I just attended a workshop organized by the National University of Ireland, Maynooth and the Office of Naval Research(Global) on the possibility of using military spectrum for civilian purposes. The workshop was held at Maynooth University, in Kildare, just outside Dublin, Ireland. The Chairmen Luis DaSilva (Trinity College) and Ronan Farrell (Maynooth University) had put together an impressive program with most leading European Researchers in spectrum sharing and “cognitive radio” in place. Several talks reported on the progress in spectrum sharing research, which lately has been dominated by practical trials both of TV White Space (at KCL in London, UK) and of Licensed Shared Access (LSA) in Finland (VTT Oulu and University of Turku). Practical trials have many benefits and highlight implementation problems, but they have limitation in accessing scalability, e.g. what happens when there are thousands of terminals, which is very important for the commercial and regulatory interest.
Many, including me, showed healthy skepticism about the use of TV-White Space for any kind of cellular or even short range high capacity use. It seems that train has left the station as cellular operators clearly have shown preference for exclusive spectrum in the “digital dividends” in 800 and now in the 700 MHz band .What remains as interesting applications for TVWS is the low end of the TV broadcast spectrum 200-400 MHz where antenna size prohibit smartphone usage. Here there seems to be a market for rural applications and wide-area M2M (cf. Weightless).
A large part of the discussion was focused on the secondary use of military and maritime radar bands – primarily the S (2.7GHz) and C-bands(5GHz). From a technical perspective, several presenters beside myself pointed out that sharing between radars and indoor low-power devices makes perfekt sense. What does the military think ? Lt Cmdr Phil Watson of the Irish Navy gave an interesting exposé of the plethora of mostly high-power communication and navigation equipment onboard a naval vessel. Whenever you are requested to share, the question “what’s in it for me ?” arises. What are the incentive for the military to use less spectrum ? This was a hot discussion item. Whereas spectrum this is mainly an economic question in the civilian world, national security and safety-of-life are arguments that are hard to deal with. One interesting proposal was referring to the electromagnetic signature of the ships. In visual ligth, their grey paint makes them hard to spot. In the electromagnetic spectrum however, a naval vessel looks like a bright, multicolored christmas tree. Could saving spectrum be combined with low probability of detection ? Could in fact sharing with other services make it more difficult to be detect the ships ? Interesting questions!