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Gigabit Passive Optical Network

Gigabit Passive Optical Network. 指導教授：吳和庭教授 Speaker ：蘇泳蒼 Date ： 2010/04/28. Outline. Introduction Media Access Control Downstream GTC frame structure Upstream GTC frame structure GEM frame structure Dynamic Bandwidth Allocation Conclusion Reference. Introduction.

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Gigabit Passive Optical Network

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  1. Gigabit Passive Optical Network 指導教授：吳和庭教授 Speaker：蘇泳蒼 Date：2010/04/28

  2. Outline Introduction Media Access Control Downstream GTC frame structure Upstream GTC frame structure GEM frame structure Dynamic Bandwidth Allocation Conclusion Reference

  3. Introduction • GPON的標準化是由Full Services AccessNetwork (FSAN) consortium來執行，並且在2003年通過了InternationalTelecommunication Union — TelecommunicationStandardization Sector (ITU-T)的標準。

  4. Introduction • GPON主要由Optical Line Terminal (OLT)、Optical Network Unit (ONU)、Optical Distribution Network (ODN)所組成。

  5. Introduction • GPON從central office到user的傳送距離可以到達20km。 • GPON可以支持到64個用戶。 • GPON有兩種傳送速度的組合： • 1.2 Gbit/s up, 2.4 Gbit/s down • 2.4 Gbit/s up, 2.4 Gbit/s down

  6. GPON transmission convergence layer • G-PON transmission convergence (GTC) layer is cmprised of two sublayers, the GTC framing sublayer and the GTC adaptation sublayer. • GTC framing sublayer主要是將資料組成GTC frame。 • GTC adaptation sublayer主要是將Service data units轉成GEM protocol data units。

  7. GPON transmission convergence layer

  8. GPON transmission convergence layer • Physical layer OAM Operations, Administrations and Maintenance(PLOAM)是管理PMD and GTC。 • The ONU management and control interface (OMCI) 是用來做GTC上層服務的管理。

  9. Media Access Control • OLT會用upstream bandwidth map (BWmap) field of the downstream physical control block (PCBd)送出pointers控制upstream traffic。 • pointers會指示每一個ONU可以上傳的開始時間和結束時間。 • 在任何時間內只有一個ONU可以access the medium。

  10. Media Access Control

  11. GTC frame structure

  12. Downstream GTC frame structure

  13. Downstream GTC frame structure • Physical synchronization (PSync) field：PSync field是一個固定的32-bit pattern，它的coding是0xB6AB31E0，用來實現同步機制。

  14. Downstream GTC frame structure • ONU一開始是在Hunt state，接著ONU會搜尋PSync pattern，一旦發現正確的PSync pattern，ONU就會進入Pre-sync state，假如一個不正確PSync field被發現，ONU就會回到Hunt state ，若是收到M1-1個連續的正確PSync pattern就進入Sync state，此時ONU會開始處理downstream GTC frame，假如ONU偵測到連續M2個的不正確PSync field，ONU就會回到Hunt state。M1建議值是2， M2是5。

  15. Downstream GTC frame structure

  16. Downstream GTC frame structure • Ident field：用來指示較大的framing structures。 • physical layer OAM (PLOAM)：用來傳送管理資訊。 • BIP：用來提供bit error rate estimation。

  17. Downstream GTC frame structure • PLend field分成下列3個部份 • length of the bandwidth map (Blen)：說明BWmap的長度。 • length of the ATM partition (Alen)：應該全部填0。 • CRC：對PLend field提供error detecting and correcting functions。

  18. Downstream GTC frame structure

  19. Downstream GTC frame structure • bandwidth map (BWmap)：BWmap是一長串的8-byte allocation structure， 每一個allocation structure都代表一個T-CONT的bandwidth allocation。

  20. Downstream GTC frame structure

  21. Downstream GTC frame structure • Allocation ID field：指出T-CONT。 • Flags field： • Bit 11 (MSB)：指示送出power levelling sequence (PLSu)。 • Bit 10：指示送出PLOAMu。 • Bit 9：指示利用FEC。 • Bit 8 and 7：指示送出DBRu (mode)。

