An 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 and lower out-of-band (OOB) emissions. We propose a DD-OFDM modulation scheme by introducing precoding across frames of frequency sub-carriers. 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.