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UBC Publications

Focus 1990

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19 15-1990
Vol. 1, No. 2
Fall 1990
CICSR researchers are
developing techniques
that will be used in the
communications networks
of the 21st century.
■ People have come to rely on their
communications systems as an everyday
part of their business and personal lives.
For most people, this communications
system is the telephone. In the future,
people will have their own personal
communications systems that will enable
others to reach them at any time, anywhere
in the world. „
... continued on page 2
CICSR researchers Samir Kallel and Cyril Leung
are working on ways to reduce error in
transmission of information over mobile radio
channels. The techniques they are developing
could be used to improve data transmission over
communications networks such as the MDI
system for public safety forces (right).
Photo: Mobile Data International (MDI)
Director's statement
Dr. James Varah
More on CICSR researchers and
their work in communications
technology page 2
Norm Hutchinson joins CICSR and
UBC Department of Computer
Science page 3
CICSR Calendar
page 4 Director's Statement
This is our second CICSR newsletter,
meant to cover the events of Fall,
1990. As you can see, we are highlighting the area of Communications
in this issue, to coincide with our Distinguished Lecture Series for 1990/91.
This approach also serves to bring
your attention to the excellent research
in communications and related areas
presently in progress at UBC. For
example, these CICSR researchers
form an important node in the Institute
for Telecommunications Research, the
Federal Network of Centres of
Drs. Peter Lawrence and James Varah
Excellence in Telecommunications. The
members are well-represented in both
the Departments of Computer Science
and Electrical Engineering.
I would also like to take this opportunity
to inform you that I will be on leave for
the first six months of 1991. During my
absence, Professor Peter Lawrence from
the Department of Electrical Engineering will be Acting Director. Peter is
well-known for his research in telerobotics, and has always been a strong
advocate of the CICSR concept. ■
UBC Dept. of Electrical Engineering professors Victor Leung and Takis Mathiopoulos..
COMMUNICATIONS ... continued from front        demodulator even for a digital signal.
Dr. James Varah
Professor Takis Mathiopoulos in the UBC
Department of Electrical Engineering has a
keen interest in the communications
systems of the future. He is working on an
important aspect of the global communications network of the future: digital cellular,
the next evolution of cellular technology.
Currently, cellular transmissions are
analog. There are about two million users
of cellular technology in North America,
and Mathiopoulos estimates that in a few
years, there will be ten million users.
Already, cellular networks are operating at
near-capacity in many large cities.
Mathiopoulos is working on a new
approach to digital cellular that will allow
five users in the same 30 kilohertz
bandwidth where there is now one. He is
also working to improve system efficiency
to allow up to ten users per channel.
Mathiopoulos is also concerned with
minimizing what he calls "spectrum
pollution," a phrase that carries a lot of
weight in these days of environmental
awareness. "The spectrum is a very
precious resource," says Mathiopoulos.
"We have to ensure we don't take up too
much of the spectrum and that we don't
create interference."
Digital cellular communications will be
introduced by the end of the year, but there
will be a five-year transition period before
analog systems will become obsolete. In
the meantime, users will need hybrid
systems. Mathiopoulos is working on such
systems which can use an FM (analog)
Mathiopoulos is especially interested in
cellular because of the large market out
there for the technology. "My group's
research is applied. We always try to adapt
our research to industry's needs."
Mathiopoulos' group consists of himself
and four graduate students.'Tm so excited
about our research, I'm working 12 hours a
day," said Mathiopoulos. "It's an exciting
field, so we have the drive. We feel we can
contribute a lot to the area of personal
Samir Kallel is another communications
specialist in the UBC Department of
Electrical Engineering. His main area of
research is in controlling error in communications systems.
One way to reduce error is to increase
transmitted power, but in some situations,
this isn't possible. Kallel is developing
error control coding that requires less
power but still extracts good performance
from communications systems.
Kallel says there are two ways to control
error in digital communications. One is to
send an automatic repeater request to each
information bit and add parity bits to detect
errors in transmission. If there are errors,
the transmitter sends the information
packet again until it is received correctly.
Another alternative is to incorporate
redundancy bits into each block of data for
the purpose of error correction. The more
redundancy bits the better the error-
correction performance, but less information is transmitted. Kallel's research involves developing a system that will
adapt the number of redundancy bits
transmitted according to channel variations: the more noise on the channel, the
more redundancy bits will be sent.
