  This paper proposes orthogonal time sequency multiplexing (OTSM), a novel
single carrier modulation scheme that places information symbols in the
delay-sequency domain followed by a cascade of time-division multiplexing (TDM)
and Walsh-Hadamard sequence multiplexing. Thanks to the Walsh Hadamard
transform (WHT), the modulation and demodulation do not require complex domain
multiplications. For the proposed OTSM, we first derive the input-output
relation in the delay-sequency domain and present a low complexity detection
method taking advantage of zero-padding. We demonstrate via simulations that
OTSM offers high performance gains over orthogonal frequency division
multiplexing (OFDM) and similar performance to orthogonal time frequency space
(OTFS), but at lower complexity owing to WHT. Then we propose a low complexity
time-domain channel estimation method. Finally, we show how to include an outer
error control code and a turbo decoder to improve error performance of the
coded system.