  22. Downstream GTC frame structure • StartTime field：指示傳送的開始時間。 • StopTime field：指示傳送的停止時間。 • CRC field：對BWmap field提供error detecting and correcting functions。

  23. Upstream GTC frame structure

  24. Upstream GTC frame structure • preamble：用來做同步。 • delimiter：用來表示frame開始。 • BIP：用來提供bit error rate estimation。

  25. Upstream GTC frame structure • ONU-ID field：ONU-ID是在ranging process期間指派給ONU。 • indication field：提供real time ONU狀態回報給OLT。 • physical layer OAM (PLOAM)：用來傳送管理資訊。 • Dynamic bandwidth report upstream (DBRu)：有兩個欄位分別是DBA field和CRC field， DBA field包含T-CONT的traffic status， CRC field用來對DBRu做錯誤偵測。

  26. Mapping of GEM frames into GTC payload

  27. GEM frame structure

  28. GEM frame structure • PLI：PLI指出payload有多少大小， PLI field有12bits，因此fragment最多只有4095 bytes。 • Port-ID：Port-ID提供4096個traffic identifier，可以有一個以上的Port-ID在Alloc-ID/T-CONT傳送。 • PTI：PTI指出payload的content type。 • HEC：HEC對header提供error detecting and correcting functions。

  29. GEM frame structure

  30. GEM frame structure

  31. GEM frame structure • user data fragment必須是連續的，也就是user data fragment不能橫跨GTC frame boundary。

  32. GPON time division multiplexing architecture In the downstream direction，是用GEM Port-ID去識別GEM frames，ONU只會擷取屬於自己的GEM frames。 32

  33. GPON time division multiplexing architecture In the upstream direction，upstream bandwidth allocation是用allocation ID (Alloc-ID)去識別，ONU用GEM Port-ID去識別GEM frames是屬於哪種logical connections。 33

  34. Dynamic Bandwidth Allocation 不論ONU有多少Alloc-ID，GEM frames都在上面傳輸，且每個Alloc-ID都有logical buffer。 DBA會藉由推斷buffer的佔有資訊，創造出BWmap來和ONU溝通，以達成DBA。 34

  35. Dynamic Bandwidth Allocation 35

  36. Dynamic Bandwidth Allocation DBA方法可以被分為兩種： Status reporting (SR) DBA：所有的ONU會回報data占住多少buffer，OLT會利用回報回來的資訊來做計算。 Non status reporting (NSR) DBA： ONU不會回報資訊，OLT會藉由觀察idle GEM frame，來做bandwidth allocation。 36

  37. Transmission containers GPON會利用Alloc-ID對應到一個Traffic descriptor來做Quality of Service (QoS)。 Transmission containers (T-CONTs)依據其服務方針可以分為五種。 37

  38. Transmission containers T-CONT 1 guarantees fixed bandwidth allocation for time-sensitive applications. T-CONT 2 guarantees fixed bandwidth allocation for not time-sensitive applications. T-CONT 3 is mix of minimum guaranteed bandwidth plus additional nonguaranteed. T-CONT 4 is best effort, dynamically allocated without any guaranteed bandwidth. T-CONT 5 is mix of all service categories. 38

  39. Conclusion • GPON對於fiber to the home (FTTH)和fiber to the building/curb (FTTB/C)提供了一個選擇。GPON有很大頻寬和利用DBA來支持QoS，以滿足用戶的需求。

  40. Future works • 對於GPON的架構做更詳細的研究。 • 更加了解GPON的運作和管理。 • 對GPON的Dynamic Bandwidth Allocation作更深入的探討。

  41. Reference • ITU-T Recommendation G.984.1, 2008. • ITU-T Recommendation G.984.3, 2008. • Liu Yang, Zhang Guoping Li Qing, “An Improved Dynamic Bandwidth Allocation Algorithm for GPON”, Symposium on Photonics and Optoelectronics, 2009. • Effenberger, F. ,Clearly, D. ,Haran, O. ,Kramer, G. Ruo Ding Li ,Oron, M. ,Pfeiffer, T. , “An Introduction to PON Technologies”, IEEE Communications Magazine, vol.45,March 2007.

  42. Q&A Thanks for your attention

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