Kallel plans to adapt this technology to
data transmission through mobile communications networks. Kallel believes
adaptive error control techniques will be
applied in the next generation of cellular
Kallel likens the systems he is working on
to the way people communicate when
they're talking to each other. "If you feel
the person is not understanding you
correctly, you add more
information, and you
repeat what you're saying.  I
That's basically what this
system does — it repeats
itself until the message is
received correctly."
Cyril Leung, a faculty
member in the UBC Department of Electrical
Engineering is conducting
some research very
similar to Kallel's:
reducing error in data
communication over
mobile radio channels. He
is working on error-correction coding, adding
redundant bits to reduce
the effects of transmission
errors and in automatic
repeat request (ARQ) 	
With an ARQ system, if an error is
detected, the receiver sends an automatic
request to retransmit the information
packet. Leung is developing a system
where the faulty information packet is not
automatically discarded. Instead, if the
system receives a number of these
erroneous copies, they could be combined
to deduce a correct copy.
Another area of interest for Leung is in
overcoming the problem of signal fading
due to distance and obstacles. "Fading
greatly complicates data communication
over mobile radio channels," says Leung.
One solution which Leung is investigating
is called orthogonal frequency division
multiplexing (OFDM). In conventional
modulation schemes, information bits are
transmitted serially over the communication line. Using OFDM, a block of bits is
transmitted simultaneously, each bit
occupying a narrow frequency band.
"Since the time duration of each bit is now
much longer than if one used the conventional serial scheme, signal fades will
affect each bit only slightly," said Leung.
Leung is also working to solve the multiple
access problem encountered by users of
mobile communications networks. A
typical system will have one fixed base and
a number of mobile terminals. When there
are several terminals transmitting to the
fixed base at once, which is often the case,
there are severe contention problems which
greatly degrade system performance. "One
of my objectives," said Leung, "is to
design a good multiple access system to
minimize the contention problem."
Cyril's namesake, Victor Leung, is also
interested in mobile communications, but
those based on satellite, not terrestrial,
networks. The bulk of Leung's research
land-based systems. He is looking at the
design of multiple access protocols in
frequency division multiplex for fibreop-
tics. Currently, fibreoptics offer tremendous bandwidth with far more capacity (in
the terrabits-per-second range) than
electronic transmitters and receivers can
keep up with. "To overcome the electronic
bottleneck, you divide the band into
channels of lower capacity," said Leung.
This is called multiplexing.
Leung is working on a protocol to ensure
users efficient access to the different
channels. He says it's much like controlling access to and from a multiple-lane
superhighway. ■
Dr. Cyril Leung
Dr. Norm Hutchinson
involves network design for the mobile
satellite system (MSS) to be launched in
North America within five years.
Leung's work uses the Demand Assignment Multiple Access (DAMA) scheme
which he says is "like a switch in the sky
being controlled on the ground." The
scheme allows the system to determine
available capacity for a call, monitor the
call, recoup capacity and re-assign it.
A future application of satellite networks
that interests Leung is mobile radio
communication applied to satellite.
Satellites have an advantage over terrestrial-based networks in their wide area of
coverage. Three satellites can easily cover
the entire planet. Land-based systems rely
on numerous transmitter towers and are not
economical in sparsely-populated areas.
Still, it takes a lot of engineering money to
launch satellites, and the use of them is
expensive. Leung is involved in the design
of a communications protocol for data
messaging via satellite. The goal is to use
satellite channels as efficiently as possible.
In his research, Leung has not ignored
UBC welcomes
Norm Hutchinson
Beginning in January, the UBC
Department of Computer Science and
CICSR will have a new member. Norman
Hutchinson, currently assistant professor
in the Department of Computer Science at
the University of Arizona will take on a
similar position at UBC.
After teaching in Arizona for almost four
years, and taking his Masters and PhD
degrees in Computer Science at the
University of Washington, Hutchinson said
he was anxious to return home to Canada.
He chose UBC because "the university
seems really committed to building a
strong department."
Hutchinson is interested in two main
research areas, communication protocol
and distributed programming languages.
