Stuy On Reducing PAPR Based On Indoor LED Visible Light Communication System

Compared with other modulation technique,OFDM modulation technology because it has good resistance to narrow-band pulse noise and multipath interference and high spectrum efficiency,easily combined with other technologies,and many other advantages,is widely used in indoor LED visible light communication system.However,due to the OFDM symbol is composed of multiple independent through modulation of sub-carrier signal superposition,and when the same or similar each carrier phase superposition signal will be under the same initial phase modulation signal,resulting in a large instantaneous power peaks,thus further bring higher peak average power ratio.Research has shown that a higher PAPR signals through nonlinear components of communication system,the signal will have serious in-band nonlinear distortion,and will cause the interference and cause spectrum extension,produce very big band power,thus lead to system of the whole communication quality declined dramatically.Therefore,reduce the PAPR of OFDM modulation technology based indoor LED visible light communication system is crucial,and is of great significance.Considering the probability algorithm and signal pre distortion algorithm there are complementary in PAPR reduction aspect,this thesis fully balanced the algorithm complexity,to reduce the PAPR effect and the relationship between the introduction of error of three aspects,first put forward by a partial transmit sequence(PTS)and pressure of expansion(Companding)algorithm combined algorithm--PTS-Companding is used to reduce the PAPR of the system.Then carries on the detailed analysis,established the optimal cascade structure,and through the simulation software has proved its superiority.In order to further reduce the PAPR of the system,in a joint algorithm on the basis of preliminary judgment technology and Hadamard matrix is introduced.Through the preliminary judgment technology,can make part of the signal does not need to reduce PAPR algorithm operation,thus improves the BER performance of the system,strengthen the flexibility of the system.Hadamard matrix to join reduced since the correlation between OFDM signal,the PAPR characteristics of signal has very good effect.At the same time,the algorithm is relatively simple,and the frequency spectrum of the signal,transmission rate and BER performance of the system are not an effect,Theoretical analysis and MATLAB simulation results show that the proposed improved PTS-Companding joint algorithm can increase the computational complexity,lower BER performance of the system,reduce the PAPR of the system,which can effectively improve the quality of LED visible light communication system,communication.