Research On Interference Suppression Technology Of Cognitive MB-OFDM System

With the rapid popularization of various smart wireless terminals,the amount of wireless services such as mobile Internet has increased dramatically,the scarcity of existing wireless communication spectrum resources has become increasingly serious.Cognitive radio can detect the free frequency band in the wireless channel environment and distribute the spectrum dynamically and intelligently;The UWB system has the characteristics of low transmission power,high transmission efficiency and strong anti-electromagnetic interference.Therefore,cognitive multiband-orthogonal frequency division multiplexing(MB-OFDM)combined with cognitive radio and ultra-wideband technology will undoubtedly effectively solve the problems faced by existing spectrum utilization.This paper focuses on the interference suppression technology of cognitive MB-OFDM systems,which mainly includes the principles and key technologies of cognitive MB-OFDM systems;interference suppression methods based on improved windowing in the time domain;joint subcarrier closure and time domain windowing interference suppression techniques.The specific research content is as follows:1.An improved time-domain windowing method is proposed to realize the interference suppression of cognitive MB-OFDM systems.By selecting part of the raised cosine window function starting from the periodic cognitive MB-OFDM symbol,the spectrum structure of the system is optimized without introducing the system spectral components,and the sidelobe interference to the overlapping frequency band is suppressed.Simulation results show that,compared with the traditional subcarrier weighting and active interference cancellation,the improved time-domain windowing technique can accelerate sidelobe attenuation,improve system transmission performance,and have better interference suppression effect.2.An interference suppression technique for cognitive MB-OFDM systems combining subcarrier closure and time-domain windowing is proposed.By turning off several sub-carriers around the overlapping frequency band,the sidelobe leakage of interfering subcarriers issuppressed,and the windowing method in the time domain is introduced to further accelerate the attenuation of the frequency spectrum sidelobe.The simulation results show that the combined subcarrier off and time-domain windowing techniques can more effectively suppress the mutual interference between cognitive MB-OFDM systems and narrowband systems,and improve the system's transmission performance.