He is working with the x-kernel to define
operating system abstractions that make it
easier to implement network protocols. H Passing notes
Building update
We are continuing detailed planning of
the CICSR/CS Building; we expect to
complete the planning phase by the end
of the year. Construction is expected to
begin in the Summer of 1991 and be
completed by the Summer of 1992.
Model of the CICSR/CS Building.
Lecture reviews
Dr. Mike Brady, Professor and Chair of
Engineering Science at Oxford, visited
UBC in May as a Distinguished
Lecturer. His talk covered major recent
advances in intelligent robotics, with
emphasis on mobile robotics and active
perception, especially vision. He also
outlined his views to the overflow crowd
on the current research agenda.
In Brady's visits to the CICSR robotics
groups, old friendships were renewed,
and common problems discussed. His illustrated talk, and reprints of his recent
Oxford papers, are available from the
CICSR office.
A five-day intensive course on the
Cambridge HOL system, was held here
June 4-8. The course was sponsored by
CICSR and the UBC Centre for Continuing Education, and organized by Jeffrey
Joyce of the Computer Science Dept.
The Cambridge HOL system is an
interactive environment for machine-
assisted theorem-proving in mathematical logic. The system can be used to
construct formal proofs about the
correctness of computer hardware or
software with respect to a formal
description of system requirements.
The five-day course consisted of both
lectures and hands-on laboratory
sessions. It attracted local and international participants, including representatives from British Telecom, IBM
(France), Mitsubishi, Boeing Aircraft
and Unisys. It will likely be offered
again in June 1991.
For those interested in knowing more
about CICSR, drop by our office and
Susan Perley or Gale Ross will be
happy to assist you. If you like, ask them   \
to add your name to our CICSR FOCUS
mailing list. ■
Distinguished Lecturer Dr. Mike Brady spoke to a
full house on advances in intelligent robotics.
CICSR Distinguished Lecture Series:
Window on Digital Communications
October 18, 1990
Crytography in the Computer Age
Dr. James L. Massey,
Member, the Swiss Academy of
Engineering Sciences.
Growing computer interconnection to
sensitive data bases sharpens the need for
privacy and authenticity of messages. In
the first lecture of the 1990/91 season, Dr.
Massey will discuss relevant and recent
cryptographic techniques.
November 1, 1990
A Trot Through the Future World of
Gigabit Networks - Can We Get There
From Here?
Dr. David J. Farber,
Director of the Distributed Systems
Laboratory, University of Pennsylvania.
Lectures run from 1:00 p.m. to 2:30 p.m., Room 100,
November 22, 1990
Formal Specifications for Testing
Designs and Implementations: Applications to OSI Protocol Testing
Dr. Gregor V. Bochmann,
holder of the IDACOM-NSERC-CWARC
chair of industrial research on communication protocols, University of Montreal.
December 13, 1990
Forward Error-Control as a Central
Design Concept for Digital
Communications Systems
Dr. Andrew J. Viterbi,
Vice Chairman and Chief Technical
Officer,Qualcomm Inc.; Professor of
Electrical Engineering, UCSD.
February 7, 1991
The Limits of Layering
in Network Protocols
Dr. David Clark,
Senior Research Scientist,
MIT Computer Science Lab.
March 7, 1991
The Opening Up of Communications -
Towards Wideband Telecommunications
Dr. Robert Lucky, Executive Director,
AT&T Communication Sciences Research.
April 4, 1991
Networks in the Nineties
Dr. Leonard Kleinrock,
Professor of Computer Science and
Chairman of TTI, UCLA.
SCARFE Building. Guests welcome at no charge.
The UBC Centre for Integrated Computer
Systems Research (CICSR) is an interdepartmental research organization made up of computer-
related research faculty members in the Departments of Computer Science, Electrical Engineering and Mechanical Engineering. Currently there
are more than 50 CICSR researchers who direct
over 100 graduate students and collaborate with
dozens of industrial firms in areas such as robotics, artificial intelligence, communications, VLSI
design and industrial automation.
CICSR FOCUS is published twice a year.
EDITOR:     Leslie Ellis
DESIGN:     Rob Bishop
Office: 2053 - 2324 Main Mall,
Vancouver, B.C. V6T1W5
Tel: (604)228-6894,fax: (604)228-7006
Contact: Susan Perley
19 15-1990


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