Professorial_PublicLecture_2015

04/08/2015
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Inaugural Professorial Lecture, 14 April 2015, Conference Centre, USW
Trials, Tricks and Triumphs of a
Digital Journey
Ifiok Otung
To my late Dad Rev Charles Otung (1918 – 2008)
To my Mum Sylvia Otung
To my wife Buchi Otung
“The most important thing in this life is not so
much where we stand as in what direction we
are moving.”
 Words my Dad made me memorise at an early age. Source unknown.

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Précis
We have come a long way from January 1845, when
the arrest by telegraph of John Tawell for the murder
of his mistress sparked mass excitement, to year 2015
where ‘broadband’ anytime anywhere hardly raises
any eyebrow.
This talk examines the tricks and technologies that
have made this massive transformation possible and
highlights the challenges ahead
Contents
• My roots and early influences
• Mobile and Satellite Communications at USW
• Digital Journey: We’ve come a long way!
• Digital Journey: Trials and Travails
• Digital Journey: Tricks and Triumphs
• Digital Journey: There’s still a long way to go!

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My Roots and Early Influences
Go back in time until you can go no further,
For trillions of years if you have to.
What do you see at this beginning?
You see a particle, or you see God.
Neither is more scientific, neither more religious.
Both involve a leap of faith beyond reason.
Complexity is always a combination of simplicity.
The art of solving a complex problem is to break
it into its simple parts.
Caveat:
Simplism ignores underlying complexity.
So don’t be remiss and slipshod

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What’s remiss?
• Apart from 6 o’clock, at what time instants
will the minute and hour hands of a clock
be exactly 180 apart?
• If you thought, “5 past 7 of course”,
that’s remiss!
12
6
39
Every human being has huge potential, having
been purposefully crafted by an Indescribable
God.
The Big Challenge:
How to unlock this potential by minimising the
hindrances caused by a damaged packaging.

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MSc in Mobile & Satellite Communications
• Six taught modules and a major project
– Satellite Communications;
– Satellite Networking;
– Digital Communication systems;
– Applied DSP;
– Mobile communication technologies;
– Product innovation and entrepreneurship
• Avenues for collaboration with Industry
– Internship; 16‐week major project; Industrial Lecture
Research in Mobile & Satellite Comms
• Design of satellite communication systems for
resilience, spectrum efficiency & energy efficiency
– Interference mitigation in HTS systems
– Spatio‐temporal signal processing
– Mobility enhancement
– Ka/V‐band link measurements
– Channel modelling and short‐term fade prediction
– Adaptive modulation & coding
• Ka‐band Earth observation & surveillance

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Main Facilities
• Two ground stations for satellite beacon
measurements
• Weather stations
• Anechoic chamber
• Simulation platforms (STK, MATLAB/SIMULINK,
FEKO, OPNET, etc.)
• Wireless and Digital Communications Labs.
Earth Stations: Outdoor Units
Pontypridd
ChilboltonObservatory

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The Team
• MSc Project Students
• Researchers and Interns
• Academic Supervisors
– Judith Agnew
– Jon Eastment
– Francis Hunt
– Ifiok Otung
– Jurgen Richter
Our Interest Spans GEO, MEO, LEO orbits
Watch this video at
https://www.youtube.com/watch?v=bvLTSTVne7I

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Telegraph in January 1845:
“Them cords that hung John Tawell”
A MURDER HAS JUST BEEN COMMITTED AT SALT HILL AND THE
SUSPECTED MURDERER WAS SEEN TO TAKE A FIRST CLASS
TICKET TO LONDON BY THE TRAIN WHICH LEFT SLOUGH AT 7.42
PM. HE IS IN THE GARB OF A KWAKER WITH A GREAT COAT ON
WHICH REACHES NEARLY DOWN TO HIS FEET. HE IS IN THE LAST
COMPARTMENT OF THE SECOND FIRST CLASS CARRIAGE
Internet Penetration:
From 0.8% in 1995 to 40.4% in 2014
1B
0
3B
2B
4B
6B
5B
7B
1995 ‘6 ‘7 ‘8 ‘9 ‘00 2002 2004 2006 2008 2010 2012 2014
No. of people, billions (B)
World population
Internet access
Year

