Abstract
The limitation of the spectrum bands is a major bottleneck for the development of next generation wireless networks. Cognitive Radio (CR) aims at improving the spectrum utilization by taking advantage of licensed but currently unused spectrum. CR has broad applications including dynamic spectrum access and interference management, which will largely impact the next generation of wireless devices and networks. In this paper, we conducted a survey on CR networks from various aspects such as waveform, spectrum management and sensing, testbeds, performance evaluations and etc.