Travel Report from
University of South Australia, Adelaide, Fall 2002
Introduction
In the fall 2002 I spent
two months at the Institute for Telecommunications Research (ITR) at University of South Australia
(UniSA) in Adelaide, Australia supported by travel grants mainly from ARTES but also from Ericsson.
ITR is a research institute
at UniSA in Adelaide, specializing in technology for digital wireless
communications, including both fixed and mobile satellite and terrestrial radio
services. ITR is located
in the Signal Processing Research Institute building at The Mawson Lakes
Campus. This campus is located at Mawson Lakes, 14 km north of the center
of Adelaide. The 80 staff and postgraduate students in ITR engage in research
programs designed to be of direct benefit to industry.
Purpose of Visit
The ITR has a recognized
reputation for both theoretical research and practical implementation in the
area of concatenated coding and iterative decoding a currently very hot
topic. Iterative decoding is a sub-optimal decoding method with good accuracy
and significantly lower complexity than the optimal method. Generally it is
known that most block codes are good, provided that they are long enough.
However, the complexity of optimal decoding is NP-hard and exponentially
increasing with code length. Recently, a sub-optimal coding and decoding
strategy has been discovered where, provided that the code is concatenated, the
output of a sub-optimal decoder can be fed back again in order to be refined
iteratively. This procedure, termed iterative decoding or turbo-decoding, has
performance close to the optimal one with manageable complexity increase.
For real-time communication
purposes iterative decoding and concatenated codes are very interesting topics.
We want to benefit from the high quality that the long concatenated codes
provide, but at the same time keep the decoding complexity, and hence the time
to decode, at a minimum. This deadline dependent coding and decoding procedure
is what I am currently looking at in my research.
Dr. Alex Grant is the
leader of the Coding and Information Theory group at ITR and I was invited to
work closely together with him and the members of his group during my visit.
Dr. Grant is a recognized expert in iterative signal processing with a
particularly emphasis on analytical tools for performance evaluation.
Currently, Dr. Grant has four students working on various aspects in iterative
signal processing. In addition, my main supervisor Prof. Lars K. Rasmussen was
visiting the ITR during most of 2002 and could, consequently, provide me with
necessary supervision.
Results
The work resulted in two
conference papers; one is accepted [1] and will be presented at the IEEE
Wireless Communications and Networking Conference. The other is submitted and
decisions are due in March. A poster presentation of the work in [1] will also
be presented at the Australian
Communications Theory Workshop in Melbourne [2]. Furthermore, I took a course in Multi-user
detection given by Dr. Grant and Prof. Rasmussen. Finally, on the way back to Sweden I stopped in San Jose, California, USA
to attend and present a paper at the Real-Time and Embedded Technology and Applications Symposium, RTAS 2002.
Graduate Studies in Australia
The Ph.D. program in
Australia is typically only three years. No coursework is mandatory but is
often encouraged by the supervisor. Since the ITR is a research institute they
do research for both academia and industry, but provide no teaching of
undergraduate students. This means that neither professors nor Ph.D. students
have any mandatory teaching duties. If you want to become a Ph.D. student you
have to apply for funding yourself, usually through government-funded
scholarships. Upon doing this you should also state your research topic and
suggest an appropriate supervisor. This means that lots of responsibility is
put on the student from the very beginning.
Adelaide
Adelaide is the capital of
South Australia hosting 1.2 million people originating from more than 100
different countries around the world. Many migrants arrived
from Europe (especially Italy) after World War II and introduced the café
culture that lends Adelaide its relaxed atmosphere. The city was named
after Queen Adelaide, the wife of the British King William IV. Adelaide was
unusual in that it was settled by free people - the city has no convict history.
Adelaide has a
reputation of being the festival capital of Australia and also the food and
wine capital of Australia.
Superfluous details
Σor Australia versus Sweden
[3]:
If you want to cross the
street you better be fast. If you walk normally you almost make it half way
across the street before the lights become red again.
No stores have the opening
hours listed on their doors! It is very annoying. There is a little supermarket
very close to where I live, but no one knows its opening hours.
The water tastes like a mix
of chlorine and seaweed. Adelaide is located in the driest
part of the driest continent, which makes it hard to access clean water. Most
people in Adelaide buy bottled water or install purifying filters in their
homes.
When at a restaurant you
seldom order your food at the table. You notice this by the fact that nobody in
the staff seems to care about you. You are then supposed to go to the counter
and place your order. The weird thing is that you cannot order food and drinks
at the same counter. You pay for food at one counter and then go over to the
next and order drinks. This is regardless if you want water, coke or wine. It
may even be the same guy that took your food order that makes his way over to
the bar to take your drink order. This is especially annoying if you wish to
pay for the entire dinner with credit card and are not sure upfront how much
you will eat or drink.
The Australian milk does
not contain 3% fat, but is 97% fat free! Why dont you write how much fat there
is in the milk instead of writing how much fat there isnt in the milk?
All buss stops are request
stops, which means you wave your hand to the bus with the appropriate number.
This is troublesome because often three buses with different numbers arrive at
the same time. How do you stop the last bus? My bus is always the last one so I
never see the number until it has already passed usually by overtaking the
other two others that have already stopped.
Buying candy is hard,
especially so called lösgodis (loose weight candy?). In Sweden there is one
price for all sorts. In Australia it isnt every sort has an individual price
stated on the respective boxΣ You have to take one bag for each sort and since
I usually buy 20 different sorts (obviously none of them with the same price),
I gave up.
Conclusions
My visit was of great
benefit to my research. Having to describe real-time communication problems to
people with non-real-time backgrounds, but with excellent communication
knowledge is very instructive and gives you new insight to your problem. In addition, it is always valuable and
interesting to visit a different research institute than the one you are used
to and see different solutions to similar problems.
References
[1]
Elisabeth
Uhlemann, Tor M. Aulin, Lars K. Rasmussen and Per-Arne Wiberg, Packet
combining and doping in concatenated hybrid ARQ schemes using iterative
decoding, accepted
for publication at the IEEE Wireless Commun. and Networking Conf., New
Orleans, LA, USA, March 2003.
[2]
Elisabeth
Uhlemann, Tor M. Aulin, Lars K. Rasmussen and Per-Arne Wiberg,
Concatenated hybrid ARQ using iterative decoding for real-time communication,
accepted for
publication at the Australian Communications Theory Workshop 2003, Melbourne, Australia, February
2003.
[3] F. Brännström, Personal
Conversation, Chalmers University of Technology, 2002.