1 / 16

Parameterizing PI Congestion Controllers

Parameterizing PI Congestion Controllers. Ahmad T. Al-Hammouri, Vincenzo Liberatore, Michael S. Branicky Case Western Reserve University Stephen M. Phillips Arizona State University April 3, 2006

zev
Download Presentation

Parameterizing PI Congestion Controllers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Parameterizing PI Congestion Controllers Ahmad T. Al-Hammouri, Vincenzo Liberatore, Michael S. Branicky Case Western Reserve University Stephen M. Phillips Arizona State University April 3, 2006 Support by: NSF CCR-0329910, Department of Commerce TOP 39-60-04003, NASA NNC04AA12A, and an OhioICE Training grant

  2. Contributions of the Paper • Complete stability region for PI • Presents examples that show • Different stable PI parameters exhibit widely different control performance • Neglecting delays in control design leads to unstable systems Parameterizing PI Congestion Controllers FeBID’06

  3. TCP-AQM Control Loop Plant P(s)= [Hollot et al 2001] x(t)=cwnd/RTT On Ack cwnd += 1/cwnd On loss cwnd /= 2 f(q(t)) q`=Σx(t) - C p(t) ControllerG(s) q(t) tf tb Parameterizing PI Congestion Controllers FeBID’06

  4. PI AQM [Hollot et al 2001] q0 q(s) e u G(s) P(s) _ + • PI vs RED • Control signal: • . • Frequency transfer fn: • . Integral term eliminates the steady-state error P PI Parameterizing PI Congestion Controllers FeBID’06

  5. Parameterizing PI AQM • Problem: • Determine the entire region of stabilizing kp and ki values • Objectives: • Stable closed-loop system • Enhanced closed-loop performance • Steady-state error, convergence time, overshoot • Challenges: • Delays Parameterizing PI Congestion Controllers FeBID’06

  6. Contributions of the Paper • Complete stability region for PI • Presents examples that show • Different stable PI parameters exhibit widely different control performance • Neglecting delays in control design leads to unstable systems Parameterizing PI Congestion Controllers FeBID’06

  7. Complete Stability Region SR [Silva et al 2005] • SR = (S0 \ SN) \ SL • S0 : • Stability region for the delay-free system • P0(s) = • SN : • . S0 S0 \ SN Parameterizing PI Congestion Controllers FeBID’06

  8. Determination of SL • Set of kp and ki’s that destabilizes the closed-loop for delays less than d0 • For given kp and ki • Find d that gives the blue curve • If (d ≤ d0), (kp,ki ) SL • Else, (kp,ki ) SL • Sweep(kp,ki ) S0 Nyquist Plot of G(s)P(s) Im{s} -1 Re{s} x d++ Parameterizing PI Congestion Controllers FeBID’06

  9. Complete Stability Region SR • SR = (S0 \ SN) \ SL SR S0 \ SN Parameterizing PI Congestion Controllers FeBID’06

  10. Contributions of the Paper • Complete stability region for PI • Presents examples that show • Different stable PI parameters exhibit widely different control performance • Neglecting delays in control design leads to unstable systems Parameterizing PI Congestion Controllers FeBID’06

  11. Example 1 • N = 75; d0 = 0.15 sec; C = 1250 pkt/sec * [Hollot et al 2001] * Parameterizing PI Congestion Controllers FeBID’06

  12. Contributions of the Paper • Complete stability region for PI • Presents examples that show • Different stable PI parameters exhibit widely different control performance • Neglecting delays in control design leads to unstable systems Parameterizing PI Congestion Controllers FeBID’06

  13. PIP Controller [Heying et al 2002] u q0 q(s) e G(s) P(s) + _ + _ Kh PI Kh PIP Parameterizing PI Congestion Controllers FeBID’06

  14. Example 2 [Heying et al 2002] • N = 60; d0 = 0.22 sec; C = 1250 pkt/sec * [Heying et al 2002] Parameterizing PI Congestion Controllers FeBID’06

  15. Future Work • Conduct packet-level simulations (ns-2) • Define a “Networks Performance” objective function • Optimize the objective function over the stability region • Analyze the queue nonlinearity (i.e. truncation) Parameterizing PI Congestion Controllers FeBID’06

  16. Thank You • Questions • Comments Parameterizing PI Congestion Controllers FeBID’06

More Related