Lecture 1 Introduction

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Lecture 1Introduction

• Principles of Communications
• Fall 2008
• NCTU EE Tzu-Hsien Sang

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Managerial Stuff

• Website http//140.113.225.188/phpBB2/
• Please register with your student ID number.
• My office Hours Thursdays 330530pm.
• TA ???,??? ED 317A (Office Hours TBA)
• Grading (tentative) Homework 25 Midterm 35
  Final 40
• Five best homework scores will be chosen (each
  counts for 5).

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A Few More Things

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• Please ask questions! I am eager to have your
  feedback. If you have any issues, please speak
  up. Dont wait until its too late!
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• To encourage the exchange on class, each
  reasonable response to my question will be
  credited with 1 extra point on the final grade.
  Each student is eligible to receive up to 5 extra
  points.

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In the beginning there was the word

• Define communication.
• Goal conveyance of information
• Methods signals and systems
• Define information
• What do we care information value or amount?
• More too often we take the convenience of modern
  communications for granted.

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Remembrance of Things Past
Source Fernand Braudel 15?18???????????????
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The Value of Information

• In 1815, the Rothchilds (a Jewish banking family)
  received in London the news of Wellingtons
  victory at the battle of Waterloo a full day
  ahead of the governments official messengers.
  (Dump the franc, bought in the British pound, and
  made a hell lot of money.)
• In 2002, Dave Cummings moved his firm's
  (Tradebot) computers in Kansas City to buildings
  in New York and New Jersey that house central
  computers for two big electronic stock exchanges.
  (Save about 20 ms. Enough to intercept orders
  before they get matched. Make 20,000,000 per
  year.)

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Modern Communications
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More on Two Perspectives
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We are what we can do

• How are we going to study these two subjects?
• How to represent a signal?
• How about the noise?
• How to measure the amount of information?
• How to visualize the information space?
• How to put a whole system together?
• Weve got two powerful weapons alright.

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My Little Two Pennies

• Linearity Probability
• How to study a complicated thing?
• First, dissect it! But you need to put it back.
  (The paradigm of analysis/synthesis)
• What can you say about things that you really
  dont know much, e.g., the noise?)
• Know thy dice! (Make the uncertainty principle
  your best friend.)

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Subject Matter

• Introduction
• Review of signals and systems
• Analog signal transmission and reception
• Random processes
• Effect of noise on analog communication systems
• Information sources and source coding
• Introduction to digital communications

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The inevitable has come
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Lets Learn Some Names

• Input Transducer
• Messages analog or digital
• Message conversion e.g. speech ? voltage
  variations
• Transmitter
• Purpose couple the message to the channel
• Primary functions modulation, filtering,
  amplification, and coupling.
• Modulation
• (1) for ease of radiation
• (2) to reduce noise and interference
• (3) for channel assignment
• (4) for multiplexing or transmission of several
  messages over a single channel
• (5) to overcome equipment limitations.

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More Names

• Channel Signal degradation.
• Receiver Primary functions are demodulation and
  amplification.
• Output Transducer Loudspeaker, tape recorders,
  personal computers, LCD screens, etc.
• Noises (Three major sources listed below)
• Internal noise noise generated by components
  within a communication system, such as resistors
  and solid-state active devices. (Thermal noise,
  shot noise, and flicker noise)
• External noise Atmospheric noise Man-made
  noise (Ignition noise Switching noise
  Radio-frequency interference (RFI), etc.)
• Extraterrestrial noise Solar cosmic noise
• Signal degradation Fading

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How many lines do you get?Channel Conditions