Reducing PAPR (CCDF) Using DFT-S OFDM Signals

In wireless communication systems, Orthogonal Frequency Division Multiplexing (OFDM) is a widely adopted multi-carrier modulation technique, but its high Peak-to-Average Power Ratio (PAPR) remains a critical challenge affecting system performance. High PAPR drives power amplifiers into nonlinear operating regions, leading to signal distortion and spectral leakage. To mitigate this issue, the Discrete Fourier Transform Spread (DFT-S) technique can be applied to optimize OFDM signals.

The fundamental principle of DFT-S involves performing DFT spreading on input signals prior to OFDM modulation, which distributes the high-amplitude signal energy originally concentrated on few subcarriers across all available subcarriers. This spreading mechanism effectively smooths the time-domain amplitude distribution, thereby reducing PAPR. Complementary Cumulative Distribution Function (CCDF) analysis provides intuitive comparison between conventional OFDM and DFT-S OFDM PAPR performance, typically showing significant reduction in high PAPR occurrence probability for DFT-S OFDM implementations.

This approach has been successfully implemented in LTE uplink transmissions (e.g., SC-FDMA), offering advantages including moderate computational complexity and no additional out-of-band interference. Practical implementation requires balancing DFT block size with PAPR suppression effectiveness to achieve optimal trade-offs between system performance and computational efficiency. From a coding perspective, the DFT-S preprocessing typically involves: 1) Applying N-point DFT to input symbols 2) Subcarrier mapping with specific allocation schemes 3) Standard OFDM modulation with IFFT operations. The key parameters affecting performance include DFT size, subcarrier mapping strategy, and modulation scheme selection.