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Research and PublicationsA Personal Perspective

• Bo Li
• Hong Kong University of Science and Technology
• Microsoft Research Asia

2
Outline

• What about research?
• How much does one have to learn?
• PhD research
• What is procedure of publications?
• How to write technical papers?

3
Research is easy!

• You have done this many times in course projects
• Take a known problem, and apply a known technique
• Obtain results, and write a report

4
Research is difficult!

• Is it technically correct?
• Does it make intuitively sense?
• Is it publishable, where and why?
• Does it offer some insights beyond what we have
  known?
• Does it have any impact?

5
Research

• There are basically four types of research works
• New problem and new solution
• New problem and old solution
• Old problem and new solution
• Old problem and old solution

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Research

• Case I comes rarely, perhaps something you could
  only wish, once a life-time experience
• Shannon theory
• Cases II and III are the ones that you should
  target for
• Packet scheduling weighted fair queuing
• Geographical routing in ad hoc networks
• Case IV is where you can start
• Plenty of out there under the category of Yet
  another paper on

7
Where do ideas come from?

• Drink a beer, relax, ideas will come to you
• The ideas fall from the sky!

• Understanding the existing works, build upon that
  incrementally

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Where do ideas come from?

• Ideas in most cases come from the deep
  understanding of a subject, and possess of broad
  knowledge
• This is not a technical training, i.e., this is
  not about solving a bipartite graph, or
  differential equations
• This is about relating them to real world
  problems
• This is about providing new insight beyond known
• This is about your creativity!

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Research What is it?

• Research Re (repeat) search
• Much of the research has been built upon existing
  works, therefore a thorough understanding of
  those is the basis
• Too many smart people in each area, so if an idea
  seems to be too good to be true, it likely is -gt
  rethink that again
• Each idea needs iterations what is it? why has
  it not been done? what is the logical connection
  with the existing approaches?

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Research Engineering Problem

• Each solution to an engineering problem is only a
  trade-off it is not a cure for all, it
  definitely has side-effect.
• Networking coding
• Potential capacity gain under loaded system
• Is it really? Is there any alternative? What is
  the penalty for doing so? Can we handle that in
  system design?
• P2P
• Facilitate the voluntary file sharing
• Can this be extended beyond that?

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Case I Adaptive Video Multicast

• The need for multicast - efficiency
• Multiple-unicast Multicast
• Fundamental problem users heterogeneity and
  network dynamics

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Case I Adaptive Video Multicast

• Layered video encoding and transmission
• Cumulative layered coding (Scalable coding)
• Base layer most important feature, low rate, low
  quality
• Enhancement layers progressively refine quality

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Case I Adaptive Video Multicast

• Existing solutions
• Multiple multicast tree, each for a layer
• Receiver adaptation users joining and leaving
  groups (receiver)
• Adaptation is performed at receivers only fixed
  layer rates and limited num of layers
• Fundamental Problem
• The mismatch between the fixed sending rate and
  the dynamic and heterogeneous rate requirement
  from receivers

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Case I Adaptive Video Multicast
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Case I Adaptive Video Multicast

• End-to-end adaptive video multicast
• Optimal rate allocation for each layer
  formulation and solution
• End-to-end transmission protocol and whether TCP
  friendly
• Complexity analysis
• Practical issues feedback explosion (sampling),
  RTT estimation (open and closed loop)

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Sample References

• B. Li and J. Liu, Multi-Rate Video Multicast
  over the Internet An Overview, IEEE Network,
  (17)1 24-29, January-February 2003.
• J.-C. Liu, B. Li and Y.-Q. Zhang, Adaptive Video
  Multicast Over the Internet, IEEE Multimedia,
  (10)1 22-33, January-March 2003.
• J. Liu, B. Li, and Y.-Q. Zhang, An End-to-End
  Adaptation Protocol for Layered Video Multicast
  Using Optimal Rate Allocation, IEEE Transactions
  on Multimedia, (6)7 87-102, February 2004.

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Summary

• Identify a general category of problems
• The idea should be intuitively simple
• Publications can be easier

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Outline

• What about research?
• How much does one have to learn?
• PhD research
• What is procedure of publications?
• How to write technical papers?

