Trace based evaluation of rate adaptation schemes in vehicular environments
Sponsored Links
This presentation is the property of its rightful owner.
1 / 18

Trace-based Evaluation of Rate Adaptation Schemes in Vehicular Environments PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Trace-based Evaluation of Rate Adaptation Schemes in Vehicular Environments. Kevin C. Lee WiVeC 2010, 5/17/10. Rate Adaptation Overview. The 802.11 a/b/g/n standards allow the use of multiple transmission rates 802.11b, 4 rate options (1,2,5.5,11Mbps)

Download Presentation

Trace-based Evaluation of Rate Adaptation Schemes in Vehicular Environments

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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Trace-based Evaluation of Rate Adaptation Schemes in Vehicular Environments

Kevin C. Lee

WiVeC 2010, 5/17/10

Rate Adaptation Overview

  • The 802.11 a/b/g/n standards allow the use of multiple transmission rates

    • 802.11b, 4 rate options (1,2,5.5,11Mbps)

    • 802.11a, 8 rate options (6,9,12,18,24,36,48,54 Mbps)

    • 802.11g, 12 rate options (11a set + 11b set)

  • The method to select the transmission rate in real time is called “Rate Adaptation”

Why Rate Adaptation?

  • Ideally, the transmission rate should be adjusted according to the channel condition


Signal is good

12MbpsSignal is weaker




  • MANY rate adaptation algorithms yet no fair comparison

    • Unrealistic propagation (unrealistic)

    • Dynamic changing conditions (non-repeatable)

    • Long system setup and device driver implementation (impractical)

Framework & Goal

Repeatable evaluation of rate adaptation schemes

Implementation of different application

Application Layer

Rapid deployment independent of hardware spec

Implementation of various rate adaptations schemes

MAC Layer

Realistic SNR to reflect the environment

Use field-collected SNR to replace synthetic value

Physical Layer

Physical Layer

  • Collect SNR traces from moving cars

    • Server broadcasts @ 6Mbps

    • 2 Clients receive and record SNR

  • Increase range and power of signal with an external 7dBM antenna

  • Replace SNR logic with SNR from the field

  • Derive BER and then bit error probability

Trace Collection

  • Traces from 3 different areas: City, Residential, and Highway

Trace Collection Map

Static Traffic Route

  • Car A centered at the mid point, stationary

  • Car B and C move back and forth toward and away from A

Rate Adaptation Schemes Implementation

  • RRAA-DYN adjusts rates before the current estimation windowm

Static Traffic Route Result

  • SNR from 440s to 540s

  • 40 seconds to complete one loop

  • Signal strength

directly proportional to the distance between them

Instantaneous Throughput for All Algorithms

  • Packet-based rate adaption schemes react similarly to the SNR-based scheme (RAM)

  • Sample rate plateau from 460-470s and 500-530s

Throughput in Different Transmission Rates

  • Throughput increases with transmission rate

  • ARF, RRAA-DYN, and RAM top 3

  • AMRR and Sample bottom 2

Rate Distribution for All Schmes

  • 6Mbps occupies the largest fraction for top 3 schemes but there are other rates => short-term lossy channel

  • Sample & AMRR can’t adapt to short-term fluctuation

Success of ARF

  • Comes from the fact that rate increases conservatively and decreases drastically

  • Not too good if the channel condition does not change frequently

  • Conclusion: Packet-based scheme does a subpart job because of fixed parameters of packet statistics; adaptive parameters to improve

Impact of Environments

  • Throughput degradation from residential, highway, city; speed & traffic density play a factor

  • RRAA-DYN beats


    => changing trans-

    mission wind. helps

    improve responsive-


Impact of Propagation Model

  • Rayleigh has higher throughput b/c it considers fading where there is no dominant propagation along a line of sight between transmitter and receiver

  • A more accurate

    prop. model to use

    b/c lead car and

    trailing car are often

    separated by cars in



  • An integrated framework that utilizes empirical data collected from the testbed to objectively compare different rate adaption schemes

    • Repeatable

    • Rapid

    • Realistic

  • Login