Lecture Series in Mobile Telecommunications and Networks (1583KB)

To the edge of chaos?
The complexity and the promise of a technology and service-neutral future
There is an enormous amount of computing required in many of these things. There can be extremely complicated
reasoning and analysis to be done to take in a whole load of information to process that and make decisions. However
the ability to do this kind of comuputataion is more widely available.
I have a small example here, of the spectrum correlation
Useable Bandwith
function. Essentially, if you want to detect the presence of a
signal for example, you can use an energy detector – but an
energy detector may not be good for signals with low power,
like a spread spectrum, but people sometimes use what they
call cyclo-stationary analysis to detect the presence of a very
Useable Bandwith
low powered signal. Signal inherently have cyclo-stationary
features in them which occur as a by product of the natural
processing of the signal (e.g. modulation of the signal).
The cyclo-stationary feature detector allows you, having some
knowledge of the signal in advance, to look for these features.
If you try to do this on a general purpose processor, for
software radio currently, it can be quite difficult, because the processing involved is extremely complicated and the GPP
cannot handle the processing fast enough.
What comes to the rescue is the Playstation 3 and you will see that, more and more now, people are using the Cell BE to
do all sorts of interesting things. The Cell BE can do real time cyclostationary processing with ease – the video here
capture the output of the process and was recorded in my lab. [Video not shown]
Essentially, you can do a spectral correlation function – a live spectral correlation function – just using the Playstation 3.
It can take an 8 MHz signal and do a real time spectral correlation function. The only reason I am showing that is
because it is indicative of what can be done when it comes to processing data, and the really high, super-duper
processing that exists. When we started our research into cognitive radio function, it was really hard to do an FM
receiver on a PC, whereas now we can do all sorts of incredibly complex things. Playstation 3 has 6 SPEs in it but you
can get larger numbers in other systems. The Playstation 3 is only about $400. It just goes to show that the price
ranges are changing and that complex processing needed for the brain of a cognitive radio is more and more possible.
There are very exciting advances in the design of heterogeneous fabrics on which signal processing can be done.
The focus is the world is very much on parallel processing, and that is what happens in the Cell BE, as I mentioned.
You do not need to think just in terms of arrays of homogenous processors but you can actually think of things in terms
of arrays of heterogeneous processors. It will be possible to map different processing challenges to different processing
elements in your heterogeneous array of processors.
So when you talk about reconfigurability, you are actually talking about a lot of different things now. You are talking
about reconfiguring your signal, shaping and sculpting your signal, and changing your waveform. You are talking about
reconfigurability at the MAC layer and reconfigurability at network layer. You are also talking about reconfigurability of
the resources you use. Sometimes, it might be more appropriate to use an FPGA, a mixture of DSP, or a mixture of GPP
or whatever. More and more, you see high level design that allows you to direct your resources to where and when it is
needed. This underlies the fact that much of what we are talking about here is more and more possible as time goes
on.
As I said at the beginning of this section, there are so many different areas that contribute to filling out the picture of
how this world is emerging and what is happening. What I have here is a screen chart of a policy-based management
approach to radio. This allows you to instruct the radio about how to behave in quite a dynamic fashion. You could
have a regulator who sets policies in some kind of centralised fashion, and those policies would filter out to the radios,
which in real time would implement that. They could download new policies as they move to new jurisdictions, and
the policies can also be hierarchical and dynamic. You see more of this policy-based management filtering through
much of the radio work that you see today. Again, you are adding to this whole picture, and not only do you have
reconfigurable entities that sculpt and shape and make best use of resources, you have ways of instructing and
managing those radios that weren’t so dynamic when they existed before.
The Royal Academy of Engineering 33