Low-complexity tone reservation method for PAPR reduction of OFDM systems

The OFDM communication system has a serious drawback that the peak signal value can be much higher than the average signal value. High peak signals can be easily distorted by the nonlinearity of power amplifiers, and can increase the symbol error rate (SER) significantly. Though many techniques have been proposed to reduce the peak-to-average-power ratio (PAPR), they are usually based on iterative FFT computation, needing lots of computation time. Based on the tone reservation method, this paper proposes a low complexity DFT structure in order to lower the complexity of PAPR reduction techniques. In the proposed method, several approximations are employed to reduce the computational complexity and to substitute complex multiplications with simple shift operations. The performance of the proposed tone reservation method is compared with that of the conventional method based on the radix-2 FFT. Simulation results show that there is almost no performance degradation if the radix-2 FFT is replaced with the proposed approximate DFT.