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系統識別號 U0026-1708201810110900
論文名稱(中文) 距離可調適型半透明彈性光網路中探討基於長度閥值之虛擬化彈性再生器放置及配置議題
論文名稱(英文) Length-Threshold-based Placement and Assignment of Virtualized Elastic Regenerator in Distance-Adaptive Translucent Elastic Optical Networks
校院名稱 成功大學
系所名稱(中) 資訊工程學系
系所名稱(英) Institute of Computer Science and Information Engineering
學年度 106
學期 2
出版年 107
研究生(中文) 高豪辰
研究生(英文) Hao-Chen Kao
電子信箱 kaochen930@gmail.com
學號 P76051276
學位類別 碩士
語文別 英文
論文頁數 67頁
口試委員 指導教授-許靜芳
口試委員-張燕光
口試委員-林輝堂
口試委員-廖冠雄
中文關鍵字 彈性光網路  距離可調適型  半透明光網路  虛擬化彈性再生器  繞徑  調變格式選擇與頻譜配置問題  再生器放置與配置 
英文關鍵字 Elastic optical networks(EONs)  Distance Adaptive  Translucent Optical Networks  Virtualized Elastic Regenerator(VER)  Routing, Modulation format and spectrum assignment(RMSA)  VER Placement and Assignment 
學科別分類
中文摘要 隨著科技發展的日益進步,使用者對於網路傳輸量的需求漸漸提高,如何能夠有效率的提供傳輸便是在網路發展上相當重要的議題,而光纖網路正是在這其中扮演著重要的角色。在傳統的光纖網路-波長分波多工網路中,是以波長作為傳輸的基本單位。因此,這種剛性粒度的資源分配環境容易使得頻譜的使用效率降低,並造成資源配置的浪費。隨著技術發展的進步,利用光正交頻分多工的技術,使得載波彼此之間可以有部分的重疊,因而發展出彈性光網路。在彈性光網路的環境中,資源分配的單位變為粒度較小的頻率槽,傳輸需求即可彈性地依照其需求量配置對應數量的頻率槽,大幅改善頻譜的利用率,能更有效地使用頻譜資源。
而在距離可調適型的彈性光網路架構下,傳輸的繞徑、調變格式的選擇以及頻譜配置是最主要的議題。適當地決定傳輸繞徑所走的路線,並盡可能選用較高階的調變格式,可使得頻譜資源能夠較節省地使用,因而讓其他傳輸需求更有機會被服務。而也因為傳輸上會有傳輸距離的限制,若需求欲傳輸的距離較遠,可能會因為超過網路環境能提供的最遠傳輸距離而導致傳輸失敗。在彈性光網路中,可使用彈性再生器來使傳輸被再生。再生後的傳輸需求得以傳輸到更遠的目的點,也就較不容易因距離而造成傳輸上的失敗;另外,彈性再生器還能帶來重新選擇調變格式以及打破不同鏈路間的頻譜連續性限制,因而更能有效地改善頻譜資源的使用情況。
而再生器資源是有限的,如何在網路拓樸上擺放再生器便是一項重要的問題,這種再生器資源有限的網路環境即屬於半透明型光網路。在討論半透明型彈性光網路的相關研究中,除了再生器的放置外,再生器的使用策略是另一項需要考慮的問題。先前的研究在再生器的放置與使用上較無搭配調變格式的傳輸距離限制一同考量,再生器的擺放位置相對較差,且在再生器的使用策略上也無法搭配擺放策略來相互配合。因此,雖然使用了再生器,頻譜利用效率的改善幅度卻不高。而本篇論文即針對這種情況提出了兩種再生器的擺放策略以及一種再生器的使用策略。我們傾向把再生器放置在傳輸距離較長的區段上,使得該區段能以較少的頻率槽進行配置,藉此來提升整體的頻譜利用效率,讓更多的傳輸需求得以成功傳輸。在模擬結果方面,我們所提出的TLTP再生器擺放策略在頻寬阻塞率表現上獲得相當大的改善;另外我們也發現再生器的使用策略相對於擺放策略較不重要。若再生器擺放的位置恰當,就算使用策略非最有效益,但會因為技巧性地擺放而使得其他的再生器使用策略在頻寬阻塞律上也有不錯的成效。
英文摘要 With growing development of technology, requirements on network traffic have become insatiable. Providing an efficient network environment is an important issue in the development of Internet, and optical networks also play an important role in it. In Wavelength-Division Multiplexing (WDM) optical networks, a wavelength is a basic transmission unit. However, this kind of rigid granular resource allocation architecture is liable to worsen the spectrum efficiency. With improving techniques, Optical Orthogonal Frequency-Division Multiplexing (O-OFDM) has make the wavelength carriers possible to partially overlap with each other. Thus, it has promoted the innovation of Elastic Optical Networks (EON). In EON, the allocation unit is transferred to Frequency Slot (FS) with smaller granularity, transmission demands can flexibly assign the corresponding number of FSs according to the required bandwidth. Therefore, we can not only raise the spectrum efficiency but allocate the spectrum resources more efficiently. In distance adaptive EON, routing, modulation format, and spectrum assignment (RMSA) is the main issue to be solved. Appropriately choosing a routing path, and trying to select a higher-level modulation format, the spectrum resources can be assigned efficiently. Thus, other requests can have more opportunities to be served. Since there is maximum transmission distance (MTD) constraints, if the transmission distance of requests