. The present invention relates to a readable recording medium.

In the distributed virtual environment, in order to reflect the result of the user's work to other users, manipulate the object shared in the distributed virtual environment and send the changed state to all users sharing the object when the state changes. do.

However, due to the delay of the network, other users are notified of the change after the delay time, so that the shared state is not inconsistent among the users, and the changed state is sampled and sent in consideration of the limited resources of the network. The problem was that only the sampled results were seen.

The problem is one of the problems faced by distributed virtual environments, and many researches have been conducted to solve this problem, such as a dead reckoning algorithm.

The dead reckoning algorithm is a tracking algorithm that predicts the state of the current time based on the velocity, acceleration, etc. of the state change sampled on the side that receives the state change, and considers the new state change when the state changes again. It consists of a convergence algorithm for continuously converging to a newly predicted state. Using this, users are aware of state changes in real time and naturally, although there are errors.

Early systems used linear functions as tracking algorithms for state prediction. Later, commercial systems such as SIMNET (U.S. Army's Simulation Networking System) or DIS (Distributed Interactive System, IEEE standard 1278) used quadratic functions as tracking algorithms. Recently, a lot of dead reckoning algorithms specialized for the characteristics of each shared object such as a tank and a vehicle have been studied.

In contrast, in the PARADISE project, the tracking algorithm is created by taking only the state values except velocity and acceleration, and calculating the velocity and acceleration from its history. The method used was used.

On the other hand, the sender sets a threshold so that a change in state is made to another user only when the difference between the current state value and the state value predicted from the state most recently sent to another user is greater than or equal to the threshold value. By sending it, you control the rate.

However, these results are based on the assumption of a peer-to-peer distributed virtual environment, which is difficult to apply on a client-server basis. Due to the network delay in transmitting to the network, the side receiving the state change has a larger difference between the actual value and the predicted value at the time of receipt. This means that the larger the network delay, the bigger the user, and the poor the threshold value. In other words, a user with a high network delay is inaccurately aware of the shared state, causing a problem of receiving poor quality service.

Therefore, the above methods have a problem of not guaranteeing a fair service to all users.

The present invention has been proposed to solve the above problems, and is suitable for a client-server based distributed virtual environment, and a shared state management method for guaranteeing a fair service to network users of different bandwidths through delay prediction. It is an object of the present invention to provide a computer-readable recording medium having recorded thereon a program for realizing the method.

In other words, the present invention uses a state change transfer method that considers a network transmission delay when transmitting a state change of a distributed shared object in each client to another client, so as to ensure a fair service to network users having different bandwidths. It is an object of the present invention to provide a computer-readable recording medium recording a state management method and a program for realizing the method.

1 is an exemplary configuration diagram of a client-server based distributed virtual environment system to which the present invention is applied.

2 is a diagram illustrating an embodiment of an event packet exchanged between a client and a server according to the present invention.

3 is a flow diagram of an embodiment of a process of communicating and processing shared object state in a client in accordance with the present invention.

4 is a flow diagram of an embodiment of a process for transferring and processing shared object status in a server computer in accordance with the present invention.

* Explanation of symbols for the main parts of the drawings

110: client computer 1120: client computer 2

130: client computer 3

111, 121, 131: user program

112, 122, 132: Event Filtering and Delivery Module

113, 123, 133: Object Tracking and Convergence Module

114, 124, 134: Graphics Drivers

115, 125, 135: Display

140: network 150: server computer

151: Event Filtering and Delivery Module 152: Shared Object Database

According to an aspect of the present invention, there is provided a method of managing a shared state applied to a client device in a distributed virtual environment, the method comprising: a first step of determining whether an event arrives from a server or an event in a client itself; A second step of transmitting an event packet to the server by calculating a transmission delay if the event arrives from the server as a result of the determination in the first step; And a third step of determining whether the prediction error is equal to or greater than the threshold value by comparing a prediction error with a threshold value as a result of the determination in the first step, and transmitting an event packet to the server. It features.

In addition, another method of the present invention, a shared state management method applied to a server device in a distributed virtual environment, comprising: a first step of determining whether the event arrives from the client or the event in the server itself; A second step of transmitting an event packet to the server by calculating a transmission delay if the event arrives from the client as a result of the first step; And a third step of determining whether the prediction error is equal to or greater than the threshold value by comparing a prediction error with a threshold value as a result of the determination in the first step, and transmitting an event packet to the server. It features.

On the other hand, the present invention provides a client device having a large capacity processor, comprising: a first function of determining whether an event arrives from a server or an event in the client itself; A second function of calculating a transmission delay and transmitting an event packet to the server if the event arrives from the server as a result of the determination of the first function; And as a result of the determination of the first function, if it is an event in the client itself, compares a prediction error with a threshold value, determines whether the prediction error is greater than or equal to the threshold value, and implements a third function of transmitting an event packet to the server. A computer readable recording medium having recorded a program is provided.

