Comparisons of TDM and FDM Pilot Signals for Phase Noise Estimation with High-Order QAM for DFT-Spread OFDM

This paper presents comparisons of time division multiplexing (TDM) and frequency division multiplexing (FDM) based pilot signal multiplexing methods for estimating the time-varying phase noise (PN) in a high-order QAM scheme for discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing (DFT-S-OFDM). Computer simulation results show that the peak-to-average power ratio at the complementary cumulative distribution function of 10⁻⁴ of DFT-S-OFDM with FDM pilot multiplexing is increased by approximately 1.8 dB and 1.2 dB compared to that for DFT-S-OFDM with a TDM based pilot signal and that for DFT-S-OFDM without a pilot signal, respectively, for 256QAM. We also show that the required received signal-to-noise ratio (SNR) satisfying the bit error rate (BER) of 10⁻⁸ for the TDM based pilot signal is decreased by approximately 1.1 dB, 1.2 dB, and 1.3 dB compared to that with the FDM based pilot signal for the low-density parity-check (LDPC) coding rate of 1/2, 3/4, and 8/9, respectively, for 256QAM assuming the same frequency bandwidth. Hence, we show that the TDM based pilot signal for PN estimation achieves superior performance to that for the FDM based pilot signal although FDM based pilot multiplexing has the potential for improvement by using elaborate cancellation of single-carrier distortion.