Date Added: Apr 2011
Lack of frequency spectrum is becoming one of the major problems in the telecommunication field with the introduction of several new radio communication technologies. Cognitive Radio (CR) technology promises to be one possible solution to this problem, by allowing access of unlicensed users in licensed bands, based on an opportunistic approach and without interfering with the licensed (primary) user. In order to identify which frequency bands are more suitable for such purposes, it is necessary to evaluate the degree in which licensed bands are actually used. Although some measurement campaigns have already been carried out, most of them were done in the USA and only a few in other locations worldwide.