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How much does one have to learn?

• I have learnt all the mathematics, and I am
  loaded
• Discrete algorithms, partial differential
  equations, dynamic control, probabilistic
  modeling, information theory and etc.
• I still dont have a clue what to do in research.
  
• Where in the world is research topic?

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How much does one have to learn?

• I have read all papers out there from journals
  and conferences
• Can I do research now?
• There is no way you can cope with all of them
• Majority of the published works are junks, and
  can cause brain damage and can be misleading

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The minimum needed for research

• Logical thinking, after all we are in engineering
  world
• Basic skills
• You have to know the Dijstra algorithm in order
  to understand the OSFP (?)
• the ability to learn
• Life long learning process, esp. in CS

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The minimum needed for research

• Abstraction. Take a problem, you have to know
• What is/are the fundamental problem(s)
• You have to see both forest and trees
• What have been done, why?
• What are seemingly undoable?
• Understand your strength and weakness

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The minimum needed for research

• Open mind
• We are not dealing with math problem in that
  there exists perfect solutions
• Engineering solutions are subject to argument and
  debate, i.e., each solution is a trade-off, and
  it only works in a constrained environment
• Critical mind
• When you read others, it is equally important to
  understand what circumstance that it does not
  work as in which it works
• If you can not identify such scenario, you are
  not understanding the problem

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Case II Proxy Placement

• How to place the proxy (mirror sites) in the
  internet
• B. Li et al., On the Optimal Placement of Web
  Proxies in the Internet, Proc. IEEE Infocom'99
• ACM Communications Review (2001) cited as the 1st
  ever work on this topic

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Case II Proxy Placement

• Formulation graph theory problem, k-median
  problem given N nodes, how to select K nodes to
  place the content so certain optimal criterion
  can be met
• For general graph, this is NP-hard
• For tree, we solved this using a known dynamic
  programming technique
• This turns out to be the fundamental problem for
  object replication in DB, which has been cited
  over 300 times since then

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Sample References

• J.-L. Xu, B. Li and D. Lee, Placement Problems
  for Transparent Data Replication Proxy Services,
  IEEE Journal Selected Areas in Communications,
  20(7) 1383-1398, 2002
• A. Vigneron, L. Gao, M. Golin, G. Italiano and B.
  Li, An Algorithm for Finding a k-Median in a
  Directed Tree, Information Processing Letter,
  74(1-2) 81-88, 2000
• B. Li, Content Replication in a Distributed and
  Controlled Environment, Journal of Parallel and
  Distributed Computing, 59(2), pp. 1-21, Nov. 1999

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Summary

• Finding a problem is more important, and
  difficult than solving a problem
• You need out-of-box thinking

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Outline

• What about research?
• How much does one have to learn?
• PhD research
• What is procedure of publications?
• How to write technical papers?

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PhD Research

• Make a plan earlier, for 3-4 years
• The research topics must be of current interest,
  and state-of-the-art
• Dont work on packet scheduling, and IEEE 802.11
  MAC protocol ?
• Beating the performance of Ethernet is like
  kicking a dead horse!
• It has to be something that within your
  capability
• You need to understand your strength and
  weakness, and be realistic (dont shoot stars)
• You should know your interest, self-motivation is
  one of the single most important factors

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PhD Research

• Read top 10 or 20 papers in the area
• Understand the basics, fundamental problems, and
  open issues
• Think and read
• Put all papers into perspective
• Start from a small yet concrete problem
• Build you skill and confidence
• Discussions generates ideas

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Reading

• Top conference or workshop first
• ACM Sigcomm, ACM Mobicom, IEEE Infocom
• IEEE ICNP, IWQoS, MobiHoc
• Second tier conference only for reference
• IEEE Globecom, ICC
• Avoid bad conferences
• Regional, and less reputable ones
• Read journal papers only it has not been
  published else where, or when it contains more
  detailed and complete treatment

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PhD Research

• Focus!
• Dont over-estimate your ability
• Dont diversify too much
• Start with small idea(s), publish in an easy
  conference in the 2nd year
• Working plan target at 2 conferences (20 or less
  acceptance rate) and one journal paper per year
  (in 2-3 years)
• The thesis is a collection of the papers
• So you need to have a focus!

