Date Added: Mar 2012
Today's wireless networks are regulated by government organizations where a fixed spectrum is assigned to license holders for a specific geographic region. The spectrum usage is dominated in some areas and a major amount of it is underutilized. The spectrum utilization ranges from 15% to 85% depending on the area and time of usage. The limited spectrum availability and its inefficient use have lead to the development of new approaches where licensed and unlicensed networks can exist in the same area and utilize the existing spectrum in the most efficient manner.