The present invention also provides a server device having a large capacity processor, comprising: a first function of determining whether an event arrives from a client or an event in the server itself; A second function of calculating an event delay and transmitting an event packet to the server if the event arrives from the client as a result of the determination of the first function; And as a result of the determination of the first function, if it is an event in the server itself, compares a prediction error with a threshold value, determines whether the prediction error is greater than or equal to the threshold value, and implements a third function of transmitting an event packet to the server. A computer readable recording medium having recorded a program is provided.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is an exemplary configuration diagram of a client-server based distributed virtual environment system to which the present invention is applied.

As shown in FIG. 1, client computer 1 110, client computer 2 120, and client computer N 130 are the first, second, and Nth client computers connected to the server computer via network 140. Respectively.

Each client computer (110, 120, 130), the user program module (111, 121, 131) for providing a user interface, such as shared object manipulation and shared object display to each client user, network delay time for the change of the shared object, etc. The event processing and the result of processing in the event processing and processing module 112, 122, 132, the client computer (110, 120, 130), and delivers the processed result to the server computer 150, Object tracking and convergence module 113, 123, 133 for state estimation and state change of shared object in consideration of delay time, graphics driver module 114, 124, 134 for rendering on display unit 115, 125, 135, And display units 115, 125, and 135.

The server computer 150 includes an event filtering and forwarding module 151 and a shared object storing a shared object, which performs a function of forwarding an event to all client computers 110, 120, and 130 connected to the server computer 150. Object database 152.

The server computer 150 is connected to the client computers 110, 120, and 130 through the network 140, and has a network delay time for the shared object change event transmitted from each client computer 110, 120, and 130. Consider the case and handle the case.

Detailed operations of the client computers 110, 120, 130 and server computer 150 will be described in detail with reference to FIGS. 3 and 4 described below.

2 is a diagram illustrating an embodiment of an event packet exchanged between a client and a server according to the present invention.

As shown in FIG. 2, an event packet passed between the event filtering and forwarding module 112, 122, 132 on the client computer 1 110 side and the event filtering and forwarding module 151 on the server computer 150 side. The configuration of the object name area 210 indicating the type of the predefined event, the time area 220 indicating the time when the event occurred, the object ID (ID) area indicating the shared ID (ID) of the target object on which the event occurred 230, a location area 240 indicating a current position of the object, a speed area 250 indicating a moving speed of the object as a three-dimensional vector, and a network delay area 260 indicating a network delay at the client.

In the case of the network delay area 260, the client calculates and sends the average network delay from the server to the client when the event packet is sent from the client to the server. The server calculates and sends the maximum network delay it takes to send to the client.

3 is a flowchart illustrating an embodiment of a process of delivering and processing a shared object state in a client according to the present invention, and illustrates a detailed procedure of an event filtering and delivery module and an object tracking and convergence module on a client computer side.

First, an event type is determined by checking whether an event packet arrives from a server or whether an event in the client itself occurs.

As a result of the determination, if the event arrives from the server, the maximum transmission delay from the server to another client is extracted from the last field of the event packet and stored in the database 320 (302). Then, the transmission delay time from the server computer 150 to the client computers 110, 120, and 130 is calculated and stored using the arrival time of the event packet and the event occurrence time in the event packet (303). Adding the delay value is the maximum network delay it takes to reach the other client computer via the server computer 150 from the current client computer.

Next, attach the calculated delay to the event packet (304) and send the event packet to the server (311).

As a result of the determination, if the event is in the client itself, the actual value is obtained from the real model in the client computer 110, 120, 130 (305), and the prediction value is obtained from the predictive model stored in the database 320 (306).

A prediction error is obtained by obtaining a difference between the actual value in the real model at the obtained current time and the prediction value in the predictive model of the client computer having the maximum transmission delay (307). When the prediction error is equal to or greater than a different threshold value according to various applications of the client computers 110, 120, and 130 (308), the prediction model is modified (309), and the modified contents are included in the event packet. Attach (310) to forward the event packet to the server computer 150 via the network (311) to modify the prediction model of the other client computers (110, 120, 130). However, if the prediction error is not greater than the threshold (308), an event occurs in the client itself, and the process proceeds to the process of obtaining the actual value from the real model (305).

4 is a flowchart illustrating an embodiment of a process of delivering and processing a shared object state in a server computer according to the present invention, and illustrates a detailed procedure of an event filtering and delivery module of a server computer.

As shown in FIG. 4, first, an event type is determined by checking whether an event packet arrives from a client or whether an event in the server itself occurs.

As a result of the determination, if the event occurred when the event packet arrived from the client, the transmission delay from the client computer to the server computer is extracted from the last field of the event packet and stored in the database 420 in the server computer (402). The difference between the arrival time of the event packet and the occurrence time of the event in the event packet is calculated to calculate and store a network transmission delay from the client computer 110, 120, 130 to the server computer 150 (403). The delay is appended to the event packet (404) and the event packet is sent to the client computer.

