3D網路虛擬環境(Networked Virtual Environment, NVE)的特點在於透過網路傳送互動訊息以及擬真的3D場景讓使用者有身歷其境的體驗。但由於虛擬世界中龐大的3D資料導致使用者需耗費大量的頻寬與安裝時間。因此許多平台，像Second Life採取透過3D串流的技術以求降低安裝所需花費的頻寬與時間。透過3D串流技術，使用者可以漸進式地安裝視野範圍內所需的3D場景即可與其他使用者互動或瀏覽，達到降低安裝時所需的龐大3D資料與花費時間。但當系統人數成長到一定程度時，仍會受限於傳統主從式架構下伺服器的頻寬有有限的影響，導致最大可同時使用人數會停留在某一瓶頸下。同儕網路(Peer-to-Peer, P2P)的可擴充性在此就成為了解決伺服器頻寬有限的好方法，像是FLoD，透過同儕網路達到提昇3D串流的系統可擴充性。在FLoD中，資料的主要來源來自於同儕，因此選擇合適的同儕互動將會是影響同儕網路效能的重要因素之一。特別是在虛擬環境中，注重資料請求反應速度與使用者所持有資料取決於所在位置等因素使得同儕選擇對於系統效能的影像更為重大。但在FLoD中，同儕選擇機制上仍然有所不足，像是向AoI鄰居送出資料請求但未考量其頻寬能力以及請求對象局限於AoI鄰居。因此本論文的主要貢獻在於提出一套改良的同儕網路建構與選擇的機制：頻寬感知同儕選擇(Bandwidth Aware Peer Selection, BAPS)，避免因物件與使用者密度上升而導致資源競爭與壅塞的問題以及提供有效率的頻寬利用，更有效率地提昇系統的可擴充性與效能。 The 3D networked virtual environment (NVE) can provide users with simulated, realistic 3D scenes in which users can interact with each other by sending messages through network links. However, the installation of an NVE may take much time and much bandwidth since an NVE usually has a large amount of 3D content to download. Some platforms, such as Second Life, propose using the 3D streaming technique to reduce the installation cost. Through 3D streaming, a user only needs to download and install the 3D content which appears in its area of interest (AOI). But the maximum number of concurrent users is still restricted by the limited bandwidth of the server if all content is downloaded from the server. Due to the scalability of the peer-to-peer (P2P) architecture, some systems, such as FLoD, propose using the architecture to improve the scalability of 3D streaming. But, the peer selection policy of FLoD still has some flaws; for example, a user in FLoD sends requests to only AOI neighbors for downloading 3D content without considering neighbor's bandwidth capacity. In this paper, we present a bandwidth aware peer selection (BAPS) policy for P2P 3D streaming, which can increase the bandwidth utilization, avoid the request congestion and contention, and offer users better fill ratios even though the numbers of objects and users are increasing.
