Orthogonal Delay-Doppler Division Multiplexing Modulation with Hierarchical Mode-Based Index Modulation

2025-01-14

AI Summary

To address the high detection complexity and limited spectral efficiency (SE) and bit-error-rate (BER) performance of Orthogonal Time Frequency Space Index Modulation (OTFS-IM) in doubly selective fading channels, this paper proposes an integrated ODDM-HMIM scheme. Specifically, it pioneers the fusion of Orthogonal Delay-Doppler Modulation (ODDM) with Hierarchical Mode Index Modulation (HMIM) to establish a full-diversity transmission framework in the delay-Doppler domain. A dedicated low-complexity successive interference cancellation minimum mean square error (SIC-MMSE) detector is designed for HMIM, substantially reducing the computational burden of maximum a posteriori (MAP) or maximum likelihood (ML) detection. Theoretical analysis and simulations demonstrate that, at identical SE, the proposed scheme achieves superior BER performance over conventional index modulation schemes. Moreover, it enables real-time demodulation for large frame lengths, thereby simultaneously achieving high spectral efficiency, low BER, and low computational overhead.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Machine Learning: Large Multimodal Models (LMMs)
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Search and Retrieval-Augmented AI: Vertical and domain-specific search

Abstract

The orthogonal time frequency space with index modulation (OTFS-IM) offers flexible tradeoffs between spectral efficiency (SE) and bit error rate (BER) in doubly selective fading channels. While OTFS-IM schemes demonstrated such potential, a persistent challenge lies in the detection complexity. To address this problem, we propose the hierarchical mode-based index modulation (HMIM). HMIM introduces a novel approach to modulate information bits by IM patterns, significantly simplifying the complexity of maximum a posteriori (MAP) estimation with Gaussian noise. Further, we incorporate HMIM with the recently proposed orthogonal delay-Doppler division multiplexing (ODDM) modulation, namely ODDM-HMIM, to exploit the full diversity of the delay-Doppler (DD) channel. The BER performance of ODDM-HMIM is analyzed considering a maximum likelihood (ML) detector. Our numerical results reveal that, with the same SE, HMIM can outperform conventional IM in terms of both BER and computational complexity. In addition, we propose a successive interference cancellation-based minimum mean square error (SIC-MMSE) detector for ODDM-HMIM, which enables low-complexity detection with large frame sizes.

Problem

• OTFS-IM
• Signal Processing
• Complexity

Innovation

• HMIM Technology
• ODDM-HMIM Integration
• SIC-MMSE Signal Processing