選擇性映射在降低OFDM與OTFS峰均功率比的比較

Comparison of Selective Mapping (SLM) for Peak-to-Average Power Ratio (PAPR) Reduction in OFDM and OTFS Systems

在本篇論文中，我們比較選擇性映射（SLM）在正交分頻多工（OFDM）與正交時頻空間（OTFS）峰均功率比（PAPR）的降低。考慮了N×M延遲-多普勒網格上的調製符號，其中N個符号和M個子载波组成。我們推導了OTFS訊號的PAPR的上限，並表明最大PAPR隨N線性增長（而不是如OFDM隨多子載波M載波的數量）。使用矩形脈衝的OTFS的PAPR的互補累積分佈函數（CCDF），以及對於大的N值，對於不同脈衝形狀的OTFS的模擬PAPR與OFDM的比較。OTFS顯示出比OFDM更低的PAPR。由於不會造成失真且易於實現，因此在各種PAPR降低方案中，選取映射選擇性映射方法套入OFDM與OTFS系統進行比對。模擬結果表明，選擇性映射在OFDM與OTFS系統都可以獲得比較好的PAPR降低效果，並且具有較低的計算複雜度。

This paper investigates the effectiveness of Selective Mapping (SLM) for reducing the Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Time Frequency Space (OTFS) systems. Considering modulation symbols on an N×M delay-Doppler grid, comprising N symbols and M subcarriers, we derive an upper bound on the PAPR of OTFS signals. Our analysis reveals that the maximum PAPR increases linearly with N, unlike OFDM where it scales with the number of subcarriers M. We present the Complementary Cumulative Distribution Functions (CCDFs) of PAPR for OTFS with rectangular pulse shaping and compare simulated PAPR for different pulse shapes of OTFS with OFDM, particularly for large N values. OTFS exhibits lower PAPR compared to OFDM. Due to its distortion-free nature and ease of implementation, SLM is selected as a PAPR reduction scheme for comparison in both OFDM and OTFS systems. Simulation results demonstrate that SLM achieves notable PAPR reduction in both OFDM and OTFS systems, with lower computational complexity.