Suppression PAPR Algorithms For OFDMA System

Orthogonal Frequency Division Multiplexing Access(OFDMA)can satisfy the communication needs by orthogonal multi-carrier modulation and utilizing the inherent time-diffusion efficiency of ratio channels,high bandwidth effciency.The OFDMA signal includes narrowband signals that are simultaneously transmitted at various frequencies.When the narrowband signals of the same phase are superimposed,the peak value of the signal is much higher than the average value.Therefore,a key disadvantage of the OFDMA system is the peak average power ratio generated when using multicarrier transmission.This disadvantage reduces the efficiency and cost of high power amplifiers(Higher-Power Amplifier,HPA),producing signal distortion in the nonlinear region of the HPA.Reducing the system PAPR can not only improve the efficiency of the HPA,but also reduce the number of base stations(BS)by expanding the coverage of the transmitted siganal.The construction cost of the BS is an improve driving factor for the future mobile communication system.Therefore,reducing the PAPR of the system has become a research hotspot.Based on the existing theoretical research,this paper has conducted in depth research on this,and the specific work is asfollows:(1)Because a single algorithm can not get the ideal system performance,the thesis designs a joint algorithm of Discrete Cosine Transform(DCT)and Active Constellation Extension(ACE).The characteristic of the DCT transform energy concentration reduce the probability of a large peak signal appearing after the transform.The ACE algorithm can extend the constellation point position to reduce the probability that the signals are in phase.The joint algorithm not only reduces the PAPR of the system,but also optimizes the BER performance.The simulation experiment verifies the superiority of the algorithm.In order to further reduce the PAPR of the syste and obtain the relatively ideal PAPR optimization level,the DCC algorithm of DCT and improved nonlinear companding algorithm is designed.By properly adjusting the companding parameters,the PAPR optimization effect and BER performance can be effectively considered.The DCC algorithm first performs DCT transform in the frequency domain to reduce the autocorrelation of the signal,and then enterss the companding algorithm module to reduce the PAPR of the system while taking into account the BER performance.The algorithm achieves an improvement in PAPR suppression capability and optimization of BER performance.(2)Aiming at the problem that the iterative limiting filter algorithm needs multiple iterations to achieve the ideal PAPR optimization effect,anew filter function restriction rule is proposed.This rule abandons the idea of using the traditional rectangular window filter function,introduces a new SOCP criterion,and can obtain a relativeely ideal PAPR optimization effect under a few iterations.Based on the new filter function restriction rule,the DCF algorithm combined with DCTis first designed.The algorithm first performs DCT transform in the frequency domain,and then enters the iterative limiting filter module to reduce the appearance probability of the peak signal and further optimize the PAPR.The DCF algorithm not only achieves the original intention of suppressing PAPR,but also reduces the computational complexity of the system.The improved PTS algorithm replaces the segmented sequence with phase flipping instead of phase factoring,greatly reducing system complexity.The PCF algorithm breaks the conventional serial idea and divides the input signal into two parts,one part enters the iterative limiting filter module,and the other part enhe improved PTS module.The parallel design reduces the number of complex additions and complex multiplications of an IFFT,further reducing the computational complexity of the system.The new algorithm reduces the computational complexity of the system based on the optimization of PAPR and has practical value.