Multidimensional Eigenwave Multiplexing Modulation for Non-Stationary Channels

TL;DR

This paper introduces a novel multidimensional eigenwave multiplexing modulation technique that leverages channel decomposition to mitigate interference in non-stationary, multi-dimensional channels, including space, time-frequency, and delay-Doppler domains.

Contribution

It proposes the Multidimensional Eigenwaves Multiplexing (MEM) modulation based on HOGMT decomposition, enabling orthogonal data transmission across multiple channel dimensions in non-stationary environments.

Findings

Achieves orthogonality across multiple degrees of freedom

Effectively mitigates inter-Doppler interference in non-stationary channels

Supports multi-user MIMO with inherent interference mitigation

Abstract

While interference in time domain (caused by path difference) is mitigated by OFDM modulation, interference in frequency domain (due to velocity difference), can be mitigated by OTFS modulation. However, in non-stationary channels, the relative difference in acceleration will cause Inter-Doppler Interference (IDI) and a modulation method for mitigating IDI does not exist in the literature. Both methods in the literature use carriers in a specific domain which achieve orthogonality in the target domain to mitigate interference. Moreover, those modulation cannot directly incorporate space domain, which requires additional precoding technique to mitigate inter-user interference (IUI) for MU-MIMO channels. This work presents a generalized modulation for any multidimensional channel. Recently, Higher Order Mercer's Theorem (HOGMT) [1] has been proposed to decompose multi-user non-stationary channels into independent fading subchannels (Eigenwaves). Based on HOGMT decomposition, we develop Multidimensional Eigenwaves Multiplexing (MEM) modulation which uses jointly orthogonal eigenwaves, decomposed from the multidimensional channel as subcarriers. Data symbols modulated by these eigenwaves can achieve orthogonality across each degree of freedom(\eg space (users/antennas), time-frequency and delay-Doppler). Consequently, the transmitted remain independent over the high dimensional channel, thereby avoiding interference from other symbols.