EPOC Upstream Mapping - Ed Boyd, Broadcom - IEEE 802.3bn EPoC San Antonio November 2012

Sep 14, 2026

Uploaded by Mabel

Baseline technical proposal mapping EPON’s one-dimensional GATE times to EPoC’s two-dimensional OFDMA upstream. Defines a fixed delay and fixed efficiency approach while avoiding PHY changes to the existing EPON MAC REPORT and GATE frames. Analyzes why direct TDMA mapping onto the RF PHY is inefficient for long PHY symbols, discusses two-dimensional scheduling complexity, and motivates a simpler solution aligned with Ethernet constraints. Covers symbol-block allocation in time and frequency and outlines alignment using downstream PLC and PHY-link feedback.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages13

Reading Time33 min

AccessFree to download

Overview

Disclaimer

True TDMA (Direct Mapping)

Two Dimensional Scheduling

Rotating Bursts from Time to Time & Freq

Upstream Symbol/Burst Alignment

PHY Link for Symbol Alignment

Time to Frequency Conversion

EPOC Upstream Mapping Ed Boyd, Broadcom IEEE 802 .3bn EPoC – San Antonio, November 2012 Overview • This presentation is a baseline proposal for mapping the EPON’s one dimensional GATE times to EPoC’s two dimensional OFDMA Upstream . • This presentation is a continuation of the subject from the EPoC study group presentations for technical feasibility. • This solution provides a fixed delay and fixed efficiency for the upstream . • This solution does not require the EPoC PHY to make modifications to the REPORT or GATE frames currently used by the EPON MAC. IEEE 802 .3bn EPoC – San Antonio, November 2012 2 Disclaimer • The drawings in this presentation show upstream bursts carried in fixed sized blocks with multiple symbols . – The burst blocks contain multiple data carrying symbols with 1 or more preamble symbols. – This is the most challenging scenario to describe and it makes a colorful picture. • The need for preamble symbols, the number of symbols ina burst block, and the size of the upstream symbols are not discussed in this presentation. • This methodology described can be used with single symbol blocks, multiple symbol blocks, or any number of preamble symbols (including 0) . This presentation does not attempt to advocate orjustify any particular PHYlayer parameters. 3 Symbols Of Preamble for Red CNU Burst Burst from Blue CNU IEEE 802 .3bn EPoC – San Antonio, November 2012 3 True TDMA (Direct Mapping) CLT OLT EPON Upstream MAC Layer Burst in TQs TIME Multiple Carrier PHY Burst (Time & Freq) Wasted BW C NU ON U FR EQ Why Can’t we directly map TDMA onto the RF PHY? • EPON MAC Layer bursts are mapped across ALL sub‐carriers. • Symbol is unit of granularity for PHY. • Short Symbols can have reasonable granularity and efficiency. (e.g. 1us @ 1Gbps = 125 Byte granularity) • Long Symbols will have poor granularity and efficiency. (e.g. 20us @ 1Gbps = 2500 Byte granularity) • Since Longer Symbols maybe required to achieve BER or provide narrower frequency control, a more complicated mapping will be considered. (The symbol size is a discussion for another presentation) Direct TDMA will be too wasteful for Long Symbol PHYs IEEE 802 .3bn EPoC – San Antonio, November 2012 4 Two Dimensional Scheduling Multiple Carrier PHY Bursts from 5 CNUs TIME • Multiple transmitters share a symbol but occupy different carriers. • Different delays and efficiencies can be achieved by allocating different shapes – High Latency, High Efficiency (Orange Burst) has burst overhead for 2 carriers but longer delay – Low Latency, Low Efficiency (Blue Burst) has burst overhead for many carriers but data burst completes much sooner. • Significant complexity is added to the PHY layer and MAC layer to support a fully flexible 2 dimensional scheduler. • Bursts will arrive with different delays; Filling complex shapes is more difficult for the transmitter; The receiver must handle a complex mapping; The receiver must buffer data from multiple streams as they come in. X The Ethernet MAC doesn’t support a multiple path PHY layer. (e.g. Orange starts before white and finishes after it) X Constant overhead and delay in the PHY layer is expected by higher layer protocols. X EPON OLT schedulers and EPON MACs are one‐dimensional We need a simpler solution that fits with Ethernet IEEE 802 .3bn EPoC – San Antonio, November 2012 5 Rotating Bursts from Time to Time & Freq EPON PHY Bursts (Time Only) BST 1 BST 2 BST 3 BST 4 OLT ON U CLT C NU TIME 8 Symbol Blocks EPOC PHY Bursts (Time & Freq) • TDMA EPON GATEs are mapped into time and frequency at symbol block boundaries. • Symbol blocks are divided in frequency by allocating a subset of sub‐ carriers to bursts sharing the symbol time. IEEE 802 .3bn EPoC – San Antonio, November 2012 6 Upstream Symbol/Burst Alignment 8Symbol Blocks CLT S p l i t t e r • CNUs must transmit i

FAQs

What problem does the EPOC upstream mapping proposal address?

It maps EPON one-dimensional GATE times to EPoC two-dimensional OFDMA upstream, providing fixed delay and fixed efficiency without changing the REPORT or GATE frames used by the EPON MAC.

Why isn’t direct TDMA mapping onto the RF PHY efficient for long symbols?

PHY symbol granularity makes long symbols yield poor time/frequency granularity and efficiency, which would waste bandwidth under direct TDMA mapping.

How are upstream symbol blocks aligned across CNUs and the CLT?

CNUs use the downstream PLC to obtain frequency lock and a configured upstream symbol-block size, delineate aligned symbol blocks, then the CLT measures phase offset from the broadcast PHY link response to correct CNU alignment so common boundaries are achieved.

Sep 14, 2026

Uploaded by Mabel