Research On Improved Constellation Algorithm For Optimizing PAPR Of OFDM System

Orthogonal Frequency Division Multiplexing(OFDM)as a multi-carrier modulation technology is favored in the current 4G technology and the just-coming 5G technology.Because this technology has many advantages,such as high spectrum utilization,more resistant to the impact of multipath fading than single carrier systems,etc.,this technology is widely used in wireless communication systems.but Orthogonal Frequency Division Multiplexing also has drawbacks.The peak-to-average power ratio that it may engender will have great influence on the entire system.for the sake of making the OFDM signal no distortion,it will have quite stringent demand on power amplifiers,digital/analog converters(D/A)and analog/digital converters(A/D),In order to work out the problem of the high peak-to-average power ratio of the orthogonal frequency division multiplexing system,the traditional algorithm is construed firstly in the paper,and the traditional algorithm is improved in latter.The main contents are as follows:Frist,the tenet of OFDM is introduced in the paper,then a figure is used to represent the elementary model of the OFDM system,and then the strengths of OFDM and weaknesses of OFDM technology are described particularly,and then draw forth a major drawback of OFDM technology—high PAPR,and thus the reasons and the causes of high PAPR are introduced,traditional algorithm in the constellation diagram expansion method are analyzed,and its shortcomings are pointed out.Secondly,the traditional algorithm is not effective in reducing the PAPR of the OFDM system.the traditional algorithm is improved to advance the PAPR property of the OFDM system.Familiar with and use the least square method.the PAPR of the system is reduced by associating the least square method with the constellation diagram expansion method in new method.As a result,the improved algorithm can be comparable to the original ten iterations after one iteration,which greatly decreases the number of iterations,and at the same time,thus the time complexity is greatly reduced.concerning bit error rate,the improved algorithm has almost the same bit error rate performance as the traditional algorithm.Then the traditional ACE-SGP algorithm is not productiveness in reducing PAPR,band the Hadamard code matrix together the traditional algorithm to gain an improved algorithm.Since Hadamard code conversion can transform the ordinary sequence to an orthogonal sequence,the orthogonality between the signals is heightened,simulation manifest that the improved algorithm is more excellent than the traditional algorithm in lessening PAPR.with respect to bit error rate performance,the improved algorithm is more excellent than the traditional algorithm.concerning the time complexity,the time complexity is not aggrandized by and large in improved algorithm.