A Research On Reducing PAPR Of The OFDM System

As one of the key technology for the fourth-generation communication systems,Orthogonal Frequency Division Multiplexing (OFDM) has the limitation of having a highPeak to Average Power Ratio (PAPR). High PAPR will not only reduces the efficiency ofamplifier, and may lead to serious nonlinear distortion and extend band radiation, so it willaffect the cost of operation and efficiency of OFDM system. In order to study the PAPRsuppression in OFDM systems, it is a key technology for OFDM system to find a goodbalance in reducing PAPR,increasing spectrum efficiency, and lowing computationalcomplexity.In this paper,the technologies for reducing PAPR of OFDM system were studied.Bysimulation analysis, we summed up the technology of signal pre-distortion, and peakcancellation in existing lower PAPR method, then on the basis of simulation analysistechnology and choice of mapping (SLM) technology. By combining the two algorithms, animproved algorithm on reducing the PAPR of OFDM system of SLM-peak offset cascade isproposed. That is first selecting the mapping process, then peak cancelling the input signal,the simulation results show that the algorithm can reduce the PAPR to6.7dB in the case oflow complexity.To further reduce PAPR of OFDM system and the redundant information introduced bySLM-peak cancellation algorithm. An improved algorithm for integration of superimposedtraining is presented. That is to choose a suitable chaotic sequence to superimpose the inputsignal, then apply it on selecting the mapping and partial transmit sequences algorithm. Thesimulation found that the introduction of the chaotic sequence can not only reduce the PAPR,but also reduce the redundant information. And then by introducing the chaotic sequence intothe SLM-peak cancellation cascade algorithm. A new SLM-peak cancellation the cascadealgorithm which based on the integration of the training sequence is put forward. Lots ofSimulation results show that the algorithm can reduce the PAPR to6.1dB effectively. At the same time, because of the introduction of the chaotic sequence, it does not need to transmittransmission of side information which the cascade algorithm required, so that it improved thebandwidth efficiency of the system.