- 學位論文
WDM PON的動態頻寬分配機制之研究
A Research of the Dynamic Bandwidth Allocation Mechanism in WDM PON
摘要
在傳統的EPON中，由於其樹狀架構的關係，下載是以廣播(broadcasting)的方式，分配到每個ONU(Optical Network Unit)中。但在上傳時，由於會經由分歧器(Splitter)匯流到OLT(Optical Line Terminal)中，因此必須經由TDM(Time Division Multiplexing)的技術來上傳以避免碰撞的情況發生。但隨著技術的演進，WDM(Wavelength Division Multiplexing)的技術也可以使用在EPON中，簡稱WDM EPON。在此架構中，網路節點的通訊可由波長來做區分，且上傳方式由TDM與WDM混合的技術來達成。本篇論文分兩大方向來探討WDM PON，首先是波長分配(Wavelength Assignment)的問題，藉由網路流量來決定波長的分配方式，以達到最大的頻寬利用率。再來是優先權排程的問題，根據封包優先權順序來決定較佳的排程需求，讓高優先權封包的平均延遲時間確保低於低優先權封包的平均延遲時間，以滿足不同服務等級的需求。
並列摘要
In EPON, a tree topology is the most popular architecture with a central office located at the root and the subscribers connected to the tree as the leaf nodes. The downstream traffic is transmitted from the OLT to the individual ONU by using the broadcasting mechanism. In the upstream direction, the traffic is transmitted via the combiner and then converged onto the OLT. The TDM (Time Division Multiplexing) access technology is often applied to avoid collision in the upstream direction. As the traffic demands grow, WDM technology may play a significant role in overcoming the bandwidth shortage of just employing TDM mechanism alone. In this thesis, we consider both the bandwidth allocation and scheduling issues occurred in the WDM/TDM PON architecture. We first propose a wavelength assignment mechanism to arbitrate the wavelength usage of each ONU. In this way, the bandwidth utilization level can be efficiently achieved. The scheduling algorithm is then proposed such that the high priority traffic enjoys better quality of service than the low priority traffic.