Research On PAPR Suppression In OFDM System And GNU Radio Noise Interference Technology

Orthogonal Frequency Division Multiplexing(OFDM)technology and software radio technology have been rapidly developed and widely used with the development of wireless communication.OFDM is a kind of multi-carrier modulation,which uses orthogonal sub-carriers to transmit information.It has the advantages of flexible spectrum allocation,high spectrum utilization,anti-frequency selective fading and supporting high speed data transmission.However,the peak-to-average power ratio(PAPR)of the time-domain signal that modulated by OFDM is large,which will decrease the transmission performance of system.Therefore,research on PAPR suppression for OFDM signal is one of the key issues in OFDM system.At the same time,wideband,multi-mode,multi-functional application requirments are supported in software radio with the development of software radio technology.As a result,it has a bright future in mobile communications,satellite navagition,electronic warfare and other fields with reconfigurable,scalable,and upgradable features.Firstly,the transmission model of OFDM system is introduced.Besides,the basic principle,orthogonality conditions,advantages and disadvantages of OFDM modulation are analyzed in detail.Meanwhile,the definition of OFDM signal PAPR and typical PAPR suppression methods such as pre-distortion,coding and probability method are briefly introduced.Aiming at the high PAPR of OFDM signal and the high comput ational complexity of partial PAPR suppression methods,an improved PAPR suppression method is proposed.Firstly,the basic principle and performance of partial transmission sequence PAPR suppression method(PTS)are analyzed.In order to solve the problem of high comput ational complexity of PTS,an improved low-complexity PAPR suppression method(L-PTS)based on PTS is proposed.Simulation results show that L-PTS method has lower comput ational complexity than PTS method under the condition of equivalent PAPR suppression effect.Secondly,the precoding PAPR suppression method and of signal pre-distortion PAPR suppression method such as clipping method,clipping filter method and Compression expansion method are analyzed.Then a joint PAPR suppression method VLM-CF is proposed based on Chebyshev-Vandermond matrix precoding and clipping limiting filter.Simulation results show that compared with Chebyshev-Vandermond matrix precoding method and clipping filter method,the PAPR suppression effect is improved by using VLM-CF method.Finally,the concept of software radio and the architecture of GNURadio software radio are introduced and a smart noise jamming signal generation method based on OFDM modulation is introduced by using the advantages of flexible spectrum allocation of OFDM.Then a smart noise interference signal generation system using OFDM modulation is developed based on GNURadio software radio platform and USRP hardware front-end.The system is tested by spectrum analyzer and the test results are consistent with expectations.