Flexible Spectrum Resource Allocation in Elastic Optical Networks

• Other Authors: Fan, Zheyu (author.)
• Format: Others
• Language: English; Chinese
• Published: 2016
• Online Access: http://repository.lib.cuhk.edu.hk/en/item/cuhk-1292195

現今，像高清視頻流和數據中心之間的傳輸這樣需要很大帶寬的應用引發了對傳輸容量的極大需求。光纖通信提供了一個有效並且可的方法來實現高速的傳輸，而且光纖通信在當今的電信網絡當中扮演了不可替代的角色。光網絡可以有效地支持單播傳輸和組播傳輸，並且在近十年來吸引了廣泛的研究。 === 在光網絡中，波分複用技術利用了光頻率的緯度并且極大地提升了網絡吞吐量。然而在以數據爲中心的網絡中，各種各樣的應用產生了形形色色需求不同帶寬資源（例如從10 GHz 至 400 GHz）的業務請求類型。傳統的波分複用網絡給每個請求分配一個50 GHz 固定帶寬的波长信道，這樣的分配方法并不能有效的利用頻譜資源。近來，彈性光網絡被提出並且被當作有前景的備選。彈性光網絡採用了更加合適的柵格粒度（例如12.5 GHz 和6.25 GHz），並且分配適當數量的頻率隙給每個連接來達到更高的頻譜效率。因為每個連接可能需求不同的帶寬，所以在彈性光網絡中，每次會同時分配多個頻譜連續的频率隙給每個連接。因此在彈性光網絡中，頻譜資源的分配成為一個更加複雜的問題，並且需要更加複雜精妙的算法來安置業務请求。這個問題也被稱為路由和頻譜分配問題。在本論文中，我們研究了在彈性光網絡中對於單播和組播連接的路由和頻譜分配問題。 === 在第一個話題中，我們研究了在彈性光網絡中單播連接的路由和頻譜分配問題。我們提出了一個基於多路徑路由和業務量疏導的機制。多路徑路由機制將一個連接拆分為多個亞連接，因而每個亞連接可以佔用更少的帶寬。雖然多路徑路由機制可以通過利用較小大小的频谱资源來靈活地安置各個連接，但是頻譜虛耗卻會降低頻譜的利用效率，尤其是當原本的連接被過度拆分的時候。在引入業務量疏導之後，多路徑路由機制可以更有效地利用頻譜資源並且極大的提升網絡吞吐量。 === 在第二個話題中，我們研究了在彈性光網絡中全光組播連接的路由和頻譜分配問題。我們提出了一個基於多樹的機制來靈活地安置組播請求。由於頻譜連續性和頻譜鄰接性的限制，用單一的光樹來安置每個組播請求會比較困難並且效率不高。我們提出的多樹機制減小了每一個生成樹的大小，而且可以利用不同的調製格式來提升頻譜效率。這樣，頻譜使用量和阻塞率都會被減少。 === 在第三個話題中，我們研究了在彈性光網絡中全光組播連接的專用保護問題。我們提出了一個基於通路的專用保護機制。我們還評估了對于不同大小的組播請求，彈性光網絡的靈活柵格較波分複用網絡的固定柵格所帶來的提升。相比于基於兩步的算法，使用基於頻譜窗口平面的算法顯著地降低了頻譜使用量。 === Nowadays, the bandwidth-intensive applications, such as high-definition video streaming and inter-datacenter connections, trigger drastic demand in transmission capacity. Fiber-optic communication provides an efficient and reliable way to realize high-speed transmission and plays an indispensable role in today’s telecommunication networks. Optical networks can support unicast and multicast transmissions and have aroused extensive research interests over the last decade. === In optical networks, wavelength division multiplexing (WDM) technology utilizes the dimension of optical frequency and significantly improves the network throughput. However, in nowadays data-centric networks, various applications generate heterogeneous traffic types that require different sizes of bandwidth (e.g. from 10 GHz to 400 GHz). Traditional WDM networks assign a fixed 50-GHz wavelength channel to each connection, and may not efficiently utilize the spectrum resources. Recently, elastic optical networks (EONs) have been introduced and treated as promising alternatives. EONs adopt finer granularity (e.g. 12.5 GHz and 6.25 GHz) and allocate an appropriate number of frequency slots (FSs) to each connection in order to achieve higher spectrum efficiency. As each connection may require a variable bandwidth, multiple consecutive FSs can be allocated in EONs. Therefore, the problem of spectrum resource allocation in EONs becomes more complicated and requires sophisticated algorithms to accommodate the traffic. The problem is also known as the routing and spectrum allocation (RSA) problem. In this thesis, we investigate the RSA problem for unicast and multicast connections in EONs. === In the first topic, we investigate the RSA problem for unicast connections in EONs. We propose a scheme using multipath routing with traffic grooming. The multipath routing scheme can split a connection into multiple sub-connections, each consuming less bandwidth. In this way, the multipath routing scheme can flexibly accommodate connections by utilizing the small-sized spectrum resources, but the spectrum overhead may reduce the efficiency of spectrum utilization, especially when the original connection is over-split. With traffic grooming, the multipath routing scheme can efficiently utilize the spectrum resources and significantly improve the network throughput. === In the second topic, the all-optical multicasting RSA problem is studied for EONs. We propose a subtree scheme to serve multicast requests. Due to the spectrum continuity and spectrum contiguity constraints, serving each multicast session through a single light-tree can be difficult and inefficient. The proposed subtree scheme reduces the spanning size of each routing tree and utilizes diverse modulation formats in order to improve the spectrum efficiency. In this way, both the spectrum usage and the blocking probability can be reduced by using subtree scheme. === In the third topic, we investigate the dedicated protection problem for all-optical multicasting in EONs. We propose a path-based dedicated protection scheme and evaluate the improvement of the flexible grid in EONs over the fixed grid WDM networks for different sizes of multicast sessions. By using spectrum-window-planebased algorithms, the spectrum usage is significantly reduced as compared to that of two-step-based algorithms. === Fan, Zheyu. === Thesis Ph.D. Chinese University of Hong Kong 2016. === Includes bibliographical references (leaves ). === Abstracts also in Chinese. === Title from PDF title page (viewed on …). === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only.