Message Transmission Through Underspread Time-Varying Linear Channels

It is common to model rapidly varying communication channels by time-varying linear systems. The output of a time-varying linear system can be described by a superposition of time-frequency (delay-Doppler) shifts of the input signal. This paper investigates a novel message transmission scheme over time-varying linear channels which are sufficiently sparse in the delay-Doppler domain. In order to deal with the time-varying nature of the channel the usual training stage for channel estimation is skipped. The channel state information and the transmitted message, both are estimated by the receiver simultaneously. The main contribution of this paper is that the suggested message transmission scheme over time-variant communication channels enables data transmission in scenarios where previously no communication was possible.