Mr. Thilak de Silva.
BSc. Eng., MSc, CEng, FIE(SL), FIET(UK), CITP(UK),
MBCS(UK), MIEEE (USA)
M.Sc. in IT - Year 1 Semester II - 2012
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Jitter
Digital to Digital Conversion
Line coding
Block coding
Scrambling
Analog to Digital Conversion
M.Sc. in IT - Year 1 Semester II - 2012
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At the end of this session you will have a
broad understanding of Digital to Digital
conversion and Analog to Digital Conversion
of signals.
M.Sc. in IT - Year 1 Semester II - 2012
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All data packets may not follow the same
route.
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Due to delays (in routers, media etc) different
data packets reach the destination at
different times.
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Then jitter occurs.
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Is vital in multimedia applications.
M.Sc. in IT - Year 1 Semester II - 2012
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Line coding – converting digital data into a
digital signal that can be transmitted through
a transmission media.
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Data elements – what we need to send
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Signal elements – what we can send
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Signal elements are the carriers who carries
data elements.
M.Sc. in IT - Year 1 Semester II - 2012
Ratio (r)= Data elements
Signal elements
Source - http://train-srv.manipalu.com/wpress/wp-content/uploads/2011/10/clip-image0044-thumb4.jpg
M.Sc. in IT - Year 1 Semester II - 2012
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Unipolar - NRZ
Polar – NRZ,RZ and biphase(Manchester and
differential Manchester)
Bipolar-AMI and pesudoternary
Multilevel – 2B/1Q , 8B/6T and 4D-PAM5
Multitransition – MLT 3
M.Sc. in IT - Year 1 Semester II - 2012
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8 binary values in 6 signals
10110011
-0++0-
Data
Signal
2^8 =256
3^6 =729
Additional Combinations = 729 – 256 = 473
M.Sc. in IT - Year 1 Semester II - 2012
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256 number of combinations are already
defined and if there are any undefined
combinations, that means there is a error.
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Having additional combinations leads to easy
error detection at the receiving end
M.Sc. in IT - Year 1 Semester II - 2012
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Every line coding schema should have,
 Error Detection and
 Self Synchronization (done by PLL)
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PLL will not Operate if there are no state
changes
 Eg: All 0 s in RZ
M.Sc. in IT - Year 1 Semester II - 2012
R - resistance per unit length,
L - inductance per unit length,
G - conductance of the dielectric per unit length,
C - capacitance per unit length,
j - imaginary unit, and
ω - angular frequency.
Source :http://www.google.lk/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Transmission_line_element.svg/220pxTransmission_line_element.svg.png&imgrefurl=http://en.wikipedia.org/wiki/Characteristic_impedance&usg=__mIMtU47Cbk5Fjqt5yYJ1BPgoJYI=&h=134&w=220&sz=4&hl=en&start=1&zoom=1&tbnid=_
6PLMVwREZh4GM:&tbnh=65&tbnw=107&ei=n6kmT_6EE87NrQf8lvyoCA&prev=/search%3Fq%3Dcharacteristic%2Bimpedance%26hl%3Den%26gbv%3D2%26tbm%3Disch&itbs=1
M.Sc. in IT - Year 1 Semester II - 2012
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Because of capacitor signal gets charged,
In Manchester coding it gets charged to a
some extent and remains.
We need to have a way of discharging DC
component, (avg =0), Eg: AMI
M.Sc. in IT - Year 1 Semester II - 2012
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Changes a block of m bits into a block of n
bits. (n>m)
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Eg:
 4B/5B coding – 4 bits converted to 5 bits
(32-16 = 16 number of redundant combinations)
 8B/10B – 8 bits are converted to 10 bits
M.Sc. in IT - Year 1 Semester II - 2012
DATA
Block
Coding
Line
coding
Sender
For Error
detection
DATA
Block
Coding
Convert data to
signal
Transmissi
on media
Line
coding
Receiver
M.Sc. in IT - Year 1 Semester II - 2012
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Long sequence of zeros (0) are converted into
a combination of bits.
000000
010110
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Mainly for synchronization.
Useful to achieve security.
Eg:
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 B8ZS
 HDB3
M.Sc. in IT - Year 1 Semester II - 2012
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Converting an Analog signal to a Digital
signal.
Used in telephone systems to convert the
voice signal to digital signal.
Eg:
 Pulse Code Modulation
 Delta Modulation
 Adaptive Delta Modulation
M.Sc. in IT - Year 1 Semester II - 2012
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Data Communications and Networking,
Forouzan, Chapter 04, 4th Edition
M.Sc. in IT - Year 1 Semester II - 2012
M.Sc. in IT - Year 1 Semester II - 2012