Low complexity hybrid algorithm for improving PAPR BER and PSD in OTFS under diverse channel conditions.

Area of Science:

• Wireless Communications
• Signal Processing
• Information Theory

Background:

• Orthogonal Time Frequency Space (OTFS) modulation offers advantages in high-mobility scenarios.
• Non-Orthogonal Multiple Access (NOMA) enhances spectral efficiency by allowing users to share resources.
• High Peak-to-Average Power Ratio (PAPR) and Bit Error Rate (BER) are critical challenges in OTFS-NOMA systems.

Purpose of the Study:

• To investigate and improve PAPR and BER performance in OTFS-NOMA systems over Rayleigh fading channels.
• To evaluate the effectiveness of various PAPR reduction techniques, including a novel Vandermonde matrix-based Partial Transmit Sequence with Companding (Vm-PTS+Companding).
• To analyze the system's performance under channel estimation errors.

Main Methods:

• Simulations were conducted using 256-QAM and 512-QAM on 256 subcarriers.
• Evaluated techniques include Vm-PTS+Companding, Vm-SLM+Companding, conventional PTS, SLM, Companding, and Clipping & Filtering (C&F).
• Performance metrics analyzed include PAPR, BER, Signal-to-Noise Ratio (SNR), and Power Spectral Density (PSD).

Main Results:

• The proposed Vm-PTS+Companding achieved up to 9 dB PAPR reduction for 256-QAM and 8.9 dB for 512-QAM.
• The scheme demonstrated significant PAPR gains (2.9-9.9 dB) over conventional methods even with channel estimation errors.
• BER analysis showed SNR improvements of 3.5-13.7 dB in ideal channels and up to 16 dB under error conditions.
• Reduced spectral leakage was confirmed with PSD evaluation.

Conclusions:

• Vm-PTS+Companding effectively optimizes PAPR and BER in OTFS-NOMA systems.
• The proposed method enhances system performance, particularly in challenging wireless environments with channel estimation errors.
• This technique supports high data rates in error-prone wireless communication systems.