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Research Topics

• Theoretical vs. practical
• Can this be related to a real world problem
• Engineering approach
• It should have a clear boundary
• Focus on what can or/and can not be done
• Dont lose the bigger picture
• Tree and the forest
• How does it help to solve one or more pieces in
  the bigger problem

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PhD Research

• System works
• System work usually involves team efforts
• Building from scratch is a dangerous thing
• The prototype has to demonstrate significance in
  that either this is a proof of a concept, or
  demonstrate the feasibility
• Less than 5 chance being useful, yet worth the
  investment for technical break through
• Theoretical works
• Theoretical work usually provides an elegant
  solution to a generalized problem
• The significance can be greatly enhanced if
  practical insight can be drawn

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Advisor/Mentor

• Choosing an advisor could be the single most
  important factor for your research
• Understanding the general problem, the ability to
  identify the significance and yet another
• Personal and professional relationship
• Junior vs. senior, hands-on or hands-off
• Regular guidance vs. direction
• Independent and close collaboration
• Group or individual effort
• Time, efforts and experience

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You really need an Advisor/Mentor

• Can a rabbit eat a dog, fox and wolf?

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You really need an Advisor/Mentor

• Punch line
• It really does not matter what the topic is, and
  what you are doing, all it matters is who your
  advisor is

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Example I My PhD research

• What you need is a jump start for confidence
  building
• A. Ganz and B. Li Performance of Packet Networks
  in Satellite Clusters, IEEE Journal on Selected
  Areas in Communications, (10)6 1012-1019, August
  1992
• Be objective, dont lose the bigger picture
• The research topics are both important and not so
  important
• The research works in PhD study is simply a
  training process, be realistic.
• Usually the most productive period for ones
  career is within the 5 years after ones PhD

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Example II My student

• Jiangchuan Liu
• Who has written close to 20 top journal papers
  since 1999, largely on video multicast
• Assistant Professor at Simon Fraser Univ., former
  with Chinese Univ. of Hong Kong.
• Won the prestigious Hong Kong Young Scientist
  award in 2003, given to one individual annually
  by Hong Kong Institute of Science (HKIS)
• Sometime direction is all a student needs

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Collaborations leads to Productivity

• Working with the right people
• Skill complementary
• Same interests
• Working with smart people

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Case III Cellular Networks
Number of cells per cluster
Frequency Reuse Factor, If total of S channels
available, Each cell can be assigned k channel
If M clusters within the system, the total system
capacity
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Case III Cellular Network

• There were several fundamental problems in
  cellular network when moving to multi-service
  environment
• Bandwidth within a cell have to be shared
• Erlang assumption (Poisson arrival and
  exponential sojourn time and exponential call
  duration time) fails due to data traffic
• Gaussian approximation for a cell capacity fails
  given the cell is small

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Case III Cellular Network

• Relaxing Erlang, by considering heavy tail long
  range dependency LRD) distribution, i.e., Pareto
  distribution
• Failed since 1997

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Case III Cellular Network

• Gaussian approximation
• Particle movement and diffusion equation
• S. Wu, K. Y. M. Wong and B. Li, A Dynamic Call
  Admission Policy with Precision QoS Guarantee
  Using Stochastic Control for Mobile Wireless
  Networks, IEEE/ACM Transactions on Networking,
  (10)2 257-271, April 2002.

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Summary

• Working on hard and open problems
• Persistence pays off

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Summary

• The idea has to be simple, this is a hard lessen
  we have learn
• 10 years of research on ATM are pretty much a
  waste
• Internet
• POTS or PSTN

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Outline

• What about research?
• How much does one have to learn?
• PhD research
• What is procedure of publications?
• How to write technical papers?

