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An Overview of PON Technologies

An Overview of PON Technologies. Pu -Chen Mao 3/21/2011. Outline. Background G-PON EPON NG-PON Future Studies References. Background (1/3). Access technologies Wireless 802.11, 802.16, etc. Low cost deployment

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An Overview of PON Technologies

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  1. An Overview of PON Technologies Pu-Chen Mao 3/21/2011

  2. Outline • Background • G-PON • EPON • NG-PON • Future Studies • References

  3. Background (1/3) • Access technologies • Wireless • 802.11, 802.16, etc. • Low cost deployment • Insufficient capacity for high bandwidth (revenue) applications such as IPTV • Copper • DSL • Point-to-point architecture allows unshared bandwidth • Limited distance due to noise • Cost of deployment only slightly less than an all-fiber approach

  4. Background (2/3) • Fiber • Low noise • Long reach • Topology • Tree • More cost effective • Point-to-point • Dedicated fiber plant from CO to subscriber • Ring • Fault tolerant

  5. Background (3/3) • Shared fiber architectures • Active Ethernet • Signals split by electronic equipment • PON • Signals replicated passively by splitter • Higher reliability due to no electronic equipment in outside plant • Signal format transparency • Can be more flexibly upgraded • Requires no electric power source

  6. G-PON • Specified by ITU-T G.984 series • Began in FSAN consortium in 2001

  7. G-PON Layers

  8. G-PON Transmission Convergence (GTC) Layer • Performs adaptation to the physical-medium-dependent (PMD) layer • Adaption methods • ATM • G-PON encapsulation method (GEM) • Preferred method • Ethernet adaptation • TDM adaptation • MAC function • Coordinates interleaving upstream traffic from individual ONUs

  9. GTC Layer • Control functions • Defines protocols & procedures for registering & performance monitoring of ONUs • Configuration of transport features • FEC • Encryption • Bandwidth allocation

  10. GTC Layer • GTC framing sub-layer • Downstream frame format • 125 us • 8 KHz signal for ONU reference clock • Physical Control Block (PCBd) • Framing, PHY operations, PLOAM fields • Message-based protocol for PMD & GTC mgmt. • Bandwidth map field for upstream transmission allocation • Payload follows PCBd

  11. GTC Layer • GTC framing sub-layer • Upstream frame format • Same as downstream 125 us • Physical layer overhead (PLOu) field • Preamble & delimiter configurable by OLT • Dynamic bandwidth report (DBRu) field for DBA traffic queuing reports from ONUs • PLOAM identical to downstream frame • DBRu & PLOAM are optional, requested by OLT

  12. GTC Layer • GTC TC adaption sub-layer • GEM • Protocol independent connection-oriented encapsulation for variable-sized packets • Virtual connection unit: GEM port • 5 byte header • Port ID & frame size • Frames may be fragmented • G.984 specifies transport of Ethernet & TDM over GEM

  13. GTC Layer • T-cont • Each T-cont aggregates one type of traffic out of 5 classes • Composed of multiple virtual port connections

  14. Upstream Bandwidth Allocation • Static method • Dynamic Method (DBA) • Status reporting DBA • ONU reports via DBRu field • Non-status reporting DBA • T-cont utilization monitored by OLT

  15. GTC Control Plane • Operated via PLOAM message protocol and embedded OAM • Management functions • PMD layer management • Upstream config, PHY monitoring, generate stats • GTC layer management • Framing, requesting PLOAM / DBRu, etc. • ONU activation • Activate ONU, ranging protocol, optical power tuning • Encryption management • AES, key exchange procedure

  16. G-PON Management • G.984.4 specifies the ONT management and control interface (OMCI) • OMCI • ONU management information base • ONT mgmt. control channel protocol (OMCC) • Conveys MIB info between ONU & OLT • Models equipment configuration, port types, and service types • QoS

  17. EPON • Ethernet sub-layers

  18. EPON • 1 Gb/s bidirectional links • 1490 nm downstream • 1310 nm upstream • 1550 nm reserved for extensions • 802.3ah EPON • Minimum 1:16 split ratio • Up to 1:64 commercially available • 802.3 similarities • Standard inter frame gap (IPG) • Uses same MAC • Multi-Point Control Protocol (MPCP) for P2MP connectivity • Uses standard Ethernet packets in MAC sub-layer • Modified preamble

  19. EPON Downstream

  20. EPON Upstream

  21. EPON ONU Registration • MPCP handshake • OLT broadcasts GATE message • Unregistered ONUs respond with REPORT and REGISTER_REQ • OLT approves and replies with REGISTER • ONU responds with REGISTER_ACK

  22. EPON Operation • OLT controls ONU transmission windows with GATE messages • ONU responds queue status with REPORT • OLT calculates transmission window length using DBA • Synchronized to PON clock with 16 ns resolution counter in MPCP messages • OLT and ONU exchange timestamps to measure RTT for upstream scheduling

  23. EPON Frame • Downstream preamble • Logical link ID field specifies the destination ONU • ONU filters frames by LLID • ONU receives unique LLID assigned by OLT • Special value of LLID reserved for broadcast • Upstream preamble • LLID marks the source ONU • Ensure preamble field integrity by CRC • One ONU may have multiple LLIDs (virtual ONU) • FEC • Based on RS(255,239) • Frames encoded separately, parity bytes appended to end • Encryption • AES-based

  24. EPON Management • Link layer management • OLT remotely manages attached ONUs • Remote link monitoring • OAM • Established after discovery process • Maintained by periodic messages • Remote failures conveyed in flags of OAM msgs. • OAM using SNMP

  25. NG-PON • Next-generation PON technologies to extend current bandwidth to 10 Gb/s • XG-PON by ITU-T • 10GE-PON by IEEE 802.3av

  26. NG-PON Direction

  27. 10 Gb/s PON

  28. 10 Gb/sPONs • Similarities of XG-PON & 10GE-PON • L-band downstream 1575 – 1580 nm • O-minus band upstream 1260 – 1280 • Mandatory FEC • RS(255, 223) • Video overlay 1550 – 1560 nm

  29. 10 Gb/sPONs • Uniqueness • 10GE-PON • Conflict in EPON 1260 – 1360 nm and 1260 – 1280 nm band used • Share overlapping spectrum using TDMA • XG-PON • 32-bit word aligned framing • XGEM extension • PLOAM, DBRu, bandwidth allocation, ranging functions as clients to XGEM system, with XGEM becoming the main protocol

  30. Future Studies • System architecture, specifications of XG-PON and 10GE-PON • Long-reach PON • DBA comparison for EPON, GPON, and next-generation PON

  31. References [1] Effenberger, F., et al., “An introduction to PON technologies,” IEEE Communications Magazine, Vol. 45, Issue: 3, 2007 [2] Effenberger, F., et al., “Standardization trends and prospective views on the next generation of broadband optical access systems,” IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 28, NO. 6, AUGUST 2010 [3] Paul E. Green Jr., “Fiber to The Home: The New Empowerment”, Wiley, 2006

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