Research And Implementation Of Related Technologies In Cognitive Radio Systems

Cognitive radio can realize the importance of the dynamic usage of frequency band on an opportunistic basis and other under-utilized licensed spectrum to improve use of the spectrum. For a long time, researchers devote to upgrading transmission rate per frequency for better use of spectrum, based on this, people will use cognitive radio technology to increase the efficiency of spectrum.This paper studies the influence of the power detection caused by several factors under IEEE 802.22 spectrum sensing scenarios. Then, it proposes the method to improve the performance of power detection. OFDM has been introduced to IEEE 802.22 standard as an efficient technique for improving spectrum usage. A time domain channel estimation technique for OFDM systems based on comb-type pilot arrangement is investigated. The techinique will reduce the number of pilots used to channel estimation. It also studies the channel fading and multipath character considering the need of channel estimation technique research. A new statistical simulation models for WSSUS channel is introduced. FFT is used to modulation and demodulation in OFDM systems. In the last chapter, it mainly researches about the FFT realization in FPGA, and fulfills the complex FFT algorithm in the form of recursion. Besides, it introduces the method of how to improve the FFT algorithm by using rotation mode of CORDIC rotator.