Lecture Series in Mobile Telecommunications and Networks (1583KB)

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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
I apologise for hopping between topics in this section, but this is the reality of this type of area. That is why we now hop to combinatorial auctions. Auctions come in to play when dealing with spectrum trading. There is some very interesting work in combinatorial options that can support the fluid spectrum management concepts I have been referring to throughout the talk. Rather than saying, ‘I am putting in a bid for this one chunk of spectrum’, you can use a combinatorial option say that you want to bid for this chunk or that chunk, but you can even make that bid more expressive and you can say, ‘I would like any piece of spectrum here, or I would like it there, or I want it anywhere along there.’ – these kinds of expressions. This is becoming a much more key topic of research and essentially the whole point here is that the more expressive you allow the auction to be, the more efficiently you can help fill in the pattern you want to develop. So, on one side, we have the technology advances and on the other side we have the kinds of ouction mechanisms that you can imagine tie into those Rubik’s cube diagrams that existed in the first place - certainly at the initial stages and if not, there are other options that are being signed up to in spectrum-type approaches. CRFS When you think of this kind of spectrum world view, you will have to think differently, first of all about how it is policed, but you also need to think differently about any entities needing information to make the kinds of decisions we have to make. This leads you to think differently about different business models. There are opportunities for companies who do spectrum monitoring and provide usage databases, in this case for spectrum monitoring systems, that actually feed in as a live service into radios, to use that information to make decisions. It makes you think in a different way about how a mobile or radio communications entity can be divided up. I told Dave Cleevely I would include a picture of his company! These kinds of companies feed into the reality of being more liable. Continuing the move from topic to topic we now move on to another challenge. In a very dynamic world radios need to be able to find each other without knowing in advances the frequencies at which they will operate. Just in time spectrum users may fall into this category as well as dynamic spectrum access users. One technique you can that can be used to let another communication device know the frequency you are using, without the need for a control channel is a cyclo-stationary signature. As I mentioned earlier, many signals have inherent periodicities in them and those inherent periodicities are sometimes useful in helping you to find or identify that that signal is present. What you do with a cyclo-stationary signature is you intentionally embed a signature in the signal and, in this particular case, you intentionally embed it as an OFDM signal by correlating various sub-carriers, and you get something like this shown on the slide. This enables automatic frequency acquisition, because the signature tells you something about the frequency of operation of the transmitting device and it also tells you something about the identity of that network. This signature is like some kind of digital watermark that can be found by other users. You can obviously make the signature more complex in order to make it robust to multipath environments where you might have frequency selected fading. It can be combined with MIMO. In this case one antenna fist transmits the signature and later the second antenna transmits the signature – this happens repeatedly – and we get a diversity gain. That is the whole beauty of this reconfigurable world, where you can build blocks and you can combine them together, and see what kind of gains you get from them. I had a little video, showing one of these systems working in reality, but I will not try to run that now. The upshot of all of this is that, again, there is an enormous number of devices and a whole world of reconfigurable systems that allows you to think about this much more fluid way of allocating spectrum. CTVR bands More and more around the world, we also see now the opportunity to experiment with real-life spectrum. In Ireland in particular, they have a whole range of test licence schemes and my research goes back to what happens to be the frequencies we own for our testing of various ideas that we have. In Japan, they talk about the ubiquitous zones of deregulation and in various other countries, such as Singapore, there are areas where you can go and test. And while in itself this is not some kind of technological advance, it is yet another factor which contributes to the broader picture of allowing experiments with real spectrum, with real equipment that can explore whether these ideas can work. 34 The Royal Academy of Engineering
Page 1 and 2: Lecture Series in Mobile Telecommun
Page 3 and 4: Foreword This compilation brings to
Page 5 and 6: From wireless networks to sensor ne
Page 7 and 8: From wireless networks to sensor ne
Page 9 and 10: As far as the routing of packets is
Page 11 and 12: easons. In the internet, one never
Page 13 and 14: Implementation with laser pointers,
Page 15 and 16: here of laptops, and all these lapt
Page 17 and 18: adds a great deal of discrete compl
Page 19 and 20: Questions & Answers Mike Walker: Th
Page 21 and 22: Human beings will also evolve and w
Page 23 and 24: Welcome and introduction Professor
Page 25 and 26: ComReg Collection - Start 16/Apr/20
Page 27 and 28: evidence that people give in favour
Page 29 and 30: chunks of spectrum where you are in
Page 31 and 32: As an aside, I was reading a few of
Page 33: Of course, it is not just one mask,
Page 37 and 38: Questions & Answers Michael Walker:
Page 39 and 40: Nobody - believe you me, it came ou
Page 41 and 42: The second aspect of my comment is
Page 43 and 44: want to call it - that sits there a
Page 45 and 46: From plain old Telephony to flawles
Page 47 and 48: From plain old Telephony to flawles
Page 49 and 50: You can see that there is much room
Page 51 and 52: 1024, we transmit 10 bits, so to sp
Page 53 and 54: Bandwidth extension with hidden sid
Page 55 and 56: 4 Vision: ambience audio communicat
Page 57 and 58: Questions & Answers Michael Walker:
Page 59 and 60: I said five years ago and what I he
Page 61 and 62: them and perhaps leave out some of

Lecture Series in Mobile Telecommunications and Networks (1583KB)

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