  Orthogonal time frequency space (OTFS) modulation is a 2-dimensional (2D)
modulation scheme designed in the delay-Doppler domain, unlike traditional
modulation schemes which are designed in the time-frequency domain. Through a
series of 2D transformations, OTFS converts a doubly-dispersive channel into an
almost non-fading channel in the delay-Doppler domain. In this domain, each
symbol in a frame experiences an almost constant fade, thus achieving
significant performance gains over existing modulation schemes such as OFDM.
The sparse delay-Doppler impulse response which reflects the actual physical
geometry of the wireless channel enables efficient channel estimation,
especially in high-Doppler fading channels. This paper investigates OTFS from a
signal detection and channel estimation perspective, and proposes a Markov
chain Monte-Carlo sampling based detection scheme and a pseudo-random noise
(PN) pilot based channel estimation scheme in the delay-Doppler domain.
