Investigation of Feedback Level Limiter Algorithm to Anticipate the Deep Fade Conditions on Closed Loop Rotate Modulations for Multicarrier Systems

This closed loop rotate modulation goal is to improve the multicarrier systems performance in slow fading channels, by utilizing complex channel state information feedback. The rotate modulation process uses the precoding principles applied to multicarrier systems with the Inverse Discrete Fourier Transform (IDFT) and Discrete Fourier Transform (DFT). If the deep fade channel is an input for the rotate modulation process that is inversely proportional to the channel response of each subcarrier, it will produce a signal with a large power. To limit the peak power of the system output, we propose the level limiter algorithm for feedback channels to anticipate deep fade conditions. The simulation results show the addition of a limiter can reduce the peak of the output power of the multicarrier modulator, which means the peak-to-average power can be reduced. However, it has a consequence that the bigger the limiter will result in an increased probability error, so we propose the optimal limiter level is 0.01 volt. The probability of error in low-level modulation like Binary Phase Keying shows good results even though the limiter's level process is added. At high-level modulation like 16-quadrature Amplitude Modulation, the greater level limiter causes the probability of error to worsen.