WDM 網路資源有效分配之研究

Study of Effective Resource Allocation Schemes in WDM Networks

彭亦暄(I-Hsuan Peng)

指導教授 ： 陳彥文

國立中央大學/資訊電機學院/通訊工程學系/博士(2008年)

摘要

本論文主要探討WDM 網路中的以下幾個議題:多播訊務的光波長分配方式、保證備援光路徑切換時間的路由機制和階層式網路的建構方式。 在多播訊務的光波長分配方式中，我們假設WDM 網路中有部分節點具有波長轉換之能力(Sparse Wavelength Conversion Network, SWCN)，並在此網路架構中，提出一個有系統的波長分配機制，依據此機制可以將一個多播樹狀網路分成具有相同波長的數個子樹狀網路，每個子樹狀網路只分配一個波長，因此可以有效節省波長之使用。除此之外，我們將SCG 方式延伸擴展至可適用於SWCN 的網路環境中。從模擬結果可看出所提出之方式有較好的效能，此外，也觀察到隨著波長轉換節點的數量增加，並非效能也一定比例之增長，當一個網路的波長轉換節點數達35%以上時，效能的增長會達到飽和狀態。 為了減少因為光鏈路失效而被影響的傳輸訊務，且希望在指定時間內恢復傳輸品質，因此在路由路徑安排時必須考慮備用路徑所需切換的時間，在本論文中，我們研究並提出一個保證備用路徑切換時間的路由機制，此方法是基於短跳躍共享機制概念衍生而來，其提供有效程序決定每個主要路徑能滿足切換時間需求之備用路徑，此外，也同時考量備用路徑所需耗費之網路資源。從模擬結果可看出所提出之方式不但能保證備用路徑所需切換的時間，且備用路徑所耗費之網路資源能達到與共享路徑(shared path)機制相仿之效能。 在階層式網路中，我們提出一個有系統的建構方式，將網路分成數個邏輯路由區域(logical routing area)，在劃分區域時需考量每個區域的大小和節點與鄰節點之連接數等因素，使得建構出的階層式網路之整體資源能有效被利用且降低路由和波長分配之複雜度。從模擬結果可看出所提出之建構方式優於單純以平均分配節點數之劃分方式。 有線和無線網路的整合被視為下一代網路推動的重要方向和趨勢，在本論文中，我們也研究了一些WiMax 和EPON 可能的整合架構，尋找有潛力的研究議題以作為未來研究的基礎。

關鍵字

WiMax ； 被動光纖網路 ； WDM網路 ； 階層式網路 ； 切換時間 ； 保護和復原 ； 光波長分配 ； 波長轉換 ； 多播

並列摘要

In this dissertation, we focus on the following WDM network related issues. The first is the wavelength assignment algorithm of multicast traffic; the second is the routing scheme of lightpath with guaranteed protection switching time; and the third is the construction of hierarchical WDM topology.
In the first issue, we assume the WDM network to be with sparse wavelength conversion nodes (SWCN) and a systematic approach for the assignment of wavelength in networks is proposed. Based on the MWA-SWC scheme, a multicast tree is divided into groups based on common wavelengths so that the wavelength can be assigned effectively. The simulation results show that the proposed scheme demonstrates much better performance than that of the SCG scheme, in which we extended the original to be applicable for SWCN network. We also found that the performance is not always improved proportionally to the increment of the wavelength conversion nodes. The improvement reaches saturation when the number of conversion nodes is above 35% of the total number of nodes.
In order to minimize the influence on transmission quality caused by the failure of link and to provide a definite time for the recovery from the failure in optical network, the protection switching time (PST) should be taken into consideration during path arrangement. The PST-guaranteed scheme, which is based on the concept of short leap shared protection (SLSP), for the arrangement of data paths in WDM network is proposed and studied. The proposed scheme provides an efficient procedure to determine a just-enough PST-guaranteed backup paths for a working path. In addition, the network cost is also considered in a heuristic manner and the simulation results illustrate that the required cost of the selected path in the proposed scheme is competitive with which of the shared path scheme.
In the third issue, a systematic approach is proposed to construct the hierarchical topology in a heuristic manner so that the network resource can be effectively utilized. The proposed scheme groups nodes into logical routing area (LRA) by considering the appropriate group size and the degree of each WDM node. Simulation results demonstrate that the performance of the proposed scheme is superior to that of the evenly grouped scheme.
The integration of wired backbone and wireless access network is recognized to be the trend of next generation network. In this dissertation, we also survey the possible integration architectures of WiMax and EPON networks to seek for potential research topics as our future works.

並列關鍵字

WDM network ； wavelength assignment ； EPON ； WiMax ； multicast ； wavelength conversion ； hierarchical network ； protection switching time ； protection and restoration

參考文獻

[1] B. Mukherjee, “WDM optical networks: progress and challenges,” IEEE Journal on Selected Areas in Communications, vol. 18, no. 10, Oct. 2000, pp. 1810-1824.

[2] J. Wang and B. Chen, “Dynamic Wavelength Assignment for Multicast in All-Optical WDM Networks to Maximize the Network Capacity,” IEEE Journal on Selected Areas in Communications, vol. 21, no. 8, Oct. 2003, pp. 1274-1284.

[3] SLA Management Handbook GB917 Jun. 2001.

[4] Changcheng Huang, Vishal Sharma, Ken Owens and Srinivas Makam, “Building Reliable MPLS Networks Using a Path Protection Mechanism”, IEEE Communications Magazine, March 2002, pp. 156-162.

[5] Pin-Han Ho and Hussien. T. Mouftah, “A Framework for Service-Guaranteed Shared Protection in WDM Mesh Networks”, IEEE Communications Magazine, Feb. 2002, pp. 97-103.