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1995 2000 2005 2010 2015
5
0
15
10
25
20
35
30
40
43
Year
Internet Penetration (%)
Internet Penetration: Percentage of World Population
Access Through Various Media
• DSL or ADSL
• Optical Fibre
• Cable modem
• High speed leased lines
• ISDN
• Analogue dial‐up modem
• Powerline
• Satellite broadband network
• Terrestrial Mobile broadband networks

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2000 2002 2004 2006 2008 2010 2012
Year
Percentage of World Population (%)
0
10
20
30
40
50
60
70
80
90
2013
Growth in Mobile Phone Subscription
Trials and Travails
• Signal travels at nearly the speed of light, but
– Intermediate nodes give best‐effort service
– Path loss and attenuation
– Noise and interference
– Pulse spreading

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Impossible is a lie peddled on the back of a wrong method.
• How is it possible that 75 trillion emails (to
cite just one traffic class) are reliably sent
through the Internet each year?
When it rains …

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Time diversity solution being developed in our Group

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Puzzle 1: Extracting Certainty from Uncertainty
• You come to a junction of two paths (P1 and P2), one of which is
safe and the other unsafe, but you don’t know which one. There
are two friends at the junction who know, but one of them (Mrs
T) ALWAYS tells the truth and the other (Mrs L) ALWAYS lies. The
problem is that you don’t know their identity and you are
allowed to ask only one question to only one of them to which
the answer can only be either YES or NO.
• Design a solution that identifies the safe road with absolute
certainty.
Failed Attempt
Mrs T
Is P1 unsafe? NO
Mrs L
Is P1 unsafe? YES
(a) P1 is actually safe
Mrs T
Is P1 unsafe? YES
Mrs L
Is P1 unsafe? NO
(b) P1 is actually unsafe

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Correct Solution
Mrs T
Would your friend
say P1 is unsafe?
YES
YES
(a) P1 is actually safe
Mrs L
Would your friend
say P1 is unsafe?
NO
NO
(b) P1 is actually unsafe
Mrs T
Would your friend
say P1 is unsafe?
Mrs L
Would your friend
say P1 is unsafe?
(a) P1 actually safe
Mrs L
Is P1 unsafe? YES
Mrs T
YES
Mrs T
Is P1 unsafe? NO
Mrs L
YES
(b) P1 actually unsafe
Mrs L
Is P1 unsafe? NO
Mrs T
NO
Mrs T
Is P1 unsafe? YES
Mrs L
NO
Equivalent Representation of Correct Solution

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1
10
100
1000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.999
Probability of packet failure, p
Average No. of attempts until
successfully delivered
Success is not the absence of failure but the triumph of repeated attempts
If at first you don’t succeed, strategise
• Don’t orchestrate repeated attempts
willy‐nilly
• Have inbuilt mechanism for
congestion control
• Minimise packet errors

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Information in numbers
• Command, control, status, text, voice, music,
sound, sensor, graphics, video: All are
represented as a sequence of numbers.
ASCII
Encoder
Hello
72, 101, 108, 108, 111
0100100001100101011011000110110001101111
Even analogue information can be changed to numbers
Low Pass Filter
( )g t
g(t)
t
Analogue Signal
( )g t¢
t
( )g t¢
Sampling
( )sg nT
nTs
g(nTs)
gq(nTs)
Quantisation
( )q sg nT
nTs
100
101
110
111
000
001
010
011
Encoding
Digital Signal
(in binary format)
100110111110101001010011010000110111110101001010011010

