Optimization Of Power Efficiency In Cognitive NC-OFDM System

In 5G system,OFDM technology has been applied.OFDM technology can be applied in Cognitive Radio to form non-continuous OFDM(NC-OFDM)to realize the data transmission of Secondary User due to it can allocate subcarriers flexibly.In NC-OFDM system,the Peak to Average Power Ratio(PAPR)severely lowers the power efficiency of a High Power Amplifier(HPA),and the sidelobe interference power from the Secondary User(SU)to Primary User(PU)also makes the power efficiency greatly reduced.Therefore,the research of this topic is of great significance.This subject starts from the following aspects:Firstly,this subject analyzed the statistical characteristics of PAPR in NC-OFDM system.The correlation coefficient p was introduced for the characteristics of NC-OFDM system to indicate the relationship of different allocation schemes.The simulation results show that the PAPR can be effectively reduced by about 6%by selecting the appropriate allocation scheme.Secondly,a PAPR suppression algorithm(PCF)for NC-OFDM system was proposed by analyzing the performance of different PAPR suppression algorithms in NC-OFDM system.The simulation results show that compared with the PTS algorithm,the PAPR can be effectively reduced 10%.At the same time,when SNR is 6dB,the receiver error rate can be reached below 10-4.Finally,for sidelobe power interference of SU to PU in the NC-OFDM system,conducting the time-domain windowing for the NC-OFDM signals.The average relative interference power function PR?L.was defined to measure the performance of different window functions.The simulation results show that the two order continuous window function can effectively reduce the interference power when compared with the typical raised cosine window,and the parameters of SOCW can be selected according to the system's BER at the receiver.