下一世代OFDM-based全光封包交換都會網路之技術與實現---子計畫一：全光WDM都會網路之OFDMA/WDM媒介存取控制與頻寬分配系統

Abstract

隨著高容量寬頻固定式擷取網路與無線行動式擷取網路之出現，以及網際網路高頻寬需求與支援語音、視訊、數據、行動性之quad-play服務需求日漸成長，未來趨勢將朝向全光網路科技，同時光纖傳輸無線電頻訊號(radio over fiber)技術已經引起廣大的興致。為了執行下世代無線通訊系統，正交分頻多工系統(OFDM)在現有主要多工技術上，被認為是最佳技術。現在除了促進全光分波多工技術(WDM)之發展外，在下一世代全光網路Layer-1設計與實現，混合型OFDM/WDM亦成為經得起考驗之技術。 就網路Layer-2/3技術而言，當全光長途網路採用相對而言簡單與固定WDM通道使用之線路交換(OCS)技術，全光都會網路則顯出訊務特性較為動態與突波，以致靜態WDM通道運用方式不符需求。因此，全光都會網路需要所謂的全光封包交換(OPS)技術，包含高效能媒介存取控制(MAC)機制，以確保有效率與細緻的頻寬分配，並提供各類型服務品質保證(QoS)來支援Quad-play。OPS面臨的挑戰可以藉由幾種方法實現。第一種就是僅僅提供WDM技術進行封包交換，此方法卻非常耗費成本(譬如昂貴之可調式雷射元件)，並且缺乏彈性進行動態頻寬分配。為了抵消此效應，兩種具前瞻性之OPS解決方案為混合式TDMA/WDM與混合式OFDMA/WDM。然而，TDMA系統需要複雜的burst-mode還原技術(譬如高速burst mode receiver)，更甚於此的是下世代無線網路系統已不採行TDMA技術。因此OFDMA/WDM成為下世代全光網路之關鍵全光封包交換技術。 在這三年期計畫中，我們的主要目標是對全光都會WDM環狀網路之OFDMA/WDM媒介存取控制系統進行設計、分析，並建構雛形研究平台，目標在支援各類型有線與無線應用，以及應用程式所 98年度 99年度 Study of Optical OFDM/WDM Metro Ring Network Technology 年度 計畫項目 97年度 Design of Optical OFDM/WDM Metro Ring Network and Node Architectures Design of Basic OFDMA/WDM MAC scheme at each Node Detailed Design of Optical OFDM/WDM System at each Node Throughput/Delay Performance Analysis of MAC scheme 3. Network Prototyping 1. Optical OFDM/WDM Metro Ring Networking Technology 2. Quad-Play OFDMA/WDM MAC Technology Study of Optical OFDMA/WDM MAC schemes Throughput/Delay Performance Analysis of Quad-Play MAC Design of Quad-Play MAC at each Node Optical OFDM/WDM Metro Ring Network Testbed 圖11-1、子計畫一時程表 需之動態頻寬分配技術。這三年中將進行的工作整理於圖11-1的時程表中。基本上，在計畫的第一年中，我們將進行深入的文獻研讀及初步的系統架構設計。工作包含研讀與設計全光OFDM/WDM都會環狀網路與節點架構，以及在此網路上所操作的基本OFDMA/WDM媒介存取控制機制；第二年我們將完成全光OFDMA/WDM媒介存取控制系統之詳細設計與分析；在第三年將設計分析OFDMA/WDM媒介存取控制系統，加強服務品質保證能力，特別在支援Quad-play服務。與其他三子計畫之合作，透過FPGA與IC晶片實現之雛形實驗平台建置，會在第一年期中過後開始執行，預計在計畫結束前完成。

With the emergence of both high capacity broadband fixed and mobile wireless access networks, and the ever-growing demand for high Internet bandwidth and support of quad-play (i.e., video, voice, data, and wireless), the future trend toward optical networking and optical transport of radio frequency signals, referred to radio over fiber, has attracted great interest. For implementing the next-generation wireless communication systems, OFDM systems have been considered the most promising technology among prevailing candidates. Such fact, in addition to recent advances in optical Wavelength Division Multiplexing (WDM) technologies, makes hybrid OFDM/WDM a future-proof underlying Layer-1 technology for the design and implementation of next-generation optical networks. Regarding Layer-2/3 networking techniques, while optical long-haul networks basically follow the Optical Circuit Switching (OCS) paradigm by making relatively simple and static WDM channel utilization, optical metro networks exhibit traffic that is more dynamic and bursty in nature, rendering static WDM channel utilization completely infeasible. Ultimately, optical metro networks require the so-called Optical Packet Switching (OPS) technique including a high-performance Medium Access Control (MAC) mechanism, to ensure efficient and fine-grained bandwidth allocation and various Quality-of-Service (QoS) guarantees for supporting quad-play. Such OPS challenge can be realized via several approaches. The first option is to provide optical packet switching solely on WDM basis. The approach has been found costly (e.g., tunable lasers) to achieve high flexibility for dynamic bandwidth allocation. To compensate for this, two other promising OPS solutions are hybrid TDMA/WDM and hybrid OFDMA/WDM approaches. However, 98年度 99年度 Study of Optical OFDM/WDM Metro Ring Network Technology 年度 計畫項目 97年度 Design of Optical OFDM/WDM Metro Ring Network and Node Architectures Design of Basic OFDMA/WDM MAC scheme at each Node Detailed Design of Optical OFDM/WDM System at each Node Throughput/Delay Performance Analysis of MAC scheme 3. Network Prototyping 1. Optical OFDM/WDM Metro Ring Networking Technology 2. Quad-Play OFDMA/WDM MAC Technology Study of Optical OFDMA/WDM MAC schemes Throughput/Delay Performance Analysis of Quad-Play MAC Design of Quad-Play MAC at each Node Optical OFDM/WDM Metro Ring Network Testbed 圖11-2、Roadmap of sub-project 1 TDMA systems require complex burst-mode signal recovering technology (e.g., high-speed burst mode receiver). In addition, TDMA systems are not employed in next generation wireless systems. As a result, OFDMA/WDM becomes the key OPS technology for the next-generation optical networks. In this three-year project, our main objectives are the design, analyses, and prototyping of such OFDMA/WDM MAC system for optical metro WDM ring networks, capable of transparently supporting various wire/wireless applications and enable dynamic bandwidth allocation among these applications. In summary, the tasks to be accomplished in these three years are depicted in the roadmap. In principle, we give the decent study and preliminary design in the first year. The work includes the study and design of optical OFDM/WDM metro ring network and node architectures, and the basic OFDMA/WDM MAC scheme governing the operation of the optical OFDM/WDM network. In the second year, we carry out the detailed design and analyses of the OFDMA/WDM MAC system. Finally, we design and analyze the OFDMA/WDM MAC system augmented with QoS, particularly to support Quad-play in the last year. The network prototyping via FPGA and IC chips through the collaboration with three other subprojects will be carried out from the last quarter of the first year till the end of the project.