The Study Of The Channel State Information Estimate Technology In The Cognitive Radio Environment

In this paper, based on the Cognitive Radio (CR) system which adopts adaptive OFDMA (Orthogonal Frequency Division Multiplexing Access) technology, the estimation techonolgy of Channel State Information (CSI), including the Channel Impulse Response (CIR) and the Signal to Noise Ratio (SNR), in OFDM system is studied. Firstly, the basic principles of OFDM technology are introduced, then the channel estimation and SNR estimation of OFDM systems are studied. Secondly, the CR system which is defined by the IEEE 802.22 standard is introduced and its OFDMA scheme is studied. Then, based on the Most Significant Taps (MST) algorithm and the OFDMA scheme, a improved joint CIR and SNR estimation algorithm, which uses the methodology of time-frequency transformation, weighting and channel taps fade back to reduce the influence of noise on the Least Square (LS) estimation, is proposed and applied in CR system. Further more, the performance of the proposed algorithm is evaluated through simulations, and the result shows that the proposed algorithm can estimate the CSI effectively and accurately in CR systems Finally, a CR simulation platform based on IEEE 802.22 standard is designed and constructed. Then the proposed algorithm is loaded and tested in the platform.