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 ComReg Collection - Start 16/Apr/2007. 18:02:30. Stop: 18/Apr2007, 12:09:00 Source: Shared Specturm Company (http://www.sharedspecturm.com/) As a result of these kinds of measurements, many people have asked why we can’t do different things. Why can’t we, to a certain extent, ‘squat’ in the spaces that are empty? People talk about overlay approaches, where you find a gap in the spectrum and you temporarily use it, or here, for example, you might just use the spectrum at night time and then give it back to the main owners during the course of the day. They also talk about underlay approach, where you sneak in under the signal in such a way that you are not going to adversely affect the other users. This concept of dynamic spectrum has been very much on the agenda in recent years. People are saying that they are not happy with how the spectrum is managed and they ask why we can’t have this dynamic approach. The story does not stop there. As most people will know, in the world we currently live in we have digital TV coming into effect soon, and analogue TV will have to be switched off by 2012. The dynamic spectrum story and the use of what we call ‘white spaces’, or TV white spaces, is very on the agenda because of the move to digital TV. The New American Foundation has carried out analyses in various different cities around the US and they show if you switchover to digital TV from analogue TV, you will have a large amount of white space left over - so why can’t we use that? In the UK, you use the term ‘interleaved spectrum’ to refer to this white space and actually the UK is very forward-looking and Ofcom are considering the use of what they call ‘cognitive radio’ to make use of the TV white spaces here, which is quite an exciting development. These kinds of things of developments are continuing to push how ideas about how we use spectrum. And it is not just in areas where very few people live that there is lots of available white space, but also in cities like San Francisco and high density cities. The New American Foundation has done analyses across all sorts of different geographical areas. If we allow the use of white spaces/ interleaved spectrum, or dynamically use spectrum throughout the day, it would certainly lead to more efficient usage. However, there is another debate that has been ongoing since the fifties that encourages us to think of spectrum in property terms. Why can’t we decide that there is a set of rights that you can associate with spectrum (akin to property rights and which are tradable. Hence rather than stipulating that this spectrum has to be used to deliver a specified service, using a certain type of technology, why not let the spectrum consumer use spectrum as they see fit and trade it when they want to? A very famous economist in the 1950s, Ronald Coase, was one of the first people to question this. Since then, many economists have become involved in this debate and I usually find that, if you read any of the economists’ papers, one will say this is right and another will say it is wrong, but not necessarily support it with evidence. However, the main question, first, is whether spectrum is a scarce resource and, if it is, can we treat it as property, in a property-like fashion? Is it feasible, from a technical point of view, to consider it like property and to think about trespassing in terms of signals rather than in terms of trespassing on somebody’s property? And, if so, how should we go about it? So various economists and engineers have contributed to the debate over the years, including economists currently, like Tom Haslett, who is a very famous proponent of property rights for spectrum. Essentially, he argues that spectrum is scarce resource and those people who value it most should get it. On the other hand, there are those people who say that spectrum is only a scarce resource because of how we currently manage it, and that we should really consider more spectrum commons. One of the major pieces of The Royal Academy of Engineering 25
evidence that people give in favour of this is approach is that they huge innovation took place in the ISM bands. The availability of unlicensed spectrum gave rise to a huge amount of innovation and a huge amount of growth in the wireless industry. The way that we typically define a commons today, is by some kind of power limitation, i.e. we do not permit devices that are unlicensed to radiate too much, so they can’t cause too many problems. However, the proponents of the commons argue that you could take a much more advanced approach and develop etiquettes and more complex ideas around how you can encourage behaviour through using a shared resource in a way that you all appreciate each other’s needs. John Crowcroft (computer scientist) and Bill Lehr (economist) wrote a very interesting paper on how you would go about thinking in a more advanced way about spectrum commons. This work is a really good example of technologists and economists working together and thinking through these problems. The big problem that people talk about when they talk about a commons is the notion of the ‘tragedy of commons’. Essentially the tragedy occurs when somebody behaves selfishly and overuses the commons resource to the detriment of others. This slide shows quite an interesting piece of work by artist Jonah Brucker-Cohen called Wifi Hog. In this work he was challenged this Utopian idea that wifi is a fantastic thing and easily available to all. You go to your hotspot and get the access you want. In Wifi Hog the system, as the name suggest, hogs the whole of the spectrum and stops other people from entering. This illustrates the concept of the tragedy of the commons very nicely. The overall point I am making here is that spectrum management has continued for years in a particular direction. Many people – and the number of voices is growing – are challenging the way we look at how spectrum is managed. Whether the challenge is from the point of view of taking a commons approach or from the point of view of property rights, or whether the focus is dynamic spectrum access the challenge is growing and this is a hugely exciting field of study. Spectrum management approaches are also being challenged from an application perspective. Here I have a picture of fire-fighters. Public safety spectrum is often considered differently from other spectrum – you cannot put a value on people’s lives – hence the spectrum for these services is very important. However, we now hear people talking about the notion of the ‘interruptible spectrum’. One example of this is when a public safety service provider uses gets access to commercial spectrum in emergency scenarios. Hence some of the spectrum resources are therefore transferred from the commercial users to the public safety users. Thinking from an application perspective helps think of how we should access spectrum. Let me move on to my Utopia, the way in which I think spectrum should be managed. To a certain extent, this takes many of the ideas already discussed and puts them together . To express this Utopia, I will use these diagrams that are based on the Rubik’s cube, which a couple of people will have seen and heard before. To a certain extent, they sum everything up in the best way of describing what is happening here. To understand what I am about to explain, you now need to think of spectrum from this kind of cube point of view. In the diagram you have frequency, space and time. The X,Y,Z coordinates of space are represented as one and I have placed some places around Ireland on the diagram. If we look at spectrum like this we can begin to see other things. For example, this could be Vodafone in Ireland, and this could be their GSM licence – the space between frequencies is 26 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: ComReg Collection - Start 16/Apr/20
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 and 34: Of course, it is not just one mask,
Page 35 and 36: I apologise for hopping between top
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

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