網路虛擬環境(Network Virtual Environment – NVE)是一個由電腦產生的虛擬世界，它可以讓使用者們透過網路連線，經由訊息交換來與其他使用者們互動。每位使用者在網路虛擬環境中都只注意一個有限的範圍，並只與在此範圍內的使用者們做互動，我們稱此範圍為一個互動範圍(Area of interest - AOI)。網路虛擬環境通常都需要支 援許多使用者同時使用，所以提升其擴充性(scalability)是很重要的。由於擴充性的問題也就是資源上的問題，要提升擴充性，就必須要減少資源消耗，我們將著重在減少頻寬消耗方面。目前一些同儕式方法已經被提出來用以改善系統的擴充性，但是關於互動範圍內的擴充性卻仍未有方法來提升它。我們提出的兩個方法VoroCast和FiboCast，希望能夠改善互動範圍的擴充性。其中VoroCast讓訊息的傳輸沒有多餘的封包以及可以應用彙整(aggregation)和壓縮(compression)的機制來減少頻寬消耗。而FiboCast 則是VoroCast 的一個改進，通常是應用於使用者處於擁擠的環境下，靠著調整訊息散佈的範圍來更進一步地減少頻寬消耗。我們利用模擬實驗來衡量我們所提出的方法的效能。實驗結果證明了我們的方法的確可以達到較少的頻寬消耗，而且還保有很高的鄰居關係的一致性(neighborship consistency) 及較少的偏移距離(drift distance)。 A networked virtual environment (NVE) is computer-generated virtual world where users interact with each other by exchanging messages via network connections. Each user in NVE only pays attention to a bounded area called area of interest (AOI). NVE usually has a lot of users, so it is important to higher the scalability. Several peer-to-peer (P2P) schemes are proposed to improve the system scalability which indicates the ability to handle growing amounts of users in the system. However, they do not consider the AOI scalability which indicates the ability to handle growing amounts of users within AOI. We proposed VoroCast and FiboCast to improve the AOI scalability. VoroCast makes the message transmission non-redundant and applies aggregation and compression mechanisms to reduce the bandwidth consumption. FiboCast is the improvement of VoroCast. It is used especially for a user who is in a crowded environment and further reduces the bandwidth consumption by adjusting the message dissemination range. We perform simulation experiments to evaluate the performances of VoroCast and FiboCast.
