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


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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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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

  • Extensions to algorithm VDO and FDO

  • Simulation results and extensions

  • Comments


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”


Motivation (Problem Statement)

  • Power control with

    • Entry and

    • Egress from the network

  • While maintaining QoS

    • For existing users

Admissible?


Model

QoS constraint


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


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”


new

DPC/ALP Algorithm – continued

admitted

Geometric power up

Protection margin or buffer zone


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


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


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


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


Extensions

  • Probing

    • Predict admissibility from two SIR samples

Solve for X Y

Admit after k=


Comments

  • Dynamics of admission control

    • Critical to ad-hoc networks

    • Rapidly changing user group

  • Results are very parameter sensitive


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