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Rethinking Next-Generation Signal Waveform: Integration of Orthogonality and Non-Orthogonality

Tongyang Xu, Shuangyang Li, Zhongxiang Wei, Gan Zheng, Izzat Darwazeh

TL;DR

The comparative analysis highlights that SC-NOFS(2D) provides a broader range of capabilities, particularly those requiring high data rate, high mobility, low-latency communication, sustainability, and interoperability, positioning it as a versatile solution for next-generation 6G communication.

Abstract

As 6G communications advance, the demand for new services and capabilities, as defined by the international telecommunication union (ITU), is increasing. A crucial aspect of 6G advancement lies in the development of signal waveforms that can meet these demands while maintaining compatibility with existing standards. This paper explores sustainable physical layer waveform options, focusing on a balanced approach that integrates non-orthogonality with orthogonality to achieve both backward compatibility and forward innovation. Specifically, we investigate two key signal formats: single-carrier orthogonal frequency division multiplexing (SC-OFDM) (1D,2D) and single-carrier non-orthogonal frequency shaping (SC-NOFS)(1D,2D). Both can use 1D frequency and 2D time-frequency precoding, offering enhanced frequency and time diversity, simplified processing, and resilience to delay-Doppler effects. SC-NOFS(2D) further introduces advantages such as improved spectral efficiency and reduced latency, making it a strong candidate for future 6G applications. The comparative analysis highlights that SC-NOFS(2D) provides a broader range of capabilities, particularly those requiring high data rate, high mobility, low-latency communication, sustainability, and interoperability, positioning it as a versatile solution for next-generation 6G communication.

Rethinking Next-Generation Signal Waveform: Integration of Orthogonality and Non-Orthogonality

TL;DR

The comparative analysis highlights that SC-NOFS(2D) provides a broader range of capabilities, particularly those requiring high data rate, high mobility, low-latency communication, sustainability, and interoperability, positioning it as a versatile solution for next-generation 6G communication.

Abstract

As 6G communications advance, the demand for new services and capabilities, as defined by the international telecommunication union (ITU), is increasing. A crucial aspect of 6G advancement lies in the development of signal waveforms that can meet these demands while maintaining compatibility with existing standards. This paper explores sustainable physical layer waveform options, focusing on a balanced approach that integrates non-orthogonality with orthogonality to achieve both backward compatibility and forward innovation. Specifically, we investigate two key signal formats: single-carrier orthogonal frequency division multiplexing (SC-OFDM) (1D,2D) and single-carrier non-orthogonal frequency shaping (SC-NOFS)(1D,2D). Both can use 1D frequency and 2D time-frequency precoding, offering enhanced frequency and time diversity, simplified processing, and resilience to delay-Doppler effects. SC-NOFS(2D) further introduces advantages such as improved spectral efficiency and reduced latency, making it a strong candidate for future 6G applications. The comparative analysis highlights that SC-NOFS(2D) provides a broader range of capabilities, particularly those requiring high data rate, high mobility, low-latency communication, sustainability, and interoperability, positioning it as a versatile solution for next-generation 6G communication.
Paper Structure (15 sections, 5 figures, 1 table)

This paper contains 15 sections, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Motivation
  3. Problem Statement
  4. Sustainability and Interoperability for 6G
  5. Physical Layer Waveform Potentials for 6G
  6. OFDM
  7. NOFS
  8. SC-OFDM(1D)
  9. SC-NOFS(1D)
  10. SC-OFDM(2D)
  11. SC-NOFS(2D)
  12. Performance Comparisons
  13. Computational Complexity
  14. Potentials for 6G Standard
  15. Discussion and Future Work

Figures (5)

  • Figure 1: Physical layer waveform innovations from 1G to future 6G communications.
  • Figure 2: Principle of orthogonal waveforms (OFDM, SC-OFDM(1D), SC-OFDM(2D)) and non-orthogonal waveforms (NOFS, SC-NOFS(1D), SC-NOFS(2D)). Orthogonal OFDM-based waveforms are generated using deterministic mathematical models, whereas non-orthogonal NOFS-based waveforms are generated via neural networks, with each generation coefficient optimized through machine learning.
  • Figure 3: Performance comparison of orthogonal waveforms (OFDM, SC-OFDM(1D), SC-OFDM(2D) [OTFS]) and non-orthogonal waveforms (SC-NOFS(1D), SC-NOFS(2D)) in AWGN channel. Q=492, M=600, N=1024, CP=72. The compression ratio for SC-NOFS(1D,2D) is 0.82 (492/600), the spectral efficiency is increased by approximately 22%, calculated as (1-0.82)/0.82. SC-OFDM(2D) and OTFS share the same signal structure based on 2D precoding. Their performance is expected to be equivalent in AWGN channel.
  • Figure 4: Performance comparison of orthogonal waveforms (OFDM, SC-OFDM(1D), SC-OFDM(2D), OTFS) and non-orthogonal waveforms (SC-NOFS(1D), SC-NOFS(2D)) in time-variant multipath frequency selective channel. Q=492, M=600, N=1024, CP=72. The compression ratio for SC-NOFS(1D,2D) is 0.82 (492/600), the spectral efficiency is increased by approximately 22%, calculated as (1-0.82)/0.82. SC-OFDM(2D) and OTFS share the same signal structure based on 2D precoding. Their performance is expected to be equivalent in scenarios where both waveforms can achieve accurate channel estimation.
  • Figure 5: Side-by-side comparison of SC-OFDM (orthogonal) and SC-NOFS (non-orthogonal) waveforms for 6G, evaluated across new capabilities, enhanced capabilities, and user scenarios. Colored blocks indicate the functions supported by SC-OFDM (2D) or SC-NOFS (2D), while uncolored blocks denote unsupported features.