  In the tradition of Gabor's 1946 landmark paper [1], we advocate a
time-frequency (TF) approach to communications. TF methods for communications
have been proposed very early (see the box History). While several tutorial
papers and book chapters on the topic are available (see, e.g., [2]-[4] and
references therein), the goal of this paper is to present the fundamental
aspects in a coherent and easily accessible manner. Specifically, we establish
the role of TF methods in communications across a range of subject areas
including TF dispersive channels, orthogonal frequency division multiplexing
(OFDM), information-theoretic limits, and system identification and channel
estimation. Furthermore, we present fundamental results that are stated in the
literature for the continuous-time case in simple linear algebra terms.