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Puzzle 2: Reliability in Chinese Whispers
• Bob wants to send a code of 4 bits to Alice, which Alice does
not know in advance. However, Bob can only reach Alice
through Chinese whispers in which one and only one of the
bits may or may not be changed before reaching Alice.
• Devise an arrangement that Bob and Alice can use so that
Alice will always know with certainty if any of the 4 bits has
been changed and which one.
Solution: Bob’s End
• To send 4 bits m1m2m3m4 to Alice,
Bob appends another 4 bits r1r2c1c2
as shown, determined so that there
is always an even number of 1s in
each row and each column.
m1 m2 r1
m3 m4 r2
c1 c2
• For example, to send 1010 11 0
1 0 1
0 0• Bob therefore sends 10101100

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Solution: Alice’s End
• Alice copies into the array the sequence
m1m2m3m4r1r2c1c2 that she receives.
m1 m2 r1
m3 m4 r2
c1 c2
• For example, Alice receives 10001100.
Recall that Bob sent 10101100.
11 0
0 0 1
0 0• She then checks the columns and rows for
even parity
• Hey presto, she has located the error and flips the bit to correct it.
• She therefore knows with certainty that the message from Bob is
1010
When nature gives you free lunch, you pay with your dinner
• Alas, there’s a price! There always is!!!!!!
• But there’s no limit to the ingenuity you can bring into
inventing new ‘tricks’ to solve this puzzle!
• Here’s your guide if you ever want to join in the game:
– Use smallest number of extra bits
– Minimise error non‐detection
– Minimise error mis‐correction

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You can never be certain that it is right, but you can know
when it is wrong
• In reality there’s no bidirectional certainty.
Who said you can’t eat your cake and have it too?
Welcome to modern communication engineering where you can
Well, almost!
• You are allocated 36000 kHz of bandwidth to
provide ‘broadband’ services for a large region.
Each user when connected uses 30 kHz of your
allocated bandwidth.
• Devise a solution that allows more than 30,000
users to be simultaneously served
Puzzle 3:

04/08/2015
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Solution: Frequency Reuse
• Using the 36000 kHz bandwidth in one large
beam that covers the entire area gives
network capacity = 36000/30 = 1200 users
• Using one‐third of the allocated bandwidth in
spot beams A, B, C as shown, allows 400 users
per spot beam, and hence 30,800 users!!!!
• Using orthogonal polarisation in each beam
doubles this capacity to 61,600 users
B
C
C
A
B
C
B
C
A
B
C
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
A
B
C
A
B
C
A
A
B
C
A
B
B
C
A
B
C
C
A
B
C
A
B
C
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
A
B
C
A
B
A
B
C
A
A
B
A
Total allocated
spectrum
(A + B + C)
Solution Extended: Elastic Capacity
• Why does each user require 30 kHz bandwidth?
• Scrutinise the process and use new tricks, tools
and trade‐offs to reduce each user bandwidth
requirement to say 7.5 kHz
• This would increase capacity to 246,400 users
• Wow! From just 1200 users. That’s impressive!

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Fundamental Trade‐offs Involve
• Signal Power
• Transmission Bandwidth
• Time
0010
11 01
2 bits per signal
000110
011 101
100
010
111
001
Conclusions – 1/3
• Digital communication
triumphs over trials and travails
through
tricks, techniques, tools and trade‐offs
• We did not explore these T’s in detail, but we
did solve 3 illustrative puzzles.

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Conclusions – 2/3
• We have come a long way from the era when we
built separate roads and parks for separate
traffic classes.
• We now have one highway for all – The Internet
and one multipurpose park – The smart device
• But broadband anytime anywhere is in year
2015 still an overstatement or hype.
• The digital divide is still entrenched within
and across the nations of the world.
Conclusions – 3/3
• But we are today still going out in all weather dressed
in rain coat just in case it rains.
• We face significant security threats from petty cyber‐
burglary to crippling denial of service.
• We need fresh insights, new tricks and smarter design
of resilient and secure communication systems that
use resources efficiently and sustainably.
• Yes, we’ve come a long way but there is still far to go.
• Could you help shape the journey?

04/08/2015
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Thank you
Live in hope for the best, design in
fear of the worst.

Professorial_PublicLecture_2015

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