Doppler Shift Keying Modulation for Uplink Multiple Access over Doubly-Dispersive Channels

TL;DR

This paper introduces Doppler Shift Keying (DSK) modulation for uplink multiple access in high-mobility wireless channels, addressing high PAPR and detection complexity issues in delay-Doppler domain modulation.

Contribution

It proposes a low-complexity DSK transceiver based on orthogonal delay Doppler division multiplexing and extends it to multi-user uplink scenarios with optimized Zadoff-Chu sequence assignment.

Findings

DSK modulation outperforms existing methods in PAPR and BER.

The proposed scheme reduces detection complexity in high-mobility channels.

Simulation results confirm the effectiveness of DSK for uplink multiple access.

Abstract

The delay-Doppler (DD) domain modulation has been regarded as one of the most competitive candidates to support wireless communications for emerging high-mobility applications in the sixth-generation mobile networks. Unfortunately, most of the existing designs for DD domain modulation suffer from high peak-to-average power ratio (PAPR) and unbearable detection complexity under uplink transmission since large time duration and bandwidth are required to guarantee high DD resolutions. To address these issues, the Doppler shift keying (DSK) modulation based on the orthogonal delay Doppler division multiplexing modulator is proposed in this paper, where the input-output characterization in the DD domain is fully exploited. The principle of the DSK transceiver is first established with the one-hot mapper and low-complexity iterative successive interference cancellation-maximum ratio combining detector for point-to-point scenarios. The proposed scheme is then generalized to the zero auto-correlation sequence-based implementation, which benefits the extension of multi-user (MU) uplink DSK frameworks. For uplink DSK transmission, Zadoff-Chu (ZC) sequences are adopted as the basis sequences. We optimize the assignment of ZC roots to different user equipments (UEs) by minimizing the maximum inter-user interference. This optimization process, which analyzes the root allocation, directly assigns a specific ZC sequence to each UE. The PAPR and bit error rate performance of the proposed DSK modulation with the low-complexity detector is finally verified by extensive simulation results under doubly-dispersive channels, which demonstrates the superiority of DSK modulation especially for uplink multiple access over doubly dispersive channels.