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Conference Paper

• Start earlier for a conference submission
• Deadline is the best drive for making progress
• What make a good paper content and writing!
• Clear, convincing, simple and good English
• This is a never-ending optimization process, do
  this within the time and page limits
• Review process 5/30 rule
• 5 minutes - Abstract, introduction, figure and
  conclusion
• 30 minutes understand 90 of the paper

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Journal Paper

• A good conference paper (10-25 acceptance rate)
  can be submitted to a journal, with 30 new
  results
• Report more complete and focused results
• Give yourself a deadline
• Be patient with the long review and re-review
• At the earlier stage of ones career, dont quit
  if asked for major revision
• But dont do seemingly impossible

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What does a reviewer look for

• New problem or new solution?
• Are the main results significant?
• Is the paper technically correct?
• Does the paper provide a fair assessment of its
  strength and limitation?
• Is the paper clearly written, thus accessible to
  general readers?
• Are the references adequate?
• Is the paper appropriate for conference/journal?

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Outline

• What about research?
• How much does one have to learn?
• PhD research
• What is procedure of publications?
• How to write technical papers?

52
Writing

• Writing is a process of self-clarification
• Habit of writing, notes, random thoughts
• There are plenty of books teaching you how to
  write
• Imitation might be the best way to start
• Writing is part of the work
• Writing can be difficult and painful for all of
  us, there is no short cut, it improves along the
  process

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Writing

• Iterative refinement, outlines 3-5 times
• Start with existing work, introduction, your own
  work, experiment
• Abstract and summary (many hours work)
• Revise many times, ask others to read
• Lots of efforts for small improvement
• Is there a better way to say, a better word to
  use?
• Is the paper logically connected?
• What are the questions reviewers might have?
• Never ending optimization subject to time and
  page limit

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Review Process

• Low acceptance rate
• Reviewers are potential competitors
• Convincing but less critical
• Reviewers are very busy
• Try to make their job easier
• English is not our strength
• Dont try your luck, it wont work!

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Problem I

• Reviewers have to understand me
• Only you know your work well, not reviewers
• Make it easier to understand
• Motivation and rationales
• Control the level of details
• Make connection throughout the paper
• Use examples, graph, flow chat whenever needed
• Pose questions, and answer them

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Problem II

• Formality leads to elegance
• I am good at math, formal is high class, I have
  20 definitions and 15 theorems
• Keep it simple, perhaps stupid
• Start with motivations and rationales
• Avoid unnecessary formality

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Problem III

• I have 10 contributions
• Reviewers should see this is a masterpiece
• Focus in the key
• One problem, one solution in a conference paper
• One problem, more complete solutions in a journal
  paper
• Thorough and deep
• Emphasize but not exaggerate your contributions
• Say it is significant only if it is, and
  justify it
• If it is the first time, say This is, to the
  best of our knowledge, the first time

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Problem IV

• It is ok to be informal as long as understandable
• Technical writing is formal
• Avoid casual writing
• believe me, this is really a good work
• Dont use long sentences, break them
• Flow and logic is much more important, proof
  reading does not help you with that
• Top-down organization and outlining
• Use good papers as sample imitate!
• Write down your mistakes and eliminate them

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Problem V

• Reviewers are evil
• They reject paper so their papers can be accepted
• They reject my paper, so to steal my ideas
• Reviewers are critical
• You have to be a good salesman to convince them

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Closing Thoughts

• Research needs creativity, patience, hard
  working, persistence
• Writing is a self-improving process
• Understanding the process of publication, in
  particular review process helps
• KEYS
• Balance the search and re-development and
  out-of-box thinking
• Working with smart people

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Closing Thoughts

• We have done so much for networking!
• 10 years ago IP vs. ATM
• Since then
• QoS, network Calculi, intServ, diffServ,
• CNDs, DDoS, VoIP, SIP, multicast
• TPC, closed-loop control, measurement,
• LRD traffic, power laws,
• Streaming, WWW protocols, caching

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Closing Thoughts

• Yet this conversation happened in a major
  research lab (NJ) ?
• Q given the traffic and network topology, how do
  we optimize the routes?
• A1 Uh .
• A2 We dont really think it that way
• A3 We dont know the traffic, we dont know the
  topology, the routers do not automatically adapt
  to traffic, and we dont know how to optimize the
  route configuration. BUT, other than that, we are
  all set!

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Closing Thoughts

• Dont believe anything you read, esp., those
  obviously correct ones!
• Challenge the fundamental!

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Acknowledgement

• Students, collaborators, and MSRA
• Charles X. Ling (Univ. of Western Ontario), Qiang
  Yang (HKUST), Jim Kurose (UMass at Amherst)