Design Of Subband Filter On The F-OFDM System And Research On The Method Of PAPR Reduction

In recent years,as the increasing demand for high-rate and high-bandwidth wireless communication networks,higher requirements have been put forward for the 5th generation mobile communication system(5G).Due to its large out-of-band radiation and high peak-to-average power ratio(PAPR),OFDM technology,widely used in 4G Long Term Evolution(LTE),is not suitable for 5G communication.In order to solve the above problems,people have proposed a Filtered-OFDM(F-OFDM)technology based on sub-band filtering.In addition to the advantages of the traditional OFDM technology,F-OFDM technology performs well in the suppression of out-of-band spectrum leakage in the system.Therefore,F-OFDM becomes one of candidate air interface waveform technologies of 5G.In order to solve the problem of large radiation and high peak-to-average power ratio in F-OFDM system,this paper proposes sub-band filters using Nuttall’s Blackman-Harris window design and a combination of clipping amplitude and selected mapping(SLM)algorithms method to improve the performance of the above two aspects respectively.First of all,the paper introduces the main application scenarios,business requirements and dynamic air interface technology framework of the 5G mobile communication system,and briefly analyzes the current research status of several popular air interface waveform technologies.Design of subband filter on the F-OFDM system,and reducing peak-to-average power ratio.Then,the paper discusses the basic principle and mathematical model of OFDM technology,and studies the basic principle of F-OFDM technology,summarizes the advantages and disadvantages of F-OFDM technology.Paper also briefly introduces the principle of digital filters,which focuses on the characteristics,design methods and design steps of FIR filter.Secondly,in order to solve the problem of large out-of-band radiation in F-OFDM system,the paper proposes a kind FIR filter that uses Nuttall’s Blackman-Harris window constructed in F-OFDM systems.It can be achieved a better suppression of system spectrum leakage.The paper gives the specific methods and steps to realize.Through MATLAB simulation,the performance of OFDM system and F-OFDM system’s power spectral density(PSD)are compared and analyzed under the same signal condition.Simulation results show that the added filter can effectively suppress the out-of-band radiation of the sub-band spectrum,so that the interference between adjacent sub-bands can be well suppressed by setting only a very low protection interval between different sub-bands.Finally,in order to solve the problem of high peak-to-average power ratio in F-OFDM system,the paper proposes a method combining clipping and improved SLM.It can be achieve better PAPR reduction.Firstly,the method,definition and distribution of peak-to-average power ratio in OFDM system are introduced.Simulation results show that there is still a high PAPR in F-OFDM system.Then,the paper focuses on two ways to reduce the PAPR in F-OFDM system:the clipping method and the SLM algorithm.The traditional SLM algorithm needs to send extra band information and take up the redundant band resources.The improved SLM algorithm saves the band resources without sending the edge band information.The effect of suppressing PAPR in F-OFDM system is simulated and compared respectively.The specific method of combining the clipping method and the improved SLM algorithm proposed in this paper is that after the improved SLM algorithm is processed and followed by the clipping method.Through the simulation and comparison of MATLAB,it can be obtained that this combination method in F-OPFDM system can achieve better effect of reducing PAPR.