  Waveform design for interference cancellation in next-generation wireless
systems, which includes precoding and modulation, aims to achieve orthogonality
among data signals/symbols across all Degrees of Freedom (DoF). Conventional
methods struggle with non-stationary channel states due to high mobility,
density, and time-varying multipath propagation. In this article, we review the
HOGMT-Precoding and MEM modulations for non-stationary channels. We also
discuss practical challenges and future directions.
