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.

Course IntroductionDr. Nawaporn Wisitpongphan

What do you need in order to conduct a PhD Research?A lot of reading in order to

Find a PhD thesis topicFind out what other have been done/doingFind 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 AnalysisGood Presentation *** (Journal Papers!!!)Self-Discipline & Self-LearningMotivation

What will we study in this class?Different types of Research

Theoretical StudySimulation StudyEmpirical Study

Some techniques about Data collectionsExperimental set upData Analysis toolsPresentation

Collaborative Learning. Learning by sharing. Nobody knows everything!!!

Goal of this classStudents obtain research skills necessary to conduct PhD-level research

Or better… Students obtains techniques that can be used to conduct their own research

Week Topics Remarks

1 (Nov 17)

Course Introduction + Research Topic Finding Class Activity

2 (Nov 24)

Students’ Presentation + Literature ReviewMini Research Project (Introduction)

Presentation

3 (Dec 1) Writing Technical Paper

4 (Dec 8) Reading Assignment (Data Clustering) No Class5 (Dec 15)

Data Clustering Techniques (Discussion)

6 (Dec 22)

(Project Proposal ) No Class

7 (Dec 29)

Take Home Exam (Writing Literature Review) No Class

8 (Jan 5) Literature Review Presentation (Exam Due) Presentation/HW#1

9 (Jan 12)

กี�ฬามหาวิ�ทยาลั�ย No Class

10 (Jan 19)

กี�ฬามหาวิ�ทยาลั�ย HW#1 Due No Class

11 (Jan 26)

Advanced Research Techniques (Optimization, Regression, Goodness of Fit, etc.)

HW#2

12 (Feb 2)

Advanced Research Techniques (Part II) HW#2 Due

13 (Feb 9)

Queuing Theory HW#3

14 (Feb 16)

Invited Talk (TBA) HW#3 Due

15 (Feb 23)

Project Presentation Presentation

16 (Mar 2)

Final Exam Paper Due

Class Info:References Grading CriteriaProbability, 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%

Class ProjectIndividual ResearchYou 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 resultsWrite a paper about it : 5-6 page double

columnPresent it in the class

Class FormatClass Lecture: 1.5-2 hrsResearch Advising: 1-1.5 hr after the lecture

Class Presentation: 3 hrsGroup HW presentation: 0.5 hr

Assignment for next weekPresent your past research work1. Motivation & Goal2. Data Collection Technique3. Tools for Analyzing Data4. Your Potential PhD Topic

ExampleTitle:

Analysis of TCP and self-similarity of network traffic.

Motivation: Internet traffic is not Poisson!!! It’s heavy-

tailed.Data Collection Tool

OPNET simulatorStatistical/Analytical Tool

Variance-Time plotHurst Parameter

Self-Similarity in Traffic Measurement

Self-Similarity: Proper DefinitionA 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:

HX

X

H

H

a

asatRstR

a

atXVartXVar

a

atXEtXE

2

2

3

2

1

),(),(.

)]([)]([.

)]([)]([.

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 processH = 0.5 Absence of self-similarityH = 1.0 Greatest degree of persistence or long-range dependence

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

Slowly Decaying Variance

Mathematically SpeakingThe 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,

...),,( )(3

)(2

)(1

)( mmmm XXXX

m

Njm

mji

mj jX

mX ,...,2,1

1

11

)(

m

N

j

mj

mN

m XXXVar1

2)()( 1

mXVarXVar m /)(

21 H

Methods of showing Self-Similarity

H=0.5

H=0.5

H=1Estimate H 0.8

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 flatterVariance-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, …

Variance-Time Plot

Variance-Time PlotVariance-Time PlotV

aria

nce

m

Variance of sampleon a logarithmic scale

0.0001

0.001

10.0

0.01

100.0

Variance-Time PlotVariance-Time PlotV

aria

nce

m

Sample size mon a logarithmic scale

1 10 100 10 10 10 104 5 6 7

Variance-Time PlotVariance-Time PlotV

aria

nce

m

Slope = -1for most processes

Variance-Time PlotVariance-Time PlotV

aria

nce

m

Slope flatter than -1for self-similar process

Example of Variance-Time Plots

Data Collection TechniquesCollect throughput at the Network Bottleneck

Collect the throughput every 10 ms from OPNET Modeler

Use MATLAB to process data, e.g., Construct aggregated process, Find variance of aggregated process, plot V-T graph

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

STEP 1:How to find Research IdeasReading 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.

Rule of ThumbAvoid spending all your time doing literature

reviewGood 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.

How to select a paper to read?First, find the major conferences in your

field.Find the conference programList the conference trackLook 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/