Research On Peak-to-Average Power Ratio Of Mobile Broadband Access System

With WiMAX(Worldwide Interoperability for Microware Access)and LTE(Long Term Evolution)being recognized as IMT-Advanced 4G standard,mobile broadband brings the public a high-speed wireless data transmission experience.As a key technology of the fourth generation mobile broadband multiple access,OFDM has attached much attention due to its advantages of simple modulation and demodulation,large transmission capacity,etc.However,one of the obvious drawbacks of OFDM is that the modulated time domain signal exhibits a high peak,which leads to a large line arrange of power amplifiers and increases the burden on the amplifier.Therefore,this paper focuses on the suppression of OFDM peak-to-average power ratio.After analyzing several algorithms,an improved peak-to-average power ratio suppression algorithm is proposed.This paper first introduces the concept of mobile broadband access system and the structure of fourth generation mobile broadband orthogonal frequency division multiple access(OFDMA),and compares OFDMA with CSMA-OFDM,TDMA-OFDM,FDMA-OFDM in spectrum resource allocation.Orthogonal frequency division multiple access mainly consists of two parts: resource allocation and OFDM,so the key technologies such as IFFT/FFT and synchronization are discussed in OFDM system.The analysis of OFDM/OQAM shows that this modified technology of OFDM can improve inter-symbol interference and carrier-to-carrier interference,low spectral efficiency,and frequency-sensitive,which has a certain reference for the future research of multiple access technology.Then the high peak-to-average power ratio of OFDM is analyzed and simulated,due to the reason that the superimposed signal on each path,results in time domain signal with a high peak which can be detected by the correlation of the signal.For the problem that the OFDM peak-to-average ratio is too high,several common suppression peak-to-average power ratio algorithms are studied in the predistortion and nondistortion methods,and the advantages and disadvantages of the selection mapping method,partial transmission sequence method and clipping method in terms of power utilization efficiency,spectrum utilization rate,computational complexity and transmission performance are also discussed emphatically and analyzed by simulation.As a multi-carrier modulation(MCM),OFDM / OQAM also has a high peak-to-average power ratio,so the similarities and differences between OFDM and OFDM/OQAM in peak-to-average power ratio are analyzed and simulated.Finally,a joint algorithm is proposed by combining the clipping filter method and the improved partial transmission sequence method.The simulation indicates that the algorithm adds no more computation,but reduces the distortion from the clipping.