Lecture Series in Mobile Telecommunications and Networks (1583KB)

From plain old Telephony to flawless mobile audio communication
Matthew Baker (Philips Research): At the beginning of your presentation, you described the original model for the
voice codecs, based around two filters modelling broadly the vocal tract. As we move towards new, higher data rate
communication systems, like UMTS LTE, there may perhaps be greater use of the system not for listening to speech but
for music and video. Do you see a need for new codec models built around filters or parameterisations perhaps based
on musical instruments or other sound sources than the vocal tract?
Peter Vary: I have two answers to that. There is a nice European research project called FLEXCODE – like flexible
coding. If you type that in your WEB browser, you will end up with the server in Aachen and there is a nice project with
KTH, Bastiaan Kleijn and with Nokia Ericsson and France Telecom. We tried to design a universal codec which might be
used in the future, which could be the future codec – I don’t know. In the standardisation world, we observe presently
the development that we take a standard codec – for example, there is an ITU codec, G.729, which has 8 kbits/s. On top
of that bit rate, there is then additional bit rate, up to 12 to 14, 16, 18 up to 32 kbits/s. The add-on, beyond 12 to 14
kbits/s, is transform coding, so what we are seeing there is the base layer. It is a hierarchical coding scheme. If you
transmit only the 8 kbits/s you can transmit speech. However, if the affordable bit rate is higher, you can have
transparent quality for music.
On top of the base layer, there is transform coding – techniques we know from audio coding. The reasoning behind
that is that you could imagine, let us say, a broadcast service from a central station, and some of the subscribers have a
DSL connection and would like to have the full bit rate, while some just have a GSM phone and they have a reduced bit
rate, or just the base layer. For reasons of compatibility, that seems to be a good idea. However, you clearly see a
convergence of speech coding and audio coding, which is mostly frequency domain-based coding.
John Lowe: This question will involve Mike as well. It is appropriate that Keith Davis is here in particular. From my own
background knowledge, Peter, I find what you have talked about this evening very exciting. However, we are in the
hallowed halls here where they are doing something much bigger than this particular technology subject, which is
encouraging young people to take up engineering. I suspect that the situation in your industry is no different than it is
in mechanical engineering, where we have a shortage of young people at whatever level you might choose. Can we
use this sort of exciting development to enhance the attraction of young people into engineering? And what, Mike, are
Vodafone doing within this industry – and I am not particularly thinking of Vodafone but the industry as a whole – in
this country and in others, particularly in Europe, to attract more young people? Can we use this to aid Keith Davis’s
efforts, and those efforts taking place at the Institution of Mechanical Engineers and other places?
Peter Vary: I can speak for Aachen University, where we have what we call the ‘science truck’. This is a truck which we
drive to schools and then demonstrate experiments there, from mechanical engineering, electrical engineering,
chemical engineering – all kinds, from all the faculties we have. From my group, we have an experiment there which is
called ‘mobile radio’, where the pupils can have hands-on and listen to radio transmissions with bit errors and without
bit errors, and vocoders. We try to attract them. We see the problem. We have open days, but we find that it is better
to drive to the schools and give some lectures and show some experiments.
John Lowe: If I could ask you to be generic, I know that taking technology to schools in individual areas works. I also
run an industrial museum and we try to do that, with hands-on works and so on. However, I was looking for the general
lessons that we can share across the broader picture. We cannot go into every school with a science truck – and I know
our schools reasonably well.
Peter Vary: I think we should educate the teachers. In their study schedules, there should be more engineering
science, because the teachers do not know enough about engineering.
John Lowe: I am really looking for practical help to make that happen.
Michael Walker: Exactly on that point of helping the teachers, there is a project in the UK called Project Enthuse, which
was started by the Wellcome Trust, and we are a member of that. The idea of Project Enthuse is that we provide
continuous professional education to science teachers. We bring science teachers into the National Learning Centre
and other places and we send engineers from industry to that centre and show those science teachers how their
science is being applied today in industry. They can then take that back to the schools, to make their lessons perhaps
more interesting to the pupils, to stimulate them to go on to study science and engineering at university. It aims to add
that extra to the course. To go to your specific question, the Academy could take lectures like this, or the key parts of
The Royal Academy of Engineering 59