Here, the event packet received from the client computer (110, 120, 130) is received based on the client computer (110, 120, 130) having the largest transmission delay from the server computer 150. Therefore, the maximum delayed client computer (110, 120, 130) is sent according to the transmission delay in order to receive other clients at the same time to receive the event packet (411).

In other words, the client computers 110, 120, and 130 may all receive the same service by making the same time received by the client computers 110, 120, and 130. At this time, if a new event packet comes in again before sending the event packet, the existing event packet is replaced with the newly received event packet and sent at the same time.

As a result of the determination, if the event occurred in the server itself, the actual value is obtained from the real model in the server computer 150 (405), and the prediction value is obtained from the predictive model stored in the database 420 (406).

The difference between the actual value in the real model in the server computer 150 and the prediction value in the predictive model of the server computer having the maximum transmission delay at the obtained current time is obtained (407). If the prediction error is greater than or equal to another threshold value according to various applications of the server computer 150 (408), the prediction model is modified (409), and the modified contents are attached to the event packet ( 410 In order to allow all clients to receive the event packet at the same time through the network, the client first forwards the event packet from the client having a high transmission delay (411). This can prevent the prediction value from exceeding the threshold value because the prediction is performed in advance as much as the transmission delay. However, if the prediction error is not greater than the threshold (308), an event occurs in the server itself, and the process proceeds to the process of obtaining the actual value from the real model (405).

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, in the client-server based distributed virtual environment, when the state change of the distributed shared object at each client is transmitted to another client, the state change propagation method considering the transmission delay of the network is used. It has the effect of ensuring a fair service to network users.

Claims (10)

In the shared state management method applied to client devices in a distributed virtual environment, A first step of determining whether the event arrives from the server or the event in the client itself; A second step of transmitting an event packet to the server by calculating a transmission delay if the event arrives from the server as a result of the determination in the first step; And A third step of transmitting an event packet to the server by confirming whether the prediction error is equal to or greater than the threshold value by comparing a prediction error with a threshold value as a result of the determination of the first step; Shared state management method comprising a. The method of claim 1, The second step, A fourth step of extracting and storing a maximum transmission delay from the server to another client from the event packet; A fifth step of calculating and storing a transmission delay time from the server to the client; And A sixth step of forwarding the incident packet to the server by attaching the calculated delay to the incident packet; Shared state management method comprising a. The method of claim 1, The third step, A fourth step of obtaining a prediction error using the actual value and the predicted value; A fifth step of comparing the prediction error with a threshold value; And A sixth step of confirming whether the prediction error is equal to or greater than a threshold value and attaching the content to an event packet and transmitting the same to the server; Shared state management method comprising a. In the shared state management method applied to server devices in a distributed virtual environment, A first step of determining whether the event arrives from the client or the event in the server itself; A second step of transmitting an event packet to the server by calculating a transmission delay if the event arrives from the client as a result of the first step; And A third step of transmitting an event packet to the server by comparing a prediction error with a threshold value to determine whether the prediction error is greater than or equal to the threshold value as a result of the determination of the first step; Shared state management method comprising a. The method of claim 4, wherein The second step, Extracting and storing the maximum transmission delay from the event packet; A fifth step of calculating and storing a delay from the event packet to the current client at the server; And A sixth step of attaching the calculated delay to the event packet to transmit the event packet from the client having a high transmission delay; Shared state management method comprising a. The method of claim 4, wherein The third step, A fourth step of obtaining a prediction error using the actual value and the predicted value; A fifth step of comparing the prediction error with a threshold value; And A sixth step of confirming whether the prediction error is equal to or greater than a threshold value and attaching the contents to the event packet to transmit the event packet from a client having a large transmission delay. Shared state management method comprising a. The method according to any one of claims 4 to 6, The process of transmitting the event packet to the client, A method of managing a shared state, in which a sending time is transmitted differently according to a transmission delay, so that other clients may also receive other packets at the same time that the maximum delay client receives the event packet. The method according to any one of claims 1 to 6, The case packet, An object name area indicating a predefined type of event, a time area indicating a time when an event occurred, an object ID area indicating a shared identifier (ID) of a target object on which an event occurred, a location area indicating a current position of an object, And a speed range indicating a moving speed of the object and a network delay area indicating a network delay at the client. In a client device with a large processor, A first function of determining whether the event arrives from the server or the event within the client itself; A second function of calculating a transmission delay and transmitting an event packet to the server if the event arrives from the server as a result of the determination of the first function; And A third function of transmitting an event packet to the server by checking whether the prediction error is equal to or greater than the threshold value by comparing a prediction error with a threshold value as a result of the determination of the first function; A computer-readable recording medium having recorded thereon a program for realizing this. In a server device having a large processor, A first function of determining whether the event arrives from the client or the event within the server itself; A second function of calculating an event delay and transmitting an event packet to the server if the event arrives from the client as a result of the determination of the first function; And A third function of transmitting an event packet to the server by checking whether the prediction error is equal to or greater than the threshold value by comparing a prediction error with a threshold value as a result of the determination of the first function; A computer-readable recording medium having recorded thereon a program for realizing this.