A New Micro-Subcarrier OFDM Based Waveform for Delay Doppler Domain Communication

This paper presents a new OFDM based modulation scheme for communication in doubly dispersive channels. We call this Delay-Doppler OFDM (DD-OFDM). Our waveform has the same sparse-channel benefits as orthogonal-time-frequency-space (OTFS) modulation, while offering advantages in terms of simpler channel estimation, lower symbol error rate and lower out-of-band (OOB) emissions. We propose the DD-OFDM modulation scheme by introducing precoding across frames of frequency subcarriers. We show that the resulting waveform has different data carrying basis functions compared to OTFS modulation. We present the DD-OFDM receiver and derive the base-band model equations. We show that the base-band model for DD-OFDM leads to a simple and accurate channel estimation algorithm in non-integer fractional Doppler channels.