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Course Introduction

Course Introduction. Dr. Nawaporn Wisitpongphan. What do you need in order to conduct a PhD Research?. A lot of reading in order to Find a PhD thesis topic Find out what other have been done/doing Find out techniques which could be used in your thesis

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Course Introduction

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  1. Course Introduction Dr. NawapornWisitpongphan

  2. What do you need in order to conduct a PhD Research? • A lot of reading in order to • Find a PhD thesis topic • Find out what other have been done/doing • Find out techniques which could be used in your thesis • Good Problem formulation (well-begun is half-done) • Good techniques/tools • Data Collection & analysis • Good Results Analysis • Good Presentation *** (Journal Papers!!!) • Self-Discipline & Self-Learning • Motivation

  3. What will we study in this class? • Different types of Research • Theoretical Study • Simulation Study • Empirical Study • Some techniques about • Data collections • Experimental set up • Data Analysis tools • Presentation • Collaborative Learning. Learning by sharing. Nobody knows everything!!!

  4. Goal of this class • Students obtain research skills necessary to conduct PhD-level research • Or better… Students obtains techniques that can be used to conduct their own research

  5. Class Info: References Grading Criteria • Probability, Random Variables and Stochastic Processes by Athanasios Papoulis • Queuing Systems: Vol 1 by Leonard Kleinrock • Homework 30% • Midterm 15% • ResearchPresentation 10% • Written Paper 15% • Final Exam 30%

  6. Class Project • Individual Research • You will get to • Analyze Huge amount of Data collected by NECTEC or Dek-D.com • Think about the research goal: • What can you do with this data? • What kind of information will be useful? • Generate some results • Write a paper about it : 5-6 page double column • Present it in the class

  7. Class Format • Class Lecture: 1.5-2 hrs • Research Advising: 1-1.5 hr after the lecture • Class Presentation: 3 hrs • Group HW presentation: 0.5 hr

  8. Assignment for next week • Present your past research work • Motivation & Goal • Data Collection Technique • Tools for Analyzing Data • Your Potential PhD Topic

  9. Example • Title: • Analysis of TCP and self-similarity of network traffic. • Motivation: • Internet traffic is not Poisson!!! It’s heavy-tailed. • Data Collection Tool • OPNET simulator • Statistical/Analytical Tool • Variance-Time plot • Hurst Parameter

  10. Self-Similarity in Traffic Measurement

  11. Self-Similarity: Proper Definition • A stochastic process X(t) is statistically self-similar with parameter H (0.5  H  1) if for any real a > 0, the process • a-HX(at) has the same statistical properties as X(t) • This relationship may be expressed by the following conditions: Degree of self-similarity: Hurst parameter (H) or self-similarity parameter is a measure of the persistence of a statistical phenomenon & is a measure of the long-range dependence of the stochastic process H = 0.5  Absence of self-similarity H = 1.0  Greatest degree of persistence or long-range dependence

  12. Slowly Decaying Variance • The variance of the sample decreases more slowly than the reciprocal of the sample size • For most processes, the variance of a sample diminishes quite rapidly as the sample size is increased, and stabilizes soon • For self-similar processes, the variance decreases very slowly, even when the sample size grows quite large

  13. Mathematically Speaking • The m-average process of a discrete-time stationary parent process X1, X2,Xn, … is • The variance is defined as • The variances of the aggregated process X(m) decrease linearly for large m • Hurst parameter,

  14. Methods of showing Self-Similarity Estimate H  0.8 H=1 H=0.5 H=0.5

  15. Variance-Time Plot • The ‘‘variance-time plot” is one means to test for the slowly decaying variance property • Plots the variance of the sample versus the sample size, on a log-log plot • For most processes, the result is a straight line with slope -1 • For self-similar, the line is much flatter • Variance-Time plot is obtained by plotting log(Var[X(m)] )against log(m) where m is typically equal to 1 ms, 10 ms, 100 ms, 1 s, 100 s, …

  16. Variance-Time Plot 100.0 10.0 Variance of sample on a logarithmic scale Variance 0.01 0.001 0.0001 m

  17. Variance-Time Plot Variance Sample size m on a logarithmic scale 4 5 6 7 m 1 10 100 10 10 10 10

  18. Variance-Time Plot Slope = -1 for most processes Variance m

  19. Variance-Time Plot Slope flatter than -1 for self-similar process Variance m

  20. Example of Variance-Time Plots

  21. Data Collection Techniques • Collect throughput at the Network Bottleneck • Collect the throughput every 10 ms from OPNET Modeler • Use MATLAB to process data, e.g., • Construct aggregated process, • Findvariance of aggregated process, • plot V-T graph

  22. Reference • N. Wisitpongphan and J. M. Peha, “Effect of TCP on Self-Similarity of Network Traffic,” Proceedings of 12th IEEE International Conference on Computer Communications and Networks (ICCCN), Dallas, USA,Oct. 2003

  23. STEP 1:How to find Research Ideas • Reading other papers (Lots of them) and write a summary which answers some of these questions: • From where did the author seem to draw the ideas? • What exactly was accomplished by this piece of work? • How does it seem to relate to other work in the field? • What would be the reasonable next step to build upon this work? • What ideas from related fields might be brought to bear upon this subject? • Exposing yourself to research • Make a weekly effort to read at least the abstracts from good journals in your field. Read 1-2 papers in detail. • Attend a research seminar. • Directed Study • Should you find the thesis advisor first or thesis topic first? • Develop a thesis topic with your advisor using independent study approach.

  24. Rule of Thumb • Avoid spending all your time doing literature review • Good research topic typically aims to solve a certain problem (not EVERY PROBLEM) so.. • Be clear on what your problem/motivation is • Make legitimate assumptions on certain unknowns • Be practical and realistic • Research = Work done by STUDENT not advisor • “Student should know more than an advisor on the topic” • Do not wait for an advisor to tell you what to do, advisor’s job is to give student a feedback.

  25. How to select a paper to read? • First, find the major conferences in your field. • Find the conference program • List the conference track • Look for a keyword e.g., name of the technique, name of the problem, area of the study (typically listed in the title, abstract, or keyword of the paper) • For example: VLDB 2012 http://www.vldb2012.org/general-information/advance-program/

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