Selective Mapping with Polar Coding for PAPR Reduction of OTFS Modulation

Orthogonal time frequency space (OTFS) modulation is a promising technique to improve wireless communication system performance, particularly in high-mobility environments. However, a notable challenge with OTFS is its high peak-to-average power ratio (PAPR), which can negatively impact system efficiency and performance. We propose a novel PAPR reduction method for OTFS modulation to mitigate this issue, which integrates polar coding (PC) with selective mapping (SLM). SLM is a widely recognized technique for PAPR reduction that generates multiple candidate signal versions and selects the one with the lowest PAPR. PC, on the other hand, is an advanced error correction technique known for its capacity-achieving performance. By integrating these two methods, our approach aims to leverage the advantages of both to achieve a substantial reduction in PAPR while maintaining reliable communication. In this study, we first outline the theoretical foundation of OTFS modulation and the principles of PAPR. We then describe the SLM technique and its application in the OTFS context. Next, we introduce PC and explain how it can be incorporated into the SLM framework. The proposed SLM-PC scheme is evaluated through extensive simulations to assess its effectiveness in reducing PAPR compared to conventional OTFS modulation. For large values of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$N$</tex>, we analytically characterize the CCDF of the PAPR for OTFS modulation using rectangular pulse shapes. Furthermore, we compare the simulated PAPR CCDF for OTFS with various pulse shapes to that of generalized frequency division multiplexing (GFDM) and OFDM. The results demonstrate that OTFS exhibits superior PAPR performance in comparison to both GFDM and OFDM.