DFT-p-FDMA: A Waveform for Doubly Selective Channels

CP-OFDM exhibits degraded performance in high mobility situations, primarily due to selective fading in both frequency and time. To address this issue, we propose a novel waveform, discrete Fourier transform phase rotated and permuted frequency division multiple access (DFT-p-FDMA), which efficiently handles a range of mobility scenarios. Unlike CP-OFDM, which assigns distinct modulation symbols to fixed subcarriers, DFT-p-FDMA spreads the modulation symbols in both time and frequency. By leveraging frequency-time spreading, DFT-p-FDMA captures both delay and Doppler diversity, resulting in a near-uniform effective SNR across the demodulated symbols. The DFT-p-FDMA waveform can be generated by applying a DFT and a permutation with phase rotation before performing the IDFT of CP-OFDM, and allows for UE-specific implementation on top of the CP-OFDM framework. Performance evaluation demonstrates that DFT-p-FDMA outperforms CP-OFDM by providing up to 2.5 dB gain at 1e-2 block error rate (BLER).