ABSTRACT
Future wireless communication will focus on wideband multi-media communication, its best-possible obstacle is imbalance and scarcity of frequency source. Cognitive radio provides a technology to resolve above contradiction, which can exploit the limited frequency source effectually by spectrum assign to adjust some parameters such as modulation type, central frequency(Ciucu et al., 2006). Its key technologies include spectrum sensing, spectrum assign, channel state estimation and so on.
