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P. M. Santiago del Río , J.A. Hernández, V. López, J. Aracil, B. Huiszoon

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 NOC June 12th, 2009 Valladolid (Spain) ‏. Outline. Introduction Analysis

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P. M. Santiago del Río , J.A. Hernández, V. López, J. Aracil, B. Huiszoon

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  1. 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 NOC June 12th, 2009 Valladolid (Spain)‏

  2. Outline • Introduction • Analysis • Numerical Experiments • Conclusions 2

  3. Introduction (I)‏ • Architecture • Each PON contains Ni ONUs • Multiplexing solutions: • Synchronous: TDMA (well-established technology)‏ • Asynchronous: OCDMA (simplifies control and management plane)‏ 3

  4. 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 4

  5. 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

  6. 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 6

  7. Introduction (V)‏ • Goal of this paper: • Analyze blocking duration under several traffic conditions and varying networking parameters 7

  8. Analysis (I)‏ • 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)‏ 8

  9. 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 9

  10. Analysis (III)‏ • Evaluation criterium of the Feasibility: • P(D>2τts)‏ • We are interested in finding the optimum values for L, B, EXonand 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 10

  11. Numerical Experiments (I)‏ • L vs. P(D>2τts) (Geometric): • 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. 11

  12. Numerical Experiments (II)‏ • L vs. P(D>2τts) (Heavy-tailed): • 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. 12

  13. Numerical Experiments (III)‏ • B vs. P(D>2τts) : • P(D>2τts) decreases as B increases. • If we want to assure • P(D>2τts)≥0.8: • if M=8 then Bmust be ≤ 800 Mbps • if M=4 then Bmust be ≤ 2 Gbps 13

  14. 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)‏ 14

  15. 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.

  16. Thank you for your attention • Questions? 16

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