Orthogonal Time Sequency Multiplexing Modulation: Analysis and Low-Complexity Receiver Design

TL;DR

This paper introduces orthogonal time sequency multiplexing (OTSM), a low-complexity modulation scheme that enhances performance over OFDM with efficient detection and channel estimation methods, leveraging Walsh-Hadamard transforms.

Contribution

It presents a novel OTSM scheme with a low complexity detection method and channel estimation, outperforming OFDM and matching OTFS performance at reduced complexity.

Findings

OTSM achieves higher spectral efficiency than OFDM.

OTSM offers similar performance to OTFS with lower complexity.

The proposed detection and estimation methods are computationally efficient.

Abstract

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.