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Channel Access Algorithms with Active Link Protection for Wireless Communication Networks with Power Control

Channel Access Algorithms with Active Link Protection for Wireless Communication Networks with Power Control. Nicholas Bambos, Shou C. Chen, Gregory J. Pottie. Agenda. Overview Motivation (Problem statement) Foundation work DPC/ALP algorithm Properties of DPC/ALP algorithm

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Channel Access Algorithms with Active Link Protection for Wireless Communication Networks with Power Control

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  1. Channel Access Algorithms with Active Link Protection for Wireless Communication Networks with Power Control Nicholas Bambos, Shou C. Chen, Gregory J. Pottie

  2. Agenda • Overview • Motivation (Problem statement) • Foundation work • DPC/ALP algorithm • Properties of DPC/ALP algorithm • Extensions to algorithm VDO and FDO • Simulation results and extensions • Comments

  3. Overview: DPC/ALP • DPC: An Algorithm for transmit power control • Adaptive • Distributed • On-line • Different QoS levels • ALP: Admission control algorithm • Protect existing users form disruption • Method for new users to enter wireless network • “Smooth dynamics”

  4. Motivation (Problem Statement) • Power control with • Entry and • Egress from the network • While maintaining QoS • For existing users Admissible?

  5. Model QoS constraint

  6. Foundation Work: DPC • Distributed Power Control • P(k+1)=FP(k)+u • P->P* where • But • Convergence path may lead to “outage” or QoS problems • Alternative form: Foschini and Miljanic

  7. DPC/ALP Algorithm • Based on DPC (above) • Active link protection – Ensures existing users QoS is maintained when new users are added. • Distributed admission control • Extended – Voluntary drop out Mechanism for “hot spots”

  8. new DPC/ALP Algorithm – continued admitted Geometric power up Protection margin or buffer zone

  9. Properties of DPC/ALP • User is admitted when • Once admitted continuously admitted • bounded power overshoot • New users • Increasing SIR’s • If admissible then admitted in bounded time • But infinite power may be required Admissibility vs. admissibility

  10. DPC/ALP/VDO • Voluntary Drop-Out • When too many new users none wins • Solution is one or more links backs off • Types of VDO • Coin flipping after a parameterized number of tries • Timer based

  11. DPC/ALP/VDO/FDO • Power constraint • FDO – forced drop out • Active user nears max • Signals local users seeking admission to drop out • Reduces contention for resources

  12. Simulation results • VDO • Increases number of users significantly • Results in backlog of users not yet admitted • Threshold effect for great enough arrival rate of new users! Clogging effect • VDO and FDO • Decrease in time to admission • Higher through-put Hot spots Congestion control

  13. Extensions • Probing • Predict admissibility from two SIR samples Solve for X Y Admit after k=

  14. Comments • Dynamics of admission control • Critical to ad-hoc networks • Rapidly changing user group • Results are very parameter sensitive

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