”Our input to the European regulatory body was accepted and included in their recent major updates of the regulatory framework”

Lei Shi came to School of ICT in 2007 for master studies in Wireless systems. Two years later when he had graduated he continued his academic carrier as a PhD student in Communications systems. Now he has defended his licentiate thesis "Availability Assessment for Secondary Access in TV White Space".

Where are you from and where did you study before coming to School of ICT at KTH?

– I had been studying at the master program on wireless systems at KTH during 2007-2009 before I started the PhD at School of ICT. Before that, I was studying at University of Electronic Science and Technology of China in Chengdu, China.

What is your topic and why did you choose it?

– The general topic of my study is about radio spectrum management with a focus on secondary access in TV bands. This topic was one of the main focus of the successful FP7 project QUASAR which started at the same time as I started my PhD, and I was mainly involved in this project during the last two years. This study is very interesting, because there were big expectations about this concept of secondary access in TV bands, many had hoped this would be possible to levitate the Spectrum shortage issue faced by the mobile operators. However, there was little concrete evidence showing the real potential of this secondary spectrum, and our research was aimed at providing the quantitive assessment to either support the argument or 'break the myth'.

Describe your topic in short

– Basically, my topic is about how to quantify the potential of TV bands, if it could be used by other types of wireless services, for instance mobile broadband. But this type of access is on a secondary basis, meaning that the TV service should not be affected by the secondary service.

Tell us something about your results

– Well, we have identified a few key challenges for evaluating the TVWS potential or availability, like cumulative effect of multi channel interference on TV reception, and protection of TV against interference from secondary uses located close by transmitting on adjacent channels. We developed analytical models and frameworks for the evaluation on top of the European regulator's framework, and our input to the regulatory body was accepted and included in their recent major updates of the regulatory framework.

Our quantitative assessment of a few sample scenario using the proposed models and approaches indicate considerable potential for dense deployment of low power secondary system in the TV band.

What will the future bring for your research, how will you continue and what focus will you have on your PhD thesis?

– The short term 'next step' is to evaluate different approaches, other than secondary access, to improve the utilisation of TV band. But the recent European level regulatory decision on the second digital dividend, reallocation of 100MHz out the 320 MHz TV band for mobile broadband service, leaves less room for any future study on TV band.

Find the licentiate thesis by Lei Shi here

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