Speedy creation of a cognitive radio demo!
We have had two visitors here for the last two weeks. They came to us via the COST short exchange programmes or Short-Term Scientific Missions (STSM) as they are officially called. These provide finance to enable researchers to visit an institution (university, company, R&D laboratory, etc) in another participating country of the COST initiative.
COST TERRA is the COST action from which Jacek Kibilda visited us. The aim of COST TERRA is to establish a multi-disciplinary European forum, a Think-Tank, focused on coordinating techno-economic studies for the development of a harmonised European regulatory framework to facilitate the advancement and broad commercial deployment of Cognitive Radio/Software Defined Radio (CR/SDR) systems. Oscar Tonnelli visited us from Aalborg University in Denmark. Oscar is part of the COST Action IC0902. The main objective of the action is to integrate the cognitive concept across all layers of communication systems, resulting in the definition of a European platform for cognitive radio and networks. Both Jacek and Oscar came to use Iris – our software radio platform. They achieved a lot in two weeks.
I want to describe Jacek’s work here. Jacek set up demo that focused on dynamic spectrum access. In his implementation a basestation and a number of mobile stations avail of whatever empty spectrum they can find. They use a licensed frequency as a control channel and use the spectrum they dynamically access for data. I was impressed that he got this working in two weeks starting from a basis of no knowledge of Iris. In the demo a ‘primary user’ appears and the secondary network moves to ‘new spectrum’ at the appearance of the primary user – all coordinated via the control channel. One thing I found interesting is the fact that the primary user does not appear exactly in the bands being used by the secondary user but a relocating of the secondary user still takes place because of adjacent channel interference between primary and secondary. Jacek worked with Luiz DaSilva and Keith Nolan while here.
This demo could be interpreted as an example of how a cellular system could use ‘other spectrum‘ it dynamically finds apart from the spectrum it has been statically assigned. Indeed we already hear mutterings of handset manufactures such as Nokia about future handsets that might more holistically deal with spectrum resources (i.e. not just think of discrete bands of spectrum (licenses and unlicensed) and discrete radios that use the spectrum (3G and wifi) and instead think of how all spectrum resources are effectively used).
The image above is a screen grab from the spectrum analyser that was used to view what was happening. The large OFDM signal is the primary user and the signal to the right is the secondary user. There is a faint trace of the control channel to the left of the primary user.
The image here shows the general setup. The node in the middle is the basestation. The platform is Iris as mentioned already and the USRP.
The demo is only a start but it is great that someone can put something like this together very quickly. We are happy that Iris supports such quick prototyping.