# Web Browser Network Based on a BA Model for a Web-Based Virtual World
## 1 Introduction  
A virtual world is a key feature for creating virtual reality applications and video games. In a virtual world, a user creates and controls their own avatar, and the user moves around the virtual world and interacts with the other users via the avatar. Within this world, the user needs to share the chat message, action, and location of the avatar with the other users. A client-side software displays the virtual world using the shared information. Virtual world applications involve a server-client architecture. The server stores all of the dynamic information such as the text messages as well as user information such as the appearance of the avatar and the location of the avatars. The client-side software stores static information such as the world images and the sounds, and it retrieves dynamic information from the server. Then, the client-side software displays the game world and the characters. A traditional type of virtual world divides a game world into many blocks. A server manages blocks, meaning that the server manages the dynamic information regarding the characters on the block. In this type of game world, a user reloads the game world when the user reaches the edge of the block. Communication between servers occurs when the user moves into the other block. In contrast, open-world virtual worlds are gaining attention. This type of game world appears undivided. The user can move around the world without reloading the map and possesses a higher degree of freedom of movement. However, in an open world, communication between servers occurs frequently because the user can move to neighboring blocks smoothly. Therefore, open-world applications require more frequent communication and considerable computing resources. In our study, we focus on web-based multiplayer online games owing to the numerous games available and because multiplayer games typically involve some open-world functionality. The web-based game uses web servers to store the information and web browsers as the client-side software. In our previous study, we proposed a system using multiple web servers to construct an open-world web-based game [1]. This system reallocates information that the server should manage to another server to balance the server load. However, the communication traffic becomes a problem. We can balance the amount of communication between the server and the browser. However, an increase in the number of users leads to more frequent communication if we cannot increase the number of servers. Subsequently, we proposed a method to use web browsers to host information because the number of browsers increases when the number of users increases [2; 3]. Furthermore, the web browser displays a part of the virtual world, indicating that the browser requires limited information. This could possibly reduce the number of communications. We try sharing the information using a network of web browsers. Our system constructs a web browser network by using web real-time communication (WebRTC) [4] to provide features to communicate among web browsers without web servers. This network achieves approximately 50% of data coverage, which is insufficient for the virtual world. The web browser cannot display the complete game world. For example, the browser cannot display the other users even though the user exists in the game world. This situation inhibits the fairness and consistency of the game. Therefore, we must achieve 100% data coverage. To increase data coverage, we need to construct a more efficient network. In this paper, we use the Barabasi-Albert model (BA model), which is an algorithm that constructs a scale-free network. In an online game, the user logs into the virtual world. Therefore, the new user is the new node in the network. The number of nodes gradually increases. We consider that this characteristic is similar to the BA model. Therefore, we consider that the BA model is familiar with our system. The remainder of the paper is organized as follows. Section 2 introduces some research related to our study.