Making better use of the spectrum - CTVR
When mobile phones and radios communicate over the airwaves they use part of what people in telecommunications refer to as the spectrum. Spectrum is scarce, and becoming scarcer all the time, because the number of new devices is increasing fast and they all need a share of it. Prof Linda Doyle has been researching ways that the airwaves can be used more efficiently than today and she has come up with a ‘cognitive radio’ that can find signalling space, no matter where it is located.
The Centre for Telecommunications Valuechain Research, or CTVR, is a national centre - headquartered at TCD - that does research into future telecommunications systems. “The mission of the CTVR,” said Prof Doyle, “is to do outstanding research in the telecommunications sphere, to think about what the telecommunications networks of the future are going to be like, and to do this work in collaboration with industry.”
The CTVR has researchers based at UL, NUIM, UCC, DIT, DCU as well as TCD. It is one of the nine well funded, prestigious Centres for Science and Engineering Technology (CSET) supported by SFI. There are five research strands within the CTVR and Prof Doyle is the research leader for the‘emerging networks’ strand.
One of the key areas for Prof Doyle is what is called ‘spectrum’. In telecommunications the word is used to mean all the airwave space that is available for devices to send or receive communications. Every communication device, whether it is a mobile phone, or a radio, needs some spectrum in order to operate. These devices also all need to operate at different frequencies – in a defined ‘space’- in order not to interfere with each other. This is becoming more difficult as the number of devices is growing relentlessly, as the amount of available spectrum throughout the world shrinks.
Spectrum is seen by telecommunications people as a scarce resource, as there are a finite number of frequencies that exist. Some of these frequencies, might, using real estate jargon, be considered ‘beachfront property’ – something everyone wants. The reason that everyone wants these frequencies is that they have good physical properties that make them behave and propagate in a way that is conducive to the kind of communication system that any given entity wishes to introduce or build.
There are tonnes of new wireless devices, requiring spectrum, emerging all the time, and this is putting pressure on the limited amount of spectrum that remains. This is where Prof Doyle comes in. She examines how people are using the spectrum and she has found that people are not using it effectively or efficiently. There are many people around the world, she said, that are looking at ways to better improve spectrum use, and she is one of these. This work can also help prevent spectrum running out in coming years.
There are national and international regulators that decide who gets to use precious available spectrum and for what purpose. In this sense the regulators are extremely powerful. In the UK, there is the Ofcom (the Office of Communications), for example, while in Ireland we have ComReg (the Commission for Communications Regulation). Some of the regulations that cover this area are quite outdated, however. For example, in Ireland, the Wireless Telegraphy Act, 1926, remains the main legislative plank on which decisions on spectrum are made. A long time before the wireless internet explosion. The sinking of the Titanic on 5th April, 1912, was a catalyst for introducing spectrum regulations. On that terrible night some ships close by did not hear the distress signals of the Titanic as she sank. The ship that eventually arrived to rescue survivors was the Carpathian, but that vessel was further away than nearer ships that didn’t pick up the distress signal. The signals weren’t heard because of the mess in spectrum back then. The Titanic was broadcasting on spectrum that some nearby ships weren’t listening to. The authorities began to clean up the free-forall that was spectrum usage after the sinking. From that time, almost a century ago, right up to today, there are very strict and stringent rules worldwide on how spectrum can be used. For example, there are a range of frequencies set aside for mobile phone usage.
The regulations governing spectrum make it very difficult for newcomers to the telecommunications scene to secure space to operate. This had led a lot of researchers, including Prof Doyle, to try and find a better way of doing things, and she began to think that a ‘dynamic approach’ to spectrum was the way forward. Prof Doyle came up with the idea of a ‘cognitive radio’, a radio with a ‘brain’. “The radios look around and see where they can find empty wide spaces. They hop into the space and then they move out of the space quickly when the owner comes back.” “Think of a car park,” she said, “if the owner of a space in the car park is not using the space at that particular time, then someone could use the space until he comes back. A cognitive radio works in the same way. It searches for spectrum space at a given location, finds it, then dashes into the space, and out again when the owner returns.” TV ‘wide space’ is one good source of un-used spectrum. A cognitive radio must reconfigure itself to make use of any spare space. It changes the frequencies that it operates on and its parameters to ‘scope’ the signal that it is transmitting to fit into the available wide space ‘hole’. “This is a terrific way to make better use of spectrum”, said Prof Doyle.
Ireland holds many advantages for those that wish to do tests and trials using spectrum. On the continent of Europe, and Britain, the population is denser, and this means that most of the spectrum is being already used. Ireland, which has just one border, and just four million people, has a relatively good spare spectrum capacity. The CTVR has its own spectrum and it is free to operate in the heart of Dublin city. This would not be possible in other European cities. Prof Doyle and her colleagues, thus, are promoting Ireland as a ‘playground for spectrum’ – somewhere where leading academic researchers and top flight industry could come to experiment.
Prof Doyle graduated in Electrical Engineering from UCC in 1989. She worked for Siemens AG, Germany before she returned to academia to do an MSc (1992) and a PhD (1996) – both in TCD. She was appointed as a lecturer in the Department of Electronic and Electrical Engineering at TCD in 1997. Prof Doyle Director of the CTVR and leader of the ‘Emerging Networks’ research strand.
