Transcript Information_Age_ReCompressed

The Age of Information
Nathaniel J. C. Libatique, Ph.D.
Science 10, Topic 4: Technological Underpinnings
Ingredients
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Broadband wireline transmission
Wireless transmission
Digitization of the Analog World
Democratization of content
http://www.analog-girl.net, http://blog.analog-girl.net/
http://www.time.com/time/specials/2007/article/1,28804,1704856_1704855_1704824,00.html
Beacon Hills of Gondor
In the film version of The Lord of
the Rings, the signal beacon in Minas
Tirith was lit by Pippin Took contrary
to Denethor's orders.
ww.tuckborough.net/images/beaconhills.jpg
The Optical Telegraph
A semaphore telegraph, optical telegraph, shutter
telegraph chain, Chappe telegraph, or Napoleonic
semaphore is a system of conveying information by
means of visual signals, using towers with pivoting
shutters, also known as blades or paddles. Information is
encoded by the position of the mechanical elements; it is
read when the shutter is in a fixed position.
http://en.wikipedia.org/wiki/Optical_telegraph
Semaphore vs. Telegraph
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The semaphore system was cleverly designed, and provided a
strategic advantage for France in a difficult time. However, it was
almost 30 times more expensive per message than the electric
telegraph. Here's a brief breakdown using (inflation-adjusted to
unknow date by unknown method) US$[citation needed]:
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Semaphore line, 120 miles (Paris to Lille)
15 towers ($1,500,000), At least 15 full-time operators
($450,000/year), operates at most ten hours a day.
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Sends roughly 2 words per minute (1 symbol per
minute, at 2 symbols per phrase, using the efficient
directors' codebook).
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* Cost to send one word one mile (1.6 km), at 10% markup:
$0.0114
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Electric Telegraph line, 120 miles (190 km)
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At least six full-time operators ($180,000/year)
Poles, right-of-way, wires, installation: $15,000/mile, ($1,800,000)
Operates 24 hours a day.
Sends 15 words per minute (includes breaks for the operators).
Cost to send one word one mile (1.6 km), at 10% markup:
$0.0003809
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http://en.wikipedia.org/wiki/Optical_telegraph
Fields and Waves
f l=c
Carrier Frequencies
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Wireless information is carried on top of a
“carrier frequency”
The higher the carrier frequency, the more
information can be sent via this carrier
Light waves have frequencies in the hundreds of
THz! (100 THz = 100 x 1012 Hz = 100,000
GHz, one hundred thousand times the carrier
frequencies for mobile wireless (about 1 GHz)
Bandwidth increases
with carrier frequency
The larger the carrier
frequency fc the
greater its bandwidth
Df or B.
Nature of Light
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Reflection
Refraction
Diffraction
Interference
Is light a wave or a particle?
Answer: It is BOTH.
Particle: Reflection
Incident angle = Reflection angle
True locally, even for curved surfaces
Symmetric Property
Particle: Refraction
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Snell’s Law: n1 sin a1 = n2 sin a2
Fermat’s Principle (Least Time)
n1
a1
In the denser
medium, light
bends towards
the normal
n2
a2
TIR: Total
Internal
Reflection
Refraction
http://www.fas.harvard.edu/~scdiroff/lds/LightOptics/FishTankTIR/FishTankTIR.ht
ml
Critical
Angle
TIR
Creating a Light Guide
Propagation in MMF Fiber
fc
Critical
Angle fc
MMF = multimode fiber
Lowest Loss in the Infrared
Diffraction of Water Waves
Water waves are
like rays when
aperture is large
with respect to
wavelength
As the aperture size
decreases …
Diffraction of Water Waves
The incident wave diffracts
out of the aperture as if it
was a point source …
Light “rays” also act like waves in similar diffraction experiments!
Wave: Interference
Interfering water waves in a ripple tank
Wave: Doppler Effect
Blue Shift
Red Shift
Red Shift
Absorption lines in the optical
spectrum of a supercluster of
distant galaxies (right), as
compared to absorption lines in
the optical spectrum of the Sun
(left). http://en.wikipedia.org/wiki/Redshift
Fiber Modes: Light Ray Picture
Fiber Modes
LP01
LP11
LP03
LP13
Fiber Modes
LP21
LP41
LP22
LP17 16
LP28 5
Analog Signal
s(t)
t
Quantization and Sampling
s(t)
111
110
101
100
011
010
001
000
t
Quantization and Sampling
s(t)
111
110
101
100
011
010
001
000
t
001 001 011 011 100 101 111 110 100 100 011 010 100 010 001 010
Quantization and Sampling
s(t)
t
s(t)
001 001 011 011 100 101 111 110 100 100 011 010 100 010 001 010
t
The Signal is Reconstructed at
the Receiver!
001 001 011 011 100 101 111 110 100 100 011 010 100 010 001 010
Digital to Analog
Conversion
Original
Analog Signal
Aliasing
One has to sample/digitize the original analog
signal at a rate at least twice the frequency of the
signal – the Nyquist criterion. Otherwise, if we
sample too slowly, when the digital signal is
subsequently reconstructed we will come up with
an erroneous signal.
