Analysis of DFT-Spread Technique for Mitigating Nonlinear Effects of HPA in FBMC/OQAM Systems

Filter Bank Multi Carrier with Offset Quadrature Amplitude Modulation (FBMC/OQAM) exhibits lower Out-of-Band (OOB) radiation compared to Orthogonal Frequency Division Multiplexing (OFDM) due to the use of a prototype filter as a pulse shaping filter. However, similar to OFDM systems, the Peak Average-to-Power Ratio (PAPR) in FBMC/OQAM is also high. In Nonlinear High Power Amplifier (HPA), signals with high PAPR can lead to increased OOB radiation in the HPA output signal and a decrease in Bit Error Ratio (BER) performance at the receiver. The Discrete Fourier Transform - Spreading (DFT-Spread) technique is a widely applied PAPR reduction technique in multicarrier modulation systems. In this paper, we analyze the performance of the DFT-Spread technique for mitigating the nonlinear HPA effects in the FBMC/OQAM system. The applied DFT-Spread technique involves adding DFT and Subcarrier mapping processes at the transmitter side, and Subcarrier de-mapping and IDFT processes at the receiver side. In PAPR testing, the DFT-Spread technique can reduce PAPR by 1.4 dB to 2 dB. In BER performance testing with the addition of nonlinear HPA effects (IBO=20 dB), the DFT-Spread technique can improve BER performance by 1.6 dB.