Pilot Channel Estimation for Improve the Non-Linear Effects on GFDM-MIMO Scheme

This paper analyzes the performance of a generalized frequency division multiplexing scheme for multiple-input multiple-output configuration (MIMO-GFDM) in the presence of nonlinear power amplification with pilot insertion at the transmitter side to evaluate the saturation effects. For this purpose, two non-ideal transfer functions of high power amplifiers (HPA) are modeled: a Traveling Wave Tube Amplifier (TWTA) and a Solid State Power Amplifier (SSPA). In addition, for nonlinear distortion cancellation, we explore some peak-to-average power ratio (PAPR) reduction techniques, such as selective mapping (SLM), clipping, and clipping and filtering (C&F), to evaluate the best response and adaptability for the MIMO-GFDM scheme. The results show that an optimal power transmitter in the amplifier saturation region with large-scale input back-off (IBO) can mitigate out-of-band (OOB) radiation effects and consequently reduce the error floor in terms of bit error rate (BER) caused by amplifier saturation effects. In addition, we can control some trade-offs between PAPR, OOB emissions, BER performance, and power when the large-scale IBO reaches 4 dB. Finally, multicast effects in the Rayleigh channel can further saturate the amplifier when the transmit power increases, causing a proportional increase of the background noise with the channel variance. Thus, we can determine the maximum transmit power to avoid distortion and error-floor noise in poor channel conditions.