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![Page 1: On the feasability of transmission scheduling in a code-based transparent passive optical network architecture P. M. Santiago del Río, J.A. Hernández,](https://reader035.fdocuments.us/reader035/viewer/2022062423/56649e365503460f94b256cf/html5/thumbnails/1.jpg)
On the feasability of transmission scheduling
in a code-based transparent passive optical network
architecture
P. M. Santiago del Río, J.A. Hernández, V. López, J. Aracil, B. Huiszoon
14th European Conference on NOCJune 12th, 2009 Valladolid (Spain)
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Outline
Introduction Analysis Numerical Experiments Conclusions
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Introduction (I) Architecture
• Each PON contains Ni ONUs
• Multiplexing solutions:• Synchronous: TDMA (well-established technology)
• Asynchronous: OCDMA (simplifies control and management plane)
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Introduction (II) OCDMA:
• Data is signed with unique orthogonal optical code.• Optical carrier can be shared by all the users.
Problem:• Degradation caused by Multiple User Interference
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Introduction (III) Contention resolution:
• Transmission scheduling:– Requires user monitoring functionalities at the ONU– ONU derives accurate information and acts accordingly
• Packet-level analysis
Transmission scheduling:• Before transmitting, it must to check the media
availability (active users < Maximum of users allowed):
» If u<M, it can transmit the data» If u=M, it must wait until one of ONUs finishes.
• The system enters a blocked situation when Mth connection arrives 5
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Introduction (IV) Issue:
• The information sent by one ONU, it is sensed 2τ seconds in the future by the remaining ONUs
• Transmission delay• “Old” information available about state at passive
coupler
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Introduction (V)
Goal of this paper:• Analyze blocking duration under several traffic
conditions and varying networking parameters
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Analysis (I)
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Time-slotted scenario:• 1 time-slot = 1packet• Times-slotted scenario to facilitate analysis
Burst length probability distribution:• Geometric distribution:
– Memoryless– Model traffic highly-multiplexed
• Pareto distribution:– Self-similarity– Model traffic from residential end-users (not multiplexed)
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Analysis (II) Blocking-time probability distribution:
• When Mth connection arrives to the system sees the residual life of the other M-1 connection
• D is given by the minimum of the M-1 residual lives and the duration of the Mth arrival
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Analysis (III) Evaluation criterium of the Feasibility:
• P(D>2τts)
• We are interested in finding the optimum values for L, B, EXon and M such that P(D>2τts)≥1-ε
• For instance, it is interesting to know, the maximum bit rate, B, such that P(D>2τts)≥0.8 i.e. there is coherence of state 80% of the blocking time
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Numerical Experiments (I) L vs. P(D>2τts) (Geometric):
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• P(D>2τts) does not depend on L for values up to 2 km, because is smaller than one time-slot.
The fiber length is not an important parameter (if L<2km).
• P(D>2τts) decreases as M increases since ED is smaller.
Blocking lasts less time when the number of active users is higher.
• P(D>2τts) increases with an increasing EXon since the value of ED increases.
Blocking lasts more time when the bursts are longer.
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Numerical Experiments (II) L vs. P(D>2τts) (Heavy-tailed):
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• Behavior similar to geometric case.
•P(D>2τts) is smaller because the variance of Xon is infinite in the Pareto case.
• P(D>2τts) is too small to do transmission scheduling.
• If the traffic is not highly multiplexed, it is less interesting to deploy the transmission scheduling medium access mechanism.
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Numerical Experiments (III) B vs. P(D>2τts) :
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• P(D>2τts) decreases as B increases.
• If we want to assure P(D>2τts)≥0.8:• if M=8 then B must be ≤ 800 Mbps• if M=4 then B must be ≤ 2 Gbps
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Conclusions This work provides a set of guidelines for
designing PONs assuming:• Topology constraints: Fiber length (L)
• Observed pattern traffic: EXon
• Maximum number of active users: M
These parameters determine the maximum bit rate such that coherence of state holds (transmission scheduling is feasible)
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Acknowledgements This work was carried out with the support of:
• BONE project (“Building the FutureOptical Network in Europe”), a Network of Excellence funded by the Europea Commission through the 7th ICT-Framework Programme.
The authors would also like to acknowledge the support of the Spanish MEC:: • DIOR project (TEC2006-03246/TCM), • Juan de la Cierva post-doctoral research program.
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Thank you for your attention
Questions?
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