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A Novel Multiple Access Scheme for Ethernet Passive Optical Network
Professor : Ho-Ting WuSpeaker : Rui-Yi Jian
2004 – 08 – 11
Introduction
Propose a novel multiple access scheme to efficiently share the upstream channel in an EPON
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Propose
The multiple access scheme contains three parts that operate autonomously but are closely related to each other Parameter-based CAC Mechanism EDA BGP Scheme
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Terminology OLT
Optical Line Terminal ONU
Optical Network Unit SLA
Service Level Agreement RTT
Round-Trip Time BG
Bandwidth Guaranteed 2004 – 08 – 11
Generally three class of traffic
Expedited Forwarding (EF) Voice or Video
Assured Forwarding (AF) Best Effort (BE)
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Operation Steps
Parameter-based CAC Mechanism EDA BGP Scheme
Bandwidth Guaranteed Polling
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Parameter-based CAC Mechanism
Call Admission Control Admits customers in consideration of SL
A, through which ONUs can be divided into two disjoint groups served by the OLT differently BG ONUs Non-BG ONUs
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CAC - Parameter
<C, D> C specifies the minimum peak bandwidth an
ONU requests D indicates the maximum waiting delay an O
NU can tolerate E(Di)
the worst case average delay E(Di) for each ONU that the OLT pre-calculate
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EDA
Evenly Distributed Algorithm Determines the polling sequence of ON
Us for the scheduling scheme
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EDA – Step1
Process the BG ONUs from the one with maximum entries to the one with minimum entries
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EDA – Step2 (1/3)
After determining the first entry Ei[1] and other entries Ei[j] (j=2,3,…Ni) for BG ONUi with Ni entries, fill the Table with this ONU’s ID i
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EDA – Step2 (2/3)
Let entry i to be the first entry of ONU i Ei[1] = i
If the entry i is occupied by other ONU Ei[1] = i ± n ,
n = 1,2,3,…
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ONU2
ONU6
EDA – Step2 (3/3)
Other entries Ei[j] (j=2,3,…Ni) , and N is the total entry number of the Entry Table
Ei[j]=mod(Ei[l]+int(j-1)*N/Ni , N )
Ei[j]=mod((Ei[l]+int(j-1)*N/Ni) ± n, N )
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ONU3j = 3Ni = 4N = 8
EDA – Step3
All entries that are not occupied by BG ONUs will be blank in the Entry Table, then assigned to non-BG ONUs dynamically
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EDA – Step4
The List for non-BG ONUs is sequenced in ascending order based on non-BG ONUs’ IDs
The total number of the elements in the List is not fixed
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EDA – Benefit
It will benefit to the BG ONUs with high traffic since the packets in the buffer can be allowed to transmit after the same intervals
Thus there will be no burst, caused by the scheduling, introduced to the data transmission
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BGP Scheme
Bandwidth Guarantee Polling The proposed scheme is able to guaran
tee bandwidth for high-demand users , and provide a best-effort service to low-demand users
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BGP - Steps
The Entry Table & List will determine the scheduling order of ONUs
The OLT sending a control message locate which ONU occupies this entry grants a transmission window to the ONU
Duration of the transmission window The ONU starts to transmit data frames reports its buffer occupancy status
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BGP - Benefit
Entries in the Table that are not occupied by BG ONUs or the superfluous transmission window in one entry that is occupied yet unconsumed by an ONU can be assigned to non-BG ONUs dynamically
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BGP - Problem
How to defined a threshold to determine whether to use the superfluous transmission window or give it up
2004 – 08 – 11