Sapna,
To elaborate on Peter's response, the US operates differently than the UK (and most other EU countries for that matter) with regards to PSME spectrum allocations. First, there are maybe two or three people at the FCC (all in the Office of Engineering Technology) who actually come close to understanding the work flows and types of entities when it comes to wireless microphones and similar devices. The call center operators have no idea who to even send you to. But fear not; you found a great resource in these forums.
Secondly, FCC licenses are not issued on a per event basis; rather they are issued for three, then seven year terms to those persons/entities meeting certain eligibility requirements. What wireless mic users can do - currently both unlicensed and licensed until after our 600MHz auction, then just licensed users - is register in the white space geo-location database(s) to obtain interference protection from WSD's/TVD's at the time(s) and location(s) specified. Basically, registering in the database simply removes those TV channels from the WSD/TVD availability pool. It offers no protection from any other type of user, nor is it any type of coordination process.
As far as coming up against WSD's/TVD's in the field, fixed base type devices are showing up in convention centers and stadiums. We've experienced and had reports both from other coordinators and the NFL about WSD/TVD installations [done improperly as they apparently were either not connected to the geo-location database. or had the incorrect coordinates programmed in]. There are currently no personal/portable products in the market place.
As for the rest of Peter's comments, all very sound advice, as usual. And his Best Audio web site is a fantastic resource.