PAPR Reduction in OFDM Systems using Clipping and Filtering Techniques

PAPR reduction using clipping and filtering is a fundamental technique for minimizing the Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) signals. This method enhances system performance by applying clipping and filtering operations to OFDM signals, effectively reducing the PAPR. The clipping operation is typically implemented by threshold-based amplitude limiting, where samples exceeding a predetermined clipping level are either truncated or compressed using mathematical functions like soft clipping (tanh function) or hard clipping (saturation function). This reduces the signal's dynamic range while maintaining essential characteristics. The filtering operation employs low-pass filters (often implemented using frequency-domain filtering with FFT/IFFT operations or time-domain FIR filters) to smooth signal peaks and eliminate out-of-band radiation caused by clipping. In practical implementations, the clipping and filtering process may be iterative, with multiple rounds applied to achieve optimal PAPR reduction while balancing EVM (Error Vector Magnitude) and BER (Bit Error Rate) performance. The clipping ratio (CR) parameter, defined as the ratio of clipping threshold to signal RMS value, is a critical design parameter that typically ranges from 1.0 to 2.0 dB in practical systems. Therefore, PAPR reduction through clipping and filtering represents an effective approach that maintains the core OFDM principles while enabling enhanced system performance through careful parameter optimization and algorithmic implementation.