Conceptual
Browse Instruct Curate

Fundamental Limits of Modulation over Delay-Doppler Channels

Establishes that no modulation scheme, including OTFS and vector OFDM, can compensate a non-trivial (delay-dependent) Doppler spread, because the Doppler term in the received signal depends on absolute time independently of the transmitted waveform; and explains that the gains such schemes show on time-varying channels come from block or vector-wise demodulation rather than from any special treatment of Doppler.