Does 6G Need a New Waveform: Comparing Zak-OTFS with CP-OFDM

2026-01-22

AI Summary

This study addresses the critical challenge of severe interference in 6G communications under high-delay and high-Doppler (doubly dispersive) channels, where conventional waveform assumptions may no longer hold. It systematically evaluates the performance of Zak-OTFS against CP-OFDM in representative 6G scenarios, such as large-cell and high-mobility environments, revealing that waveform selection fundamentally entails a system-level trade-off. Specifically, Zak-OTFS proactively mitigates inter-symbol interference through predictable input–output relationships, whereas CP-OFDM relies on the idealized assumption of negligible inter-carrier interference. Through extensive simulations over doubly dispersive channels, the work analyzes differences in interference characteristics, equalization complexity, and environmental adaptability. Results demonstrate that Zak-OTFS significantly outperforms CP-OFDM under strong time–frequency dispersion, leading to practical waveform selection guidelines tailored to real-world deployment conditions and offering theoretical support for 6G standardization.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems

Abstract

Across the world, there is growing interest in new waveforms, Zak-OTFS in particular, and over-the-air implementations are starting to appear. The choice between OFDM and Zak-OTFS is not so much a choice between waveforms as it is an architectural choice between preventing inter-carrier interference (ICI) and embracing ICI. In OFDM, once the Input-Output (I/O) relation is known, equalization is relatively simple, at least when there is no ICI. However, in the presence of ICI the I/O relation is non-predictable and its acquisition is non-trivial. In contrast, equalization is more involved in Zak-OTFS due to inter-symbol-interference (ISI), however the I/O relation is predictable and its acquisition is simple. {Zak-OTFS exhibits superior performance in doubly-spread 6G use cases with high delay/Doppler channel spreads (i.e., high mobility and/or large cells), but architectural choice is governed by the typical use case, today and in the future. What is typical depends to some degree on geography, since large delay spread is a characteristic of large cells which are the rule rather than the exception in many important wireless markets.} This paper provides a comprehensive performance comparison of cyclic prefix OFDM (CP-OFDM) and Zak-OTFS across the full range of 6G propagation environments. The performance results provide insights into the fundamental architectural choice.

Problem

• 6G
• waveform
• Zak-OTFS
• CP-OFDM
• doubly-spread channels

Innovation

• Zak-OTFS
• CP-OFDM
• inter-carrier interference (ICI)
• doubly-spread channels
• 6G waveform