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Multichannel cognitive radio (CR) has been proposed to improve system throughput by selecting multiple idle subchannels for transmissions. However, these idle subchannels are often noncontinuous, which cannot be utilized by the traditional access models, such as orthogonal frequency division multiplex and multicarrier code division multiple access. In this paper, a CR system based on transform domain communication system has been designed to access the non-continuous spectrum, which detects the spectrum status by energy detection and marks the spectrum availability as a spectrum marker vector. A basis carrier generated from the spectrum marker vector may concentrate the power on the idle subchannels. The bit error rate of the CR system is analyzed both in the cases of spectrum inconsistency and multiple access. The transmission data is modulated on the basis carrier using binary modulation and cyclic code shift keying modulation. A system optimization unit is designed to improve the system throughput by jointly optimizing sensing threshold and transmission power of each subchannel. The simulation results have shown that the proposed CR system may outperform the spread spectrum system and achieve larger throughput through performance optimization.

A Multichannel Cognitive Radio System Design and Its Performance Optimization