Nyquist Criterion: f.sampling < f.max
Digital Channel Requirements
• 200 page novel (100,000 Words); Holy Bible (775,000 Words)
For 5 letters/word and 7 bits/character = 3 Mbits
1 sec transfer of information  3.5 Mb/s
• Voice Communications
Intelligible speech with 300 Hz to 3.5 kHz
Sample at 8 kHz with 8 bits/sample  64 kb/s
• Compact Disk
Dynamic range of >80 dB and 20 kHz bandwidth
Sample at 44 kHz with 14 bits per sample  640 kb/s
From G. Tangonan, 1988 First SEA Laser School, UP, Diliman
Digital Channel Requirements
• Video Channel
55 to 65 dB S/N needed for good quality
Sampling at 4x color subcarrier (4 x 4.43 MHz)
8 bits/sample at 17.7 MHz  142 Mb/s
With compression: 5 bits/sample at 8.86 MHz  44.3 Mb/s
• HDTV 720p: 720 lines by 1280 columns = 1 Mpixel
• High Speed Computer I/O
32 lines at 25 MHz typical
multiplexing leads to 800 Mb/s
• High Speed Computer I/O
Line Rates and Protocols
• E1 - leased line, 2 Mb/s
• DS3 - pt. to pt. private line, 44.7Mb/s
• STM-1 - 155.52 Mb/s
• Fast Ethernet - 100 Mb/s
• Gigabit Ethernet - 1 Gb/s
• Fiber Channel - storage area networks, 1 Gb/s
• Wifi 802.11n - 248 Mbps max
• Wifi 802.11g – 54 Mbps
Digital Advantages
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Less Susceptible to Noise: boolean decisions, error
detection and correction
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Circuits easier to fabricate at larger scale
Higher fidelity, quality
Compatible with computing platforms
More easily encrypted
Google’s Daily Doodle for
27 April 2009
Number as Abstraction
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Quantization Error
Bit Stream vs. Analog
Abstraction into a series of
Yes and No bits of
information
“The shadow of the shadow
of the shadow…”
Real or Abstract?
 Who
you are
 Facebook
 Digital
passports
 How
much you own or are worth
 Whether you exist or not
 Birth
certificates
 Citizenship
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India Fingerprinting, Iris Scanning Over One
Billion People
The Indian government is ramping up efforts to
fingerprint and iris scan the entirety of its 1.2
billion citizens in an ambitious scheme to issue
national ID cards with biometric details. The
plan has so far already enrolled 110 million
people and issued 60 million numbers, with the
aim of enrolling 200 million by this March and
600 million by 2014.
VEIN Scanning
Also see: spectrum.ieee.org/computing/software/bitcoin-the-cryptoanarchists-answer-to-cash/0
Thermodynamics: 1st and 2nd Laws
Energy is conserved, it is neither created nor
destroyed
 Entropy always increases until it reaches a
maximum value (Disorder vs. Order)
Time’s Arrow
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Second Law of Thermodynamics
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/seclaw.html
Paradox: Maxwell’s Demon
James Clerk Maxwell
Information is Energy!
Einstein and Szilard
The measurement process, in which the demon acquires a
single “bit” of information (i.e., the information as to
whether an approaching molecule is a slow one or a fast
one) requires energy and must produce at least as much
entropy as is decreased by the sorting of that molecule
into the left or right side of the box. Thus the entire
system, comprising the box, the molecules, and the
demon, obeys the second law of thermodynamics.
Claude shannon: Information
Content
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Information has
Entropy – the
information
content of a
message
Degree of Surprise
I(m) = - log[p(m)]
http://en.wikipedia.org/
wiki/File:Monkeytyping.jpg
FUTURE OF DATA: Encoded in DNA
By ROBERT LEE HOTZ (Wall Street Journal, 16 Aug
2012; http://online.wsj.com)
In the latest effort to contend with exploding quantities
of digital data, researchers encoded an entire book into
the genetic molecules of DNA, the basic building block
of life, and then accurately read back the text.
Harvard biologist George Church, in his office Wednesday,
recently encoded a book he wrote into the genetic molecules of
DNA.
Photos by Kelvin Ma for the
Wall Street Journal
Dr. Church keeps a vial of
DNA encoded with copies of
his latest book
The experiment, reported Thursday in the journal Science,
may point a way toward eventual data-storage devices with
vastly more capacity for their size than today's computer
chips and drives.
"A device the size of your thumb could store as much
information as the whole Internet," said Harvard
University molecular geneticist George Church, the
project's senior researcher.
In their work, the group translated the English text of a
coming book on genomic engineering into actual DNA.
DNA contains genetic instructions written in a simple but
powerful code made up of four chemicals called bases:
adenine (A), guanine (G), cytosine (C) and thymine (T).
Demos
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Single slit diffraction
Sinusoid + Noise on LabView
Total Internal Reflection
Visualizing IR via silicon CCD camera
Refraction
Aliasing