is too long, the transport may be failed caused by the optical reach (OR). Besides, virtualized elastic regenerators (VERs) can be assigned to regenerate transmission, and the one be regenerated can be transmitted to a farther destination. Therefore, the requests are not such easy to be blocked. In addition, VERs can re-modulate and convert spectrum, which improve the spectrum efficiency. However, due to cost control, placing VERs strategically on topology has become an important issue. This kind of limited VERs network structure is the so called translucent optical networks.
In related researches of translucent EONs, VERs assignment strategies is another considerable issue. In previous studies, they designed VER placement and assignment strategies without considering transmission distances and modulation formats. The VER placed nodes were worse, and it did not consider about assignment strategies with placements, either. Thus, though VERs are used, spectrum efficiency is not much improved. We proposed two VER placement and one assignment strategies to solve this problem. Our strategies tend to place VERs on the nodes in longer transmission segments. It enables the segments to consume fewer FSs, improves the overall spectrum efficiency, and allows more requests to be successfully served. In simulation results, our proposed TLTP gets a considerable improvement in the performance of bandwidth blocking probability (BBP). In addition, we also found that VER assignment are less important than placement. Even if the assignment is not the most effective one, if VERs are placed to right positions, the overall BBP will also improve.
論文目次 摘要 III
Abstract V
致謝 VII
Content VIII
List of Figures X
List of Tables XII
Chapter 1 Introduction 1
Chapter 2 Background 4
2.1 Wavelength-Division Multiplexing (WDM) 4
2.2 Elastic Optical Networks (EONs) 5
2.2.1 Orthogonal Frequency-Division Multiplexing (OFDM) 5
2.2.2 Modulation Format 6
2.2.3 Routing, Modulation Format and Spectrum Assignment (RMSA) 6
2.3 Translucent Optical Network 9
2.3.1 Virtualized Elastic Regenerator (VER) 10
2.3.2 VER Placement Problem 10
2.3.3 VER Assignment Problem 11
Chapter 3 Related Work 15
3.1 VER Placement Strategies 15
3.1.1 Uniform Placement (UP) 15
3.1.2 Nodal Degree based Placement 16
3.1.3 Distance Adaptive Regenerator Localization Algorithm (DA) 17
3.1.4 Traverse Weighted Placement (TW) 18
3.2 VER Assignment Strategies 20
3.2.1 First Narrowest Spectrum (FNS) 21
3.2.2 First Longest Reach (FLR) 22
3.2.3 Flow Chart 23
Chapter 4 Proposed Scheme 31
4.1 Motivation 31
4.2 Proposed VER Strategies: LTP, TLTP 32
4.2.1 Length-Threshold-based Placement (LTP) 32
4.2.2 Traversed Length-Threshold-based Placement (TLTP) 33
4.3 Proposed VER Assignment: Length-Threshold-based Assignment (LTA) 35
4.3.1 Motivation and Introduction 35
4.3.2 LTA Algorithm 36
4.3.3 Flow Chart of LTA 40
4.4 Complexity Analysis 42
Chapter 5 Performance Evaluation 44
5.1 Parameter Settings 44
5.2 Performance Metrics 46
5.3 Simulation Results 46
5.3.1 Comparison among VER placement strategies 47
5.3.2 Comparison among VER assignment strategies 52
5.3.3 Impact of number of VER node candidates 56
5.3.4 Comprehensive Comparison 59
Chapter 6 Conclusion 63
References 64
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