Peak-to-Average Power Ratio reduction in OTFS modulation using companding technique

OTFS (Orthogonal Time Frequency & Space) is one of the recent 2D modulation scheme suitable for 5G.In which information symbols in the delay-Doppler grid of NxM are multiplexed over new class of carrier waveforms, which are localized pulses represented in delay-Doppler domain. Where M represents number of delay bins and N represents number of Doppler bins. For smaller values of N the PAPR of OTFS is lower than the OFDM but as the N value increases PAPR of OTFS and OFDM are almost same. In order to decrease the PAPR of OTFS for higher values of N (N>4), we have proposed a conventional Mu-Law companding technique, which will reduce the PAPR of OTFS by 2.5dB with respect to original OTFS signal with slight degradation in bit error rate(BER) performance. The MATLAB simulation is carried out for different values of companding factor(mu) and CCDF of PAPR of OTFS and BER is plotted. The optimal value of companding factor(mu) is found from simulation results.